| 00:25 | Okay. Okay. Any any any from what we talked about yesterday? |
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| 00:37 | we move on ST okay. So uh next thing on the agenda is |
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| 00:47 | sort of one more uh thing to about to introduce you to more terminology |
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| 00:54 | we put everything into some sort of . And uh and that's just to |
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| 00:58 | review some of the key sedimentary structures we encounter and carbonates a number of |
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| 01:06 | you also encounter in classic rocks But let me just briefly take you |
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| 01:12 | these and talk about some of the . And uh if you look in |
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| 01:17 | slide set that I sent you, first slide actually contrast The two types |
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| 01:22 | sedimentary structures. There's a mm hold . The two types of sedimentary structures |
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| 01:37 | what we call primary or send oppositional the other is post deposition which relates |
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| 01:44 | die genesis. Okay. And they see the list here on the left |
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| 01:55 | the so called primary or sin deposition penny contemporary structures and carbonates. And |
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| 02:01 | on the right are all the post positional structures which all relate back to |
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| 02:05 | genetic processes that we're gonna talk about uh today. So let me just |
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| 02:11 | take you through the list on the . I'm not gonna talk about every |
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| 02:15 | of those that are listed there. then I'll take you through the list |
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| 02:19 | the right to show you some examples talk about the significance of some of |
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| 02:26 | sedimentary structures either from a deposition standpoint a die genetic history standpoint. And |
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| 02:33 | this will be tied back into our detailed discussion of, of carbonate faces |
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| 02:38 | environments uh next weekend or the die that we're gonna talk about later |
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| 02:47 | So we're going to start first with lamination and cross stratification. And then |
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| 02:53 | going to show you some stuff about . I've talked a little bit about |
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| 02:57 | activity yesterday and in crustacean, marine grounds. We'll talk a little bit |
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| 03:05 | geo pedals that how we use geo in the rock record. Uh There's |
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| 03:09 | funny fabric called strom attack tous that in some of these upper uh well |
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| 03:17 | not just upper paleozoic, but paleozoic so called mud bounds that are common |
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| 03:24 | the devonian up through the upper part the paleozoic. And this fabric is |
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| 03:32 | some bearing on reservoir quality. So why I wanna introduce you to |
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| 03:37 | And then graded bedding sedimentary brunches. then we'll finish up with these desiccation |
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| 03:42 | , finessed, real fabric cracks and what we call teepee structures. |
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| 03:49 | we'll start first with some of the lamination fabrics and when when you really |
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| 03:55 | about it preserving lamination and carbonates is pretty hard to do. There are |
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| 04:02 | only a couple of environments where you preserve lamination. Right? So this |
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| 04:06 | example here again, if it's it's bright, let me know, we |
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| 04:11 | shut another light off. But you in in this view here from this |
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| 04:16 | of devonian limestone. He can see nominations, Right? You guys have |
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| 04:23 | feel for? Yeah, maybe that's . You guys have a feel for |
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| 04:28 | you what this what this signifies In other words, how do you |
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| 04:33 | parallel lamination? It's one or the , whatever you guys want. I |
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| 04:50 | , we'll leave it like that. I see him falling asleep, then |
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| 04:53 | turn it down. Um So, lamination. So you guys have a |
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| 04:59 | for how this is formed? Certainly energy. Right? And how do |
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| 05:08 | how do you create the lamination? stuck in suspension, right? It |
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| 05:15 | settles out onto the sea floor. ? So that's obviously going to be |
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| 05:20 | to the sea floor. And so produce these repetitive, parallel oriented |
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| 05:28 | Okay, And you see the dark there and you see on the label |
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| 05:34 | T. O. C. Do do you know what? T. |
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| 05:36 | . C. Is? Total organic , but basically the same thing. |
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| 05:45 | uh we're going to talk about carbonate rocks later, but the amount of |
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| 05:51 | . O. C. In the is used as a proxy for the |
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| 05:57 | for that rock to yield hydrocarbon. , and in a shale, if |
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| 06:02 | get one or 2% T. C. That's considered to be a |
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| 06:05 | good source rock for a plastic And this carbonate has 8% which is |
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| 06:12 | high and actually in this sequence it up to 18%. So this is |
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| 06:18 | out to be a world class carbonate rock in Western Canada, But the |
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| 06:23 | color is related to the fact that have a lot of that preserved organic |
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| 06:28 | . Alright, dark color doesn't always to that. There are other ways |
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| 06:32 | create dark color, but the high is consistent with that darker color. |
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| 06:39 | the question now is, you I guess the other question, you |
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| 06:45 | , why isn't this borough in other , why did you preserve the |
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| 06:53 | What would eliminate burrowing organisms? Now, A lot of people think |
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| 07:03 | lot of people think it's water but actually it's not water depth because |
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| 07:09 | you can go to the Atlantic Ocean and in 10,000 ft of water and |
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| 07:13 | burrow amounts produced by worms and stuff that. All right. Remember I |
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| 07:19 | you a borough man yesterday by produced a shrimp. But you go you |
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| 07:25 | the deeper water and find similar kinds burrow structures. So, water depth |
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| 07:29 | se doesn't control their distribution. It is water quality. So, the |
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| 07:36 | is, how do you change the quality? Right. What? There |
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| 07:40 | two variables that would influence anything that to live on the sea floor? |
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| 07:45 | the first would be oxygen. All these organisms need oxygen. |
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| 07:50 | if you create low oxygen conditions on sea floor, which we term |
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| 07:56 | then that's one way to eliminate the . And of course, that's a |
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| 08:02 | one way to preserve organic material. ? So if you're trying to think |
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| 08:06 | where you get a carbonate source you want to be thinking, |
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| 08:09 | how can I create a condition where set up an oxy on the sea |
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| 08:14 | ? And unfortunately, water depth is really part of the story. All |
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| 08:19 | , So that doesn't by itself, create anoxia. And then any other |
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| 08:25 | about water quality takes place. What's name again? Well, I |
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| 08:36 | you could you could have that would ephemeral, right? Or temporary, |
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| 08:43 | ? It wouldn't change the nature of environment. I mean, we don't |
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| 08:47 | how much time is represented in this of rock, but historically millimeter scale |
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| 08:54 | , you know, a couple of , usually in modern day deep |
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| 08:58 | deeper water sediments equates to a few years. So it's the other likely |
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| 09:07 | is going to be related to salinity the water. Remember we talked about |
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| 09:12 | salinity yesterday, that's 35 parts per today. And if you jack up |
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| 09:18 | salinity, you have that potential to , first of all, any cal |
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| 09:24 | organisms that want to live there. if you jack it up enough to |
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| 09:28 | what we call hyper salinity, where get up to say 60 or 70 |
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| 09:33 | per 1000 basically double the salinity, you can also eliminate, boring |
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| 09:39 | Okay, so parallel eliminations are actually difficult to preserved. Right? You |
|
| 09:49 | settle out this material, but what's usually happen on the seaports gonna get |
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| 09:54 | and they're gonna destroy the stratification. also going to eat the organic |
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| 09:58 | So they're going to kill the source potential. Okay, so, parallel |
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| 10:04 | or have some strong environmental significance. . They don't prove whether it's anoxia |
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| 10:09 | hyper salinity, but if it was hyper saline, um you might expect |
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| 10:17 | see precipitation of evaporate minerals out of . Alright, we'll talk about evaporate |
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| 10:24 | later in the course. So, would be one thing you might want |
|
| 10:28 | look for if you think it's hyper . Right? I have some early |
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| 10:32 | , say gypsum crystals ran hydrate, like that. Right. Those are |
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| 10:37 | sulfate minerals that precipitate out of seawater it evaporates. So, um that |
|
| 10:47 | be something you look for. and then the other style of stratification |
|
| 10:54 | what we call cross stratification. you see in this core here where |
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| 10:58 | stratification is angled, right? And is a reflection of ripples on the |
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| 11:03 | floor. And ripples are created either tidal currents or by wave. Wind |
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| 11:09 | oscillation. All right, So, get a symmetrical ripples or symmetrical |
|
| 11:14 | but you can't really recognize. And sectional view. You can't differentiate |
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| 11:20 | but in a tidal current system, ? That we'll talk about this next |
|
| 11:26 | . The currents come like this right the platform very strongly, then they |
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| 11:33 | , right? There's a lag time and then they turn around and come |
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| 11:38 | the other way. Alright, so can see where when the currents come |
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| 11:42 | way onto the platform, the stratification going like this, right? And |
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| 11:46 | when it comes back, the stratification coming the other way. So you |
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| 11:51 | sets of opposed angled stratification. That's herringbone cross stratification where one set goes |
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| 11:59 | way, but right on top of other set goes this way. |
|
| 12:03 | so that's pretty characteristic of the title driven system. Right? And here |
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| 12:09 | don't see that you just see the directional cross stratification which may suggest maybe |
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| 12:14 | more wave. Wind wave oscillation, ? Where the ripples are moving in |
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| 12:19 | to to wind wave oscillation. but again, the question is, |
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| 12:25 | isn't this borough? Right. Can see, I don't know if you |
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| 12:32 | see that you can actually almost see little grains there. Those are |
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| 12:36 | It's this is analytic grain stone. that's a high energy environment. |
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| 12:43 | So when the currents or wind wave occurring, you get a lot of |
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| 12:48 | sand on the sea floor. If were a boring organism, that would |
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| 12:53 | really hard to deal with, Because sand would be coming in your |
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| 12:58 | and you have to keep trying to it. Which some of these can |
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| 13:02 | , but most of them don't want do. Okay, so here's the |
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| 13:07 | way to preserve stratification being a high setting. But it's a completely different |
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| 13:12 | than what I showed you for the example. Okay, so you're going |
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| 13:16 | see how this all ties in. we start talking about environments uh next |
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| 13:22 | , I just want you to appreciate we try to use some of this |
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| 13:26 | . You know? Again, we're to piece together a better understanding of |
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| 13:30 | de positional environment. What does what ? That's the depth? That's a |
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| 13:49 | sample taken from below the land Alright, so this is this is |
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| 13:59 | , This is from a a gas in east texas. Uh So that's |
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| 14:06 | 11,000 ft below the Kelly Bushing. is the drilling floor. Right? |
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| 14:13 | where they measured the total depth that thrill on a rig. Right? |
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| 14:18 | the kelly bushing or rig floors maybe ft above ground level. But that's |
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| 14:26 | data. Okay. That's what they for data. Alright. So that |
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| 14:29 | was taken from 11,000 that core pieces 11,800 and something below the drilling |
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| 14:38 | The drilling floor. Okay. Just deeply buried. I mean, I |
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| 14:46 | know how much you know about the depth site drill, but I |
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| 14:52 | most of the drilling doesn't get Say well, it just depends where |
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| 14:55 | at. I mean, so all , it turns out that the most |
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| 15:06 | in the rock record end up being we call bio probated borough to varying |
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| 15:11 | . Okay. In fact to the that when we look at outcrop but |
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| 15:16 | look at core. If we don't preserve stratification, we assume that rock |
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| 15:22 | been buying abated or burrowed probably many over. Okay. And so sometimes |
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| 15:30 | borrowers leave behind what we call trace . And this is one example of |
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| 15:36 | trace fossil of the burrowing shrimp. . It has different names. Ring |
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| 15:43 | rind burrow. That doesn't really Just appreciate that. That that's about |
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| 15:51 | ? About $1.5. You don't see half dollars anymore of a half dollar |
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| 15:56 | . Right? About that big. that's basically the same diameter as the |
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| 16:02 | day shrimp burrows that I showed you . All right. So this is |
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| 16:06 | byproduct of the shrimper was going through sediment. They destroyed the stratification. |
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| 16:13 | can see how the rock is lighter because they've removed most of the organic |
|
| 16:19 | . All right. A sample like might have .1% t. o. |
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| 16:24 | . Okay. Which is not. nothing. Okay. Alright, so |
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| 16:30 | that relationship. And well, obviously the story more. Okay, one |
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| 16:36 | example here, this is from an in central texas. And again, |
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| 16:41 | can see the this model texture is of a classical fabric created by the |
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| 16:48 | shrimp. Alright. But worms can the same sort of thing. And |
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| 16:54 | so that's the key is to appreciate model of the parents and also the |
