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00:00 | Yeah. Okay, okay. Uh we've looked at um the fluid processes |
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00:12 | are causing sediment transportation definition. So I want to look at now are |
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00:20 | the bed forms that result from And then the second part of this |
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00:25 | will be on the sedimentary structures. , when we look at and and |
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00:31 | I say bed forms, I'm I'm speaking about Sophocleus uni directional thought, |
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00:39 | means I'm not dealing with waves, not dealing with wind, I'm not |
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00:43 | with sediment to gravity. Okay. of those will have their their |
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00:47 | Okay. And when you think about , trans verse, bed forms said |
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00:52 | angles to the flow direction occur and all fluid, the fluid interactions from |
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00:59 | to air, sand, water to . I mean these are pretty common |
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01:05 | and to be honest, we don't even now have a good explanation for |
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01:13 | they're formed in detail. What we do is describe when they form and |
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01:21 | conditions from that. So you do you can do. So here are |
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01:30 | inter directional rivers. Okay, now problem is you might assume that why |
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01:39 | with ripples, their ephemeral forms, see them changing all the time. |
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01:43 | the reality is they are often preserved the rock record. In fact they |
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01:51 | sometimes be preserved layer by layer by . And so although it seems like |
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01:56 | are very fragile kinds of features, have a survival instinct that really works |
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02:05 | well for them. So we can a lot from looking at the morphology |
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02:11 | the ripples. And so one of things we see is that there is |
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02:15 | complete gradation from oscillate Torrey ripples form waves, which frankly, we're not |
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02:20 | to worry about now to uh combine . Where's waves and the current to |
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02:27 | current only. So we're only interested current form ripples at this point. |
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02:36 | what we we've seen is that the plan view changes. Is you increase |
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02:44 | strength, however we measure okay? they start off pretty straight, press |
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02:51 | pretty linear and then as we increase motion uh or at least certain grain |
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03:00 | , we go from no motion to to plain debts. And the ripples |
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03:07 | change in morphology from pretty much straight uh to kind of elongated sinuous, |
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03:16 | made ripples. And so what we is we define these transverse forms as |
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03:23 | dimensional or three dimensions. Uh Two , are straight crested, three |
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03:30 | are much more sinuous and planned this for both ripples and deuce. |
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03:35 | so it's probably a good time to between ripples and dunes. Uh The |
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03:44 | thing to know is that ripples do scale with depth dunes. Do scale |
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03:50 | death. What that means is the the water, particularly the chance, |
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03:55 | higher the dunes? Or is it matter what water depth you're in for |
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04:03 | , they're gonna be the same. other thing is they differ in terms |
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04:07 | height and weight. The short of is ripples are smaller. The |
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04:11 | but more specifically, we tend to ripples rarely over about seven cm 8 |
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04:20 | high and rarely over a meter and typically less. Okay. Uh Or |
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04:28 | typically since. So if we were kind of plot that wavelength versus |
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04:38 | you see that there's this critical break , 80 and leaders. Um 10 |
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04:56 | on weight. I'm here down Now we see this evening with the |
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05:06 | . We see this more so even the only. So we sometimes uh |
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05:16 | sloppy and the way we describe ripples dunes, they are very different |
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05:21 | both in terms of measures uh flow uh as one of those dimensions. |
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05:31 | here we see this transition from two . to three d. D. |
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05:38 | with increasing flow of lusting. And we see it looking not only at |
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05:44 | plant form but the sedimentary structures. so we'll come back to this in |
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05:51 | second part of this lecture where we at how we can reconstruct that form |
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05:58 | sedimentary structures short of it is uh straight crested bed For me, the |
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06:05 | or dunes are gonna have a difference section and strike section uh than more |
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06:14 | or three. Uh doing bed for dimensional bed forms. So here we |
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06:20 | that when we look at blue down what we're doing here, the increase |
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06:30 | lawsuit you go from to just as going to the report. So for |
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06:45 | of these hand, first bed forms and dudes, uh there's a if |
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06:50 | like a low velocity form and high for minutes. Gradation. Okay. |
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06:57 | we also have superimposed platforms uh here have uh more or less three dimensional |
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07:07 | . Look at the wavelength here the and superimposed on that or little three |
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07:16 | ripples. Okay. And so it's uncommon in certain grain sizes and flow |
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07:23 | to get the superposition of dead forms therefore the superposition of sedimentary structures. |
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07:33 | , I know this is one of students is working on the masters. |
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07:44 | let me, okay, let me a question. May have life. |
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07:53 | , would you say these are two . or three D. Bad |
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08:04 | Hey, what do you say? D. Okay, what about |
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08:16 | This is an oblique aerial photo. . Look at the chris. |
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08:33 | In fact, we've gotta scour pit being filled in by slip face. |
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08:38 | you think they're dunes or ripples then . Well, what's your guess You |
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08:49 | ripples do. Absolutely. But This is kind of a leap of |
