| 00:00 | Yeah. OK. Uh We're gonna about estuaries. Um The um list |
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| 00:09 | uh useful readings is long. Uh , this is for your reference and |
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| 00:14 | everything is on the, the uh uh fold in the reading folder and |
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| 00:21 | things that have included or not. It's kind of hard to, to |
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| 00:26 | what to push. There's been a of literature done in the last few |
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| 00:31 | . Uh But let's look for a at this diagram we've seen before and |
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| 00:37 | , it's arguably it tries to differentiate depositional environments associated with transgressive settings and |
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| 00:47 | settings. And when we do that we look at uh the transgressive |
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| 00:54 | Well, let's see, we've done planes, barrier islands, tidal |
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| 00:58 | And so it leaves estuary. So we're gonna be doing that, but |
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| 01:02 | would remind you that no strand planes in both a, a uh regressive |
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| 01:10 | transgressive setting. And in fact, our deltas and, and other uh |
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| 01:18 | uh uh estuaries of sorts. So take this diagram literally. Uh because |
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| 01:24 | , one of the things that I you, you get from these lectures |
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| 01:29 | the types of depositional systems associated with and regressive settings doesn't necessarily mean uh |
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| 01:40 | and lowering sea level. OK. there we can get regressions during rising |
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| 01:46 | level, we can get transgressions during sea level. All depending on the |
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| 01:52 | amount of accumulation space sediment supply. we're gonna see different ways that we |
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| 01:58 | transform or change these uh depositional Now, it's useful to know what |
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| 02:05 | mean by an estuary. Uh You think of it as uh an area |
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| 02:10 | uh basically transitional uh salinity, brackish in essence, or you could think |
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| 02:17 | it with tidal influence. Uh how upstream there's a tidal influence uh or |
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| 02:24 | could do on the basis of, . Uh Basically combining the processes and |
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| 02:31 | result in geological faces uh into different . And that is, of |
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| 02:36 | uh more of a geological approach. so I'll be using that having said |
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| 02:42 | , let me pause just for a . I was an expert witness in |
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| 02:45 | trial where it had to do with subsidence and whether or not um a |
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| 02:56 | group was liable for uh the loss property due to subsidence in a, |
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| 03:05 | I would say, a fluvial OK. Uh Well, it turns |
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| 03:10 | that I was using the geological but finally, the, the legal |
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| 03:19 | is based on tidal influence. And this was on the San Center River |
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| 03:26 | there's a tidal imprint all the way to lake Houston. So the San |
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| 03:32 | rivers all the way to Lake Houston a quote estuary. Now, no |
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| 03:38 | would define it that way. it's unidirectional currents, there's no reversal |
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| 03:45 | flow. There's no effect of tides sedimentation. But from a legal point |
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| 03:53 | view, uh it's, and just I decide, my client, I |
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| 03:58 | for a lost case. Ok. , here we've got, um, |
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| 04:07 | to like me, uh, get pen uh salinity. Oops, salinity |
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| 04:19 | . That would be one definition of word upstream. A little more. |
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| 04:23 | could be a lot more uh in san river tidal influence. That would |
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| 04:28 | another definition. But we're going to . Yes. And is more or |
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| 04:37 | coincident with the salinity. But it's , it's where the title processes end |
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| 04:45 | it's easier to visualize here. Uh are really marine processes. Here is |
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| 04:54 | and that could be waves and, tides. Uh We've got the fluvial |
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| 05:01 | getting less and less. And so when they begin to, to uh |
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| 05:08 | , that's the beginning of the estuary the estuary ends when it's virtually all |
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| 05:15 | and in between, we've got an , central and outer estuary depending on |
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| 05:21 | or not they're sub equal, mixed in this case, marine dominated or |
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| 05:26 | dominated. Now, Galveston Bay is big estuary. It's one of the |
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| 05:31 | national uh estuaries. Uh And I've modified a little bit to kind |
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| 05:37 | focus on some of the set of . Um The thing about where the |
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| 05:42 | is coming from, but maybe more is to look at the type of |
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| 05:48 | in Galveston Bay. And so basically about sand and mud. Uh the |
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| 05:59 | uh is here and that's gonna be and title delta. It's gonna be |
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| 06:10 | here with wash over fans and blood delta. And then there's a little |