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| 17:00 | of stratification. Alright. And we that that's been borrowed probably many times |
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| 17:07 | . Alright. And then in I talked a little bit about some |
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| 17:12 | the organisms yesterday, the scalable grains in crust. So I think we |
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| 17:17 | about things like dry zones and ethnic . Uh corals and crust stream it |
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| 17:25 | and crust red algae and crust. . And so I just want to |
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| 17:31 | you some of the fabric. Most this is from modern pieces of |
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| 17:38 | So this is a piece of dead lifted off the sea floor and you |
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| 17:42 | see this bumpy color here that's due a type of red algae. |
|
| 17:48 | the crustacean can't happen until the coral . Right? So they have to |
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| 17:54 | on the sea floor by whatever you know, they get sandblasted by |
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| 17:59 | storm, They get broken up by storm, but as soon as they |
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| 18:04 | they become an inviting surface. A hard substrate for in clusters. |
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| 18:10 | it's a red algae. Sometimes it's things like I mentioned. Alright, |
|
| 18:15 | here's another piece of coral here, with a little benthic foraminifera. This |
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| 18:22 | all this red material you see here uh a entrusting foraminifera. It's it's |
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| 18:30 | interesting foraminifera because you know, most organisms that have color like red |
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| 18:36 | Green algae that we talked about when die, the color gets bleached |
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| 18:41 | But this is the only carbonate grain know of that actually keeps its |
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| 18:46 | its red color after it dies. so that's another type of impressed er |
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| 18:51 | of course you know once once you once you kill that coral or whatever |
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| 18:58 | crust. Then it also becomes an target for the boring organisms that we |
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| 19:04 | about briefly yesterday. So all the you see here are created by various |
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| 19:11 | of boring organisms. And as I about yesterday, this is one way |
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| 19:15 | break down the rock fabric into smaller smaller pieces. Alright, and here's |
|
| 19:23 | head piece of head coral here with smaller holes. And again most of |
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| 19:28 | smaller holes are created by the uh sponge. And I think the next |
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| 19:41 | is um piece of coral just lifted of the sea floor where the sponge |
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| 19:49 | still alive. So all this red yellow fabric you see here is living |
|
| 19:56 | sponge. Alright. And so they into the coral. They create a |
|
| 20:01 | that live but to bore into that structure they actually use acid and they |
|
| 20:09 | their suda podia to reach back in pull out little pieces of uh of |
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| 20:15 | coral that they return to the environment they excavate their whole. Alright, |
|
| 20:21 | you actually can see this in the , the very distinctively shaped scallop pieces |
|
| 20:30 | . This is only created by the sponge, right? And you can |
|
| 20:35 | the scale there. So this is silt sized material. Right? And |
|
| 20:41 | you can't easily see it in a section. But you can pick it |
|
| 20:44 | in a scanning electron microscope that scalloped . And the size is characteristic of |
|
| 20:51 | chips that are made by these boring . Right? And then one last |
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| 20:58 | here again they have to be connected the open ocean when they're alive |
|
| 21:04 | This is a mollusk shell and that the boring and they're connected right? |
|
| 21:09 | have to stick out and and and feed but but appreciate the significance of |
|
| 21:17 | . This is the way we break bigger scale stuff into finer pieces. |
|
| 21:24 | . And then hard grounds. I you underwater picture were on that sand |
|
| 21:30 | system in the northern Bahamas. Some the ula Tik sand is being cemented |
|
| 21:34 | place. And the definition of a hard ground is that it is marine |
|
| 21:44 | . So you should see these unique of cement. They go around the |
|
| 21:49 | . And I'm going to talk about later today. And then the other |
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| 21:54 | of the definition is not only is marine cemented but its board and |
|
| 21:59 | Alright, so that's the definition of hard ground and you can see some |
|
| 22:03 | the holes that cut the hard ground and then you can see the n |
|
| 22:07 | including that benthic Foraminifera. But you see little worm tubes here, little |
|
| 22:14 | worm tubes that are entrusting some of uh somewhere up here there's some bride |
|
| 22:19 | that are entrusting this. So that's definition of a marine hard ground. |
|
| 22:25 | you expect to see a lot of into that structure. Okay. And |
|
| 22:33 | the holes here are created by cutting the rock. Right? So that |
|
| 22:38 | to call something. Some people get between the term burro and boring. |
|
| 22:46 | ? Burrows are created in unconsolidated The organism just pushes its way through |
|
| 22:52 | unconsolidated sediment. Okay? But to something a boring like you see here |
|
| 22:58 | had to have a hard substrate and that organism either chemically or mechanically cuts |
|
| 23:04 | that that hard substrate. Okay. if you were to look at, |
|
| 23:10 | you were to look at that whole thin section or with a binocular |
|
| 23:14 | you would actually see the sedimentary fabric , say there were grains there, |
|
| 23:20 | would see half of the grain cut that along the whole. Because you |
|
| 23:24 | right through that. You didn't push . You just cut it. |
|
| 23:31 | And we do recognize fossil marine hard in the rock record. And we're |
|
| 23:36 | talk about the significance of those But here's one from the cretaceous and |
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| 23:43 | out cropped in central texas outside of . This is analytic grain stone again |
|
| 23:50 | right at the upper part. You these holes and if you look at |
|
| 23:54 | edges again, you see some of you it's in that sand are actually |
|
| 23:59 | along that that boundary, implying it a hard ground. And when you |
|
| 24:04 | at the sediment and look at the and thin section, you can see |
|
| 24:08 | precursor first generation of that fibers, agonized cement. Like I showed you |
|
| 24:16 | yesterday. And then if you could the surface of this, which you |
|
| 24:20 | do anymore because it's an old quarry been filled in, you would see |
|
| 24:26 | surfaces plastered with oysters, right? are and Crestor. Okay, so |
|
| 24:34 | combination of the holes and the n , the fact that you have early |
|
| 24:39 | implies that this is a marine hard and it's very widespread. Okay. |
|
| 24:44 | that's part of the significance that we're talk about. Let me I'm gonna |
|
| 24:48 | you off until later to talk about strata graphic uh significance. And then |
|
| 24:57 | of the hard grounds we see developed the rock record are associated with shallow |
|
| 25:02 | carbonate systems. For the obvious reasons need to be in warm water, |
|
| 25:07 | needs to be super saturated, you stability. You need but you also |
|
| 25:11 | agitation to promote sanitation, but you get marines imitation and deeper water |
|
| 25:19 | And this is a piece of austin from central texas. This would have |
|
| 25:24 | a relatively deeper water carbonate succession and deeper water you actually can cement some |
|
| 25:32 | that sediment by taking advantage of positive where the chalk goose just sits there |
|
| 25:39 | the sea floor for some period of . And you have slow circulation of |
|
| 25:45 | through that focus that will lead to precipitation and creation of these hard |
|
| 25:51 | But they still have to be bored encrusted her scallop. Like you see |
|
| 25:57 | to meet the definition of marine Okay, So you can't because it's |
|
| 26:02 | a fine grained sediment. Right? the chalk. Who's made up those |
|
| 26:05 | co colas and some pelagic foraminifera. don't see the marine cement because it's |
|
| 26:12 | finely crystalline. But you see the evidence that it was a hard ground |
|
| 26:17 | on the boring and the scalloping. right. And sometimes you see on |
|
| 26:24 | crustaceans along those services. So just the marines imitation is not confined to |
|
| 26:30 | water, but also, I'm not confined to shallow water. It |
|
| 26:34 | can occur in deeper water successions and has some strata graphic significance to And |
|
| 26:40 | develop the same later in the in different segment. And then there's a |
|
| 26:50 | called geo pedal or geo petal Alright. And basically this is a |
|
| 26:56 | that's created in the sediment early and gets partially in filled. Right. |
|
| 27:04 | how do you instill a whole? ? You always then fill it from |
|
| 27:08 | bottom up, Right. By gravity infill. Right. And so |
|
| 27:14 | something is in true orientation, You should see the filling occurring from |
|
| 27:19 | up. And so we use that . All right. Like you see |
|
| 27:27 | to understand our true up direction. ? Especially when we're dealing with tectonic |
|
| 27:32 | active belts. If we've had, know, the folding or things like |
|
| 27:37 | where things get overturned. Uh Sometimes becomes confusing as to what the up |
|
| 27:42 | was because we always want to know deposition up direction was. Right in |
|
| 27:48 | rock record. And so we use geo pedals. Alright, so here's |
|
| 27:53 | old five AL fragment that's been re because it originally magnetic now in filled |
|
| 28:02 | unfilled by but the critics sediment. this is by definition of geo |
|
| 28:07 | Right? And the fact that you this orientation tells you that's the true |
|
| 28:11 | direction. Right? Of course, the thing filled completely with nick, |
|
| 28:16 | , you would never know of Alright, So it's gotta be partially |
|
| 28:20 | Phil right. And then I mentioned term storm attacked us that this is |
|
| 28:27 | of a definition for these funny shaped there. Their most people think they're |
|
| 28:37 | term bug. We'll we'll talk about this afternoon, but the bug should |
|
| 28:41 | used for secondary porosity. The problem the rock record. The problem in |
|
| 28:46 | literature is a lot of people use term bug for any funny shaped hole |
|
| 28:51 | that's not the definition. It has specific definition that I'm gonna talk about |
|
| 28:57 | this afternoon. I'll be our last . But these are funny shaped holes |
|
| 29:02 | occur in these MMA critic buildups. usually they look like this and usually |
|
| 29:10 | flat floored. Okay. And usually fill in with some sort of cement |
|
| 29:18 | sometimes they don't. Sometimes the holes unfilled with cement and can actually be |
|
| 29:24 | of the part of the story for equality. But I just want you |
|
| 29:28 | appreciate what these things look like. they're funny shaped holes and they are |
|
| 29:34 | flat floored. Okay. And I think people think these are g pedals |
|
| 29:40 | they don't see any any obvious way for a little tanker or hole to |
|
| 29:48 | filled up from the bottom up. nobody really understands these. But they're |
|
| 29:52 | fabrics. If you play some of so called The critic buildups that occur |
|
| 29:57 | in the paleozoic. Alright. And we talked about sedimentary brunches. |
|
| 30:08 | There die genetic branches. They're sedimentary and bridges. Are these deposits made |
|
| 30:16 | of class? And the question how do you create these class? |
|
| 30:21 | sometimes you create these class just by on the sea floor and then mobilization |
|
| 30:26 | deposition to some other environment. And would be the example you're looking at |
|
| 30:31 | from the Permian again and core bottom the core here, Top of the |
|
| 30:36 | I think is over here. And can see the you can see a |
|
| 30:42 | of these these larger pieces of sedimentary . Some of these are limestone. |
|
| 30:46 | of these are duller stones. The it's quite variable. All right. |
|
| 30:51 | you can see it's mixed up with big class of non cal Correa |
|
| 30:57 | So these are sedimentary brunches where stuff been reworked from a shallow part of |
|
| 31:02 | basin and brought out into deeper water by the black shell. Alright, |
|
| 31:09 | that's the type of sedimentary Greta. sometimes you see grading right? Where |
|
| 31:14 | go from coarse or grade, of , your grain Gretchen class to finer |
|
| 31:19 | wretched class, Right? That's normal . That's what you normally expect to |
|
| 31:22 | . Right, as your energy as energy runs out. Right, you |
|
| 31:28 | from coarser class to finer class to finer sand. And so that sometimes |
|
| 31:33 | see that. And and these rocks well. In fact, here is |
|
| 31:38 | example. Okay, so you see coarser grain fabric at the base of |
|
| 31:42 | core and then you can see the stuff at the top. Okay, |
|
| 31:48 | you can you can grade and find in some of these branches. |
|
| 31:53 | But these are sedimentary brunch is all ? And this is this is going |
|
| 31:59 | be different than the digex breaches that going to talk about later, where |
|
| 32:04 | actually dissolve the rock locally to create big enough hole. In other |
|
| 32:09 | a cave system where stuff collapses and get the class accumulate in that |
|
| 32:16 | That's a completely different style of Right? That's what we call |
|
| 32:20 | die genetic perfection. Right. And the last thing on the list for |
|
| 32:26 | Penta contemporaneous fabric where the things that relate to desiccation features and and one |
|
| 32:36 | those would be what we call finessed fabric. So here's a core from |
|
| 32:41 | permian in west texas and it's got evaporate minerals associated with it. This |
|
| 32:50 | an hydrate that is filling a bunch the porosity here. And so this |
|
| 32:56 | that you're in a relatively dry pretty airy climate to get evaporates. |
|
| 33:02 | so with evaporation, what will happen some of these carbonates? Right? |
|
| 33:07 | they desiccated and create mud cracks, like that. But sometimes you if |
|
| 33:14 | had any organic material associated with some these environments, these restricted environments that |
|
| 33:22 | organic material will disintegrate breakdown and basically oxidized and it can release either carbon |
|
| 33:32 | or hydrogen sulfide or potentially can make . And that gas will expand and |
|
| 33:39 | this prostate. So, again, know, the mud loggers at the |
|
| 33:44 | site would call all this prostate buggy it's funny shaped, but as I |
|
| 33:49 | , the term bug is a secondary type, which implies dissolution. But |
|
| 33:55 | , this is primary process. So this is a unique type of |
|
| 33:58 | porosity, but it's also called the because it's associated with these restricted uh |
|
| 34:06 | of settings. All right. I'm gonna put this into context next |
|
| 34:10 | , where you'll see where the finessed fabric uh comes into play. |
|
| 34:15 | so I'm gonna repeat this again when our in our prostate classification |
|
| 34:22 | All right. But the key here to is when you look at these |
|
| 34:27 | and thin section, you see the that butt up against the they butt |
|
| 34:33 | against the porosity. There's no dissolution the grains here. This is not |
|
| 34:38 | by dissolution. This is gas expansion in the sediment that pushes the grains |
|
| 34:44 | to create that ferocity. And sometimes preserves and actually can yield hydrocarbon, |
|
| 34:51 | sometimes it gets filled in with in case and hydrate, which looks like |
|
| 34:56 | thin section with the plain light. , And then there's another environment where |
|
| 35:05 | can produce and preserve uh financial And that's on a carbonate beach. |
|
| 35:13 | energy carbonate beach. Right? And is a a sample through a uh |
|
| 35:23 | sequence in the rock record. And , you see the funny shaped |
|
| 35:30 | But you see they line up with orientation here because they're reflecting the distribution |
|
| 35:36 | the stratification uh next time you go the caribbean on whether it's on vacation |
|
| 35:45 | work. And if you're on a energy beach where you see the big |
|
| 35:48 | breaking across the beach, watch the roll up the beach and when they |
|
| 35:54 | look at the beach, sand and see all this air come out of |
|
| 35:58 | sediment. Right? But not all air comes out. Some of it |
|
| 36:03 | trapped in the sediment to create these . Okay, so this is primary |
|
| 36:09 | . Some people informally call this bubble because beach bubble ferocity because you trap |
|
| 36:17 | trapped the air every time a wave across the front of the beach. |
|
| 36:23 | , So this is a primary support and it mimics the stratification in a |
|
| 36:29 | . Our style of stratification as general dipping plane or stratification. Alright. |
|
| 36:34 | the characteristic of each deposits. parallel stratification, general seaward dipping. |
|
| 36:43 | ? So that's the other environment where can preserve. So there are actually |
|
| 36:46 | environments what we're gonna call tidal flats weekend. And then the beach energy |
|
| 36:53 | . Right? So I think you even walk along Galveston's and see on |
|
| 37:00 | beach little holes in the beach that's where the air escaped when the |
|
| 37:06 | broke. But usually in classics you see this porosity preserve, which is |
|
| 37:10 | of interesting. And then the other related features obviously would be mud |
|
| 37:21 | I mean you've all seen this, don't even have to be in uh |
|
| 37:26 | could be mud on the street, ? That desiccated and great mud cracking |
|
| 37:32 | but but cracks against significant signify exposure air and evaporation desiccation and they actually |
|
| 37:41 | in the rock record. Um Here can see the an outcrop in the |
|
| 37:46 | sequence on a betting plane where the cracks are preserved. Right? So |
|
| 37:51 | basically in a carbonate scenario puts you a exposed tidal flat, okay, |
|
| 38:00 | um exposed muddy substrate of some type order to get the mud cracking and |
|
| 38:07 | , mud cracks, mud cracks themselves be open for some period of time |
|
| 38:12 | actually be a uh avenues for good move fluid through that rock. But |
|
| 38:20 | they cement up like you see okay, and then related to this |
|
| 38:27 | on some of these more evaporate IQ flats is the development of of the |
|
| 38:36 | called teepee structures where the sediment on tidal flats gets cemented and then they |
|
| 38:42 | what they start buckling like this. , so the buckle, the fact |
|
| 38:48 | you see here is the representation of precipitation of cement and the growth of |
|
| 38:55 | cement. In other words, is cement expands, it forces these cement |
|
| 39:00 | crust to buckle up. Okay, nothing, there's nothing else here to |
|
| 39:05 | that buckling, right? There's no or routes to push it up because |
|
| 39:09 | time this is western Australia. This way to drive for any kind of |
|
| 39:15 | . And so we actually see this in the rock record. We see |
|
| 39:20 | in our crop. This is the example along the parking lot of carlsbad |
|
| 39:26 | . If you have been up take next time you go up |
|
| 39:30 | take a look at the rocks around parking lot because they show the that |
|
| 39:37 | talked about yesterday, they occur in of these beds. But you see |
|
| 39:42 | , this major buckling effect here. . And these are basically like large |
|
| 39:48 | desiccation features. Right? With the the force of crystallization causes these cemented |
|
| 39:55 | to buckle up. All right. you can actually see this sometimes preserved |
|
| 40:00 | core in the subsurface. You'll see bads buckle up Little Teepee structures where |
|
| 40:05 | stack one on top of the And uh again, you can see |
|
| 40:10 | environmental significance. Right? You're in very shallow, restricted or periodically exposed |
