| 00:08 | you're right. Uh, they had Gs first for our floor office, |
|
| 00:41 | yeah, a couple of things on exam. Uh, I will get |
|
| 00:52 | great as soon as I can and will actually go over it tomorrow |
|
| 00:57 | So, uh, have any immediate you can ask you now in the |
|
| 01:05 | . The second thing I've been advised the reason we don't have coffee because |
|
| 01:10 | the corona, uh, constraints. so let me suggest you not provide |
|
| 01:19 | and that's also, uh, in of local. Uh, again, |
|
| 01:31 | , so it's either that or we winding. Uh, so, |
|
| 01:40 | that's, that's unfortunate. That is years. Um, the union |
|
| 01:50 | No, I don't think so. anybody have any questions that you |
|
| 01:55 | Is this for water to function? . Okay. Uh, last time |
|
| 02:04 | covered alluvial fans and more specifically recovered flow and sheep. So fans, |
|
| 02:10 | we ended with this question, are really distinctions between, uh, those |
|
| 02:19 | types of fans, these larger stream fans. And um, you'll recall |
|
| 02:26 | if you look at slope, for , there does seem to be some |
|
| 02:30 | uh, distinct differences though there in fact a few in between, |
|
| 02:36 | ultimately it, it does look like a, at least some degree |
|
| 02:41 | by modality between, uh, these fans. Um, yeah. |
|
| 02:53 | chief in the larger, so called fans. Uh, and that introduces |
|
| 03:00 | whole terminology. That is a bit . I will talk about distributed flulaval |
|
| 03:10 | and within that, I will love be smaller, bring forward. Chief |
|
| 03:17 | all things you need the so called of fans go by many names. |
|
| 03:25 | , it's almost a pick and I used mega fan kind of |
|
| 03:30 | Uh, and more or less I a consistent mm uses the length of |
|
| 03:41 | fan is pretty good first approximation, small meeting more uh, these small |
|
| 03:49 | with steep slopes or these pope alluvial And then the larger fans he breaks |
|
| 03:56 | into the intermediate. The popular would an example of the uh, medical |
|
| 04:02 | China, uh, maybe 30-100 Let's keep them close. And then |
|
| 04:08 | fans even bigger than that. I wanna hold too fast this |
|
| 04:14 | Um, but just recognize that it great asian because once people started using |
|
| 04:20 | specifically, once people started looking at , uh, satellite imagery, |
|
| 04:27 | they were able to look at hundreds fans and they realized that uh, |
|
| 04:32 | really had a pretty small sample. there's this very wide extreme a fan |
|
| 04:39 | and patterns. So for example, of the things we look at with |
|
| 04:45 | DFS distributed through the system is that , they, there's a range of |
|
| 04:56 | . Oh, very in part with to relative to charge. And what |
|
| 05:03 | means is the consistency or irregularity of that ephemeral with spikes of floods and |
|
| 05:15 | . Mhm. Such as you find the desert or is it more consistent |
|
| 05:21 | you find in the industry and also with radiant sediments upon now hardly. |
|
| 05:31 | others were the first to really put together using satellite imagery. Davidson kidnap |
|
| 05:41 | little later said, you know, gonna subdivide, do a little lumpy |
|
| 05:49 | I'm going to look at braided bifurcated threat. He answered in multi credit |
|
| 05:59 | . So you're you're looking at two streams and the extremes. Great advice |
|
| 06:07 | pain, brady gaster movie. And that's going to give us pretty the |
|
| 06:14 | models. Uh, and I use term model loosely. uh, but |
|
| 06:20 | D 3 kind of end members braided , uh sinuously angry and grated and |
|
| 06:31 | raided and immigrants uh, and She uh, and show you basically |
|
| 06:40 | a false, just what how is . Whereas by splitting more like a |
|
| 06:49 | . Okay, we'll talk more about in a few minutes. So if |
|
| 06:55 | want to think about that controls on plan, form shapes clearly how much |
|
| 07:04 | you have is going to control the , how long that fan is going |
|
| 07:07 | be. Uh that's gonna be a of time. Uh And also gradient |
|
| 07:14 | a barrier and that's going to be of functions that congress, but in |
|
| 07:19 | , the higher the gradient, the likely it is to graded and then |
|
| 07:24 | the gradient decreases. We often have convergence to meander. So these are |
|
| 07:31 | lee induced criteria. Uh, discharge a function really of climate. Anti |
|
| 07:40 | because elevation does control. Uh huh relatively. So discharge and settlement |
|
| 07:49 | things we talked about in the first of the course are also variables controlling |
|
| 07:57 | magnitude and type of thing. Uh , hi discharge has to be more |
|
| 08:03 | , lower discharge of pandering and also in the supply, the greatest spy |
|
| 08:08 | likely created, the smaller the supply likely. Andrew. Okay. And |
|
| 08:14 | variables hold for feudal systems period, can't emphasize enough that when we talk |
|
| 08:22 | these mega fans were really talking about and so this is really uh something |
|
| 08:28 | we will be reviewed and repeat uh I talk about rivers tomorrow. |
|
| 08:38 | cooking in order to get a fan need to have the ability to expand |
|
| 08:47 | the confines up. So you're going a confined to a relatively in confined |
|
| 08:53 | , not in confined flow necessary, unconfined latter moot. Um so any |
|
| 09:00 | the changes that the showed earlier, that fine uh gradient settlement survive discharge |