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08:56 | , but this is from an Their large. Absolutely. Okay. |
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09:03 | and here's what it looks like on ground. Okay. So uh these |
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09:08 | really big ripples. I mean I'm big dudes. Uh that must have |
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09:14 | because remember I said the they scale water depth they missed formed when this |
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09:21 | was at a very high status, Yukon River. Um and uh it |
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09:27 | really peaked floods during I Sprinkle well is one of the ways in which |
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09:33 | hydroxy fee or hydrology uh of the flow is conditioned by climatic conditions. |
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09:46 | is high latitude ice breakup and it reported in bed forms. These are |
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09:52 | thick bed forms reflecting very high Okay, here's a this is a |
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10:01 | earth shot, but again, it straight Preston two D dunes with a |
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10:07 | of about 8 to 12 years. I mentioned this, there's every once |
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10:11 | you'll see a um somebody say that Preston or two D dunes don't form |
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10:17 | nature. Of course they do. said that has never looked at google |
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10:23 | . Okay, so it really brings to the flow regime concept. Uh |
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10:30 | , Hayden, when, when you at L. S. U. |
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10:33 | did they talk about the flow regime with respect to uh 407 infrastructure? |
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10:46 | , what do you remember anything about ? Uhh days, 11, |
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10:53 | 13 years ago. Okay, well, fair enough. But this |
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11:08 | hugely important. And this is it says that, you know, |
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11:17 | ripples to dams. That is no ripples to due to the and that |
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11:26 | transition from dunes to flat band more less the transition from what is they |
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11:33 | as a lower floor, the upper ownership and more specifically, that's going |
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11:39 | be um low crude numbers. I . Now there's a couple of things |
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11:46 | note here. This particular concept was really as a one dimensional concept. |
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11:56 | I mean by that is the only his flow velocity. So this is |
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12:03 | change in bed form in sedimentary structures with changes lost the it was described |
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12:16 | by workers with the USgs who are on the Rio grande river of medium |
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12:21 | sand. Uh and and they described in great detail. For example, |
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12:29 | noted it alone. He the purpose out faced with death point. |
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12:39 | Upper flow regime, the circus was phase for benefits. We went from |
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12:45 | continuous to continuous transport. Now that's true after about here's a from higher |
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12:57 | of increase in concentration in face All of this sequence was done based |
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13:13 | few studies from but medium resale but the same time at Alliance, I'm |
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13:23 | colorado State University. I had a plume and the Engineering Department was looking |
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13:29 | sediment in this blue 150 ft long they came up with more or less |
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13:36 | same idea and washed out transition going station anti news. Now hydraulic jump |
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13:54 | into its court. Now this portion , the higher velocity of authority and |
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14:04 | really weren't described in that field set the advantage of the flume studies. |
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14:11 | Now just imagine that hydraulic we're talking here rather earlier with respect to going |
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14:20 | uh screaming flow to tranquil flow. , now the field study looks like |
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14:32 | . This is what the tomb study . They were able to experimentally vary |
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14:40 | grain size distribution. And they also that both dunes and ripples, there |
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14:49 | a straight press city 12 seamless three . High velocity. Again, I'm |
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14:59 | use velocity just because it's a shorthand all sorts of other measures will |
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15:07 | Now, what they showed that was shown why is what happens when you |
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15:15 | into safe? You don't have any instead. You've got the first motion |
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15:22 | you plane beds, it goes straight it. No ripples at all. |
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15:33 | , they all go into playing that . But now let's look right |
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15:42 | What this study did. This first flu study assumed that you went from |
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15:52 | that even in front of good it turns out you don't, as |
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16:08 | began to use find a great they realized that there in the brain |
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16:18 | and grace. No. Now we're that dunes are restrictive and said, |
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16:34 | course they're being, let's say that little less thanks. And that ripples |
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16:43 | restricted to about seven. Unless and only queen which immediately expand is what |
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16:58 | for their. Yes, sir. now we've got two dimensional bed |
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17:05 | Doctor showing the effect of increasing flow on different range sizes. A couple |
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17:17 | other things knows there's two flatbeds that . Now all this lower planer, |
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17:26 | upward. Uh No, it's also have sand wave versus dunes. These |
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17:33 | now two dimensional three. So the of the fields isn't changing much, |
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17:41 | we're beginning to refine what the bed are looking like. Now let's look |
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17:46 | this bed for not from plan cross section. And one thing I'm |
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17:52 | is that uh the upstream as relatively maximum velocities and as it converges towards |
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18:04 | crest. So we have converging flow and diverging flow here. So we've |
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18:17 | acceleration, approach, deceleration, The other thing about this is that |
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18:25 | you look at the velocity profile, actually those stream lines are coming out |
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18:32 | this and they reattach right about So there is a zone of |
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18:41 | This kind of a Yeah, river shadows up and so there we can |
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18:52 | have reverse flow down here. And that reverse flow. If the |