|
| 40:17 | desiccated environment in order to get something that. All right, alright, |
|
| 40:25 | I just want to introduce you to fabrics. And again, part of |
|
| 40:29 | getting through all of this is for to keep repeating some of the stuff |
|
| 40:32 | we go along. So all of will get repeated again and tied back |
|
| 40:37 | given context uh to some other lecture on, let me finish up with |
|
| 40:43 | post de positional uh sedimentary structures. can see their their fabrics related to |
|
| 40:50 | exposure when you drop sea level regionally you locally build an island up above |
|
| 40:57 | level that obviously terminates your marine firm a deposition. Right organisms don't want |
|
| 41:03 | live out of water and that now you potentially to fresh water rainfall and |
|
| 41:10 | to evaporation and evaporates. And so of the several exposure related fabrics would |
|
| 41:18 | route cast if you have vegetation or roots of these trees or plants actually |
|
| 41:24 | replaced by calcium carbonate. Alright, that's only gonna occur in a more |
|
| 41:29 | climate or maybe a uh no more a semi air climate where you have |
|
| 41:35 | rainfall to support some of those You're not going to get that in |
|
| 41:39 | true error climate, because it's not be any vegetation and then cursed is |
|
| 41:45 | to near surface cave systems where you the bigger holes by dissolution and then |
|
| 41:50 | have solution collapse. All right. then with exposure comes the development of |
|
| 41:57 | we call soil crust and cal crete another term used for soil press. |
|
| 42:03 | is basically right below the soil He replaced the upper part of that |
|
| 42:09 | fabric with this dense brown. I'm critic fabric, it looks like the |
|
| 42:14 | mimicry, but it's actually die Okay. And and sometimes in this |
|
| 42:23 | you develop the Brescia again, where get local dissolution of the carbon a |
|
| 42:28 | to create these wretched class. All . And then forms that are related |
|
| 42:33 | burial and pressure solution. Pressure solution just that. That means the carbon |
|
| 42:38 | dissolving under pressure. And the controversy the carbonate community is how deep do |
|
| 42:43 | have to be to initiate pressure solution today, I'm gonna argue. You |
|
| 42:49 | to be about 1000 m to initiate dissolution. Okay, and so there |
|
| 42:57 | three physical expressions of pressure solution. , if you don't know anything about |
|
| 43:02 | barrel history of these rocks. If see skylights or whiskey micro skylights or |
|
| 43:08 | or fabric That tells you that rock least a bit buried to roughly 1000 |
|
| 43:14 | . Okay, It could have been lot more. Right? So this |
|
| 43:17 | always a question we have working right? We don't know how deeply |
|
| 43:21 | those things were before they pop back . And so this is how we |
|
| 43:26 | to get some feel for the relative of burial. The other way would |
|
| 43:31 | again, to use some of the tools we talked about yesterday. So |
|
| 43:38 | cast. This is a piece of calcified root from an outcrop and you |
|
| 43:45 | actually see the cellular structure of the perfectly preserved by the calcification here. |
|
| 43:53 | , you know, look at The roots could look a lot like |
|
| 43:56 | the burrow structures that we talked about . And so Sometimes it's very difficult |
|
| 44:02 | discern the two. And so what want to see is the preserved cellular |
|
| 44:09 | . And not, not always you that, But if you see enough |
|
| 44:13 | the root, what does the root do? It always tapers, |
|
| 44:18 | The changes diameter as it grows Right? But a burrow structure never |
|
| 44:23 | diameter, it stays the same Okay, so an outcrop. That's |
|
| 44:28 | you would look for to differentiate between burrow and a calcified root casts. |
|
| 44:34 | again, the significance here is that this represents the barrel exposure. |
|
| 44:42 | you don't get these kinds of plants , you get sea grass, they |
|
| 44:45 | roots, but they're tiny little But these are these are too big |
|
| 44:49 | be marine related. And the fact they're calcified would suggest again, they've |
|
| 44:55 | they're related to exposure surface where you vegetation penetrating through the rock, that |
|
| 45:00 | roots will actually cut through that limestone they search for water and later they |
|
| 45:08 | get replaced by calcium carbonate. And the other fabric we mentioned was the |
|
| 45:18 | crust, er cal creed. So is the top of a major several |
|
| 45:24 | surface in the Pleistocene, we'll talk the Pleistocene record later, but for |
|
| 45:30 | last two million years we've had these ups and downs of sea level. |
|
| 45:35 | , and when sea level drops, carbonate platforms get exposed, sometimes up |
|
| 45:42 | 100,000 years or so. And so have long term exposure in this case |
|
| 45:48 | a politic grain stone. So that deposit was obviously terminated by a drop |
|
| 45:54 | sea level. Right? You shut the deposition, Then you expose it |
|
| 45:58 | too rainwater and on top of that would actually develop a soil, a |
|
| 46:04 | reddish brown soil and then right below , what do you get on the |
|
| 46:09 | of that grain stone, you this replaces fabric, that's a rock |
|
| 46:14 | structure that replaces the analytic grain grain . So it's a critic, it's |
|
| 46:22 | brown color, the red color comes the iron. The iron comes from |
|
| 46:27 | Sahara desert that's been blowing across the for the last several million years. |
|
| 46:33 | once you incorporate the iron into the carbonate member, iron can substitute in |
|
| 46:38 | calcite with exposure to fresh water, get oxidation. And what's the color |
|
| 46:44 | comes with iron oxidation? It's red reddish brown color. Alright, so |
|
| 46:50 | is a unique sedimentary exposure indicator that want to see in carbonates, |
|
| 46:57 | We're trying to understand the overall evolution these carbonate successions. Alright, so |
|
| 47:05 | it looks laminated, you're going to some more pictures of this later |
|
| 47:09 | But definitely this is replaced it because can see remnants, fluids still preserved |
|
| 47:14 | some of that fabric. Alright, just like a slow replacement by product |
|
| 47:20 | the eulogy grain stone by the democratic . And then I mentioned with long |
|
| 47:29 | several exposure you can get cave systems . Um And I'm sure you've probably |
|
| 47:34 | been in a cave or you've Certainly seen pictures of caves. |
|
| 47:38 | So that's created by a big scale and of course you get things like |
|
| 47:44 | and stalagmites, but what will happen you create the whole the whole gets |
|
| 47:49 | enough and the roof becomes thin. will happen to the roof? It |
|
| 47:54 | collapse right and break down into smaller of appreciated carbonate. And so this |
|
| 48:01 | sort of the classical karst related All right. Some people call these |
|
| 48:07 | brunches but basically that's not a soil that's a that's the same fabric that |
|
| 48:15 | the that made the cow crete that reddish brown, the critic fabric acting |
|
| 48:20 | a cement to bind all of that , politic grain stone, the Gretsch |
|
| 48:25 | together. Right? So that's this is what you want to see |
|
| 48:30 | the rock record to infer several Right? Long term several exposure. |
|
| 48:36 | uh, the problem here is that fabric by itself is not unique to |
|
| 48:43 | surface Kearse ification. Okay, so can actually get bridges developed in the |
|
| 48:51 | that have nothing to do with several . The concept is burial situation that |
|
| 48:57 | talk about later today. So you to be careful about how you use |
|
| 49:03 | of these fabrics because the tendency in literature is for people to jump onto |
|
| 49:09 | of these, jump onto one of fabrics like the Brescia and build their |
|
| 49:14 | interpretation around it. Okay, But usually not good enough. Right? |
|
| 49:20 | any interpretation of the deposition or digest has to account not just for one |
|
| 49:26 | , but for all the fabrics that see in that rock. Okay, |
|
| 49:31 | we'll build on this relationship obviously as go along and you'll see the application |
|
| 49:36 | this to the rock record later. . And then the pressure solution related |
|
| 49:43 | our style lights, jagged teeth like here. So that surface represents a |
|
| 49:52 | of dissolution. The offset that you here is called the amplitude. The |
|
| 49:59 | represents the minimum amount of dissolution Along one style light. So here are |
|
| 50:06 | amplitude that's about an inch for scale amplitude the offsets 1", that means |
|
| 50:13 | least one inch of limestone was dissolved that style light. Okay, you |
|
| 50:20 | only prove minimum, You can't prove . Alright, And I've been to |
|
| 50:26 | where I've seen style light amplitude of ft. Alright, so that means |
|
| 50:31 | least five ft of limestone were dissolved along that one skylight. Okay, |
|
| 50:38 | what does pressure solution do? It doing what to the thickness of your |
|
| 50:44 | sequence? It's going to reduce the . Right? So these carbonate sequences |
|
| 50:49 | are buried never were as thick as are now, they're probably thicker than |
|
| 50:54 | are now. Right. And then been thinned by this pressure solution. |
|
| 50:59 | , that's the first part of the . Second part of the story we're |
|
| 51:03 | develop this afternoon, is that dissolving goes where back into the poor system |
|
| 51:11 | plug up that ferocity. Right, pressure solution historically is detrimental to preserving |
|
| 51:19 | quality because your locally generating pore filling . Okay, so this is the |
|
| 51:28 | you get the jagged teeth like style . And the grainier tax stones and |
|
| 51:33 | stones. Okay. And the more critic lime stones, the lime mud |
|
| 51:39 | and wacky stones, you develop what called wispy micro style lights. The |
|
| 51:47 | is nonsense. Richard pressure solution seem don't see the vertical relief. All |
|
| 51:54 | . And I'm going to talk about in more detail later. But you |
|
| 51:59 | , a lot of people who were would not even consider these to be |
|
| 52:04 | solution. They would say these are clay seems physically compacted during shallow |
|
| 52:11 | but in carbonates, I'm gonna prove you that this is pressure dissolution. |
|
| 52:16 | . That actually occurs after the As you can see a burrow structure |
|
| 52:21 | . Right. One of those little burrows that I showed you earlier, |
|
| 52:26 | never see the pressure solution seems cut the ring burrow. Do you think |
|
| 52:32 | would happen? Right. If that the primary play scene? They always |
|
| 52:36 | around the boroughs for these scenes actually right through the boroughs. Just tells |
|
| 52:43 | they formed after the burrows and the film. So there's no way to |
|
| 52:50 | out how much material is lost along scenes because there's no vertical offset. |
|
| 52:56 | given how prevalent these things are in more MMA critic lime stones, pretty |
|
| 53:00 | that whiskey microsatellites both reduce the volume the rock thickness, right? And |
|
| 53:07 | generate potentially pork filling calcite cements. then the last part of the last |
|
| 53:15 | , fabric. Was that modular And this is uh outcrop of some |
|
| 53:23 | the famous building stone in Northern This is part of what's called the |
|
| 53:31 | , If you go into a lot the high rise hotels and look at |
|
| 53:34 | look at the flooring that they put the bathrooms and in the hallways. |
|
| 53:39 | this kind of rock that's been polished what does this represent? Well, |
|
| 53:45 | you see the model character here, , that's all furrowed. So the |
|
| 53:50 | part of the story to create modular is burrowing. Okay. And then |
|
| 53:55 | second part of the story is later and pressure solution. So those are |
|
| 54:00 | pressure solutions seems to cut it. of these are low relief style |
|
| 54:04 | some of these are the whiskey micro , but the net effect is to |
|
| 54:08 | this new modular fabric. Okay, this is actually pretty common in |
|
| 54:14 | in the mormon critic lime stones. tend to occur in either deeper water |
|
| 54:20 | restricted shallower water. They get burrowed then they get buried to create this |
|
| 54:26 | of fabric. Okay, this is modular fabric. Alright, here's the |
|
| 54:37 | view. In fact, I stole from a hotel here in Houston that |
|
| 54:40 | being torn down right where they let come in and tear out stuff before |
|
| 54:45 | demolish it. So that's from one the bathrooms in a downtown hotel but |
|
| 54:52 | and you can see this is the kind of fabric. Alright, so |
|
| 54:58 | , alright, any any questions or about the sedimentary structures? Again, |
|
| 55:10 | gonna put a context to all of fabric. Later when we get into |
|
| 55:15 | environments, when we get into our of deposition all faces and then for |
|
| 55:20 | pressure solution related stuff, I'll talk this in more detail today when I |
|
| 55:25 | into our limestone die genesis story. , Alright. So next thing on |
|
| 55:33 | agenda is a 15 minute break. it's five actors. So let's start |
|
| 55:38 | at uh 20 after. Right, at that point in the seminar now |
|
| 55:57 | we can start tying things together. , so we basically talked about grain |
|
| 56:14 | . Mm hmm. Okay. The of zoom. Uh huh. |
|
| 57:44 | Okay. Let's start over. Um gonna tie everything together now um because |
|
| 57:52 | been obviously no context to the grain discussions origin of lime mud uh sedimentary |
|
| 57:59 | . I mean now we're gonna start context of all of this. And |
|
| 58:03 | first thing we need to do is talk about how these textures and how |
|
| 58:09 | grain types come together in an environment create a de positional texture and how |
|
| 58:15 | characterize that texture and what we try glean from that textual data in terms |
|
| 58:23 | the nature of the environment or the for some of those sediments to yield |
|
| 58:29 | hydro carpets. Okay, so we're to talk about the classification schemes and |
|
| 58:38 | a bunch that have been developed Over years and all of this goes back |
|
| 58:45 | the actually goes back to the late , Alright. Back then, most |
|
| 58:51 | the major oil companies had uh their research outfits and then of course, |
|
| 58:58 | had lots of people in universities were at this angle about how to best |
|
| 59:04 | some of the carbon fabrics and uh were independently publishing stuff that they decided |
|
| 59:13 | bring everybody together into the first a pg research conference. Alright, and |
|
| 59:19 | was held in 1959, I And out of that came the first |
|
| 59:25 | of the first, a PG memoir one, which is called classification of |
|
| 59:32 | rocks. And so all these academic and researchers from various oil companies, |
|
| 59:40 | us and foreign came together and in volume they present their their classification |
|
| 59:47 | right? Every company had their own way of characterizing these carbonate rock |
|
| 59:52 | And so the test of time it's been what 60 years test of |
|
| 59:59 | , is that the one that has is the so called Shell research or |
|
| 60:05 | classification scheme? Bob Dunham was a geologist that worked for Shell research lab |
|
| 60:13 | was here in Houston used to be Bellaire texas. Alright, actually not |
|
| 60:18 | far from my house and I when I was a grad student at |
|
| 60:23 | , I actually had a chance to Dunham toward the end of his career |
|
| 60:28 | uh he was an interesting guy, creative guy, you could, you |
|
| 60:34 | just tell that from the way he himself and the kinds of questions he |
|
| 60:39 | at meetings and things like that, he wasn't always right and uh but |
|
| 60:44 | , he was one of these guys got people to think about issues |
|
| 60:48 | and uh he was really good for , he spurred the whole community on |
|
| 60:52 | try to better understand some of these , but one of the things he |
|
| 60:57 | leave the industry and academia with was classification scheme, so that's the one |
|
| 61:05 | gonna go through, that's the origin the terms like grain stone, |
|
| 61:08 | wacky stone. Okay, so I'm take you through his classification scheme, |
|
| 61:14 | you don't want you to make, want to make sure you precisely understand |
|
| 61:18 | we use that terminology because believe it not, it does get misused. |
|
| 61:24 | Then I'm going to introduce you to scheme that was published about 10 years |
|
| 61:30 | By two Canadian geologists who were working Devonian Reef Complexes and Northwest Territories of |
|
| 61:38 | and they found Dunham's classification scheme inadequate describing some of the coarser grain brief |
|
| 61:44 | fabric. And then they tried, then they decided to expand Dunham's term |
|
| 61:51 | bound stone that he used for any up. They decided to break that |
|
| 61:56 | into three terms, frame stone and stone and bind stone to reflect the |
|
| 62:04 | that create some of these build so I'm gonna take you through their |
|
| 62:08 | because people now studying reef reservoirs commonly this terminology. Right? So I |
|
| 62:15 | you to understand the rationale for Okay. And then obviously as we |
|
| 62:21 | along, you're gonna see we're gonna using this terminology all the time, |
|
| 62:25 | to characterize these ancient carbonate systems. , So these are the criteria for |
|
| 62:35 | you wanna ask yourself when you're trying apply Dunham's classification scheme. Alright. |
|
| 62:41 | the first thing you need to do is determine whether there's any lime mud |
|
| 62:45 | in the rock or not. so yesterday we talked about the original |
|
| 62:50 | but you saw there potentially a number different ways to create line mud in |
|
| 62:55 | carbonate environment. And then we talked the recognition, right? And I |
|
| 63:01 | you appreciate how hard it is to if you're just trying to look at |
|
| 63:04 | with your eyeball or a hand right? You're not gonna see |
|
| 63:09 | right? So if you don't get the thin section level, you're never |
|
| 63:13 | to fully understand whether you have lime mud or Mick right in your |
|
| 63:17 | or not. And so it When we evaluate a rock database, |
|
| 63:23 | ? The company drills the core. first thing the geologist does is he |
|
| 63:28 | through that core and he visually describes with his eyeball and a binocular microscope |
|
| 63:34 | hand lens, right? And he out packages he makes the preliminary |
|
| 63:40 | but you can't stop right there because going to miss part of the |
|
| 63:43 | So the next part of the story you have to come back in and |
|
| 63:47 | represent, you have to take representative and make thin sections to verify or |
|
| 63:54 | the interpretation. All right. And you're looking for is the presence or |
|
| 63:58 | of Mc. Right principally. Because if you miss the mic |
|
| 64:02 | you probably got the story wrong. . Because as we talked about |
|
| 64:07 | lime mud can accumulate in any I mean it can form in any |
|
| 64:12 | . Right? But where does it ? Quiet water? Right. And |
|
| 64:16 | could be shallow water? That could deeper water. Right? And so |
|
| 64:21 | only way to really answer that story to is to follow up the initial |
|
| 64:26 | description with somethin section observations. So the only way you're gonna answer |
|
| 64:33 | , I think unless you've got look you got a sequence that's completely cross |
|
| 64:40 | , right? Which means high energy , right? There's not gonna be |
|
| 64:43 | mud. Then you better make some sections to understand exactly what your texture |
|
| 64:50 | . All right? So that's the question. Right? Then the second |
|
| 64:54 | is the sand sized grains. So , the grain is defined as anything |
|
| 64:59 | than 62 a half microns all the up to, you know, multi |
|
| 65:05 | sized material to the sand sized grains . The overburden provide what we call |
|
| 65:12 | support or is it Democratic Matrix. , so that's the concept of grain |
|
| 65:18 | versus mud support and this is the challenging part of the classification scheme to |
|
| 65:25 | figure out. Alright, because Dunham asking you to think about how these |
|
| 65:31 | pack in three D. But you're two D. Observations right, in |
|
| 65:36 | outcrop in a thin section of hand , you don't have the advantage of |
|
| 65:40 | the three D. Relationship. You've to infer it from the way the |
|
| 65:45 | are packaged together and what the grain are. Okay. And so that's |
|
| 65:51 | point of the third line here is need to appreciate the effect of grain |
|
| 65:56 | on packing density and whether it creates support texture or not. Okay, |
|
| 66:03 | everybody struggles with this, I struggle this every time I describe a thin |
|
| 66:08 | . Okay, because you don't have advantage of seeing the three D. |
|
| 66:14 | , right? And that's why I to talk about the influence of grain |