|
| 09:14 | change the family. So one of we'll see and actually we mentioned it |
|
| 09:18 | time. Uh the nature of fans change the time as these vary like |
|
| 09:26 | supply, water discharge, volume of etcetera can change. Okay, now |
|
| 09:34 | Galloway in Galloway and hot days, the way, I've mentioned this |
|
| 09:39 | You'll see this reference a lot. you have a pdf of that if |
|
| 09:43 | want to download it. It's a all this somewhat out of date |
|
| 09:50 | it's a good starter and you'll see I use it a fair amount. |
|
| 09:56 | , so he had this idealized scream fan uh, and you notice rated |
|
| 10:03 | much all the way down it joins accelerated uh, it's inside uh huh |
|
| 10:14 | changes being raised, size decreased since go downstream. This basically is a |
|
| 10:19 | fat okay, uh, Galloway stream fan is the coast. Okay. |
|
| 10:26 | when we look at the fan, of the things that's striking, |
|
| 10:30 | that's coming off the no, both and life is that the british had |
|
| 10:38 | there for a long time survey that . So they looked at much progressive |
|
| 10:47 | via avulsion. Uh, pretty much to the west. We'll talk more |
|
| 10:54 | that in a moment, but these some of the dates, so we |
|
| 11:00 | a lot about at least the superficial of the Cosi fan. Uh, |
|
| 11:08 | of the interesting things though is uh, September 20, Oh |
|
| 11:16 | the Cosi fan started to evolve basically it switched the sports over |
|
| 11:26 | Never sanctions. And the working each down on this one, Major September |
|
| 11:34 | late and waterfalls should uh, pretty side because whether or not this is |
|
| 11:43 | to be a permanent change or just of those short lives things. |
|
| 11:48 | we'll have to wait and see. a big flow. Uh, and |
|
| 11:59 | , Yeah, just reached uh, upper part of that fan is predominant |
|
| 12:06 | streams. Okay. And these are some examples contra total bars as we |
|
| 12:13 | them. This bitch. General bars something more transfers. I'll talk a |
|
| 12:21 | more about this when we talk about on saturday. But this is basically |
|
| 12:29 | graded system uh in the active channel they get on to the rest of |
|
| 12:38 | rest of the mega fan, it's relic topography. And what we have |
|
| 12:47 | basically a series of meandering streams. , what's interesting about this, these |
|
| 12:53 | are, first of all, they're because they were originally braided streams that |
|
| 13:00 | were abandoned during so it's a progressively abandoned. Its hold courses. |
|
| 13:07 | that behind beheaded rivers that basically uh the angry and this braided to meandering |
|
| 13:21 | . Something we're going to see in lot of different examples. Uh and |
|
| 13:26 | what happened is that the sediment discharge our discharge decreased And so that tends |
|
| 13:35 | shift you more towards man. So it was beheaded, it lost most |
|
| 13:43 | its sediment lost a lot of it's . So it became really an under |
|
| 13:47 | street, literally angry under fifth Yeah. Now, as we go |
|
| 13:53 | down, we're getting a decreasing rates with a decrease as well. So |
|
| 14:00 | go from a gravel rich greatest dream sanding uh in some cases standing and |
|
| 14:07 | 30 and sandy red streaks have Okay. Uh huh. So is |
|
| 14:14 | Yeah. What what is that base the whole situation here, is this |
|
| 14:21 | the foreland? Um it's like a land but because it's called that's that |
|
| 14:32 | nations ex con but essentially it's a uplift of the Himalayas sediment depression of |
|
| 14:41 | cross giving you this wedge shaped basin a for the mulch and that is |
|
| 14:48 | the Ganges River flowing down. So guy jesus flowing parallel within that troll |
|
| 14:56 | into the indian ocean. And this one of a series of alluvial mega |
|
| 15:02 | that's forming this Emily and Piedmont's Uh that's been filling for 10, |
|
| 15:11 | 15 million years. Okay. Uh if you look at these individuals, |
|
| 15:17 | first of all, you see some your and channel two, but if |
|
| 15:21 | were detained a cross section of but you find are nested channels which |
|
| 15:28 | of makes sense because they're all kind , we're starting there as you get |
|
| 15:33 | and farther downstream, you're getting more more divergence as the nature of the |
|
| 15:39 | systems and so you're getting more and separation of the individual channel built. |
|
| 15:46 | you're not only getting a down fan sediment and the type of stream, |
|
| 15:54 | you're getting more and more separation of . And so that has to do |
|
| 16:00 | the risk of the analogous reservoir connectivity as we'll see in a few minutes |
|
| 16:08 | the aquifer connectivity as well. So would be the model if you like |
|
| 16:17 | the pattern of revulsion. Okay um don't have it, the river |
|
| 16:25 | but rather it evolves is with time so at any given time, most |
|
| 16:32 | the flow is in this chance to . Hi, just a little thing |
|
| 16:38 | this pandering and said in part by . Okay, now, the other |
|
| 16:47 | mega fan that's typically talked about is Okavango city right here. Uh if |
|
| 16:57 | look at that a little more it certainly does have a distributive |
|
| 17:02 | It's also called the Okavango Delta. uh really this is quite different in |
|
| 17:10 | alluvial fans that we talked about last and so it's no surprise that people |
|