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| 06:17 | of sand fringing the estuary and that's to uh erosion on the backs. |
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| 06:23 | you don't see much is sand in deltas. And the reason for that |
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| 06:28 | these deltas have been largely um submerged to subsidence and sediment reduced due to |
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| 06:38 | . Ok. So, uh so mud in the central part. |
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| 06:45 | So let's see what uh that would like. Uh You can kind of |
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| 06:49 | this for a night. Now, We'll, we'll talk about this |
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| 06:53 | but look at where the sand was and suggestion is, there's a |
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| 07:02 | there is a bay head delta here a central basin, ok. The |
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| 07:07 | basin is gonna have muds and it's transition for waves at least. Or |
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| 07:15 | wave impact cuts is uh is very much how far into the |
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| 07:24 | the wave dominant estuary, the sand , it's either gonna be a wash |
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| 07:28 | fan or an tidal delta. So it's not gonna go very |
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| 07:33 | Uh That sand and mud will extend on how big the bay delta is |
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| 07:44 | the central basin kind of depends on size of the basin. So what |
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| 07:48 | see here is that they had the wash overs and flood de deltas |
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| 07:55 | this large central base, ok. this this particular estuary, this wave |
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| 08:03 | estuary of Galveston Bay formed was initiated the rise and high standard sea |
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| 08:14 | Now, similar estuaries were in existence in the Colorado where in the Brazos |
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| 08:22 | just south of us, but there's estuary today. The reason is those |
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| 08:27 | fill. This one has not. we could anticipate what would happen if |
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| 08:35 | San Center River and Trinity River could Galveston Bay. And, and that's |
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| 08:43 | we're visualizing here. That is the of filling the bay well in cross |
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| 08:52 | and in um mat view. And this is Galveston today, Galveston's basically |
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| 08:58 | an unfilled bay, an unfilled OK. Now, it's pretty easy |
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| 09:05 | imagine the delta filling the bay, ? Until such time is, is |
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| 09:14 | filled. Now, the one exception that I would point out here is |
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| 09:22 | the bay is also filling by the landward migration of the estuary. I |
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| 09:31 | , I'm sorry, of the OK. Uh That's what's shown |
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| 09:36 | OK. And so the landward migrating and the seaward migrating delta merge uh |
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| 09:47 | form a waved dominated delta basically Now, we actually, that doesn't |
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| 09:56 | to happen that way. Um You have this barrier island continued to be |
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| 10:05 | or even pro greedy. In that's what happened to Galveston. Galveston |
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| 10:11 | It even though it did not have sediment passing from the bay head delta |
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| 10:20 | uh the marine environment. And the for that is the bay was too |
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| 10:26 | . And so the sediment that was , allowing the barrier island galaxy to |
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| 10:33 | was coming in from lands shore from longshore drift. So, erosion of |
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| 10:38 | Headlands adjacent headlands. OK. So here's the bay, here's the barrier |
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| 10:50 | is gonna allow the barrier to grow as the delta can grow as |
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| 10:59 | Ok. So those are two very scenarios of filling a waved dominated delta |
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| 11:06 | on the relative uh amount and source sediment to the barrier island. Does |
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| 11:13 | barrier migrate and fill in the inland the marine side or does it migrate |
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| 11:19 | ? And the estuary has to be filled from the delta. Now, |
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| 11:26 | is a cross section of what might . Ok. And um it's an |
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| 11:32 | cross section to spend some time Ok. Um Down on the |
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| 11:40 | we have what is in essence, entrenched valley base and as sea level |
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| 11:47 | to entrench, I mean, it to rise, it's gonna fill to |
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| 11:53 | extent. OK. And it's gonna from pluvial to urine and look what |
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| 12:02 | here, the rev service. So is a transgressive barrier island that's deviling |
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| 12:15 | estuary. Ok. And what's happening the bay where the bay, the |
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| 12:22 | valley is getting filled with sets. as sea level rises, that bay |
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| 12:30 | farther and farther inland until at some , maximum transgression of the bay |
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| 12:39 | And at that point, as sea slows down and river input is stable |
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| 12:45 | constant yet the river and more the bay had delta begins to |
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| 12:52 | And so that's what's happening here. notice at this point here, the |