|
| 66:20 | . I want you to appreciate grain yesterday. Right? So you saw |
|
| 66:24 | shapes of P. Lloyd, you the circular or spherical shapes of fluids |
|
| 66:29 | packed together differently than a potato like fragment of a mollusc or Branching |
|
| 66:37 | , like Red Algae. Right? gonna they're gonna pack together in three |
|
| 66:40 | differently. Okay, so if you involved in carbonates down the road, |
|
| 66:46 | is what you have to try to some appreciation for and and it's not |
|
| 66:51 | . Alright, So, but there's things we can look for in the |
|
| 66:55 | , maybe help you figure figure some this out. Right? So, |
|
| 67:02 | said that, that's uh Having said , let's go through the Dunham scheme |
|
| 67:14 | . Right, so this is taken out of this 1962 paper. And |
|
| 67:19 | goal here is to describe de positional . Okay, that's what we're trying |
|
| 67:26 | do. We're trying to understand the environment. Where did this, where |
|
| 67:30 | these deposits occur on a deposition Now, sometimes you can't do |
|
| 67:36 | right, because of the detrimental effects di genesis. So, sometimes dia |
|
| 67:42 | re crystallizes the fabric, right? destroy the grains with replacement by soiree |
|
| 67:49 | or more commonly, what do you ? You take that limestone fabric replaced |
|
| 67:54 | dolomite and dolomite match the deposition of . So what do you do |
|
| 68:01 | You can't obviously recognize de positional If you're dealing with these crystal and |
|
| 68:07 | , whether it's limestone or dolomite. so all you can do is physically |
|
| 68:12 | the rock as best you can. , So, I've got a coarsely |
|
| 68:17 | Dulles, stone with 20% buggy it tells people what Iraq is, |
|
| 68:22 | it has no bearing, it provides information about the deposition setting. |
|
| 68:28 | And that's the way that's how we to deal with this. Right, |
|
| 68:31 | just used to throw our hands up say, okay, there's nothing we |
|
| 68:35 | do. But now this is where want to apply those, those petra |
|
| 68:40 | techniques that I talked about yesterday. white paper technique, the fluorescence microscopy |
|
| 68:46 | . Those techniques sometimes allow you to through the masking effects of the calcite |
|
| 68:52 | dolomite and actually see rally grain Okay. And sometimes we can can |
|
| 68:58 | a story together using that that simple . All right, fortunately most of |
|
| 69:05 | we encounter in the rock record, it's out proper subsurface, we can |
|
| 69:09 | de positional texture preserved. And so drop down to the next line and |
|
| 69:14 | ask ourselves the question for the original bound at the time of deposition or |
|
| 69:22 | . Okay. And done on when talking about the the bound or binding |
|
| 69:29 | , he's talking about organic binding. , So the first thing we're not |
|
| 69:34 | about is marine sedimentation. The hard development. All right. Obviously that |
|
| 69:40 | material together to create a rock on sea floor, but that's not what |
|
| 69:44 | call a bounce stuff. Okay, for him, a bounce stone is |
|
| 69:49 | where you can demonstrate the sediment is together by organic influences. And so |
|
| 69:56 | are only two categories that fall into category of bound stone. The first |
|
| 70:01 | be a situation where uh cyanobacteria binds together on the sea floor to create |
|
| 70:08 | stromatolites. So remember our discussion yesterday stromatolites and very, very shallow water |
|
| 70:14 | flats. The stromatolites are laminated. when you go underwater they go |
|
| 70:21 | Right, that's the kilometer stromatolites. that's the first example of what donna |
|
| 70:27 | abound stone. And the second part the story would be associated with some |
|
| 70:33 | these build ups. Where you can the organic elements like corals or storm |
|
| 70:40 | roids grow together to create deposition Okay, so if you can demonstrate |
|
| 70:48 | an outcrop er core, then you use the term bound stone for that |
|
| 70:54 | as I alluded to yesterday. I showed you a picture from great |
|
| 70:59 | reef in Australia yesterday where most of reef is made up of rebel |
|
| 71:05 | rebels not bounced out. Okay, it's not held together, it was |
|
| 71:09 | the outer part of the reef, ? Where the waves are breaking that |
|
| 71:14 | the brownstone fabric. So the reef are not wall to wall bounce stones |
|
| 71:19 | we're going to learn. Okay, everybody appreciates either star melodic fabric or |
|
| 71:24 | the in situ intertwined organic organic elements a build up that done and we |
|
| 71:32 | a bounce down. So most of we encounter in the rock record is |
|
| 71:38 | to fall into one of these categories , right? Unconsolidated at the time |
|
| 71:42 | deposition. Now you've got to decide there's any mud in the system or |
|
| 71:48 | . Alright, so I've defined with mud looks like how you recognize |
|
| 71:55 | Alright, so there's no lime mud definition All of those grains have to |
|
| 72:01 | touching in three D. At the of deposition, they have to be |
|
| 72:04 | supported. So in that case you get a grain step. Okay and |
|
| 72:10 | going to see the numbers for porosity uh and permeability for some of these |
|
| 72:16 | later today. And grain stones actually start off with the highest ferocity but |
|
| 72:23 | started off with the highest permeability because poor throats are big and well |
|
| 72:30 | Okay, so grain stones historically something company has chased from a conventional reservoir |
|
| 72:40 | . Okay, no mud. The open ferocity and then good good poor |
|
| 72:47 | connection. Alright, now you can though a situation where the rock is |
|
| 72:52 | brain supported, the sand sized grains touching in three D. But there's |
|
| 72:59 | mud present. Okay, maybe a percent lime mud. Maybe the interstitial |
|
| 73:04 | completely filled with lime mud, if the case, this is what we |
|
| 73:08 | the Pakistan. Okay, now you appreciate some pack stones only have a |
|
| 73:15 | percent line mud and could have a of preserved open well connected ferocity. |
|
| 73:20 | other words they could be potential reservoirs then you could invent vision such situations |
|
| 73:26 | all of the intersectional process filled with mud, reservoir quality is very |
|
| 73:31 | right? Because there's no permeability. in the literature people subdivide the pack |
|
| 73:41 | that have a little bit of mud the pack stones that have a lot |
|
| 73:44 | mud and there's no formal way of this, these fabrics, but what's |
|
| 73:53 | in literature is the concept of low pack stone versus high blood pack |
|
| 73:58 | Okay. Or some people would say lean, mud, rich Pakistan's doesn't |
|
| 74:04 | what however you want to say but what you should tell people is |
|
| 74:08 | much mud is in that rock. ? So my low mud pack stone |
|
| 74:13 | mark, right? My high mud stone, 30% McCready, whatever it |
|
| 74:17 | . Okay, because you're trying to , you see, we're trying to |
|
| 74:22 | the nature of the environment, Is it higher energy required or |
|
| 74:26 | But we're also trying to understand now reservoir potential, right? The ability |
|
| 74:30 | these fabrics to yield hydrocarbon in the . Okay, so you should always |
|
| 74:36 | to do that if you encounter pack , so it shouldn't be hard to |
|
| 74:42 | these two. Okay, where you into a problem here is the last |
|
| 74:47 | terms here that are by definition, supported, which implies that sand sized |
|
| 74:53 | are floating and that may critic Okay, and if you've got more |
|
| 74:58 | 10% of those sand sized grains in , but supported fabric, that's what |
|
| 75:03 | him called a wacky stone. And it's less than 10% he called it |
|
| 75:08 | wacky stone. I'm sorry, mud . Okay, now I put the |
|
| 75:12 | lime on the scheme here, this actually not in his original classification |
|
| 75:18 | Okay, he just used the but stone and the reason why I |
|
| 75:23 | lime here now is because of the plays right? The shale plays what |
|
| 75:31 | the company's called? The shale plays stones. Right. And because mud |
|
| 75:36 | are so popular now, right? used to ignore mud stones. We |
|
| 75:40 | to look at shales and sealing faces maybe a source rock that we wouldn't |
|
| 75:45 | at them as a reservoir. So you work the rock record and you |
|
| 75:50 | a mud stone fabric, you want put the term lime in front of |
|
| 75:53 | if it's a limestone, so people confuse it with the shale. |
|
| 75:57 | so that's why I put it Alright, so Here you have to |
|
| 76:05 | more than 10% of the sand sized here, you have to do |
|
| 76:08 | You have to show less than You can do that with visual |
|
| 76:12 | You can point count up inception however want. Okay, Historically and |
|
| 76:19 | we don't point count, We tend visually estimate but but you can do |
|
| 76:24 | either way. Alright, um now the situation here. Right. I |
|
| 76:33 | you can see the high energy part the profile is to the right, |
|
| 76:39 | , less mud. Right. Higher conditions potential to preserve more effective permeability |
|
| 76:46 | way, the the exception might be strong catalytic fabric for the brownstone and |
|
| 76:52 | of course, quieter water form a fabric to the left. lower |
|
| 76:57 | whether it's deep or shallow. And so you can see how that |
|
| 77:02 | historically into potential reservoir development, Companies would chase the grain stones and |
|
| 77:09 | refill bound stones and the low mud stones and we would ignore the wacky |
|
| 77:14 | , mud line, mud, stone . We look at these as potential |
|
| 77:18 | faces or maybe a potential source but we never considered this to have |
|
| 77:23 | quality, right? Unless something favorably genetically happened to those rocks. |
|
| 77:30 | so that's the first, the implication the terminology, right, tells you |
|
| 77:34 | about the nature of the environment. secondly, it tells you something about |
|
| 77:38 | reservoir potential. Now, the real here for using the classification scheme is |
|
| 77:46 | right in here when you get into more MMA critic limestone, if you |
|
| 77:48 | into more of the more of the mud pack stones, the wacky stones |
|
| 77:53 | lime mud stones, what happens on sea floor when we have a muddy |
|
| 77:58 | and it's quiet water and it's normal . What's going to happen to the |
|
| 78:03 | is going to be churned up by borrowers, right? They're gonna buy |
|
| 78:07 | better bait that sediment and they're going start doing what they're gonna be mixing |
|
| 78:13 | . I think I mentioned yesterday the shrimp, they put a vertical burrow |
|
| 78:19 | , then they put out side they go down another level. They |
|
| 78:22 | outside chambers here and I think I you know when they encounter coarser grain |
|
| 78:28 | they don't try to carry it out top of the burrow. They packed |
|
| 78:30 | side chamber, they bring the lightweight pellets out the top. But they're |
|
| 78:36 | they're doing is artificially uh changing the of the Senate. Right. And |
|
| 78:42 | in a burrow succession you could see mixture of textures. Right? And |
|
| 78:49 | lot of times in the rock record have the challenges trying to differentiate between |
|
| 78:56 | Pakistan and Pakistan right? Trying to whether in these MMA critic fabrics whether |
|
| 79:01 | more grain support or much support. sometimes it's both okay because of the |
|
| 79:07 | effects and sometimes you can't tell. how do you handle that uncertainty. |
|
| 79:12 | you call it? A wacky stone paxton Because you're expressing that uncertainty. |
|
| 79:16 | not quite sure That it's great support MMA critic fabric but I'm not sure |
|
| 79:22 | all touching in three D. And then the beauty of this classification |
|
| 79:27 | is you can put a paragraph of in front of this this terminology. |
|
| 79:36 | the convention is if we have a have a limestone let's say we have |
|
| 79:40 | grain stone that's principally analytic but with lot of P. Lloyd's innit? |
|
| 79:45 | way you put that together is the grain type. The U. It's |
|
| 79:49 | next to the term grain stone. you would say polloi it'll analytic grain |
|
| 79:56 | . That would tell you the major type is are you? It's |
|
| 80:01 | So that's convention. Okay? Now can string all the grain types in |
|
| 80:06 | of that, you can put them order of abundance. Okay? Or |
|
| 80:10 | can use the generalized term like mixed where you have a lot of skeletal |
|
| 80:17 | and then tell people what those skeletal are. Later. Okay. But |
|
| 80:23 | the whole the whole point of this to communicate right to make sure people |
|
| 80:27 | understand what you described from the what you've described from the core. |
|
| 80:35 | , So you can put anything in of it. Just make sure that |
|
| 80:39 | major grain type is the term that next to brain stone or pack |
|
| 80:44 | Okay, everybody clear about this. right. So we're gonna go through |
|
| 80:49 | we're gonna go through some examples here a minute. Uh Again in terms |
|
| 80:55 | deciding on you know, percentages I mean we all do this |
|
| 81:01 | You know, you've probably seen diagrams this and again the abundance here depends |
|
| 81:07 | part on the shape of the grains how obviously how common they are in |
|
| 81:12 | of these samples. Uh Everybody has make their own guests here as to |
|
| 81:20 | abundance of these grain types. All . I mean the key the key |
|
| 81:23 | obviously is the 10% cut off for wacky stone line, mud stone |
|
| 81:28 | Okay. But yeah the way to around the visual estimates like you see |
|
| 81:36 | is actually under thin section point right? You can you can put |
|
| 81:41 | special stage on your microscope that moves Millimeter or every 500 microns and you |
|
| 81:48 | count the grains that way. And know, count 300 grains. And |
|
| 81:53 | you come up with a good statistical for that sample. So, |
|
| 81:59 | so let's look at some examples Alright, let's uh our first example |
|
| 82:04 | is a situation where we got large grains here. Okay. And you |
|
| 82:13 | tell exactly what these are. And you've got a darker matrix in |
|
| 82:17 | All right. So you've got the fine grain or darker matrix here. |
|
| 82:22 | can't call this a grain stone, ? This grain stone by definition has |
|
| 82:28 | matrix. All right. So, the challenge here? The challenges decide |
|
| 82:34 | this is grain support or matrix Right? But from our discussion |
|
| 82:42 | anybody remember the grain types that had sort of potato chip like morphology that |
|
| 82:48 | big and robust, that had growth . Remember the bracket pods were like |
|
| 83:00 | And some of the big clamshells were that. Right? The buyer |
|
| 83:06 | They were look at the scale, a centimeter, right? These are |
|
| 83:09 | , relatively speaking. And so those only two things that would fit the |
|
| 83:14 | here. The rocket pods or big , clamshells, and you can't tell |
|
| 83:21 | one it is here because you can't the micro structure. So I'm just |
|
| 83:24 | tell you these are clamshells, Okay, so it's all bivalves and |
|
| 83:30 | all the darker matrix. But now question is brain support or mud |
|
| 83:36 | So what do you guys think? do you think Robbie blood support? |
|
| 83:51 | do you say that? Well, there's more of that and you don't |
|
| 84:01 | a lot of these things touching Right. They seem to be floating |
|
| 84:07 | that darker fabric. Right? So every group I teach says much |
|
| 84:13 | Okay, so we'll come back to in a minute. Here's another |
|
| 84:18 | Same relationship, darker matrix, different type here. And you can't really |
|
| 84:25 | what it is from this view. do you see evidence for morphology? |
|
| 84:31 | some of the morphological terms are used . See this where the grain goes |
|
| 84:39 | this and takes a right hand see this where it looks like a |
|
| 84:44 | ejection. What was that? What that morphology we call that morphology? |
|
| 84:58 | things go like this? And you see they're elongated anyway, right? |
|
| 85:04 | a finger like morphology, branching, , right? Things branch like |
|
| 85:15 | Okay. And so we have some of a branching morphology. You don't |
|
| 85:21 | what that is. But what were of the things that branched? We |
|
| 85:25 | about yesterday that you don't remember which understandable. Alright. We talked about |
|
| 85:33 | red algae, branching corals, branching zones. Okay. Just the name |
|
| 85:41 | of them. Alright, so in case it's branching red algae. |
|
| 85:47 | that's the growth morphology of the branching algae. So the question now is |
|
| 85:54 | much support or grain support, What you think? It it doesn't look |
|
| 86:03 | 13 different. Right? They don't like they're touching in very many |
|
| 86:10 | Right? So most people again would it's probably mud support. Right? |
|
| 86:16 | for translating this to the terminology, would you call this? Red |
|
| 86:29 | It's not grain support, but it's more than 10% grains wacky stone. |
|
| 86:35 | . And he would have would have the same for the previous example. |
|
| 86:39 | ? More than 10% of the bivalves up that rock. Right? But |
|
| 86:44 | support, if you think it's much , that would be a wacky stone |
|
| 86:47 | . Alright, well you probably can where I'm headed with this discussion |
|
| 86:52 | Both of these are actually grain support both of these examples are artificial |
|
| 87:01 | Okay. And what we did here we mimicked or replicated what done and |
|
| 87:08 | on back in 1962. So the thing we did was we took a |
|
| 87:14 | a box of modern day clamshells. , see the growth bridges. And |
|
| 87:20 | put them in a box. So had to be touching in three |
|
| 87:24 | Right? They all had to be And then we added an epoxy resin |
|
| 87:30 | the blue dye. That's our Okay, we let it harden up |
|
| 87:35 | then we cut it to give you first view you saw previously. |
|
| 87:41 | And then that was to give give an appreciation for how these what I |
|
| 87:46 | more play D like fragments right packed in three D. They don't touch |
|
| 87:52 | lot of points and you need to that. Okay, The second example |
|
| 87:58 | the same relationship and here we took of branching red algae. These are |
|
| 88:04 | fragments. This is the growth form the living red algae on the sea |
|
| 88:10 | . I collected these on the sea . Just they're not even attached. |
|
| 88:14 | grow in a sandy substrate. Just them up off the sea floor. |
|
| 88:20 | , Of course I killed him taken every environment, but you know, |
|
| 88:25 | then we bleached them to get rid the organic material, dry them and |
|
| 88:28 | we put them in a box. , So they all had to be |
|
| 88:32 | in three D. We added the matrix. And you saw how they |
|
| 88:37 | together with a branching morphology. A of those grains you don't expect to |
|
| 88:41 | touching. Did a lot of Okay, so this is the |
|
| 88:47 | All right. You need to appreciate the influence of grain shape unpacking |
|
| 88:54 | And that was a major point of paper. Okay, So don't |
|
| 89:05 | Thanks. Thanks how they do what think this It depends where you cut |
|
| 89:18 | make the cut But in three All of those grains had to be |
|
| 89:24 | . Right notice, that's why I that this is the most perplexing part |
|
| 89:32 | the classification scheme. Okay, that have you have organisms touching each |
|
| 89:42 | Not much. Generally not touch the . Well it depends whether they're living |
|
| 89:52 | or not, whether it's fragments or , if they're living there, they're |
|
| 89:57 | gonna make up more than 10% of rock. So you wouldn't call it |
|
| 90:00 | mud stone, because by definition, stones have less than 10% of sand |
|
| 90:05 | grains. Okay, so it's unlikely going to find in a true mud |
|
| 90:13 | , you're gonna find in situ living , it's gonna be bits and pieces |
|
| 90:17 | material and if it's more than 10% a wacky stone, if it's less |
|
| 90:22 | 10% it's a lime mud stone. , so this this is the this |
|
| 90:31 | right out of Dunham's classification paper, ? This was his approach, I |
|
| 90:37 | , I told you he's a very I mean, I could see he |
|
| 90:40 | a very creative guy, just from way he published what he published on |
|
| 90:45 | the way he asked questions and things that, but you know, so |
|
| 90:48 | he did here was his first example , these are styrofoam mothballs, |
|
| 90:56 | kind of things you put in your to keep the moss away. They're |
|
| 91:03 | . Alright, and he thought, that's a good representation of brains like |
|
| 91:07 | ? It's right, I want to how spheres packed together. How would |
|
| 91:11 | would sand packed? How would you sand packed together? And so he |
|
| 91:16 | the mothballs in a box added clear resin made the artificial cut. And |
|
| 91:23 | what you see. And look at grains. Most of these grains are |
|