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19:00 | of the bed form is large we can actually get ripples migrating upstream |
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19:04 | the trough, but we'll see examples that. Yeah. So it's a |
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19:15 | confusing makers, we talked about how is higher energy and so we have |
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19:21 | erosion. Yeah, but based on illustration, it looks like sediment build |
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19:27 | here versus this to indicate where the we were to look at this in |
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19:40 | to it would look like this second three. Okay, so it is |
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19:54 | here and it is depositing here. and the other thing I just point |
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20:05 | there's a little bit of a difference the summit point and the brink |
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20:10 | We'll talk more about that later. brink point is where it starts the |
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20:16 | . So there actually is a zone the break point in the summit point |
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20:22 | you can actually get some horizontal lamination would be like the top set. |
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20:28 | . Yeah. Okay so in this is what you need to remember |
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20:37 | . Don't worry too much about wavelength but everything up there is an important |
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20:45 | to remember because I may ask a like compare and contrast ripples and tenants |
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20:52 | this is half much of the answer within the last decade and really five |
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21:04 | we're beginning to realize that um we're to realize that mud can be transported |
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21:17 | ripples. Now that's that seems really . I've already said there's something odd |
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21:24 | getting mud in motion but there are little mark can like ripples that are |
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21:35 | but not as individual part in It is saying clay populated clay parts |
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21:46 | have a dimension The Moment five and . Even though they are individually simple |
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22:01 | . Now you can see that they series of slumps downstream side. And |
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22:12 | this is what they have to look . And so there is at least |
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22:18 | potential for these third ripples to be shale record. Uh This is what |
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22:32 | want. So this is a non uh Margaret. Now the problem is |
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22:49 | . And so um this is that look. Not that this is a |
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23:00 | the reason that's important is it gives a very different view of how some |
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23:06 | rocks are deposited. The standard orthodoxy that mud is deposited from suspension very |
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23:18 | energy. But now it could be high energy with blood being. And |
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23:28 | it's causing us to reinterpret the muds you can see, I I think |
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23:33 | pretty easy to see how subtle those are. You don't see it till |
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23:42 | looking for when you look for You realize that a lot of what |
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23:47 | thought of as paper thin laminated bloods in fact repeated muds. Alright now |
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23:56 | contrast that with dunes, as I earlier, they don't form in fine |
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24:01 | sand, they're larger. Their height with depth, doesn't like ripples like |
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24:11 | two D. To three D. increasing velocity and the wavelength increases with |
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24:16 | velocity and brain cells. Now, other thing that we have kind of |
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24:25 | agreed on is terminology and I don't you to remember a lot of the |
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24:33 | , but I do want you to that there is a terminology for distinguishing |
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24:39 | small, medium large and very large . So basically students and that you |
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24:45 | where to find it in your Uh because too often we just kind |
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24:52 | say, oh they're big. I'm call him large. I don't |
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24:56 | it looks like medium to me. those are small. You are saying |
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25:01 | big ones, uh we need a criteria and uh, we can't settle |
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25:08 | this. Having said that a lot discussion. That's all right. And |
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25:15 | of the big discussions I'll bring up just a moment. That's what we |
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25:18 | the unit bar. And so some what we used to call large or |
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25:24 | large dunes turns out aren't really dunes se. But hold onto that |
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25:31 | let's look right now at a point deposit. And uh we see here |
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25:39 | lot of small dunes and then these structures. And when I first started |
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25:50 | this course I called these large gyms very large. Uh It turns out |
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25:57 | are probably what I'm going to describe unit bars. Okay, now a |
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26:04 | bar is a low that unlike dudes grow almost to the bed flow |
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26:24 | Uh, particularly great groups. In words, most of what we traditionally |
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26:30 | the dunes and are what are described these bed phase diagrams are only a |
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26:36 | proportion of the water dead, maybe third six. There's a lot of |
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26:43 | on top. These unit bars can virtually to the surface. And |
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26:49 | they scaled to the width of the , which didn't. So it's really |
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26:59 | level of bed form hierarchy that once and shown it turns out that's a |
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27:09 | common feature. Well you won't find on the bed face time because it's |
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27:16 | different type of that form. So see what we can do with having |
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27:25 | big phase diagram that you can These are the very that are measured |
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27:32 | forms and fields that's too many. let's organize a reorganization fluid, variable |
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27:41 | , variable water. Now, that's he went to the constant fresh water |
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27:52 | the difference for sentiment as keep all constant by saying uh house but standard |
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28:05 | works this water strength. No we water here and water here. We've |
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28:21 | depth, close training range size. that's the beginning of the 5th Phase |
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28:29 | . Pretty much the best weekend Meet side water. What's missing? |
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28:41 | missing in this particular Could be a D. directly. What's That? |