| 17:16 | have a blink about why I called an alluvial fan. Uh you really |
|
| 17:24 | then is its tributary food system community a mega fan. Uh One of |
|
| 17:31 | things to note is that it is it wrong and so the accommodation spaces |
|
| 17:38 | much structure and control this hand had any longer than this because I kind |
|
| 17:44 | said with the head of with the thrown horse of uh the Robin |
|
| 17:52 | That's the, that again, that's east, I can s oh, |
|
| 17:57 | african, no, no, it's different riffs system um but if you |
|
| 18:04 | back here, uh huh you'll notice this is kind of uh huh I |
|
| 18:18 | , now whether or not it's somehow but it's not part of the map |
|
| 18:23 | see the stanford research system. so that's actually more transport situation. |
|
| 18:30 | don't know. Let's just leave it that. Um, yeah, there |
|
| 18:38 | areas I'm pretty familiar with. This not one of, it's pretty fascinating |
|
| 18:43 | . It's really changed. Uh, of these immediately is this truly is |
|
| 18:51 | distributive system where water is splitting into various uh distributive. And so as |
|
| 19:02 | would expect he even shoe or will as it will have lessons discharge. |
|
| 19:13 | small words. So the downstream characteristics this fan are quite, this mega |
|
| 19:21 | are quite different than the coasting for variety of reasons. Climate certainly is |
|
| 19:27 | tectonic settings another, but the way which it splits, one being |
|
| 19:36 | the other being uh divergence. if we look at the river, |
|
| 19:42 | actually the end and what's called the , which is this upper zone view |
|
| 19:51 | this. What I find interesting is with the great show you become more |
|
| 19:59 | less straight as it gets onto the in the lower fan, you can |
|
| 20:05 | this tributary and they, with the uh channels and with the death of |
|
| 20:16 | individual channels decrease with is basically reflect with decoration is reflecting the decrease in |
|
| 20:29 | that you go farther and farther Okay, now some of this is |
|
| 20:34 | of splitting some of it's actually because infiltration, the water infiltrating into the |
|
| 20:41 | . Okay, so we've got these miles and this particular hair of examples |
|
| 20:48 | is propulsion or qualification. Uh One the on going controversies, mega |
|
| 21:00 | Uh in fact, some people great stop at, he was always a |
|
| 21:07 | . Well, that's clearly not the in the Okay Maggie and it's clearly |
|
| 21:14 | the case in the Costa. So two members representing represented by these two |
|
| 21:25 | fans. Okay. Uh the thing , is we begin to look at |
|
| 21:32 | mega fans. Uh One of the I want to remind you of this |
|
| 21:37 | really talking to you as future petroleum or ongoing petroleum geologist, is that |
|
| 21:46 | skill sets that you have and the that you need is to a large |
|
| 21:52 | the same as that as a hydro with me. So, a lot |
|
| 21:56 | the information that you might find useful not necessarily in the geologic literature. |
|
| 22:04 | there are a couple of articles about to take chrissy things like the Journal |
|
| 22:10 | Hydrology. So this is looking at couple of also coming off the Camellias |
|
| 22:17 | little more towards the northwestern part of and look at the details that's provided |
|
| 22:24 | water wells. And so, uh know a lot more about these fans |
|
| 22:31 | of the hydro geological exploration exploration and uh than we do uh many |
|
| 22:41 | so keep in mind the significance uh water wells significance of the hydro geological |
|
| 22:52 | as you continue your professional quest. , one of the things that that |
|
| 22:57 | out from this particular study of these was that the total number of money |
|
| 23:08 | . Councilor. The individualized. Mhm. Pretty or can be |
|
| 23:25 | Yeah. The practice that they bodies not changing things well with there is |
|
| 23:42 | that we're looking at a motion and different than what we saw with the |
|
| 23:48 | angle but with the indians Captain did ? Um I now have to go |
|
| 23:54 | to the earth but we need a . Um Not quite sure. We |
|
| 24:04 | scratch that part from your notes. , so let's go back to their |
|
| 24:09 | got these mega fans and these two like this little fans. Uh well |
|
| 24:18 | look at that at a little different . A shrink it and look at |
|
| 24:23 | mega fans and stuff. Uh So here's the pro see here's the |
|
| 24:31 | . Little fans are just a man. Here's a pretty big |
|
| 24:36 | large dog that's in brazil and the and 22 times that of the cozy |
|
| 24:50 | is also in brazil. So these African mega fans huge bigger even than |
|
| 24:58 | along the hem Elias. These mega are basically coming off the Andes And |
|
| 25:06 | in that uh and these defamation was . Okay. And their current |
|
| 25:13 | Uh and again, somewhat this is true for the base. So have |
|
| 25:18 | got constructed? Yeah. A large fans that are coming along here and |
|
| 25:25 | anymore complicated area in the Andes. are portions of it that have a |
|
| 25:34 | subduction is pretty much the classic our back our fold and thrust built |
|
| 25:42 | foreland basin, other parts of the the slab is much flatter. You |
|
| 25:49 | a lot of these uh block faulted mountain like deformation. And so some |
|
| 25:57 | these mega fans are actually within these that are associated with the shallow slab |