| 91:27 | touching Because when you put spheres they only touch it for part four |
|
| 91:34 | . And so any random cut, not likely to catch a lot of |
|
| 91:37 | grains touching. Okay, so you to appreciate that. That's the |
|
| 91:42 | Right? And then this is the cornflakes. Okay, He put cornflakes |
|
| 91:49 | a box, added the epoxy resin the cross sectional view. What's the |
|
| 91:55 | of cornflakes? It's the that played morphology that he thought represented. Things |
|
| 92:01 | the filament algae. We talked about of the smaller valves, organisms like |
|
| 92:06 | Osterc odds. Maybe smaller pieces of and things like that. Again, |
|
| 92:12 | at that. You don't see a of grains touching at any random cross |
|
| 92:16 | view. And then he took a gaster pods. Did the same sort |
|
| 92:22 | thing. See how they packed together . A lot of these things don't |
|
| 92:26 | . For some reason he took these uh what are called rose corals. |
|
| 92:32 | but they're so uncommon in the but I guess he was enamored with |
|
| 92:35 | corals. And he did the same with them. And then here's the |
|
| 92:39 | algae that we replicated. Here's the that we replicated. It started our |
|
| 92:46 | . Okay. Again, very, challenging aspect. Right? But only |
|
| 92:56 | question comes into play only in the lime stones. Right. In the |
|
| 93:02 | critical Einstein's okay, if you've only 5% or 10% Mike, right? |
|
| 93:07 | of that fabric has got to be supported. Okay. But if you |
|
| 93:11 | 30 or 40% McM Ride, then start getting into that situation trying to |
|
| 93:16 | whether it's brain support or mud And if you're not sure the way |
|
| 93:21 | express that uncertainty is I think I a wacky stone, tupac stone or |
|
| 93:26 | Pakistan, depending on which one do think is most abundant. And that's |
|
| 93:30 | you would describe it. Okay. a lime mud stone should be pretty |
|
| 93:35 | . Right? You should not see lot of grains. It should be |
|
| 93:40 | decried. Okay. The challenge is to differentiate between Pakistan and wacky |
|
| 93:46 | Right? Alright, let's go through examples here. And we'll start first |
|
| 93:52 | here is a uh obviously a big sample with coral with the colonial |
|
| 94:02 | And then there's a another coral over , which you don't appreciate that. |
|
| 94:07 | is lifted from a quarry in the keys is part of a map a |
|
| 94:11 | Institute reef. This reef goes for 500 m and you look at the |
|
| 94:17 | wall. All the corals are in position all along the That's right. |
|
| 94:22 | , this is just a cut through of these linear reefs in the Pleistocene |
|
| 94:26 | south florida. All right, But knowing that. Right. Not knowing |
|
| 94:33 | in place and growth position. That create a problem for you using Dunham's |
|
| 94:39 | scheme, Right? Because you have you have to show this in |
|
| 94:42 | All right. But the efforts here that these corals are in place, |
|
| 94:45 | ? There's a skeletal brain stone matrix occurs here. This is the breakdown |
|
| 94:50 | of the corals and that there are types of calculus algae live in that |
|
| 94:55 | . Okay, So wherever Dunham would something like this, where you could |
|
| 95:02 | , first of all, I have build up, Right, what you |
|
| 95:05 | in the quarry and then demonstrate that corals are in growth position creating that |
|
| 95:11 | . This is what he would call coral bounced. Okay, But you |
|
| 95:16 | want to just say coral bound stone corals don't make up all to the |
|
| 95:20 | . Right. What makes up a chunk of the reef? The |
|
| 95:24 | So, you want to say coral with a mixed skeletal or some people |
|
| 95:29 | the term core algal grain stone coral go would be smaller pieces of |
|
| 95:36 | , red algae, green algae, things like that. Okay, everybody |
|
| 95:44 | that. No, this this is quarry exposure. Right? A big |
|
| 95:49 | . I mean, this pieces about bait. Right. And imagine if |
|
| 95:56 | had a three inch four hole cut here. Right? A standard core |
|
| 96:01 | diameter. Alright. It might be challenging to know, first of all |
|
| 96:08 | anything is in place. And then you whether you even hit the institute |
|
| 96:15 | of the reef or not, Or whether you just hit some big |
|
| 96:19 | was thrown off the reef. So see the challenge. So it's really |
|
| 96:23 | to use the term down stone unless can demonstrate in since your growth of |
|
| 96:28 | reef related elements. Okay, in position, have you ever snorkeled on |
|
| 96:45 | modern reef? Okay. So but seen pictures underwater, pictures of the |
|
| 96:52 | . Right. So we have stuff living right in growth position grows |
|
| 97:00 | right, right, branches, head , Everything wants to grow upright like |
|
| 97:05 | . Alright, that's in growth Of course. Then they get knocked |
|
| 97:10 | by big storms, they create the so they're toppled at all different |
|
| 97:14 | That's not growth position anymore. And they die like that then they died |
|
| 97:19 | growth position, which they can Right? So some corals actually die |
|
| 97:23 | growth position, they get succeeded by coral. Okay, so that's what |
|
| 97:28 | mean by in place for growth Okay, So you have to demonstrate |
|
| 97:34 | you usually demonstrated by showing things are . Everything wants to grow up, |
|
| 97:39 | ? They want to grow toward the . Right? Because all these corals |
|
| 97:44 | symbiotic relationship with the what's called so kelly algae which give them their color |
|
| 97:51 | help calcify their structure. They're the that need the light. Actually the |
|
| 97:56 | don't by themselves don't need the light their algal buddy needs the light. |
|
| 98:01 | so they try to accommodate that by up. Right, okay. |
|
| 98:12 | Yes. You want to know where institute living reef was? Because then |
|
| 98:20 | can you can shed debris off of reef any direction. Right. So |
|
| 98:24 | fact that you encounter debris, it solve the problem about where is the |
|
| 98:30 | ? Right? Because you can have within the reef. You can have |
|
| 98:33 | shut off the reef behind the reef shallow water in front of the reef |
|
| 98:38 | deeper water. We'll develop this story weekend. Okay. All right. |
|
| 98:47 | example here is a Jurassic uh grains from east texas. The subsurface is |
|
| 98:55 | of an oil reservoir. And what the grain types? What's this green |
|
| 99:05 | it? All right. And then would we call a grain like this |
|
| 99:09 | a grain like this? Dark. critics. Oh boy shape. |
|
| 99:19 | Lloyd. Remember the term P Any sand sized grain that is critic |
|
| 99:24 | lima critic with an ovoid shape in rock. Oh boy 22 lips idol |
|
| 99:32 | circular. Doesn't matter. It's just funny shaped. Alright. And it's |
|
| 99:39 | MMA critic fabric in the rock We use the term P Lloyd for |
|
| 99:44 | . All right. So these maybe fecal pellets or they may be just |
|
| 99:49 | my critized you. It's remember the story from yesterday and then the blue |
|
| 99:56 | I talked about is the ferocity filled the epoxy resin died with that blue |
|
| 100:04 | material. And we haven't talked about the white cow sites are yet. |
|
| 100:09 | comes in the next lecture. That's genetic cement and what don't you see |
|
| 100:15 | these grants? There's no fine grain . Right, okay. And we |
|
| 100:23 | know that from the core sample. we saw the core sample, we'd |
|
| 100:28 | a sedimentary structure with cross lamination. ? So if if a carbonate rock |
|
| 100:35 | cross laminated, that means rippled. means high energy. That means you're |
|
| 100:41 | gonna deposit mike right, in that . Okay, so that's where we |
|
| 100:46 | the sedimentary structure to help confirm what can see in thin section, There's |
|
| 100:51 | mic right in the in this Now, what's the other thing that's |
|
| 100:55 | to this rock? This is the is another type of expression of pressure |
|
| 101:03 | . I showed a picture of this when we started but this is called |
|
| 101:08 | to grain suturing where the grains under pressure during burial actually dissolve into each |
|
| 101:16 | . Okay, that's a that's what see in grain stones. We see |
|
| 101:20 | to grain suturing. Okay, now obviously creates an artificial packing relationship. |
|
| 101:32 | ? So mentally Dunham is asking you take that out of the picture because |
|
| 101:38 | trying to describe de positional texture. he's mentally asking you to remove the |
|
| 101:45 | of burial and pressure solution. But does this have to be anyway, |
|
| 101:52 | pressure solution had to be grain Right, because there's nobody. |
|
| 101:59 | so this is a grain stone and mostly dominated by U. Ids. |
|
| 102:06 | the way I would describe this is say I'd call this a porous |
|
| 102:10 | It'll analytic brain stone. Okay, example, cretaceous fluids. In this |
|
| 102:24 | though the structure of the US is . This is that radial structure we |
|
| 102:28 | briefly about yesterday. Okay, so of fluids and this is the Mc |
|
| 102:35 | in between the grains, all of brownish light brownish material is mike, |
|
| 102:42 | , okay. And then this fabric against sparty calcite, but to confuse |
|
| 102:49 | issue you're going to learn that not starry calcite is poor filling cement, |
|
| 102:54 | carbonate material re crystallizes, in other , it changes texture on a multiple |
|
| 103:02 | from say mike right? To and that's implied by the patchy distribution |
|
| 103:08 | . Okay, see how the You Apache it wouldn't make any sense. |
|
| 103:13 | ferocity in this mic. Right locally with cement. So the fact that |
|
| 103:18 | got this patchy distribution to the mic ? And sparkle side suggests again that |
|
| 103:23 | is all the critic to begin with then die genetically altered to this fabric |
|
| 103:28 | . So in other words, we're this safari calcite to be originally |
|
| 103:35 | right? That's been re crystallized. . And then the black crystals are |
|
| 103:41 | of iron sulfide pyrite, which is common later digest over print means nothing |
|
| 103:49 | early. Okay. For for these of rocks because you need reduced environment |
|
| 103:55 | to make my ride. You can't that obviously in a high energy shallow |
|
| 103:59 | carbonate system. Right? The water going to be well oxygenated. |
|
| 104:05 | so well that's my question to So we have grains right? We |
|
| 104:18 | mud. What's the first question to ? Grain support or mud support. |
|
| 104:28 | . And why do you say that not touching? Well, not |
|
| 104:38 | I agree with that. I I I don't disagree with what you |
|
| 104:41 | , but that's I'm not sure that's best rationale for calling it must support |
|
| 104:47 | . Go back to look at his of the mothballs. Remember that picture |
|
| 104:52 | the spherical grains? Most of those were not touching. Okay, Most |
|
| 104:58 | us don't touch it in any random . Their clothes. Yes, no |
|
| 105:09 | there. But you see we're trying decide now between pack stone, wacky |
|
| 105:16 | and why is it not a mud ? Because it's got more than 10% |
|
| 105:22 | making up that rock right over half that rocket zoo. It's okay, |
|
| 105:28 | it's a question about much support wacky or or pack stone brand support. |
|
| 105:37 | , and I would actually call it a pack stone because of the way |
|
| 105:42 | it's packed together. They don't touch cross sectional views. Okay. You |
|
| 105:48 | expect a few to be touching at . Okay. But they're pretty closely |
|
| 105:53 | . All right when they're not So I would probably view this again |
|
| 105:59 | a pack more of a pack And I would call it a high |
|
| 106:03 | pack stone because all the interstitial ferocity filled in with mike right? And |
|
| 106:10 | the US didn't form here, They formed somewhere else and they got |
|
| 106:14 | into a quiet water setting represented by okay, hi mud Pakistan politic, |
|
| 106:26 | mud Pakistan. Okay, again, you're uncertain then you would say wacky |
|
| 106:36 | to Pakistan. Okay. You're letting , you're really telling people it's so |
|
| 106:42 | that I'm not sure all the grains touching in three D. And that's |
|
| 106:46 | . Okay. But just knowing how packed together, they don't have to |
|
| 106:50 | touching at a lot of points. . And then a couple of Devonian |
|
| 106:57 | here. The first one with lots P. Lloyd's, right? These |
|
| 107:01 | shaped critic grains here. Again, of these were probably fecal pellets but |
|
| 107:06 | don't know that for sure. That's we use the term p Lloyd. |
|
| 107:13 | . You know the term P Lloyd came from people not working the modern |
|
| 107:17 | came from people working the rock record it specifically came from studies done in |
|
| 107:22 | Grand Canyon. I don't know if ever been down the Grand Canyon if |
|
| 107:27 | peeked into it or if you walk the trail, but the upper part |
|
| 107:31 | the sequence in the Grand Canyon are Pennsylvanian lime stones, these bright red |
|
| 107:37 | stones, and one of them is the redwall limestone. Okay. And |
|
| 107:43 | in the sixties, uh some people studying the fabric and the redwall limestone |
|
| 107:50 | they saw fabric that looked like this the ovoid shaped grains with democratic |
|
| 107:58 | But what they didn't see in the was evidence of by observation. |
|
| 108:02 | So they weren't convinced that every one these grains was a fecal color produced |
|
| 108:07 | a foreign organism. And so to that uncertainty, they actually coined the |
|
| 108:12 | p Lloyd. Okay. And that's term. Now we used in the |
|
| 108:16 | record, we don't call these fecal unless we see the internal striations of |
|
| 108:22 | special type of pellet called the fecal . Okay, so this is political |
|
| 108:29 | what's between the P lloyds? The problem. Again, we've got a |
|
| 108:33 | of this finely disseminated mike reid and of it again, gets re crystallized |
|
| 108:38 | safari cal side. So again, inferring that the safari calcite replaced some |
|
| 108:44 | that mike right after deposition. that's a diabetic over print. We'll |
|
| 108:49 | about how we can resolve this So we have Mick, right, |
|
| 108:56 | a grain stone. We have lots p lloyds. They're closely spaced. |
|
| 109:00 | some are touching. We've got more 10% grain. So it's not a |
|
| 109:07 | stone again. So, we're back this challenges that Paxton or wacky |
|
| 109:13 | Yeah, I think here it's mostly stone, but there may be parts |
|
| 109:17 | the sample where things are more widely . That's the case. You say |
|
| 109:21 | too wacky stone. Alright. It's acceptable to do that. You're trying |
|
| 109:27 | express, you know, the right? Which is a function of |
|
| 109:31 | the critics. Some of these rocks stay in the Devonian here again, |
|
| 109:37 | sample with a couple of different grains , you still see the P. |
|
| 109:42 | and now you see these little plate thin bivalve fragments right here. And |
|
| 109:49 | those are the circular calcite spheres that talked about uh briefly yesterday. The |
|
| 109:55 | system, algae that grew on the floor, few 100 microns across for |
|
| 110:01 | . Darkman critic test. All So these are benthic calc spheres and |
|
| 110:08 | of molly's and P Lloyd a lot Mick. Right, Okay, so |
|
| 110:13 | more MMA critic the grains are I you agree they're they're more widely |
|
| 110:18 | right? Maybe a couple of them places, but overall you get the |
|
| 110:23 | that they're not touching. So more supported. So, now what's the |
|
| 110:30 | ? That's it. Right. And think, I mean, I think |
|
| 110:35 | clearly when you count the P. and the mollusk. And the calcium |
|
| 110:39 | more than 10% of that view is sized grains. Again, if that's |
|
| 110:46 | case, right? You can you evade this or Challenge it. But |
|
| 110:52 | you think there's more than 10% then that would be a wacky |
|
| 110:55 | Right? So I would call I'd probably call this a a Alaska |
|
| 111:01 | sphere of colloidal, wacky stone. , last example here, still in |
|
| 111:09 | devonian, a few vague delights High degree of re crystallization here. |
|
| 111:16 | much critic Now, I think you're that category where maybe you're around that |
|
| 111:23 | of 10%. So you have to that judgment, right? If you |
|
| 111:27 | it's less than 10% grains uh between few little calc spheres and few |
|
| 111:32 | Lloyds, which I do, then you would call this a mud |
|
| 111:38 | right, calc sphere, colloidal or colloidal mud stone. This one It's |
|
| 111:47 | right. Exactly. Because remember I the term hard fecal pellet and soft |
|
| 111:54 | pellet yesterday and I think I mentioned going to happen to the software fecal |
|
| 111:59 | when you bury them, they're going squish together. See that? So |
|
| 112:05 | why I use the term vague you know, you don't quite is |
|
| 112:09 | a grain or is that see what mean? Yeah, they're gonna squish |
|
| 112:14 | and whereas harder fecal pellets going to more distinct and less compatible. |
|
| 112:22 | so I would I think a lot these are big t Lloyd fabric, |
|
| 112:30 | discernible councils here. Again, you this judgment? You have to make |
|
| 112:35 | judgment. Right. I'm not going be looking over your shoulder when you |
|
| 112:38 | these rocks, you're gonna have to even if I was I may be |
|
| 112:42 | too. So that's the challenge. . But I would I would call |
|
| 112:47 | more of a lime, mud Big colloidal line, mud stone, |
|
| 112:53 | , sphere of a colloidal line mud . Okay. All right. So |
|
| 112:59 | that's the limestone fabric. And then another complicating element here. And that's |
|
| 113:05 | dia genesis. You've already seen that the re crystallization of the Mc. |
|
| 113:09 | . Well, the other part of story could be Delman ization. |
|
| 113:14 | sometimes dolomite, as you're gonna see that limestone and converts it to dolomite |
|
| 113:21 | very good fabric preservation. And here's example from the permit. Okay, |
|
| 113:28 | had p lloyds fluids inter class. a critic matrix in between. |
|
| 113:37 | But it's all been replaced by And how do I know this has |
|
| 113:43 | replaced by Delimar. There's no sugar crystals of dolomite here. Right. |
|
| 113:50 | wrong. Big crystals there are but so fine crystalline, you don't see |
|
| 113:57 | . So, how do I know has been replaced by dolomite outside. |
|
| 114:07 | , everything is replaced by dolomite. not an ounce of calcite in this |
|
| 114:13 | ? How do I know that? do we talk about yesterday? The |
|
| 114:21 | , what did I do to the section. Yeah. I tried to |
|
| 114:24 | in the thin section. I tried stay in it with a lizard and |
|
| 114:28 | S It didn't take any red So by inference this is all replaced |
|
| 114:34 | dolomite. Right? None of these or any of this crystalline fabric shows |
|
| 114:41 | of being quartz or an hydrate or like that in thin section. |
|
| 114:47 | so you have to stay in your section to verify or you have to |
|
| 114:50 | that sample and run it through the ray diffraction to show it's been converted |
|
| 114:55 | dolomite. Obviously when you're describing your , you want people to know that |
|
| 115:00 | a dull stone, but you still him to know what the texture was |
|
| 115:04 | the time of deposition. So how we convey that? So, there |
|
| 115:09 | two ways to do this. The way is to treat this from the |
|
| 115:16 | of Dunham, Right, as a , what would Dunham call this is |
|
| 115:20 | limestone? He'd probably call it a little paxton. Okay, most of |
|
| 115:27 | grains are pretty closely spaced. touching in a few places with Democratic |
|
| 115:33 | . Alright, but now, how we convey that? It's been replaced |
|
| 115:37 | dolomite. So, first thing you say is you can use the term |
|
| 115:43 | ized dramatized, needs completely replaced by , and you would call this a |
|
| 115:50 | sized colloidal accident. Okay, so one way, another way that's involved |
|
| 115:58 | the literature is the term dolo pack to convey the same relationship. |
|
| 116:06 | so some people will call this a little dolo paxton. They're saying the |
|
| 116:12 | completely replaced by dolomite has this political stone texture, Right. Yeah. |
|
| 116:25 | would never know that. That's all by dolomite, intense section without the |
|
| 116:31 | . Now, with a scanning electron , if you zapped all this, |
|
| 116:34 | see little Rambo crystals of Abdullah might micro dolomite crystals perfectly preserved the |
|
| 116:43 | Again, appreciate why we need to whether it's limestone or dolomite. |
|
| 116:48 | when you bury these rocks and we're talk about this later, right? |
|
| 116:52 | you have a limestone and dolomite and bury it to higher stress, which |
|
| 116:59 | gonna fracture to a greater degree during , it's always going to be the |
|
| 117:04 | . It's much more brittle. It more than four times greater than a |
|
| 117:11 | . Okay, so if you're if want fractures to provide permeability to your |
|