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28:50 | Division? No no. Just uh got to normalize the state point, |
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29:05 | velocity is defined as in any As long as it's you know or |
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29:11 | need record. Hi. Yeah. . You know what we need is |
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29:24 | variable that goes into the board for turns out that's less critical. We're |
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29:29 | talk about this moment. But this what I want you to look at |
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29:33 | the way I want you to think it like this. In other |
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29:39 | you ought to be able to draw like this museum. I notice there's |
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29:46 | transition of uh phone number two The reading breaks here breaks? Don't |
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29:57 | that. Mhm. And realize that a little different, You know this |
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30:08 | 30 years late, hasn't changed that . Pretty much settled on. And |
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30:14 | now he added this circle loss 3rd . We still get if we start |
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30:22 | here sand we still have no motion . Fan waves think two begins do |
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30:31 | three details. But look what happens in phase rays? Think anti dudes |
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30:37 | pinches up. That's a half a . So the one major distinction with |
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30:48 | to slow death is the lack of in anything deeper than or shallow. |
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30:57 | , so at least until we get some or rather sedimentary gravity flows, |
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31:06 | we dealing with kind of typical We're only gonna see any dudes shallow |
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31:15 | . Now that was based on flume . Um This is yeah based on |
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31:27 | and um field studies. So here we've looked at we're looking at |
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31:36 | Uh huh. Cross section. That the end of the three with. |
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31:46 | we've got velocity increases here. The . Here's the news coming out. |
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31:54 | sounds great with them. Yeah. we've got three different license. Now |
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32:03 | question to you is as we look this and you look at what's happening |
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32:09 | respect to the transitions in bed. I was to ask you. Well |
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32:18 | I were to tell you These represent different grain sizes. Medium grain |
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32:25 | fine grain sand, coarse grain Which of these three do you |
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32:31 | Horse Green said why robert? What you think? Well, what would |
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32:51 | predict? Made a sequence in sedimentary with increasing flow for coach wants? |
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33:14 | great working. No motion seems to a little higher here and here. |
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33:30 | . Uh huh. I'm not sure these numbers are. So let's assume |
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33:40 | right. You see science critical Your motion motion One of the three |
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34:13 | . Well, just tell me what sequence is for this as we go |
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34:18 | no motion. The office old What do you what do you speak |
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34:23 | increasing lost. You go from no to what? Yeah. Speak |
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34:32 | Who? Yes, but what bed do you get? Yeah. So |
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34:42 | go ripples upper place when you get stands right. What do you get |
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35:01 | ? So you've just gotten the So which one is sports? |
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35:32 | Which green size goes from? No , lower planner, do anything the |
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35:45 | creates. Yeah, whatever it Yeah, that other side was it's |
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36:04 | . Don't if you can remember this be able to reproduce it on exam |
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36:11 | you can answer that question which is dues. Just ripples, find no |
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36:21 | . Just unfortunately. Yeah. And important when you start looking at sedimentary |
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36:28 | because then you're looking at brain size well as sedimentary structures formed by migrating |
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36:34 | . Okay, now when you get field studies it gets a little more |
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36:39 | . The only reason I mention this that there's a lot of effort and |
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36:45 | to reconstruct the any of them. lost cities from bed forms. And |
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37:01 | for example, you had a particular grained sand. You knew that they |
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37:13 | then and you knew it was Well, first of all probably wouldn't |
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37:20 | , you know, but you got narrow velocity range. So these diagrams |
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37:32 | ways to um in for potential velocities variations in velocity. These are a |
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37:45 | out of date now, but it's type of structure that goes into that |
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37:51 | . I talked about last time fulcrum of determining uh sources of sediment discharge |
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38:00 | one of the components is reconstructing the hydrology, reconstructing the velocity of the |
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38:09 | flow and that's where a lot of . And this is just another way |
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38:16 | looking at showing him doing hi David , the board of debt. So |
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38:26 | about 10 m and over water It's about 27, 10% of the |
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38:39 | down. Again, a lot of then just go back recently that transition |
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38:47 | ripples and no ripples, ripples versus planing. That's basically that transition between |
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38:56 | smooth and so it takes again, as long as this. If it |
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39:11 | completely smoothed out, it would be hydraulically smooth and you wouldn't have enough |
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39:17 | to get into it. But if any kind of turbulence little bump that |
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39:24 | a ripple effect in the ripples If you look at the flume like |
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39:30 | form instant once that little perturbation is into the ripples form and that is |
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39:36 | form roughness that allows the setting to transported. You don't need it |
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39:43 | The grange are thick enough to breach fiscal sub layer. They move as |
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39:50 | planer bed. Now in reality this not flying a plane, It's more |
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39:56 | a bed load sheet. This is cross section with this. So These |
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40:06 | five m. So 30 or 40 . Made 77 depressed. Um maybe |
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40:30 | centimeter high. Remember that stretched over mm as they move with time C |