|
| 26:05 | . So let's look at this particular and the first thing we see is |
|
| 26:11 | 600 my kilometers law really hate uh history of graded transition career as you |
|
| 26:26 | seemingly minor decreases in slope. um, there's another fan, large |
|
| 26:35 | make a fan. Uh, so we got twice to see there. |
|
| 26:45 | entrenched with lower fan. Yeah, is just like those little Death Valley |
|
| 26:55 | . Except for scale where purity demand point. You have a deposition role |
|
| 27:04 | the scale of course is huge. as we look at that, all |
|
| 27:08 | same face this up fan. There other families and anti french. And |
|
| 27:18 | the movement policy, we have the dash lines, we have remnants of |
|
| 27:27 | former fan pattern. Okay, so we look at actually this was, |
|
| 27:36 | take a look here. If we at the fan geometry here. All |
|
| 27:42 | , it is splitting what this looks . It is actually more distributive. |
|
| 27:49 | , these channels decrease in with each minutes splitting. Okay. Uh, |
|
| 27:57 | we get down to the whole of again, similar pattern. There are |
|
| 28:02 | loves. Oh, changing Yeah, much more distributed in this area |
|
| 28:11 | Yeah, this is coming off the side of the uh no, it |
|
| 28:19 | , the east side gets a little . There's uh yeah, no, |
|
| 28:30 | don't have a short but behind the on the, on the east side |
|
| 28:37 | it's flat slab, there's a whole of lock fault and really high angle |
|
| 28:45 | folks that have large rocky mountain like coupland's and basis. So think of |
|
| 28:57 | rockies and when they form relative to seduction of pacific uh as that, |
|
| 29:05 | the pacific slab flat, you began extend the deformation of the wider |
|
| 29:13 | You can have these big box. this is coming off one of these |
|
| 29:18 | this point. The Andes group. ready. Get mm. Okay. |
|
| 29:31 | the alps, the same thing. have these series of mega fans coming |
|
| 29:37 | camps. If you look at them detail steven, get all the way |
|
| 29:44 | here is pretty much spreading more. , here they're entering into the mediterranean |
|
| 29:52 | . Okay. Um so is that big fans or say it again, |
|
| 30:02 | that one big panic color is a age? Yes, this is one |
|
| 30:08 | fan. Each color is different Uh wow chad is almost these ones |
|
| 30:20 | dated for certain steps. Well, can't good free. Oh, 15th |
|
| 30:30 | BC. Oh, so again, of this as a challenge be all |
|
| 30:41 | , almost all of these are all same. Okay. And as we |
|
| 30:48 | down screen, the upper part Stephen braided. And as you go further |
|
| 30:54 | just as we've seen into the So various integrated seniors uh, then |
|
| 31:02 | tv lost distributed breaking up together. , so overall patterns of these big |
|
| 31:10 | , uh, you begin to see that can be tied back to that |
|
| 31:15 | early slide. I showed the plan with different styles of uh uh |
|
| 31:23 | Now if you go back to this story polls or any tectonic lee active |
|
| 31:33 | but especially for fold and thrust So if you've got a river system |
|
| 31:39 | coming out all of it and Yeah. Uh, begin to see |
|
| 31:46 | interesting radius patterns and patterns of Uh, here we go. |
|
| 31:54 | That is the other thing. There's others across notice that here this is |
|
| 32:00 | the Interfax area but there are a but there are no facts and that |
|
| 32:11 | thing is most of the grain age been diverted to come out peace, |
|
| 32:19 | few exit points. There wasn't always case because it turns out that earlier |
|
| 32:28 | rivers we're flowing into the basement and by a series of stream captures peace |
|
| 32:40 | were fans got beheaded and they're up . Fuller was captured, integrated within |
|
| 32:50 | few master strings to insist 10 million ago and it looked like this. |
|
| 32:57 | today because of very actually the old is shrunk because the end is the |
|
| 33:03 | things growth. So we began to this uh huh of large fans having |
|
| 33:11 | at the expense of these smaller affairs then all along that between the mega |
|
| 33:17 | are these intra fan alluvial, smaller fans. Uh, so here we |
|
| 33:25 | it in the cardia. Uh, and well negative look at these and |
|
| 33:34 | right. And what they described here exit or it's a dumb question. |
|
| 33:42 | is for your, well the cordillera to uh, the rocky mountains. |
|
| 33:51 | mountain cordillera. What it means in I don't know, I'm not talking |
|
| 33:57 | a place here in the corner. upset again, this is a specific |
|
| 34:02 | that's called the cordillera. Well this part of the Western United States |
|
| 34:12 | Okay. Uh, form mainly in . Oh, In a couple of |
|
| 34:22 | or genic events severe Rajan one mile reminder roger. So they no, |
|
| 34:32 | this particular example this is up in . Yeah. Wyoming area. |
|
| 34:42 | these are back art fold and thrust full trust. Yeah. Mm maybe |
|
| 34:54 | . This In this six for So in this case is very similar |
|
| 35:02 | the him lights Maga fan axial Bolivia street and nowadays to the guarantees. |
|
| 35:15 | . And in fact if you look it in scale uh, these are |
|
| 35:21 | pretty much saved your react. No, it's the intent. So |
|
| 35:33 | a little fan and for fema you hear me. So basically these |
|
| 35:42 | are similar in setting. Okay, these are the same scale uh |
|
| 35:51 | Here's the whole most films again called is Sierra. Uh huh. You |