| 117:18 | , then it makes a big deal you're dealing with color stones or lime |
|
| 117:23 | . Okay, and then the last here is another Dulles stone from the |
|
| 117:34 | blue porosity. Black, dead oil thermally altered to pirate bitumen, late |
|
| 117:42 | die, genetic and hydrate. There the goal of my fabric that replaced |
|
| 117:47 | limestone. This is actually taken with white paper technique. I was trying |
|
| 117:51 | pick up a really grain fabric, you don't see it in this |
|
| 117:57 | Okay, so you don't see So you don't know texture. So |
|
| 118:03 | the white paper didn't work. So do you do with a sample like |
|
| 118:08 | ? He just physically characterize it. with dull stones, we usually pay |
|
| 118:14 | to the size of the crystals. these are medium crystalline, you |
|
| 118:17 | several 100. My crime across crystals dolomite. And so I would call |
|
| 118:23 | a forest, right? A lot blue porosity, Reservoir forests, the |
|
| 118:31 | anus and hydrate IQ medium crystalline So, it tells people what Iraq |
|
| 118:39 | , but it doesn't convey any information the deposition will set. Okay, |
|
| 118:47 | , you know, I can show a sample just a few inches away |
|
| 118:50 | this, it shows a beautiful it'll pack stone texture. Put the |
|
| 118:53 | paper so Dulles, stone can recreate can re crystallize to and every time |
|
| 118:59 | re crystallize we tend to see destruction some of that relic brain fabric. |
|
| 119:06 | , so that's the Dunham classification Alright, and again, the challenge |
|
| 119:11 | , is that wacky stone paxton transition . Okay, trying to decide grain |
|
| 119:17 | versus mud support, appreciate again, implications for reservoir quality and environmental |
|
| 119:23 | Right? It's all controlled by the of nick, right in the |
|
| 119:30 | As I said, 10 years, 10 years later, two Canadian |
|
| 119:35 | Ashton Embry and Ed Cloven published this Dunham classification scheme for coarser grain refill |
|
| 119:53 | . I told you they were working uh devonian reef outcrops in the Northwest |
|
| 119:58 | of Western Canada and they they found classification scheme, the mud stone, |
|
| 120:06 | stone, Pakistan grain stone terminology, hard to apply to some of the |
|
| 120:12 | grain fabric. And so they decided add two terms to characterize coarser grain |
|
| 120:18 | drive fabric. Alright, I showed a picture what this looked like yesterday |
|
| 120:23 | the great barrier reef, big cobble pieces of coral all the way broken |
|
| 120:29 | into smaller. Excuse me, stand material. And so they only used |
|
| 120:36 | two millimeter size cut off, Which is sort of the I |
|
| 120:40 | you know, they don't really explain they use the two millimeter cut |
|
| 120:44 | but But I was just going through I'm working a project now with some |
|
| 120:49 | mixed in with the carbonates, and having to use some of the classic |
|
| 120:54 | to characterize some of these sandstone and . And uh I was looking at |
|
| 120:59 | grain size chart and two is sort the bottom line of what people call |
|
| 121:05 | . Right, And so I think , I'm thinking maybe that's why they |
|
| 121:09 | the two millimeter cut off, Anything coarser than two millimeters would be |
|
| 121:15 | into that category of gravel in a rock. Okay, I don't know |
|
| 121:22 | sure, but that's just my guess because I always wondered why they used |
|
| 121:27 | , that two millimeter cut off, that's not very big, right, |
|
| 121:31 | two, that's two millimeters right And I showed you pieces of coral |
|
| 121:35 | big. So so anyway, they and what they basically what they did |
|
| 121:41 | they recognize first of all they're devonian have two parts. There's the in |
|
| 121:46 | reef, right? Where the strongest grow together to create topography. |
|
| 121:51 | That's what they call the top anus in situ part of the reef and |
|
| 121:57 | there's debris around it or within And that's what they called gelatinous refill |
|
| 122:03 | . Okay, now this classification scheme only to be used for refill |
|
| 122:11 | Unfortunately, people have started applying it any coarse grained limestone. Okay. |
|
| 122:17 | is not the intent. I've seen use this for analytic lime stones. |
|
| 122:23 | , so it's supposed to be limited refill deposits. But coarser grain debris |
|
| 122:32 | on this refill limestone greater Where you a deposit containing more than 10% of |
|
| 122:40 | bigger pieces greater than two. If bigger pieces are touching in three |
|
| 122:47 | that's what they call the root okay. And if they're not |
|
| 122:52 | they're supported by material less than two size. They call that a |
|
| 122:57 | Okay, now the term matrix here not mean mud. It means material |
|
| 123:03 | than two in size. So in environments, matrix could be a grain |
|
| 123:08 | in some environments. Matrix can be wacky stone. It all depends where |
|
| 123:13 | debris gets set. Okay. And stone can have a matrix to |
|
| 123:20 | so you want to describe the matrix a route step. So it could |
|
| 123:25 | rude stone with all open porosity between grains. Or it could be a |
|
| 123:28 | stone with a grain stone matrix. it could be a route stone with |
|
| 123:32 | wacky stunt matrix, Right? Because will shed material into shallow water, |
|
| 123:39 | will shed material into deeper water. ? Low energy more MMA critic. |
|
| 123:45 | you see how sometimes roots stones are critic matrix. Sometimes they have a |
|
| 123:50 | grain stone matrix. Ok, everybody the but you've got to demonstrate grain |
|
| 123:57 | for these bigger pieces. Alright, , which may be hard to |
|
| 124:01 | So sometimes people to express the they use turn float stone and ruth |
|
| 124:07 | . Alright, you're going to see this all fits into our modern re |
|
| 124:13 | next weekend. Okay, now if dealing with a finer grained material on |
|
| 124:18 | reef, you just use Dunham's classification . Okay, so two terms route |
|
| 124:25 | and float stone added for the coarser deposits associated with their reef. And |
|
| 124:30 | they took Dunham's original bound stone term their devonian, Autochthonous or institute refill |
|
| 124:39 | stones. They broke it out into types to reflect the process that creates |
|
| 124:44 | topography. So, high energy reefs they have in the caribbean, where |
|
| 124:49 | waves break across the reef. these corals or strom's have to intertwine |
|
| 124:54 | create the topography. They're gonna create frame stone. Right? So that's |
|
| 124:58 | the term frame stone comes from. gonna see that parts of these reefs |
|
| 125:02 | made up of material organically bound on sea floor, buying clusters. Red |
|
| 125:09 | , corals in the rock record It operates okay, fine stone. |
|
| 125:16 | then you're going to learn that there shallow water, low energy patch |
|
| 125:22 | There are deeper water buildups that build but not in high energy. And |
|
| 125:29 | do it because the organisms baffle or sentiment. So this is where the |
|
| 125:34 | zones come into play or the fill algae. Okay, those kinds of |
|
| 125:41 | , they're more delicate, they they trap, they die, they |
|
| 125:46 | but they do what through time they this build up topography. That's what |
|
| 125:51 | talking about here. The term baffle is applied to those kinds of |
|
| 125:56 | Okay, so here's the final Alright, so remember always two types |
|
| 126:04 | reef deposits, the in situ or refill lime stones and then the telekinesis |
|
| 126:12 | refill debris. Alright, so for course of debris where you have more |
|
| 126:16 | 10% of fragments greater than uh two . If the bigger pieces are touching |
|
| 126:24 | stone, if they're floating in a matrix, float stone. Again, |
|
| 126:30 | doesn't mean necessarily mc. Right? could be a grain stone matrix and |
|
| 126:36 | frame stone, bind stone, more , branching corals or strums or bright |
|
| 126:43 | to create the baffle stone texture. , all of this is obviously going |
|
| 126:49 | be put into context. First from some of our modern carbonate environments. |
|
| 126:55 | then later when we get into the record and we talk about play |
|
| 126:58 | you'll see where this all translates back the different place. Okay, the |
|
| 127:02 | kinds of reservoirs. Any questions or . Okay, Alright. Let's take |
|
| 127:15 | let's take at least a 10 minute here. So we'll start back at |
|
| 127:19 | say, Alright, we're back to lecture seven now on limestone. Dia |
|
| 127:31 | . So most of the rest of day we're gonna talk about carbonate dia |
|
| 127:36 | and that involves the the two processes are uh limestone dia genesis, broadly |
|
| 127:46 | . And then demonization. So I'm I'm gonna treat the organization as a |
|
| 127:50 | topic and that's what we'll talk about after lunch. But now before lunch |
|
| 127:56 | a little bit after lunch, we're get into a discussion on limestone. |
|
| 127:58 | genesis. So you can better understand of the fabrics we've been looking at |
|
| 128:03 | . I haven't had time to So that includes some of the cement |
|
| 128:07 | that I've been showing you some of prostate types and also some of the |
|
| 128:14 | digest fabrics that and cement types that made sense yet. Okay, so |
|
| 128:22 | the whole point of this, of lecture is for you to understand uh |
|
| 128:29 | happens to carbonates when they get progressively . This is obviously a fundamental question |
|
| 128:35 | terms of hydrocarbon exploration and development Right? You want to know what's |
|
| 128:40 | in porosity and permeability. Uh we'd to always be able to predict ahead |
|
| 128:45 | the drill bit, but that's almost . All right. And, you |
|
| 128:50 | , we rely on things like seismic identify anomalies that might relate to porosity |
|
| 128:55 | we pick up ferocity on well But as you're gonna learn, just |
|
| 129:01 | ferocity is not enough. You need know what kind of permeability comes along |
|
| 129:05 | that ferocity. Okay, you can great ferocity. No perm And your |
|
| 129:10 | is not gonna squeeze an ounce of out of it. Okay, so |
|
| 129:16 | need to talk about the different digest . We need to talk about what's |
|
| 129:21 | to porosity and permeability. Uh We to talk about some of the key |
|
| 129:26 | because I think if you understand what the occurrence and timing of dia |
|
| 129:33 | whether it's limestone or dolomite, that's you can exploit in the subsurface. |
|
| 129:39 | , because you're always looking for ways exploit trends in the subsurface. |
|
| 129:43 | And historically most of our trends have we chased or deposition. All |
|
| 129:48 | we're trying to chase the de positional body or a reef or something like |
|
| 129:53 | . But unfortunately, as I alluded yesterday carbonate plays are not just controlled |
|
| 129:58 | deposition. They're controlled by dia genesis die genesis can make or break a |
|
| 130:04 | play. So that's why we're talking die genesis, You've got to have |
|
| 130:08 | appreciation for the different pathways for porosity and the permeability that comes along with |
|
| 130:15 | evolution. Okay, so, we're start this discussion with this slide |
|
| 130:22 | which talks about porosity. We want talk about porosity because porosity is the |
|
| 130:29 | we track the extent of Dia genesis know we start with on the sea |
|
| 130:35 | , we know with what we end with in the subsurface. So the |
|
| 130:38 | is, how do we get there one to the other? We got |
|
| 130:42 | because of Dia genesis either favorable or in terms of its effects. |
|
| 130:49 | carbonate process is always controlled by two factors. The first factors deposition all |
|
| 130:55 | , that controls the starting process and . You're going to see the numbers |
|
| 130:59 | this in a minute and then die , which just simply means the chemical |
|
| 131:04 | the sediments of rocks undergo with progressive , that obviously dictates the final degree |
|
| 131:11 | preserved porosity and permeability. Okay, you wish it was so simple. |
|
| 131:17 | was just these two things we had worry about but the complexity of trying |
|
| 131:21 | predict ferocity comes from the fact that the deposition all faces and the Dia |
|
| 131:27 | are controlled by other factors. these are some of the factors on |
|
| 131:31 | left under faces type that we need talk about next weekend and we will |
|
| 131:36 | about next weekend that control the occurrence distribution of these different carbonate faces |
|
| 131:43 | All right. So, I'll put off until next weekend. And these |
|
| 131:46 | the things we need to consider today a diet genetic standpoint. Okay, |
|
| 131:52 | listed first as a geological age. is the age control? Because it |
|
| 131:57 | who the organisms were. Right. why I spent time yesterday going through |
|
| 132:01 | grain types, especially the fossil right? To give you a feel |
|
| 132:05 | the age distribution and things like And what does that control that controls |
|
| 132:09 | starting meteorology? So, we talked the different mineralogy is associated with malice |
|
| 132:15 | brock. Ipods versus uh plastic Okay, it makes a big difference |
|
| 132:22 | you're sediment is a reaganite dominated or dominated in terms of reactivity. |
|
| 132:29 | In terms of digest reactivity texture, started to see now how the |
|
| 132:35 | whether it's a grain stone or a mud stone controls the amount of |
|
| 132:39 | but also the permeability. And then , we used to look at climate |
|
| 132:45 | from the standpoint of a lot of or no rainfall. So humid versus |
|
| 132:51 | because you're going to see that rainfall drive some styles of dia genesis, |
|
| 132:57 | that's only part of the story. , climate also incorporates the influence of |
|
| 133:02 | trade winds that I introduced you to and trade winds actually play a role |
|
| 133:07 | some of the early die genesis of marine carbonates. And then two key |
|
| 133:14 | are the burial history and the poor chemistry that comes with progressive burial. |
|
| 133:18 | interplay of these two factors defines what call di genic environments. So for |
|
| 133:23 | limestone die genesis discussion today, we're put put everything into the context of |
|
| 133:30 | genic environments. Okay. And there three simple die genetic environments, |
|
| 133:37 | freshwater and burial. They're defined by poor fluid chemistry and the depth of |
|
| 133:44 | . And then there's a little bit a variation on the theme that comes |
|
| 133:47 | play here to sort of throw a in this discussion that I'll talk about |
|
| 133:52 | well, but it's basically those three genetic environments. Okay, so that's |
|
| 133:57 | context for talking about processes and products what effect it has on processing |
|
| 134:04 | Then. I listed tectonic activity We used to look at tectonic activity |
|
| 134:10 | from the standpoint of entrapment of right faults and folds and trapping |
|
| 134:17 | But now we realize that we realized since the late 80s, early |
|
| 134:23 | that deep seated structure, in other , basement related faults that come out |
|
| 134:29 | frenetic basement have the ability to bring fluids that are capable of dissolving carbonated |
|
| 134:36 | . Okay, so the tectonic activity can drive some of the dissolution phenomena |
|
| 134:42 | we're going to talk about today, then there's a strong interplay between what |
|
| 134:48 | early die genetically into carbonate. What when it gets more deeply buried. |
|
| 134:53 | you really need to understand the digest . These carbonates because what happens early |
|
| 134:58 | what happens late. We don't see in the world of classics because nothing |
|
| 135:03 | early. You don't modify processing a on the sea floor. You don't |
|
| 135:10 | porosity when it's severely exposed. You do it all during burial with |
|
| 135:16 | pressure phenomena. Right. Segmentation comes that. Okay, so having said |
|
| 135:24 | , let me introduce you to the process and permeability numbers that we uh |
|
| 135:30 | with on the sea floor. These essentially in situ measurements, right? |
|
| 135:35 | took the shallow course uh in areas florida, the Bahamas and they they |
|
| 135:41 | them for processing permeability. And so a lot of percent porosity versus de |
|
| 135:47 | texture. Brain stone pack stone wacky texture. Alright, and shallow water |
|
| 135:54 | . There's lime, mud stones are non existent. Okay, so you |
|
| 135:59 | see the numbers right? The yellow represents the range of porosity values. |
|
| 136:05 | black dot represents the average or mean for each texture and then the average |
|
| 136:12 | is shown under the under each of yellow bars and the range of permeability |
|
| 136:17 | that they encounter. Okay, so thing, the first thing that stands |
|
| 136:22 | here is all of these settlements start with very high porosity and maybe you're |
|
| 136:28 | that it's the mormon critic fabric that starts out with the highest ferocity. |
|
| 136:35 | stuff is always more porous than the stuff, believe it or not. |
|
| 136:39 | it's mostly what micro porosity. And but look at the permeability. |
|
| 136:45 | grain stones and low mud pack stones these incredibly high firms to begin |
|
| 136:50 | That's 30 Darcy's, that's 56 Darcy's . They start off with that |
|
| 136:56 | that permeability. Because the pore throats big, they're well connected. And |
|
| 137:01 | at the smaller numbers here. don't be misled by this big number |
|
| 137:06 | here. That's mud crack on a flat. Right? I told you |
|
| 137:10 | cracks are zones of local, high and permeability. Overall, this is |
|
| 137:17 | typical of the firm's very low permeability with. All right. So that's |
|
| 137:23 | most of this process. But Dominic mike right dominated, right? Micro |
|
| 137:29 | . But if you took all of out of context, you say, |
|
| 137:32 | , all these carbons have great reservoir , but I think you may or |
|
| 137:36 | not know. But historically, what we chase? We chase this. |
|
| 137:43 | never chased this. Okay. Unless serendipity we drilled it by accident and |
|
| 137:49 | favorable Dia genesis to create reservoir All right. In other words, |
|
| 137:53 | looked at these as the reservoirs. looked at these kinds of rocks at |
|
| 137:57 | top or side seal to those potential . Okay, now that's changed right |
|
| 138:05 | the advent of horizontal drilling and the gen three frack jobs, but you |
|
| 138:10 | where people will actually come back now track this stuff and try to squeeze |
|
| 138:14 | out of it. But historically this always the conventional story. Chase the |
|
| 138:20 | stones in the low back stones. , now let's put this into |
|
| 138:27 | All right. So here's the plot the values. I just showed |
|
| 138:33 | All right, so 35% for some the grain stones up to 80% porosity |
|
| 138:39 | some of the deep water pelagic uses we find in the deeper water |
|
| 138:44 | Okay. And the red hair. hair represents Ancient average porosity for most |
|
| 138:59 | carbonates is 5% or less. And then somewhere in between the purple |
|
| 139:06 | and green are the reservoirs. and in fact this should be extended |
|
| 139:12 | . Okay, because 1966 was before found the big giant chalk fields off |
|
| 139:19 | Norway and some of those chalk fields 55% porosity. So this should be |
|
| 139:27 | and I guess I could do that Photoshop but I'm just trying to I |
|
| 139:33 | , this is what these guys Right? So that green should extend |
|
| 139:37 | right here. Okay, so how we explain the reservoir rocks? All |
|
| 139:45 | . I've been teaching off of this for a long time and The way |
|
| 139:50 | used to explain the existence of the before the late 80s, early |
|
| 139:55 | was these reservoirs exist because somehow we Dia genesis long enough to entrap |
|
| 140:05 | In other words, up until the 80s we looked at burial and burial |
|
| 140:11 | genesis is proxy destructive, right? you progressively bury, what would happen |
|
| 140:15 | your prostate keep going down, And that would explain why you go |
|
| 140:19 | this to the red. Alright. so we will always say, |
|
| 140:24 | these reservoirs exist because somehow we stopped detrimental effect. That barrel die |
|
| 140:29 | Okay. And so what are those ? And we're gonna talk about those |
|
| 140:35 | later. Okay, so in other , that was the mindset of |
|
| 140:38 | If we're gonna chase carbonates, we to find situations where somehow we preserve |
|
| 140:44 | despite the Dia genesis. Okay, that was the mindset up to the |
|
| 140:49 | 80s, early 90s. And then happened at that time period, the |
|
| 140:55 | started to develop these reservoirs in the , both in limestone and Dolomites, |
|
| 141:02 | the porosity was created by burial So, the concept of barrel dissolution |
|
| 141:08 | existed until those studies are well Okay, so some of these reservoirs |