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40:42 | of these little bars giving you this grained sand and planer sheets. But |
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40:55 | like this. Okay. And it even be Grap and what you won't |
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41:07 | our rippled across tracks down here Now, the upper player is easily |
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41:20 | . Um But in terms of the , you're about percent in the in |
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41:32 | flume Lord Player is out of Upper planner is anything But the other |
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41:42 | is the shape that's bad for is smoother and upper play here symmetrical. |
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41:56 | , clean. We'll talk more about infrastructures in the second half of the |
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42:02 | . Okay, I showed this before transition in bed forms from lower flow |
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42:15 | to upper floor regime. Okay. if we look at upper floor |
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42:23 | uh we see you go uh from dunes, great anti doom breaking waves |
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42:33 | shoot for. So these are features are were first seen in the lab |
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42:44 | that are associated with higher and higher most. And and we really haven't |
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42:52 | any of that in those bed phase that I've shown you so far. |
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42:58 | as we get into higher and higher , we're seeing a lot of changes |
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43:05 | those bed forms incentive infrastructures. So to see things like this dude's except |
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43:21 | required Again, this is a relatively this focus on upper flow regime has |
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43:32 | been in the last decade. And so what I'm gonna ask you |
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43:38 | do is add to that diagram. asked you to remember something like |
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43:49 | Anti anti dunes kids and fools psychic and I'll be describing each and more |
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43:59 | . Yeah. Let's begin to look little bit at the sediment structures. |
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44:06 | is a little bit early, but where the notes are. Um as |
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44:12 | food number approaches but does not exceed the upper plater exactly more similar to |
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44:27 | wow. That's overpaid and the individual are a one. And if you |
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44:41 | at it and process flat so so do we have perfectly spiritual grains range |
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44:52 | are elongated in some ways. So this shows is the fact that these |
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44:58 | parallel as you increase the increase the in play there. They're still oriented |
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45:16 | . We have the individual braids dipping street. Mhm. So we begin |
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45:25 | see that transition within flatbeds upper We see a transition until finally we're |
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45:33 | into antidotes. Now the antidotes remember there kind of like hydraulic jumps are |
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45:44 | really hydraulic jumps, but what happens perversion recent and breaking ways showed the |
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46:01 | of the settings and migrating upstream. can see that you can see the |
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46:11 | and the resulting bed forms. Or me rephrase that you see the surface |
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46:17 | of the antidotes in the water. in phase with the bottom and this |
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46:22 | what they look like. So, we likely to see them beaches? |
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46:30 | all seen anti dunes having been formed the beach. And that's one of |
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46:35 | two main places that you're likely to able to see it in the |
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46:43 | Now they can go from standing waves breaking waves. You see here, |
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46:53 | the waves are beginning to break and are breaking upstream. So this is |
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47:02 | the waves are breaking upstream. And you're you're getting such large bed forms |
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47:15 | you are getting true hydraulic jumps is clear, you're getting larger troughs and |
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47:26 | upstream dipping packets. Okay, so would be the kind of thin Hackett |
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47:40 | this is an increasingly large package. finally we get a very large upstream |
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47:54 | um out of phase bus migrating Yeah. So that's what we're seeing |
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48:03 | in this flu. Now they can so large that these cyclic steps and |
|
|
48:18 | . Wait, it's politics. baby. A couple of meters up |
|
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48:35 | . We need huge pages here. these are being formed in deep water |
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48:50 | submarine fails and these are the factors migrating up the seats more. You |
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49:07 | to do something. Okay, Um, how we doing on |
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49:22 | What time is it now? It's . What? Oh 10. |
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49:31 | Um, let's stop this. Recording it is. Okay. Um, |
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49:45 | see what we can do that's preserved the rock record to be able to |
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49:50 | those bed forms is the first Just again, a little bit of |
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49:54 | . Um we talk about stratified We talk about dad's eliminations. We |
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50:02 | to use cross bedding and cross stratified cross laminated the same. Uh that's |
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50:11 | incorrect if you want to be Stay across strategy. But that is |
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50:19 | thicker than a centimeter and a lamination less than a centimeter. So strictly |
|
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50:25 | , cross bedding for thicker, thicker . Cross laminated thin strategy. And |
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50:33 | individual strata can be defined by a of different things. Bedding planes, |
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50:40 | orientation. Remember we talked about implicated , sand. So up here, |
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50:52 | here appear we've got upstream dipping implicated here, flat sand. So that |
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51:03 | be that transition. I showed in upper planer zone from the lower velocity |
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51:10 | planter to the higher velocity variations in sand. We're going to see that |
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51:14 | lot when we look at lamination. all of these are ways in which |
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51:21 | lamb in a uh or the Better sand can be defined. |
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51:26 | we've got agreed upon criteria for how describe it. I don't expect you |
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51:33 | remember anything other than this except to that if you were in the business |
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51:40 | describing layers, there is a a between uh thin bedded and very thick |
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51:50 | and thick bedded etcetera. That actually enough. So you may use it |