|
| 36:00 | your message? You see certain exit where they're gathered where they drainage established |
|
| 36:11 | the fold and thrust belt and magnetic it have been funneled out and that's |
|
| 36:19 | usually there is structural salience. So kind of see where not hold together |
|
| 36:28 | the capture of the streams to make large great. Yeah. And and |
|
| 36:41 | is basically the company business sit here and of course services formalization. |
|
| 36:53 | A peripheral bulge. The courts running carrier use the mega fans is shedding |
|
| 37:03 | of the tectonic last area. This year example now is like entering a |
|
| 37:13 | big. So this particular, it's entering the next valley. Our action |
|
| 37:22 | . It's entering up. Yeah. marine and paper but eventually was filled |
|
| 37:30 | an ACSI invalid. Mm. So is an example for now. There |
|
| 37:37 | go. It's axial river. Nothing into increased setting here. |
|
| 37:50 | you've got these negative stands. and we can actually look at the |
|
| 38:01 | , sitting here. We need my for a moment. Um, this |
|
| 38:08 | the big horn can lump. Um, and where I'm standing there |
|
| 38:17 | big fold and thrust built this uplifted and this material has been shed off |
|
| 38:24 | so what we're looking at here This is the this area here is |
|
| 38:34 | over terms of trust, here's Yes. Okay, so when you |
|
| 38:42 | at that uh we see that all and tilted four overrating Olivia and notice |
|
| 38:56 | ifs the dips are getting steeper as get home. So this is just |
|
| 39:04 | of a cent tectonic overriding where material thrust. Yeah, is bad. |
|
| 39:13 | material has been more materials. So is typical um The areas uh adjacent |
|
| 39:23 | most proximal area. When we look these we see um a lot of |
|
| 39:33 | inter bedded with more planer units, it's very gravel rich. Um These |
|
| 39:44 | matrix supported. So we're looking at downstream creating gravel bar. So these |
|
| 39:57 | braided streams. Okay, uh notice . H horizontally gradient gravel, uh |
|
| 40:10 | as class supported matric, massive Yeah, so this is the type |
|
| 40:17 | gravels that we're getting in the most area were within almost a stone's throw |
|
| 40:23 | the mountain front. And here we've class supported gravel. We don't see |
|
| 40:31 | in the terms of that much in way of the brief flows here, |
|
| 40:37 | confined flow. The unconfined flow, it's confined with strength flow and shape |
|
| 40:45 | and stream flow channels. Mhm. the ice a pack of one of |
|
| 40:52 | mega fans Up to 600 m Okay. And this is pretty much |
|
| 41:02 | it came out. The highlights. here's a fan and you can see |
|
| 41:10 | paleo currents and if you look at percent sands downstream, it decreases the |
|
| 41:20 | of the flu real section decreases mean size and thickness again. Uh So |
|
| 41:30 | looking at several 100 kilometers of sediment coming out of these exit mortgages. |
|
| 41:46 | , if we look at across let's just do it right here, |
|
| 41:50 | a cross section here and here and . If you look at a cross |
|
| 41:55 | proximal area, you basically see amalgamated . Just little practice. This is |
|
| 42:07 | global system. Yeah, highly amalgamated Street. They should go further down |
|
| 42:15 | the end of seeing these packages Mhm. You get further down |
|
| 42:24 | you have large relative screen five grades . Oh, so this is what |
|
| 42:36 | system would look like if we were an explosion moving out ST cross Church |
|
| 42:48 | . So this is kind of a of what it looks like a possible |
|
| 42:53 | . I'm not gonna go into their as we get down to this area |
|
| 43:01 | . Hello, It is an ongoing . Do these things split? So |
|
| 43:10 | look at a disproportionate and the answer what they actually do. You can |
|
| 43:16 | see the individual sand body sandstone bargains that this live, you can see |
|
| 43:24 | they're just going all directions, doing work. And so what this is |
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| 43:32 | a right. Uh huh. Surely happening disproportion we've got little stripping their |
|
| 43:44 | , you need not the best This is like a little delta at |
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| 43:52 | tail in the distal end of this fan. Yes. Uh Crevasse |
|
| 44:02 | Just kind of a sign. Uh I get to get in more detail |
|
| 44:08 | ? Uh huh. Dean for last . Um Some of the best case |
|
| 44:18 | of corvus plays are actually not in , but in mega fan. This |
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| 44:24 | one from uh South Mexico. This shows where they tip. So we |
|
| 44:34 | terminal splay which I showed to slides and that's a little harder. You |
|
| 44:40 | these uh huh displays at right angles the change those are all active at |
|
| 44:47 | same time. Uh That that's a argument be going as to how many |
|
| 44:56 | these are active. And uh it's clear there are multiple. There is |
|
| 45:05 | of the channels for But it's also So that's a detailed that may have |
|
| 45:17 | help this matter. Every mm channels two more sandy bed low chance separated |
|
| 45:30 | playing the bass. And finally these , let's in this will determine explain |
|
| 45:39 | really called you say this all over settings like this when we have this |
|
| 45:48 | to so just yes, All of pants are just caused by the one |