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| 13:01 | delta has filled the bay, there's more bay or set up. And |
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| 13:08 | look what happens here that transgressive a transgressive barrier islands has become a |
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| 13:19 | waved dominated delta. OK. this shows it in a little more |
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| 13:29 | in some ways, more simplified in . I want you to look, |
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| 13:33 | of all at that rave surface, ? That rave surface is truncating the |
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| 13:41 | and the bay settles and what do have in a bay that's not eroded |
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| 13:47 | . Things that are either extend too inland to be eroded like a wash |
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| 13:53 | fan or tidal deltas or title So that's what's shown in here. |
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| 14:01 | are little uh titled inlet fills and wash overs and uh subtitle uh uh |
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| 14:10 | overs and uh flood tidal deltas, ? Uh Notice this actually includes the |
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| 14:18 | stand here when that entrenched valley hit stand. You then had a low |
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| 14:25 | delta. And now we have a standard delta. Yeah. And this |
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| 14:31 | kind of dividing it uh to a the maximum flooding service representing the transgression |
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| 14:42 | with transgressive deposits and regressive deposits. also most of the bay fill is |
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| 14:53 | filled during the transgression. Most of delta fills or more specifically, uh |
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| 15:01 | the marine delta Phil is during the stand or tropic sea level. |
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| 15:08 | there's a lot of erosion that's going here and I'm, it, it |
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| 15:11 | a little confusing. I'm just gonna out 2 uh Maybe three erosional |
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| 15:20 | One is the entrenched valley, that's a sequence boundary. It is the |
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| 15:29 | of the valley. The 2nd 1 the rave of surface that is the |
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| 15:37 | formed during rising sea level and wave . That's during the transgressive system. |
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| 15:46 | , there are some little erosional surfaces are due to lateral migration of that |
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| 16:02 | . So there's an erosional surface at base of the title. It doesn't |
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| 16:08 | very far. OK. But it's to show you erosion and deposition as |
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| 16:13 | . So that's what is called a that surface. OK. So there's |
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| 16:22 | , a good example with the Tiber in Delta where they have a lot |
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| 16:26 | control on the cross section from. , so this is our hypothetical and |
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| 16:36 | is the reality. OK. So wanna look at this cross section in |
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| 16:41 | little more detail. OK? And that here is that basal sequence boundary |
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| 16:53 | . I'm sorry um valley erosional OK. Here is that wave of |
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| 17:05 | as it's coming in and it's truncating the bay fill. Uh But you |
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| 17:14 | see a little bit of wash over that are formed during that, that |
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| 17:22 | preserved, formed and preserved during the transgression. Eventually the delta plane begins |
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| 17:34 | fill the bay and now we're getting new delta. It's a high stand |
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| 17:46 | . OK. So if we looked a vertical section right here, we |
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| 17:53 | this erosional surface which is the valley , we see the fluvial deposits, |
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| 18:00 | see the bay deposits, oops and we began to see the pro |
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| 18:13 | We, in this case, wave delta. OK. With another erosional |
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| 18:20 | here is the wave of the So again, you can look at |
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| 18:27 | and see if you can work out these boundaries are in here. |
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| 18:37 | And you can do that on your . Now, if we were to |
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| 18:41 | at that in cross section right OK? And before the bay is |
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| 18:48 | , I guess, really better say right about here, might look something |
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| 18:53 | this. This is, in the cross section of the Buried Valley |
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| 18:59 | around Galveston Island. This on the is Galveston Island. On the right |
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| 19:03 | Bal, the peninsula in the middle b of the roads. It, |
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| 19:07 | what we see lower part flu transgressed flooded valley fill estuary and then pro |
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| 19:21 | into and separating the S S U ware from the marine environment, the |
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| 19:28 | bar and tidal sands. OK. that's what you would see here. |
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| 19:40 | . I got it here. I think you can also imagine if |
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| 19:47 | took a cross section of the Valley in different places, it's gonna look |
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| 19:53 | different, but it's not that hard visualize what they would be like if |
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| 20:00 | can visualize this kind of uh sequence , this this wave dominated face track |
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| 20:09 | time. OK. Now we talked waved dominated deltas, let's and waved |
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| 20:18 | environments. And we're talking about barrier as well to tide dominated settings where |