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51:57 | in conversation but in reports and publications it has a family. Okay, |
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52:05 | the lamination, we better set lamination best or I should say strap are |
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52:12 | formed from a variety of processes grain deposition from suspension grain flow deposition from |
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52:23 | down the slip face, translation deposited a migrating rip. It says when |
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52:32 | should be just it could be water wind. Okay. And then what's |
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52:38 | attraction carpet. And this is a zone that is a type of brain |
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52:51 | where it's, there's a disperse it . Talk about a little more later |
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52:56 | um on a plane or surface that a upward Corsini later became So I'm |
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53:07 | use wind as an example only because easier to take a picture of these |
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53:13 | in Sandon and a dude. But we got the zone up in here |
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53:20 | sediment is deposited from suspension on the face. It's over steeping and fails |
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53:28 | . So here we have the collapse the grain flow. And then up |
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53:37 | here we've got migrating ripples that are to give us our translating strap. |
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|
53:44 | just for fun we've got price fossil well or what will become a trace |
|
|
53:51 | . Now, one of the reasons interested in these seemingly academic distinctions is |
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53:58 | are huge differences in the porosity and . Especially permeability of these different types |
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54:08 | strategy. If you look at grain , You have much higher permeability average |
|
|
54:17 | eight Darcy's in this particular field study translating strata. Two diversities and inter |
|
|
54:25 | forget. Okay, so we're gonna that as we begin to parse the |
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54:35 | say cross stratification into different types of and the different layers within different bed |
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54:42 | , migrating bed forms, it has differences in the flow conditions of our |
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54:49 | rock. Now the other thing we're do is we're gonna think about how |
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54:54 | package these various straps. For we can talk about a four set |
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55:02 | is pretty straightforward saying where we've got dipping strata typically confined by less dipping |
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55:13 | . And then we can talk about set which is a genetically related group |
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55:22 | layers and then we can talk about Cosette which is a group of a |
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55:28 | . It's a package of sense. let's start with the fourth set that's |
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55:35 | of the easiest thing to visualize and basically it's going to be associated mainly |
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55:43 | transverse bet forms migrating down street. , ripples and dips Okay, now |
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55:52 | that zonal flow separation occurs right about . Uh that occurs anytime there's greater |
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56:00 | about 12° depth. And as if a much lower, more subtle |
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56:08 | we don't create that zone of but once it builds up to |
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56:15 | then we begin to have this zone we could actually develop not only a |
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56:22 | flow, but maybe even upstream migrating at the base. So here we've |
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56:31 | this then then because it's big that depositing down a slip face. So |
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56:43 | basically the result of that downstream Now, if we look at the |
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56:50 | of that, particularly that basic it can be angular and gentle or |
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57:02 | . And what that represents is the from moving mainly as bed load to |
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57:10 | amounts of suspended. So what suspended does is tends to stop and and |
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57:25 | the bottom of their slip face. is just due to avalanches drain flow |
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57:33 | , we've got the deposition of sediment suspension and actually in this particular |
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57:40 | we can actually have upstream ripples as . So we're already seeing how that |
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57:47 | shape of the cross strap, particularly the base. Tell us something about |
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57:53 | relative strength of flow and the type sediment deposition mechanism. So we here |
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58:03 | got that grain flow coming down on left and that tangential modification by deposition |
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58:14 | sediment in that eddy zone. And in some cases reverse ripples. |
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58:23 | if we look at that grain flow in here, what we see is |
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58:38 | a downstream increasing grain sauce and we see it's inversely great. The inverse |
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58:47 | is is the result of that traction disperses pressure that forces the bigger grains |
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58:54 | the grain grain contact towards the Its inverse rating in addition as its |
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59:02 | ng down the slip face if you've been on a sand dune and noticed |
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59:07 | an avalanche forms the coarser grains. the finer grains, hire women. |
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59:15 | so as a result, you go finer grain strata at the top of |
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59:21 | grain flow to of course your grain at the bottom and it's inversely great |
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59:28 | from rainfall is just the opposite. other words, once that get out |
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59:35 | money suspension, what's gonna because it first courses stuff what's transported farther the |
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59:45 | . So it's going to find down or down slow and it tends to |
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59:53 | or anyone spot The course is settling the five. So that's gonna be |
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59:59 | . So there's a significant difference between grain size patterns of rainfall versus grain |
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|
60:13 | . So let's just take a test here's the basal contact and particularly right |
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60:22 | in here. Okay, because this coming down to about here, would |
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60:31 | call that basal contact, angular tangential com K. Baby? What do |
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60:41 | think? Uh huh not concave? , so that leaves us two |
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60:47 | Uh Robbie is down to you. have 5050 chance I think so |
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60:57 | To me it looks angry. Um So yeah, I mean when |
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61:10 | look at this contact it's pretty steep the way down. Okay, it's |
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61:19 | much like this. There's not even hint. Well this is the only |