|
| 45:58 | then if they like it goes out then it drives them or to water |
|
| 46:05 | stay true to the street. The book that we have lost |
|
| 46:11 | Okay. You certainly have some things you got the bigger man where there |
|
| 46:18 | a lot of water All right. goes into an area words because infiltration |
|
| 46:24 | one of the ways you skip down decrease another word. You see a |
|
| 46:31 | complications. So he chair stop Uh in other cases channels privilege confined |
|
| 46:42 | a single strength. It shifts for next one. So you've got these |
|
| 46:49 | fans off parts of settings. Mm parents like climbing tectonics relatively sentiment |
|
| 47:02 | et cetera. Uh various It varies with tectonic setting and it varies with |
|
| 47:12 | . So, uh it's important to this potential. Um there are some |
|
| 47:21 | example declare this is what you have there's a terminal a lyrical yes. |
|
| 47:31 | in other cases. There are kind love with particular here. Here there |
|
| 47:38 | uh this it's pretty universal. The will vary a lot. Yeah. |
|
| 47:53 | this is sometimes called terminal fan The idea is there inside distance |
|
| 48:01 | Uh huh. At least these are acted at the same time. These |
|
| 48:08 | not be active in the same And this is the kind of this |
|
| 48:15 | actually from different areas, different Yeah. The patterns are the |
|
| 48:24 | Mhm. Here is the karoo mega pattern is the same. Yeah. |
|
| 48:33 | that each month on this. The more we look for these distributed |
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| 48:50 | systems. More we realize that they a large portion of base and |
|
| 48:57 | So let's look at this particular Uh, the actual street, this |
|
| 49:02 | the big grip tend to focus on it the Ganges um, is actually |
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| 49:11 | a small portion of that entire Gandhi's . The distributed fans in general Distribute |
|
| 49:20 | system constituting more than 90% of the . In most of these cases the |
|
| 49:28 | systems, it looks inter fan it is Tend to be less than |
|
| 49:35 | . This is based on satellite interpretation major basis. Okay. And we |
|
| 49:43 | what you get here. Uh, you've got a serious fans, all |
|
| 49:48 | the side, You got an exhale coming in five split. Uh, |
|
| 49:58 | the scenery, youtube of water here present the apply up was probably in |
|
| 50:06 | lake and the alluvial lakes in the I said last year. Uh, |
|
| 50:15 | this is a very common pattern, scales. I'm not, this is |
|
| 50:22 | book. I mean in your basically looking at various areas, the |
|
| 50:30 | former, Do you like this after the percentage, the area percentage of |
|
| 50:43 | distributed fluting systems. Yeah. Now distinction between these, I'm gonna say |
|
| 50:52 | fans versus the previous uh, is pretty important. Um, the problem |
|
| 51:04 | when this was a trick. mm, we didn't have the satellite |
|
| 51:15 | , the global perspective there. So idea was that these big, |
|
| 51:23 | fans called rivers did not indicate Henley used to say I ate my mom's |
|
| 51:33 | . We're in the middle of a bit of fantastic. Well we certainly |
|
| 51:37 | that the cozy does. And all those mega fans along the N. |
|
| 51:42 | . P. Plot. Do you He said these little fans have fought |
|
| 51:50 | margins to figure again, that's not . In fact some of them have |
|
| 51:58 | you an example of negotiated troll. you need is a steep change in |
|
| 52:05 | high look active Tekken is um usually , police. It was thought that |
|
| 52:14 | uh in most of these cases, . Although active as relevant because what's |
|
| 52:22 | here is climbing and you may recall I talked about sediment partitioning before it |
|
| 52:30 | to the the amazon river that deposition the glacial periods, mainly in mega |
|
| 52:40 | . And that those mega fans tend be bypassed during the high stakes. |
|
| 52:47 | that's not a active tectonic is an thickness is a tectonic lee active area |
|
| 52:55 | but it has to do with the of sentence. And so yes the |
|
| 53:01 | mechanism. Yes, it's going to . Country basin orientation. Uh Well |
|
| 53:08 | , oh here the idea is that rivers are all axle rivers but in |
|
| 53:15 | fish fan mega fans are not the roots, they are oriented right |
|
| 53:23 | just the uh huh. Salt So all of this they do. |
|
| 53:32 | really talking about economically active already calling bill fans. Um which is absolutely |
|
| 53:45 | for these um trans intentional basis. talked about, okay, but can |
|
| 53:55 | hide these magazines. And the one that is to, yes, that |
|
| 54:03 | . Little fans have little brain And so they tell you what performance |
|
| 54:09 | very local. These mega fans have mega drainage here. So they're going |
|
| 54:17 | corporate. They may be more typical the plate tectonic setting. But really |
|
| 54:24 | difference between the hands and the it's largely community here. So if |
|
| 54:31 | got big drainage areas, you've got big fan. Oh, thank |
|
| 54:36 | And so if you're a little bit still they tell you different things. |
|
| 54:41 | that charges. No, not what trying to go through, explain why |
|
| 54:49 | not Right. Right. Where it's where some. So, uh, |
|
| 54:56 | might think about this layer and no uh where there's exceptions. Yeah, |
|