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| 20:25 | gonna talk about estuaries and tidal Well, we've already talked about tidal |
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| 20:31 | . So let's move over laterally. at those tide dominated estuaries. So |
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| 20:37 | we are down here. OK. let's look at this like we did |
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| 20:45 | waved dominated delta. Yeah. Uh , we have the decrease in the |
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| 20:54 | of fluvial currents and sediment. And here though the marine influence actually increases |
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| 21:05 | decreases with time. So the upper is pretty much like we saw |
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| 21:15 | But now there's an increase and the energy as we move into this funnel |
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| 21:27 | , we talked about that on a scale. We talked about the North |
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| 21:33 | , the German Light. So we're that wedge, a wave of tides |
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| 21:41 | they're getting higher. OK. the amount of notice here we've got |
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| 21:50 | and you also get some waves but much. OK. So this is |
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| 21:56 | tidal influence. Tidal maximum is right here. We have convergence. |
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| 22:12 | bidirectional river flow, blood dominated versus . This is where you get |
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| 22:23 | a huge amount of suspended setup. ? Um And this has important implications |
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| 22:33 | we'll talk about a little more with to fluid muds. But basically, |
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| 22:38 | is the zone of sediment convergence. . If we look at the fluvial |
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| 22:46 | , they're still getting increasingly i impacted tides. And so as we go |
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| 22:53 | upstream to downstream, we're seeing more more tidal influence. We're getting inclined |
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| 23:02 | strata that we talked about earlier except , instead of being in that little |
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| 23:09 | creek, it's in that tidally influenced Chin. So just here's a I |
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| 23:19 | like the uh example zone of bed convergent. This is where most of |
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| 23:24 | sedimentation occurs where most of the suspended is concentrated. You get pluvial dominated |
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| 23:40 | , oddly dominated here. OK. you begin to see this pattern. |
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| 23:48 | these V shaped tidal deltas with elongated bars rating upstream into this highly meandering |
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| 24:01 | in which most of the settlement, bed load and mud are being |
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| 24:08 | Now let me give an example of uh permian gas field in Australia that |
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| 24:16 | illustrates both these faes components and their properties. OK. And in |
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| 24:24 | we're gonna look at the petrol petrol . It's a gas field in offshore |
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| 24:32 | . Ok. And I'm not gonna this, it just, uh, |
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| 24:37 | have those in the notes but it you something about, uh, the |
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| 24:41 | of, um, performance is about half a billion barrels of reserve. |
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| 24:48 | , barrels equivalent, um, of petroleum is got about or condensates |
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| 24:56 | four billion barrels of oil equivalent for . Ok. Uh, with peril |
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| 25:05 | up to 2.5 to 6. So here it is geographically in this |
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| 25:10 | line that we see here, that's shoreline during the mayo. OK. |
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| 25:16 | so what we see is that during MCE, there were tie dominated deltas |
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| 25:29 | this area here in wave dominated deltas strand place elsewhere. So this is |
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| 25:39 | that wave dominated delta looked like. the tidal flats give us our fining |
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| 25:46 | sequence. We've done that to The tidal sand bars. Now, |
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| 25:51 | really a kind of a new, , we talked a little bit about |
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| 25:55 | sand bars as associated with lower tidal flats and just offshore. But now |
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| 26:01 | talking about these linear tidal sand bars are filling the estuary, OK? |
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| 26:10 | they're coarsening upward. And if we at them in a little more |
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| 26:14 | uh we see that this is the of the uh sandbar. Uh It's |
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| 26:22 | different faces that's basically uh coarsening Uh It's clean, a little more |
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| 26:32 | , not quite as clean to hetero bedding with interbedded mud and sand stuff |
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| 26:41 | here. We've got interbedded, uh lithic betting that's actually forming on the |
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| 26:47 | bottoms between the channels. Ok. The next two slides are for you |
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| 26:53 | look at on your own. Uh about the type of sedimentary structures within |
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| 26:59 | face and some more details about the , etcetera. Again, that uh |
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| 27:06 | wait until you have time. What's to note right now is that when |
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| 27:12 | look at the permeability and ferocity, reservoirs are sitting up in this area |
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| 27:22 | which are mainly type one and type um Species, species two A or |