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61:28 | where it looks slightly tangential and that's a slightly different phase of pro |
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61:36 | Okay, now the the other thing like you to know besides the angular |
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61:43 | is the top is the top cut like this. I I don't see |
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61:55 | . It looks like it's gradation all plane to slip face plane. And |
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62:06 | is kind of a breaking slope right here. And that's actually the brink |
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62:14 | . Remember I said that sometimes you've a great point and it's something one |
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62:23 | . So you can actually get what like a top set if you got |
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62:30 | entire doom preserved. Now, the that's rare is because usually the top |
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62:37 | the dune is truncated by the next or next Bedford. But here we |
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62:45 | see the entire dune preserve. now over here we don't the top |
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62:57 | this spin is truncated by another dune top of it and it's truncating a |
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63:04 | below it. Okay, so the now is as before, is it |
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63:11 | tangential or concave? Robin? Okay, what do you think? |
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63:24 | agree that again? This this unit ? Yeah, I I agree agree |
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63:50 | with you painting because this part looks straight, it only begins to curve |
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63:56 | around in here and then it becomes ginger. Okay, so I I |
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64:05 | suggest that unlike the previous one which formed strictly by avalanche, this probably |
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64:13 | more suspended. Okay. Uh No. You know the other thing |
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64:29 | in here, it actually flattens out the point where it's almost the |
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64:36 | And if we got upset 4th not much of um the bottom of |
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64:49 | transverse platform, particularly if they have lot of suspended sediment. And if |
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64:54 | any reversals that becomes really important. of all, it's it's square. |
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65:00 | might see preserved those backflow ripples is to be on the bottom, said |
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65:07 | here's just an example and you can these ripples trying to go up the |
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65:20 | of the flow was giving you more a tangential flow a tangential look. |
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65:26 | it says that the host set is very distinct from the four set. |
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65:34 | . In fact, again, there see that upset four set bottom |
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65:41 | Uh Now a couple of things about bottom sets, they actually have the |
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65:45 | preservation potential and the top says the preservation potential. Yeah. Uh |
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65:54 | And so they are more important in sense not more important but their importance |
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66:02 | magnified to the point where sometimes that's you get depending on how much erosion |
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66:10 | occurring during that deposition. Okay, preservation pretty rare. That would be |
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66:17 | example of what we saw the So we didn't really have courses because |
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66:23 | was um, Lord lost a this is the second example. We |
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66:30 | didn't have the top six. We down here. I don't have an |
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66:35 | of it. But you can imagine it uh, you've lost all the |
|
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66:41 | . So again, here's the full talked about now, one of the |
|
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66:47 | that's important is that not only are bottom sets different uh morphology, if |
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67:01 | rippled, they tend to be different size and different ferocity. Especially as |
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67:10 | get more and more rainfall or suspended . Rather they're gonna be fine or |
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|
67:17 | . And so what those zones do they represent flow barriers. So you're |
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67:24 | to look at a series of low associated with these basal programming dudes. |
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67:34 | , this is most obvious in the deposits, but it can also occur |
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67:40 | uh uh area some as well. keep in mind that as we see |
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67:55 | accreting zone of dune deposition, we packages of higher and lower porosity and |
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|
68:06 | . Yeah. Phone by presidential potential grain local flow barriers for variable. |
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68:17 | can affect both vertical and lateral from building, usually unsteady flow that. |
|
|
68:26 | let's look at the forceps now and about what's going on within the forceps |
|
|
68:31 | terms of avalanche versus rainfall, the creatures. Or if we look at |
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68:48 | in a horizontal cut, you see the brain, Whoa, Evel. |
|
|
68:59 | they are working hip section. So just have a look at that saying |
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69:09 | imagine what a cross section might look going from. So the head of |
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69:15 | flow, it's going to flow and flow. So if I did a |
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69:26 | is gonna be the grain fall and , there's going to be a truncated |
|
|
69:44 | . A double scarf up in B. It's gonna be low |
|
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69:56 | So we've got a logo at the and then going down flow. We've |
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70:11 | this down flow low and if I it horizontally, you see this, |
|
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70:24 | scarves up here. Okay. And if we looked at the rating, |
|
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70:33 | going to be course towards the And if we looked at or down |
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70:40 | grading, find the course and then the grade, most of it's gonna |
|
|
70:48 | inversely grade. Now, another feature the four sets are local provocations. |
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|
70:58 | are called reactivation services. So we the flow coming in truncated and in |
|
|
71:11 | and that we see here with the here, I forgot that that was |
|
|
71:16 | same thing. Here's another one. gradation truncation, Pro gradation location. |
|
|
71:31 | , So those are the reactivation Okay, Now, those The four |
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|
71:43 | consist mainly a great falling, great . They can be locally truncated by |
|
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71:49 | services and they can be either cross or cross laminated. Any how thick |
|
|
71:57 | individual lamination czar. They can grade into bottom sets and upward into top |
|
|
72:09 | . Now what I wanna do next to begin to subdivide larger packages of |
|
|
72:19 | structures into sets and co sets. let's look at this package of sediment |
|
|
72:31 | . Okay, here is a set to here. Here's another one and |
|
|
72:41 | one. Okay, here's one That's basically what they've been looking at |
|
|
72:47 | a set and a set is basically assemblage of strata deposited by migrating |
|
|