|
| 141:14 | exist, not because of unfavorable die , but because of favorable die |
|
| 141:21 | Okay, this is where the structure into play. The faults are the |
|
| 141:27 | for bringing these fluids up after these have already been buried over 1000 |
|
| 141:34 | sometimes several 1000 m of burial. they still have some ferocity and perm |
|
| 141:38 | they see these fluids come in, gonna enhance your red support quality. |
|
| 141:44 | , so that's why the timing is important. You need to understand the |
|
| 141:47 | relationship and you need to try to where the fluids are coming from. |
|
| 141:52 | that was part of why we went the tech techniques yesterday about the |
|
| 141:57 | right, astronomy isotopes and the fluid . Those are the techniques that give |
|
| 142:02 | some indication of timing of the of dia genesis and where the fluids are |
|
| 142:06 | from. Okay. Does everybody appreciate why the reservoirs exist? Are two |
|
| 142:13 | to explain a reservoir. You preserve porosity or early form secondary porosity long |
|
| 142:19 | to entrap hydrocarbons or you just bury then create favorable porosity perm after you've |
|
| 142:28 | buried some degree. Alright, so said that, we're gonna systematically work |
|
| 142:35 | way through this. We're going to about the major carbonate digestive processes. |
|
| 142:39 | start with we'll talk about semente shin just means precipitation of a a carbonate |
|
| 142:46 | out of a poor fluid. So could be a reaganite or calcite or |
|
| 142:50 | , calcite in a dull a stone could be dolomite. It could be |
|
| 142:54 | and limestone too. But we're gonna dollarization for right now and then dissolution |
|
| 143:00 | removal of calcium carbonate from that. sediment. The term leeching L. |
|
| 143:06 | . A. C. H. N. G leaching is used anonymously |
|
| 143:11 | this solution. Okay. And you're to learn that these two processes are |
|
| 143:15 | together when you dissolve carbonate material to secondary porosity. What can happen to |
|
| 143:21 | dissolved carbonate. It goes back into and locally re precipitates as a pore |
|
| 143:27 | , calcite cement. Okay, the is donor receptor dia genesis take from |
|
| 143:35 | of the rock by dissolution but then some of that dissolved material back in |
|
| 143:39 | a pore filling cement. Okay. then I've used the term re |
|
| 143:46 | That's the buzzword in the literature. morph ism you don't need to remember |
|
| 143:52 | . Re crystallization is a multi formal of one mineral to another or one |
|
| 143:59 | to another. So one mineral to would be when we go from a |
|
| 144:04 | night to calcite. A textual change be where I showed you the |
|
| 144:08 | right? Remember in that you would stone being re crystallized of course, |
|
| 144:13 | sparkle side. Okay, so that's viewed as a process that creates |
|
| 144:19 | but it's a multiple replacement of one or one texture by another. |
|
| 144:25 | and then as we talked about what with with increased overburden pressure and stress |
|
| 144:30 | solution and you're gonna see the pressure links back to cement a shin when |
|
| 144:36 | dissolve along skylights or grain to grain that dissolved carbonate can go back into |
|
| 144:42 | and locally re precipitate as a pore cement. Okay. And then Dolman |
|
| 144:49 | will treat as a separate topic. right now, our understanding of |
|
| 144:56 | Dia genesis as you might imagine, pretty well established for for near surface |
|
| 145:05 | environments. Right? We can go to the caribbean today. And we |
|
| 145:08 | snorkel in the shallow water settings and can see what's happening die genetically. |
|
| 145:13 | can evaluate the chemistry of seawater. understand marine die genesis pretty good. |
|
| 145:19 | then we can do what we can up on the adjacent land mass. |
|
| 145:22 | . The islands in the caribbean of same kind of the rock is made |
|
| 145:26 | of the same kind of sediment. we can see what happens when these |
|
| 145:29 | get exposed to fresh water. understanding is pretty good. Right. |
|
| 145:35 | where do we lack our best knowledge the subsurface? Right. Because we're |
|
| 145:41 | about core databases and most core databases not public. Right. Most companies |
|
| 145:49 | everything close to the vest. And now most companies do not have research |
|
| 145:57 | anymore. Right. When I started Exxon, I worked for a research |
|
| 146:01 | where we tried to tackle some of questions about controls on dia genesis and |
|
| 146:06 | development. But that got thrown out window like it did for most big |
|
| 146:11 | . And so who's left? academicians right. If they can get |
|
| 146:17 | handles on court databases, which is to do or public Core databases. |
|
| 146:24 | . We have one here in texas of Economic geology in Austin. |
|
| 146:29 | They archive a lot of core data then we have a huge core repository |
|
| 146:35 | Canada. All the major provinces that production of hydrocarbons have a same kind |
|
| 146:43 | facility like the bureau has. Except bigger in the bureau. Right. |
|
| 146:48 | you go to Calgary Alberta Alberta has of the biggest core repositories in the |
|
| 146:53 | . And so all, all the in Canada are required to archive their |
|
| 146:58 | , they can't title you more than year. Okay. Usually after six |
|
| 147:03 | , they have to give half the to the government. Which is great |
|
| 147:08 | then that opens it up to study everybody. And so actually our knowledge |
|
| 147:13 | barrel dia genesis has really evolved mostly of the Canadians. Because of that |
|
| 147:20 | . Alright. And I've been up to Calgary many times. I've done |
|
| 147:24 | projects in Canada and it's just a way of disseminating the science. |
|
| 147:32 | And it's unfortunate we don't have that in the States. All right. |
|
| 147:36 | of the States except I think North require you to archive subsurface data. |
|
| 147:44 | . Alright. So what I'm saying , you know, we don't fully |
|
| 147:48 | all the controls on carbonate dia That's why we can't predict process ahead |
|
| 147:52 | the drill bit and I could spend whole course talking about carbonate geochemistry. |
|
| 147:59 | don't have time to do that and still wouldn't come to full answer what's |
|
| 148:03 | on here. But let me share you with these couple of slides |
|
| 148:07 | Some of the key controls on carbonate genesis that you need to be familiar |
|
| 148:12 | . And the first is And the geochemistry. Right. The fluids obviously |
|
| 148:20 | important to controlling the way these rocks die genetically. So what's the first |
|
| 148:27 | influence on the carbon carbonate geochemistry? is carbon dioxide. Okay, input |
|
| 148:35 | output of carbon dioxide right? Input output of carbon dioxide controls the acidity |
|
| 148:41 | the fluid that's represented by the So you remember from chemistry one oh |
|
| 148:47 | right? Low ph is acid seven neutral. Anything above seven is |
|
| 148:54 | So acidic fluid dissolves. Basic fluid the potential to precipitate. Alright, |
|
| 149:00 | that inter relationship is explained by this equation that shows calcium carbonate plus carbonic |
|
| 149:08 | in equilibrium of calcium cat ions and and ions at the same time carbonic |
|
| 149:15 | in equilibrium with water and carbon Okay. At equilibrium nothing happens die |
|
| 149:23 | . So we view carbonate dia genesis being a dis equilibrium process. So |
|
| 149:30 | question is how do we create this ? You do it by input or |
|
| 149:35 | a C. 02. So if add C. 02 to the |
|
| 149:39 | you create carbonic acid, you shift low ph that's gonna favor dissolution. |
|
| 149:47 | Conversely If you pull co two out the fluid, you heat up that |
|
| 149:52 | , you drive out the C. , you're gonna push everything to the |
|
| 149:56 | that's gonna favor precipitation, assuming your is saturated with respect to calcium |
|
| 150:03 | Okay so the input and output of . 02 is a critical control and |
|
| 150:08 | controls that in a carbonate system, temperature and pressure. So higher temperature |
|
| 150:16 | soluble Itty decreases because seo to Celje also decreases. In other words that |
|
| 150:21 | temperature you bleed off the C. , right? You've all experienced |
|
| 150:29 | you've taken a can of soda, ? Cold soda in your fridge. |
|
| 150:34 | pulled it out, he took a of sips. You put it down |
|
| 150:37 | the counter, you forgot about He came back the next day. |
|
| 150:40 | warmed up. It's flat, You've led off the c. |
|
| 150:44 | 2. Okay, so in that you're gonna favor precipitation again, assuming |
|
| 150:50 | fluid is saturated with respect to calcium . Higher pressure. If C. |
|
| 150:55 | is in the system is going to forced to react with the fluid that's |
|
| 150:59 | to create the carbonic acid, that's create low ph that's going to favor |
|
| 151:04 | . Okay, now let's think about burial setting. We take our |
|
| 151:11 | we start burying it. What happens temperature? What happens to pressure? |
|
| 151:19 | what's going on? In one case getting dissolution? The other case, |
|
| 151:24 | getting precipitation. What is the real ? The real answer is you're getting |
|
| 151:31 | ? Okay, And what effect comes play 1st? The first effect is |
|
| 151:37 | the pressure. That's when you set your grand grand suturing your pressure |
|
| 151:41 | Skylights and things like that. That's dissolution effect then that dissolved carbonate gets |
|
| 151:47 | out into the adjacent pore fluid re rates and then because of the higher |
|
| 151:53 | locally re precipitates as a poor filling as donor receptor. Dia genesis. |
|
| 152:00 | , so this beautifully this really beautifully burial di genesis, right. And |
|
| 152:07 | sort of explains why historically pressure solutions viewed as a detrimental process. Right |
|
| 152:12 | plug ferocity and kill permeability. But you can see how the two |
|
| 152:18 | operate together. And then the last here carbonate soluble itty increases with organic |
|
| 152:24 | decay because you liberate C. 02 ? As you take organic material and |
|
| 152:30 | bury it, you're gonna start to off C. 02 as you start |
|
| 152:34 | mature that organic material. What other , what other gas species can you |
|
| 152:39 | off Things like H. two Right. And C. 02 and |
|
| 152:47 | two S. Can react with water create acid fluids. Right. |
|
| 152:51 | 02 obviously makes carbonic acid. What H. Two S do? It |
|
| 152:55 | sulfuric acid. And if sulfuric acid can dissolve steel casing in the well |
|
| 153:05 | , it can certainly dissolve carbonate Okay, so you can see how |
|
| 153:10 | are potential agents for what we call dissolution. Alright, of course, |
|
| 153:15 | else could you give off here? can also create weak organic acids, |
|
| 153:19 | the ph and that can also achieve same purpose. Okay, so that's |
|
| 153:25 | that's the fluid chemistry the geochemistry part the story. The key key component |
|
| 153:30 | is the carbon dioxide. and then the other critical control is your starting |
|
| 153:36 | ? So I went through this yesterday I'm not going to go through this |
|
| 153:41 | detail because I'm going to explain this more detail with in terms of the |
|
| 153:46 | of the digest environments. But what did I tell you yesterday? |
|
| 153:51 | rag united heimat calcite are the principal that occur in shallow main carbonates, |
|
| 153:57 | ? Either fixed in the skeletons of organisms or precipitated directly these minerals we |
|
| 154:04 | unstable, which means they're very happy seawater. But when you take them |
|
| 154:08 | of seawater you expose them to air fresh water or you bury them to |
|
| 154:13 | pressure and temperature. They're gonna do they're going to convert to a more |
|
| 154:17 | form of low back calcite. so that's a driver for carbonate dia |
|
| 154:24 | and that's why we need to pay . Always the composition of our sediments |
|
| 154:29 | what the starting mineralogy was. was it a reaganite dominated settlement was |
|
| 154:34 | calc dominated. Okay, so to that in perspective, this is what |
|
| 154:40 | have today and these modern shallow water like the Bahamas. This is what |
|
| 154:45 | have now in the rock record. ? No rag. And I preserve |
|
| 154:49 | my no, no hi Mag calcite . All right, So what have |
|
| 154:54 | done here? We've transformed these two to more stable form of low mag |
|
| 154:59 | . So what's the preferred way of transformation A rag A night? The |
|
| 155:05 | of the carbonate minerals likes to dissolve . That's how you create secondary |
|
| 155:12 | Then what happens? That material goes in the solution locally Re precipitates as |
|
| 155:17 | poor filling cement as it stabilizes to back calcite. Okay, you're going |
|
| 155:23 | 2.95 specific gravity to 2.72 specific gravity when arrogant it goes Transforms to Loma |
|
| 155:34 | , you're creating almost 9% excess calcium . So from a sanitation standpoint, |
|
| 155:42 | could be very important in the in rock record. Okay, now sometimes |
|
| 155:47 | reaganite will do what it will re on a more formal basis to lome |
|
| 155:53 | . You'll see an arrogant coral change a cal siddiq coral. But the |
|
| 156:00 | structures still well preserved. Okay, re crystallization. But there still has |
|
| 156:05 | be a volume change. When you from a Dragon Knight to Loma |
|
| 156:08 | you still have to generate somehow an of almost 9% calcium. Now is |
|
| 156:16 | the opposite. Alright. Hi Michael . Usually just kicks out the magnesium |
|
| 156:21 | a structure. So it re crystallizes Lomax calcite, there's no porosity |
|
| 156:26 | there's no dissolution involved. There's no change. You just lose the |
|
| 156:31 | Okay, that's why all the I've shown you in thin section, |
|
| 156:42 | seen things like the red algae? benthic Foraminifera. The the kind of |
|
| 156:48 | . These were all high neck calcite to begin with. They show very |
|
| 156:52 | preserved fabric. Okay, because they expel the magnetism. There's no |
|
| 156:58 | There's no re crystallization. Alright. mean it is re crystallization, but |
|
| 157:02 | not any secondary process development. that's the norm. Now, the |
|
| 157:08 | flag here is when we see hi hillside grain actually dissolve that. That's |
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| 157:13 | tells you something about the fluid chemistry tells you the fluid chemistry was acidic |
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| 157:18 | to dissolve that. I met Kelsey and almost always, that's a phenomenon |
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| 157:24 | occurs during burial. Okay, so always pay attention and gets dissolved. |
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| 157:29 | expect a rag a night to go early in the diabetic history. We |
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| 157:34 | expect the calcium grains to ever But if they do, that's a |
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| 157:39 | flag for a unique, unique type fluid chemistry. Okay, so let |
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| 157:45 | see if I can get through this lunch. Uh If not, we'll |
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| 157:49 | it up on the other end. going to go through these die genic |
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| 157:52 | . Here are the three major ones . So we're gonna start first with |
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| 157:55 | shallow marine for attic for addict. means the poor system is completely saturated |
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| 158:01 | marine fluid, normal fluid. So you saw the cat ions in |
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| 158:07 | , you saw the salinity right? parts per 1000 in the tropical subtropical |
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| 158:12 | of water supersaturated with respect to calcium . So the major green processes are |
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| 158:20 | to be semente shin and shallow water this process of democratization which involved that |
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| 158:26 | boring activity and then see imitation of , right cement and the microbe |
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| 158:33 | we're not gonna get dissolution in shallow carbonates, we may get dissolution in |
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| 158:37 | water like I alluded to yesterday. , But most of what we prospect |
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| 158:42 | in the rock record or shell water where you wouldn't get this solution on |
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| 158:46 | on the sea floor or in the column. Okay, so remember |
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| 158:53 | we talked about this yesterday. The control here is stability grain sit around |
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| 158:58 | the sea floor. They get attacked micro boring algae and fungi. They |
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| 159:04 | create the mic right envelope which preserves the rock record or they completely micro |
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| 159:08 | the grain to create a pillow or crystalline grain. If if if it's |
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| 159:14 | mechanization, what ends up being the process? It's the center of the |
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| 159:19 | that leaches out or it fills in safari calcite. In other words, |
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| 159:23 | the rock record, we see fabric looks like this. Okay, take |
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| 159:27 | the Mc right envelopes. You would appreciate. That was the grain. |
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| 159:31 | was the grain. That was the . That was the grain. So |
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| 159:35 | a little bit of mechanization is a thing for highlighting the shapes of some |
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| 159:40 | these grains. Okay, so very process on the sea floor I mentioned |
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| 159:45 | quickly this starts right within a few or weeks can make right envelope within |
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| 159:51 | few months, complete grain mechanization within few years. Okay, but the |
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| 159:56 | is to have stability on the sea and not too rapidly bury that stuff |
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| 160:02 | to have it moved around daily by tidal currents. Okay, so it |
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| 160:09 | out for the shallow water carbonate sanitation is a major, major process |
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| 160:14 | for obvious reasons. Seawaters warm, respect, a calcium carbonate. These |
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| 160:20 | the two mineral species that precipitate. good news is we don't destroy all |
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| 160:24 | process usually on the sea floor. the further good news is a little |
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| 160:29 | of marine sedimentation actually creates a rigid that resists later pressure solution. So |
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| 160:36 | is one of the ways for preserving in the subsurface. Okay, so |
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| 160:41 | do you need for precipitation in shallow ? You need stability, but you |
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| 160:46 | persistent high energy. You need the rod. Right? Chemistry one oh |
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| 160:50 | . To precipitate the stuff out of water. It's not gonna come out |
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| 160:54 | a sluggish environment in shallow water. , so those are the faces or |
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| 161:01 | that are susceptible to marine sedimentation. front brain stones. Okay, that |
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| 161:07 | be subtitle or it could be the environment. All right, so I'm |
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| 161:13 | take you through and show you how things are put together and as we |
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| 161:17 | and compare the cement between marine freshwater burial. We want to pay attention |
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| 161:23 | color. Is it cloudy or light color Or is it clear inclusion |