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| 27:32 | B maybe. This is where your porosity and permeability and take a look |
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| 27:43 | the difference between this say type one up here in this type for sitting |
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| 27:55 | down here. OK. You've got complete loss of permeability and that loss |
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| 28:03 | due to for cement. Why didn't lose it here? Because you had |
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| 28:11 | digenetic chloride Cody over the graves. just as we saw in the Norfolk |
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| 28:19 | with the Olean reservoirs where under certain you were able to preserve and or |
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| 28:29 | the chloride coatings and therefore inhibit for . There were certain conditions that were |
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| 28:39 | to the formation and preservation of chloride in the estuary as well. So |
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| 28:49 | estuary actually evolved through time during a stand. It was a wave dominated |
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| 29:02 | . OK? And even during the in sea level, it was a |
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| 29:09 | dominated estuary. The problem is you good sands, clean sands, but |
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| 29:19 | were filled with or cement as The estuary evolved from a wave to |
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| 29:28 | tide dominated estuary. You've got a presence of the clay coatings which allowed |
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| 29:38 | permeability uh to, To these depths actually pro abilities were up to 25 |
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| 29:46 | 100. Now, there was a study to just compare that interpretation with |
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| 29:57 | reservoir study and is of the uh in France. And it's got pluvial |
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| 30:07 | delta, uh central basin, outer . Now this is a wave dominated |
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| 30:16 | estuary. But when you begin to at the, I'm sorry, uh |
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| 30:22 | , it's a tie dominated estuary, very elongated. There's no real barrier |
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| 30:29 | here. It's mainly linear bars. if you look at the upper bar |
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| 30:41 | of the bar, uh you get clean sand. When you look at |
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| 30:51 | base of the bar and the between , you get a lot of, |
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| 30:58 | yeah, the trid uh muds, ? And if you look at |
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| 31:11 | where the best most well sorted sand it at the top here? |
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| 31:19 | Um And I'm gonna skip this a bit except to say that when you |
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| 31:26 | at the composition of the title from top to bottom and from inner |
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| 31:48 | this was the inner one from inner estuary to or the outer estuary down |
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| 31:54 | , the inner estuary, which is . OK. You, you see |
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| 32:01 | differences and notice down in here, a lot of lithic fragments and mica |
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| 32:08 | the like and some clays that you get in the upper part. |
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| 32:16 | I'm not gonna discuss these except these the finding upward sequences that we saw |
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| 32:24 | those title channels. Instead, let just summarize and, and again, |
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| 32:29 | is for you to read at your . But what was the case with |
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| 32:33 | Jerome as well as with the Petro ? The Jeron tidal bars and the |
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| 32:42 | reservoirs is the best reservoir quality to with is in the outer este |
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| 32:50 | And more specifically at the top, have the least amount of clay. |
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| 32:59 | they tried to clay and they had most amount of clay coatings. So |
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| 33:05 | is an ideal initial conditions for the of reservoirs. But as we're gonna |
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| 33:15 | in just a moment, the problem you need to preserve the top of |
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| 33:24 | . They try to bars and the of these kind of these linear |
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| 33:33 | the top of linear tidal bars are preserved during transgressions and they are not |
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| 33:42 | well preserved during regressions. I'll explain in a moment. But what that |
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| 33:48 | is that you're best reservoir qualities are to be underneath that clay seal representing |
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| 33:59 | the transgression. So they're gonna be lower parts of these or the the |
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| 34:10 | linear bars. Ok. Not the linear. Yeah. Is like |
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| 34:43 | is that the start of the or is it? OK. Uh |
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| 34:50 | , the question was uh do the begin to be preserved during the |
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| 35:00 | Um I'm actually gonna talk much more that when I talk about shelf settings |
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| 35:05 | . But uh certainly as a our model is that we tend to |
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| 35:11 | shales offshore grading into sandstones onshore. during a transgression, yes, we |
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| 35:17 | get more and more sand, more more us. Ok. More and |
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| 35:22 | mud rocks. Um The there's also an individual faces though kind of lateral |
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| 35:34 | between shale and sand. So, example, with the um your second |
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| 35:45 | if we did. So if we |
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