| 55:03 | started studying the question but it's something think about because because you gave an |
|
| 55:08 | of dr fault that Arjun. I mean, for example, right |
|
| 55:15 | again, an example of Switzerland where was a little family, anybody's arterial |
|
| 55:21 | they change with time has changed What where the break its hopes? |
|
| 55:29 | was basically handy. I gave you example here where uh actually all of |
|
| 55:38 | uh with the cosi fan. All of it just, it's a |
|
| 55:44 | thing and the little people, it larger region. This is from the |
|
| 55:50 | . But that just means it's a fan. So this century says big |
|
| 55:57 | extend farther from the start. And is the basic orientation based on orientation |
|
| 56:06 | it to the main fall if you've some kind of use the form |
|
| 56:14 | Mhm. You've got and why is up there? 7? You got |
|
| 56:20 | truck The four long days. The fan is parallel to that face. |
|
| 56:28 | mega fans and smaller fans are at angles and shed off structural high. |
|
| 56:38 | that's what they mean by pacing Mhm. What is this? The |
|
| 56:45 | reference of course. Great river. river delta versus fine grained wizard. |
|
| 56:52 | huh. So that this this particular chart came from the same paper that |
|
| 57:01 | established uh the importance of debris flow sheep through alluvial fans. And tried |
|
| 57:10 | make the argument that these other big weren't really fans. Yeah. To |
|
| 57:17 | make the say and they don't tell since that. Well, to a |
|
| 57:23 | extent they did. It's just as matter of scale. Yeah. |
|
| 57:30 | Uh Sometimes fans enter into a standing of water about sandals and so the |
|
| 57:38 | difference is that there will be 7 Clearstream workers of the district parts of |
|
| 57:47 | fans. Okay. And so they're to be better sorted and reservoirs than |
|
| 57:53 | that are just hitting into a front or applying like. And so we |
|
| 58:01 | The three fan deltas then brain No so called violent movies. Uh |
|
| 58:12 | . Those terms bag over Great you long. Uh Common belt is not |
|
| 58:21 | much. Hello reality is this is , it is a final green dealt |
|
| 58:29 | what you spend. What attack Yes because that's a marine filter. |
|
| 58:38 | have speaking the customer. It's just a standing body of water. These |
|
| 58:44 | all in the bodies of market. . All delta is basically what rivers |
|
| 58:49 | a standing body. What you get the delta if it's not going in |
|
| 58:53 | water. Mhm. Well you The Okavango delta is not really adult |
|
| 58:59 | to said yes. It has to a standing. So the delta is |
|
| 59:06 | the biggest thing. Yeah. Okay let's just stop it right now. |
|
| 59:14 | two types Delta's subject. Uh here got the gulf of California on the |
|
| 59:23 | side series of rubio fans is emptying the gulf of California. We also |
|
| 59:33 | are bad bills go to the other of the gulf of California. You've |
|
| 59:40 | braided stream is everything to get a great delta. A delta formed by |
|
| 59:50 | . Okay so these are two examples side that side of those two types |
|
| 59:57 | delta and the reason they're different has do with the tectonic setting and the |
|
| 60:05 | of the green nature. Okay the about Yeah the yeah this is at |
|
| 60:19 | bottom. Well thank you very This is neighbor list. So this |
|
| 60:26 | the magnetic part. Yeah the kind larger than dream. It's also |
|
| 60:35 | Higher relief larger so we can establish well said sand and water. Whereas |
|
| 60:49 | So this is a summit within a base of Mexico is one that we're |
|
| 60:59 | to see a lot. So I you to keep this in mind out |
|
| 61:03 | the same basis. Can be structurally and have different types of deltas. |
|
| 61:14 | Yeah. Going back to what's controlling this which in terms of Sammons upon |
|
| 61:23 | clear discharge in bed road. I a base load which is supposed to |
|
| 61:30 | it in technomic ultimately giving us the . So we started this last week |
|
| 61:39 | with this. So let's look at of the changes fans can shit by |
|
| 61:47 | host. You saw that cozy and see it. We found delegates as |
|
| 61:54 | . That is an auto cycle It's internally wrong. Okay. |
|
| 62:01 | And if you think back to the delta as we talked about, I'm |
|
| 62:07 | , smaller alluvial fans. The degree shoes. The idea you had incision |
|
| 62:13 | load. That lobe then begins to the insides valley and until it has |
|
| 62:19 | shift together. That is an auto change. It's self induced. There |
|
| 62:25 | our site changes due to changes outside area. So for example climate |
|
| 62:33 | We see changes from succulent seminary subhuman rubio fans in the uh real grounded |
|
| 62:45 | as an example. We see a of different. Yes. All |
|
| 62:57 | These are fans forgot this. This kind of good example. Find the |
|
| 63:08 | that you respect for example. That's finished on one professor. Uh |
|
| 63:17 | Maximum eric namely sheet sands. In having sites. Mhm. Following is |
|
| 63:28 | other. Okay. Uh faulting is significant factor, particularly the smaller |
|
| 63:36 | Climate is a bigger factor in plate setting and water sets for the mega |
|
| 63:43 | . These are false scarfs right Jet. So we know that this |
|
| 63:50 | is uplifting in this area society as speak. Okay. And you can |
|
| 63:55 | the false scarfs along here. these fans definitely are. The result |
|