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| 161:28 | whitish and reflected light. What's the fibers means needle like blade. It |
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| 161:35 | stubby crystals. The common term is to spar. So if you have |
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| 161:41 | dog, go look at the dog's , that's where the term comes |
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| 161:44 | Okay. Or is it more equal , where the width and length are |
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| 161:49 | the same dimension? And then what's distribution? I suppose this means it |
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| 161:53 | all the way around the grain except the grain touches with a uniform |
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| 161:58 | Okay, Meniscus means is confined confined a point point of contact between grains |
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| 162:06 | it takes on a curvature. So in chemistry 101. When you filled |
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| 162:11 | a test tube with water, what you get right at the top by |
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| 162:15 | force. You get a little So that's where the term meniscus comes |
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| 162:19 | . Or is an echo dimensional mosaic just fills in the poor system between |
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| 162:23 | grains. Alright, so let's go these and I'll show you how we |
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| 162:27 | this these relationships. This is basically we call comparative sediment ology or comparative |
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| 162:34 | genesis. I'm gonna show you what have in the modern then. I'm |
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| 162:38 | show you how it gets preserved in rock record and how we make that |
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| 162:42 | back to the same process. so we'll start with the Dragon Knight |
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| 162:47 | or aconite is a or ceramic mineral ceramic minerals like to make needles or |
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| 162:54 | tips long crystals like you see So sometimes the crystals are square |
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| 162:59 | Sometimes they're true needles. All And then the question is for that |
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| 163:06 | fabric. What's the distribution? in the subtitle, it's icy packets |
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| 163:10 | ? Where the grain is completely immersed seawater. He end up with an |
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| 163:14 | pack, its distribution in these in carbonate sands. Okay. And you're |
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| 163:19 | to see the colors relatively cloudy. , Because we think there's junk in |
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| 163:24 | water that gets incorporated into the crystal gives it that cloudier color. And |
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| 163:29 | what if you have a larger poor ? Like in a cave? |
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| 163:33 | A reef underwater. Right? Sometimes process is large and sometimes you have |
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| 163:40 | to grow what are called radial fiber . So there are fibers organized into |
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| 163:46 | fan shaped crystals. The crystals take ice. A package distribution. And |
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| 163:54 | that's what you see in these larger systems. Okay, now, to |
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| 164:00 | the story, you can have a or agonized cements and they can precipitate |
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| 164:05 | points of contact. They can fill some of the porosity. And obviously |
|
| 164:09 | could be confused with deposition on Right. Okay. So that presents |
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| 164:14 | problem in the rock record, but need to know that this happens. |
|
| 164:21 | , So let's just look, we'll first with the refill deposits. This |
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| 164:25 | a large chunk of uh brief dynamited from the uh brief complex in the |
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| 164:33 | uh police in the western caribbean. they pulled up this chunk of reef |
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| 164:39 | with the larger core system here. what did they see? They saw |
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| 164:44 | with radial fibrous, cloudy or agonized and ice. A packet distribution. |
|
| 164:53 | . This is the first documented example marine sanitation. A modern reef. |
|
| 164:58 | right. And later people have got dated these kinds of cement with radiocarbon |
|
| 165:04 | . And you can see the numbers . They're they're shown to grow at |
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| 165:07 | of 8-25 mm per 100 years. about this much. Okay, and |
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| 165:13 | is all the cement coming from? coming from seawater. And how is |
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| 165:17 | delivered is delivered every time a wave across the reef, Right, it |
|
| 165:23 | water into the reef system. There's your agitation. There's your stirring |
|
| 165:28 | , it's super saturated. You build . Right? The reef that builds |
|
| 165:32 | own stability. So, this is marine sedimentation on a reef. |
|
| 165:37 | involving arrogant. Here's the ancient This is the Permian reef complex from |
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| 165:43 | texas. Um Dunham described all of cement as freshwater cave cement back in |
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| 165:50 | 1950s. And you couldn't argue with because nobody had a modern analog back |
|
| 165:55 | to say, nope, that's not case. All right. Look at |
|
| 165:59 | attributes of these cements. You can the little fan shaped crystals. And |
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| 166:04 | have that orientation. They still preserve of that cloudy color and they go |
|
| 166:09 | the way around the cavity spaces. right. Dead ringer for marine |
|
| 166:16 | And people suggested this in the Right? Because they see these cement |
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| 166:20 | like this. Then they get encrusted red algae. Then they grow and |
|
| 166:23 | get encrusted by red algae. But had a modern analog. So nobody |
|
| 166:29 | , you know, compelled to call marine cement. Nobody could argue with |
|
| 166:32 | . Okay. But this is what look for in the rock record. |
|
| 166:37 | not a reaganite anymore. Right. calcite. So despite the transformation from |
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| 166:42 | calcite, still preserve the morphology, distribution and some of the color and |
|
| 166:48 | the way, color is at least of these of these points. |
|
| 166:55 | All right. And then the high sites, the other common species, |
|
| 166:59 | likes to precipitate again. Asthma critic either points of contact or lining for |
|
| 167:05 | like you see here or likes to as stubby little bladed crystals with a |
|
| 167:10 | alpacas distribution. Alright, this is about in the literature, but I've |
|
| 167:16 | seen anybody show a picture of So, I don't I don't believe |
|
| 167:20 | until I see a picture. All . So that's why I put the |
|
| 167:23 | through there. But I still in the years, I've looked at |
|
| 167:26 | I've never seen fabric that looks like . That's side. So here's an |
|
| 167:32 | from a modern hard ground in the . This sustained with Clayton yellow for |
|
| 167:38 | medical side, we actually have the goods have a first phase of marine |
|
| 167:44 | pack is fibrous cement that goes around . Okay, and I'm sorry I |
|
| 167:51 | the slide. My apologies here. . And grain stones, let me |
|
| 167:58 | up your somehow, my computer just ahead. And grain stones, |
|
| 168:04 | you little grain stones, This is newly grain stone. You don't have |
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| 168:07 | big enough poor system to put fan radial fibers to agonize cements. So |
|
| 168:13 | do you put you put little needle ice pack? Ice pack is fringes |
|
| 168:18 | arrogance around the grains. Okay, a common style and a grain stone |
|
| 168:23 | the poor system is smaller. So the ancient analog. This is part |
|
| 168:28 | the Permian complex in west texas where got the marine sedimentation in the |
|
| 168:33 | This is the back brief grain These were gassy cloud green algae that |
|
| 168:38 | on an coating. So here's the energy faces. Look at the first |
|
| 168:43 | of marine see imitation relic need to cloudy cement that go all the way |
|
| 168:50 | the grains. Okay, so by , this is interpreted to be a |
|
| 168:55 | or agonized cement first and then later different phase of cement to plug the |
|
| 169:00 | of that ferocity. You see the we're playing here. This is called |
|
| 169:05 | sediment ology or more specifically comparative die . Okay. And so that's the |
|
| 169:12 | story and then story. This is high medical side story and here you |
|
| 169:18 | again a sample that has two phases marine cement. The first is the |
|
| 169:22 | or reaganite and then the second is critic, I'm at calcite cement. |
|
| 169:28 | why is this cement and not deposition mike. Right, Well, first |
|
| 169:33 | all, there's no other skeletal material in here. Right? It's all |
|
| 169:37 | . A critic fabric. The answer this is this relationship right here. |
|
| 169:42 | see this black porosity here. The system is lined with the red acrylic |
|
| 169:50 | . If this is deposition of nick , you would have created a geo |
|
| 169:53 | , right? You would have filled the bottom up. But you don't |
|
| 169:56 | that. You see why this has be cemented. It's on the top |
|
| 170:00 | the ferocity that can't be mechanical deposited mud and it's highly unusual line mud |
|
| 170:09 | be uniformly heimat calcite. Most of modern line is principally Iraq genetic with |
|
| 170:15 | heimat calcite material extent. Okay, this is hi Mag calcite. The |
|
| 170:21 | cement. Okay, I don't have I can't show you an ancient analog |
|
| 170:26 | what's gonna happen to this fabric is to transform the calcite and I told |
|
| 170:31 | a rag and I can also precipitate um a critic texture. So all |
|
| 170:37 | can do is when I go back the rock record. I can show |
|
| 170:40 | an ancient example like this where you the U. Ids in the first |
|
| 170:44 | of fibrous cement, which is probably reaganite because of the morphology and then |
|
| 170:50 | see this critic fabric here in a sorted high energy grain stone. This |
|
| 170:55 | probably not Mick, right? This probably a cement, right? Because |
|
| 170:59 | high energy you would say and you have a lot of Mc right in |
|
| 171:02 | system, right? It would winnow . But the question in the rock |
|
| 171:06 | is we could never prove whether that a reaganite Mc. Right cement or |
|
| 171:09 | MYC calcite Mick. Right cement. is it was you have to speak |
|
| 171:22 | because of that. Like uh geo , it'll fill from the bottom |
|
| 171:34 | If it's introduced into a sand, will fill the poor system from the |
|
| 171:39 | up. So you will never have you don't completely, if you don't |
|
| 171:45 | fill it, you will never have on the top here. Okay. |
|
| 171:50 | guess I'm uh part side. I'm like the bottom of crops for |
|
| 171:56 | Well, I'm telling you up Okay, that's why I put the |
|
| 172:01 | . So when we put the arrow these photographs, that usually means up |
|
| 172:05 | . Sorry. Yeah, we always to know up direction. So when |
|
| 172:09 | collect a sample in the field, first thing I do is I mark |
|
| 172:11 | direction with an arrow and then we that through to the finder scale observations |
|
| 172:18 | it's thin section or or anything. , so we always want to know |
|
| 172:23 | direction, so that I see your . All right. So you see |
|
| 172:27 | didn't fill from the bottom up. we lined the whole poor system. |
|
| 172:31 | has to be precipitation to do Okay. But I never Yeah, |
|
| 172:43 | . Sometimes I take things for And so it's good that you ask |
|
| 172:47 | ask if something doesn't make sense. . So, okay. And you |
|
| 172:53 | , it's if you guys don't I'm gonna try to finish this section |
|
| 172:57 | and then we can take lunch and give you the extra time for |
|
| 173:01 | So, I've got a few more to go through and we'll just get |
|
| 173:04 | over with and then we'll switch to next hygienic environment after lunch. |
|
| 173:09 | So the beach environment I mentioned is a site where you can get marine |
|
| 173:16 | . Alright. And that can involve mineral species origin and heimat calcite with |
|
| 173:22 | kinds of distributions. You can also more critical reaganite or heimat calcite and |
|
| 173:27 | beach cemented environment. But what's unique a beach is right, there is |
|
| 173:32 | slope to a beach, right? there's low tide and high tide. |
|
| 173:37 | what happens at low tide? The drains down. Right. And so |
|
| 173:41 | the upper part of the beach, do you do you trap water on |
|
| 173:45 | undersides of grains by capillary force. sometimes you'll favor precipitation on the bottoms |
|
| 173:51 | these grains. Okay, So that's wouldn't see this underwater, but you |
|
| 173:57 | see in a beach environment. So you see that. All right. |
|
| 174:01 | this is a closer photograph of, showed you that google photograph yesterday with |
|
| 174:07 | white. You would stand body system the bank that I study for my |
|
| 174:12 | . So this is part of one those analytics shoals and part of that |
|
| 174:16 | body is already built up to make island and look look along the |
|
| 174:21 | Here there is this uh dark zone here. That actually occurs all along |
|
| 174:26 | . Just gets covered by sand That's what we call beach rock. |
|
| 174:30 | part of the beach sand that gets in place. Alright. That's called |
|
| 174:34 | rock. And why do we want recognize beach rock? Because it tells |
|
| 174:38 | that's basically the intertidal zone. So for working older carbonates, we |
|
| 174:44 | to know where sea level was within few feet. Right? And so |
|
| 174:47 | always important to recognize beaches or tidal or beach rock for that reason. |
|
| 174:52 | right. And this is what it like on the surface. And the |
|
| 174:56 | is only about this thick. All . And then you go back and |
|
| 175:00 | sediments. So it's just the surface the beach sand that gets cemented in |
|
| 175:04 | . And then you know, sometimes storms will wash some of the sand |
|
| 175:07 | underneath and the and the stuff will and crack like you see here. |
|
| 175:12 | that's an artifact of that effect. then when you look at the |
|
| 175:16 | you see the analytics. Sand Alright, so you see the |
|
| 175:22 | it's a grain stone and you can the typical ice pack is fiber |
|
| 175:27 | I'd but you see these funny shaped . That's the beach bubble porosity we |
|
| 175:32 | about earlier. Right? That's where air gets trapped in the, in |
|
| 175:35 | beach sand. If there's air there water, no water exchange, no |
|
| 175:41 | . Right? You don't see any . So the combination of the finesse |
|
| 175:45 | fabric. Sometimes the gravitational cements. , the stratification style would be low |
|
| 175:53 | seaward dipping, right general seaward dipping stratification. Those would allow you to |
|
| 175:59 | that as a beach rock deposit. , Alright, so let's just summarize |
|
| 176:07 | and then we'll break for lunch. a couple of slides, where's your |
|
| 176:11 | briefs imitation is where you get the energy faces. Right? You need |
|
| 176:14 | stirring rod and shallow water to promote . So that's gonna be the |
|
| 176:19 | That's gonna be the energy grain stone like goods for scalable stance. |
|
| 176:25 | And cement distribution is controlled by water . So that's either tidal currents or |
|
| 176:33 | oceanic swells on reefs or you're going learn that the trade winds also provide |
|
| 176:38 | agitation and promote segmentation. The good is that sanitation is confined to the |
|
| 176:44 | water interface you're not gonna lose all of your process on the sea |
|
| 176:50 | . Strong faces control for marine sanitation we can use the presence of marine |
|
| 176:56 | actually as a faces attribute which we're to do next weekend. Okay. |
|
| 177:01 | then those are the cement species. next weekend I'm gonna give you a |
|
| 177:08 | tour of modern carbonate environments and then going to put in the context of |
|
| 177:12 | end member models and one end member , this is a shallow water carbonate |
|
| 177:19 | Developed in less than 10 m of depth, dropping off into a really |
|
| 177:23 | water basin. Historically in this the focus of my energy is right |
|
| 177:28 | where oceanic swells and tidal currents and . That's where you get the marine |
|
| 177:34 | . No marine sanitation back here because too my critic and too low |
|
| 177:38 | Okay. And usually you don't see further down the slope. Okay, |
|
| 177:45 | the story for the northern Bahamas that's by oceanic swells and tidal currents. |
|
| 177:50 | you go to the southern Bahamas, is called keiko's platform, I'm going |
|
| 177:54 | show you the same de positional but look at the greater extent of |
|
| 177:59 | sedimentation because the trade winds not only the margin along with oceanic effects swells |
|
| 178:07 | currents, but they also agitate the interior, it's not muddy bacteria, |
|
| 178:13 | carbonate sand and so that stuff is to precipitation and marine sanitation. So |
|
| 178:19 | where the trade winds play a role the distribution these brain cement and then |
|
| 178:24 | other end member model is the carbonate model by definition the slope angle from |
|
| 178:30 | to the basin is one degree or . The basins in this model are |
|
| 178:35 | very deep, a few 100 m water depth or less. Okay, |
|
| 178:40 | this profile, where do you get marine sedimentation closer to the shore |
|
| 178:45 | where you have impingement of currents or wave agitation? You don't get oceanic |
|
| 178:51 | here because you're not in a deep basin. Okay, so there's no |
|
| 178:56 | here to speak of, it's carbonate bodies and the high energy sand bodies |
|
| 179:02 | prone to marine sedimentation. No segmentation it. No, see imitations. |
|
| 179:07 | go into deeper water unless you have and sedimentation of deeper water. |
|
| 179:13 | and that's the point here, we low rates of imitation. Okay, |
|
| 179:19 | I said beyond the same with the money, there's no reef in this |
|
| 179:26 | . That's deep water to sample little reefs, but no linear barrier reefs |
|
| 179:37 | we have in the classical oceanic settings the Bahamas. Okay, so these |
|
| 179:43 | just little tiny reef complexes. Sorry, what I meant was there's |
|
| 179:50 | linear barrier reef that we have in other model. Right, If you |
|
| 179:54 | back to, So this situation the reef here would be more of |
|
| 179:58 | linear barrier reef developed on the Okay, and here we're talking to |
|
| 180:03 | rand model and we're talking about If you have some older pre exhaust |
|
| 180:08 | existing topography can get a little isolated develop their this point here that I |
|
| 180:21 | , Yes, I mentioned this morning I showed you a hard ground from |
|
| 180:24 | Austin shock. I said in deeper , if you have pauses and |
|
| 180:31 | non deposition, you have time to circulate seawater through that deeper water |
|
| 180:38 | you can submit the top of that . You can make these thin little |
|
| 180:41 | grounds. That's different than in shallow where you have more persistent agitation. |
|
| 180:49 | seems counter intuitive, doesn't it? talking about white sands that are high |
|
| 180:53 | , but I'm talking about them being together. How do you do |
|
| 180:57 | Well, I'm going to try to that next weekend. Okay, when |
|
| 181:01 | take you through the environment, I'll you how you make these a little |
|
| 181:04 | graphs. Okay, any questions before break for lunch? Okay, so |
|
| 181:13 | gonna come back for those of you , We're gonna come back at uh |
|
| 181:20 | . Okay? We have an hour lunch. So I'll see you around |
|
| 181:26 | minutes to to |
|