| 64:06 | active tectonic is um Okay. And see how large some of those false |
|
| 64:12 | are. There's nothing here. How persistent the fall thing is and |
|
| 64:22 | persistent the location of the master fault will affect the larger scale pattern accumulation |
|
| 64:28 | these deposits. Okay. Uh If persistent and it could be like this |
|
| 64:33 | like this uh you have basically vertical . You can have back stepping and |
|
| 64:42 | variety of ways. So, how border fall changes with time will affect |
|
| 64:48 | overall pattern of accumulation. The other is that the look what happens if |
|
| 64:59 | have episodic thrusting. Okay. Um say this is under non tectonic quiet |
|
| 65:10 | . The fans nice and graded. we have trusting you've got more |
|
| 65:17 | What does that do? It causes loading which causes a transgression. So |
|
| 65:25 | particularly in uh fan deltas. You changes in subsidence associated with changes in |
|
| 65:36 | activity. Okay. Uh the other is that you can go from the |
|
| 65:44 | to apply it back again, definitely late 100 m deep, 18,000 years |
|
| 65:55 | . They are applying because of the in precipitation. So here we've got |
|
| 66:02 | in lake levels. This is a , jean alluvial fan and the custom |
|
| 66:07 | . Okay. And here it is low stand and here it is during |
|
| 66:14 | sandy noticed that those mhm terminal lobes become mm delta chance. So this |
|
| 66:29 | part of the argument that goes on people are describing these are the relic |
|
| 66:36 | relative to a time when they were delta? Or is that just the |
|
| 66:42 | it splits? And increasingly we're beginning realize sometimes it's just the way it |
|
| 66:48 | . But the other thing we see fans are long lived phenomenal. So |
|
| 66:55 | have undergone want changes. What? uh Yeah. Okay. So people |
|
| 67:04 | wondering why the low lake level you the more root like patterns. |
|
| 67:09 | yeah, what they're arguing is when see this tributary pattern and you think |
|
| 67:15 | because the channel is at breaking up and smoke that maybe relic to a |
|
| 67:23 | when it was actually just dealt. the argument is, is the pattern |
|
| 67:29 | see today reflective of the water and discharge we see today Or is it |
|
| 67:39 | relic pattern from the time when that client was really late. And the |
|
| 67:49 | is, we literally see pieces both is to say we see climate changing |
|
| 67:58 | a scale that still preserved in fans lakes in particular. I'll talk more |
|
| 68:05 | the next time. They're much They change much more frequently and to |
|
| 68:12 | larger extent in marine sex. So can have a I like Last 300 |
|
| 68:20 | throughout 300 m, 10,000 years. huh. You can't have that marine |
|
| 68:28 | . Yeah. Now having said all , I believe that there are some |
|
| 68:34 | examples where these terminal loans were not from a earlier the customers set. |
|
| 68:44 | , I think that argument's been said , but there's no question that we've |
|
| 68:50 | these fans go through the custom and our faces and I'll talk more about |
|
| 68:58 | tomorrow morning In the Devonian there's a got 25,000 m 25 km thick, |
|
| 69:06 | due to costs. That clearly says an ongoing long live system and |
|
| 69:14 | yeah, typical of what are referred as trans intentional basis and his basins |
|
| 69:24 | with strike slip movement usually because of kink in that strike step system. |
|
| 69:36 | . And they are typically s If you draw a cross section, |
|
| 69:44 | a steep master fault and then a steep hand yourself. So there really |
|
| 69:56 | growth. Okay, so here's that in the north side of the master |
|
| 70:05 | . South side is kind of the slide. It's less steep, less |
|
| 70:12 | faulted and it turns out the less side over here consists of stream flow |
|
| 70:20 | fans. The northern side along the fall, consistent debris flow dominated |
|
| 70:32 | So here's the cross section as symmetrical . Smaller to refloat fans, larger |
|
| 70:47 | flow fans. Okay. And what tells me is that there is a |
|
| 70:53 | in the amount and type of sentiment water this coming into these two |
|
| 71:00 | Yeah, so here we have these stream flow fans, little bitty to |
|
| 71:06 | flow and here's the axle. I mean actually filling in via a |
|
| 71:16 | type of the delta, um, axial forces. So we've got a |
|
| 71:24 | section here and launched a new profile . I want you to keep in |
|
| 71:33 | that And let's go back to death where we had stream flow fans on |
|
| 71:38 | west and debris flow fans on the . And when we looked at that |
|
| 71:44 | saw that it was a half problem that the master fault oops um, |
|
| 71:56 | is here, it's where we had small drainage areas, deep but |
|
| 72:03 | Not much water but Fair amount of coming in uh mask movement to refloat |
|
| 72:12 | here. We have a much larger area, more water, more sediment |
|
| 72:19 | smaller concentrations larger fence. Okay, this particular case instead of this system |
|
| 72:31 | groups where it went into a Uh, this is presently going in |
|
| 72:39 | apply it. But remember this was a lake not long ago. |
|
| 72:46 | So that's where I'm going to stop . Uh huh. And It's |
|
| 72:57 | We're going to start on lakes may finish, but as I think you'll |
|
| 73:01 | , it's really a continual of what been talking about. So let's stop |
|
| 73:07 | recording, um, to |
|