72:56 | One rip one did. Yeah. set here is similar to this set |
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|
73:07 | this set. In other words there multiple dunes migrating one on top of |
|
|
73:18 | . But they're genetically related, they during the same event and then all |
|
|
73:24 | a sudden we get some change so genetically related package of sets is over |
|
|
73:38 | by something different. So we're gonna those lower sets a Cosette and now |
|
|
73:46 | gonna call all of these sets a Cosette. Now in cross section. |
|
|
73:55 | . In you these says don't look different. But why do you suppose |
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|
74:04 | decided that this said is different from set and therefore should be in a |
|
|
74:13 | Cosette. What do you see that's . Um Is that cross bedded down |
|
|
74:39 | . Not here. Okay, close this actually is a type of and |
|
|
74:47 | is what we go through. This more I mentioned it perform which probably |
|
|
74:57 | , this is what you get a D. Transfer. This is what |
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|
75:07 | get. Yes these could be any scale. This could be yes. |
|
|
75:16 | let us assume they were. Do think therefore this is going from high |
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|
75:24 | velocity, low velocity high up Thanks. Okay continue to exactly. |
|
|
75:42 | back to that diagram. Everyone the a deposition of wayne in florida. |
|
|
75:57 | . Uh now we can also look the idea of sets and cassettes into |
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|
76:04 | nature of boundaries. So The first down this here that rates two |
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|
76:14 | In other words it's street migration. in the second order that are a |
|
|
76:28 | service step rates concepts. In other this type of, that's the second |
|
|
76:41 | balance and a third order it basically together genetically related cassettes. So think |
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|
76:54 | it as a flood deposits a group sediments deposited during a single event. |
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|
77:01 | going back to this um this would a second order bounding surface. Whereas |
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|
77:12 | over here would be a first order surface and we don't see in this |
|
|
77:18 | the whole event grouping but we'll see elsewhere. Now. In fact as |
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|
77:29 | go from little that's the big first order, 2nd, 3rd order |
|
|
77:45 | 3rd and 4th uh finding event. order is the basic champ is basically |
|
|
78:00 | end. Thanks. So, going to here, we set first order |
|
|
78:10 | . So I showed you this, a lot of information you could clean |
|
|
78:15 | this folk. We're without the annotation . Um I'm gonna skip this except |
|
|
78:28 | say as we get into increasingly complex beds, mid sets. Um We're |
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|
78:40 | going to be constructing large candles. programming strong faces. Everything I've said |
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|
78:52 | respect to sets to this point is to uni directional flow, mainly in |
|
|
78:59 | . We're gonna see that concept can over into the only deposits marine |
|
|
79:11 | Deep Sea 7, 7. And is how that first order set |
|
|
79:19 | Five trans relation of these programming But look at the top versus the |
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|
79:31 | . Uh We're actually changing something is go from top to bottom. And |
|
|
79:39 | is the rate of deposition. So the top one we're actually going to |
|
|
79:53 | isolated ripples packages. These are sometimes star ripples. There's just not enough |
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80:01 | for them to climb on top of other. But as we increase the |
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80:05 | of sediment deposition of sediment supplying The ripples begin to a grade |
|
|
80:13 | And so that's what we call climbing . Okay. Each of which in |
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|
80:18 | particular case, all these ripples, could be doomed. But here they're |
|
|
80:24 | all these sets are related to the type of bed form. So they're |
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|
80:31 | part of the same Cosette. And on how much erosion occurs on the |
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|
80:37 | side, the maximum set thickness can no greater than the height of the |
|
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80:43 | form. So when we go back this, we know that could not |
|
|
80:53 | any tires any other. Now there a hint, but I didn't absolutely |
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81:06 | suspect this higher. And they want know the height of the bed floor |
|
|
81:16 | , among other things, that's going give us information about the strength of |
|
|
81:20 | in the water depth. Now, we look at climbing climbing, we |
|
|
81:35 | see a variation by only the four we had to get to see so |
|
|
81:51 | a priest, the backside. finally they just literally rolled straight up |
|
|
81:58 | we see variations of that thing Where And I don't you don't have |
|
|
82:05 | know rather remember these phrases. What do need to know is that that |
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|
82:15 | is increasing amount, relative amount of set. Okay, And so you |
|
|
82:21 | see here, uh you still see backsides. So this is the angle |
|
|
82:31 | climb. That angle of climb is to go almost vertically. So, |
|
|
82:39 | actually seeing an increase in the amount deposition suspended sediment while these ripples were |
|
|
82:47 | . And that's typical of flood events rivers. So, here's that angle |
|
|
82:55 | plan, going from literally the dark , two ripples with the backside |
|
|
83:11 | This is worse, increased amount of deposition. Now, this is what |
|
|
83:23 | were describing looking. But the problem sometimes It's hard to see the four |
|
|
83:36 | , especially if they're just saying the are thin. So sometimes what we |
|
|
83:43 | see and the lamination are really we just can't see the forces. |
|
|
83:55 | so that's what we call translate Sometimes they're called sued elimination because they're |
|
|
84:03 | actually a boundary searches and taking on like these. Now with rivers, |
|
|
84:17 | if there hasn't been a lot of . Even growth, you pretty much |
|
|
84:23 | see four cents where you can almost play where you rarely see process or |
|
|
84:35 | so one of the distinctions will Look at the only deposits is the |
|
|
84:41 | of the translating scrapple from truncated ripples almost invisible. So again, here |
|
|
84:59 | see the fine and we see that really quite strong, almost vertical. |
|
|
85:11 | down here you actually see truncated back sets to preserved. So sad and |
|
|
85:25 | almost vertically. Accreting everything here is deposition during increased volume. A rate |
|
|
85:36 | suspended self. Okay, now I this earlier, but I didn't focus |
|
|
85:42 | as much as I should have when look at two D dunes or |
|
|
85:51 | If we have a true dip section right angles to the strike of the |
|
|
86:01 | , The first order bounding surfaces separating will be sub parallel. In |
|
|
86:09 | ideally if it's a perfectly linear they will be parallel. Okay, |
|
|
86:21 | if the strike section is truly parallel the crest, you're gonna have apparent |
|
|
86:32 | that are horizontal or very low angle . There still be sets boundaries. |
|
|
86:39 | order bounding surface system, but there'll low angle because you never have a |
|
|
86:47 | plainer linear feature and you never have exposure exactly parallel to the rest. |
|
|
86:56 | we get into three D dunes, a scour pit. The dips are |
|
|
87:01 | multiple directions. And so the sets the dip section, you'll see some |
|
|
87:10 | Phil and in the strike section you'll a scallop. Their results in this |
|
|
87:19 | of the scallop pool. So this that trough cross stratified sand? There's |
|
|
87:26 | cross stratified sedimentary structure to talk Yeah, now we're gonna call these |
|
|
87:35 | across strata and trough cross strap. also see in the literature uh plainer |
|
|
87:45 | strap. I find that confusing with betting it's a lot preferred tabular but |
|
|
87:55 | hear about it. So we could a habit or cross stratified sand by |
|
|
88:04 | or about dudes. Okay, so look at some ripples. This is |
|
|
88:11 | actually let me just ask you, this saying strike section or a dip |
|
|
88:18 | , dip sections being in the direction flow? Yeah. Is what dip |
|
|
88:29 | flows here. We've got the four exposed here are the sets. I'd |
|
|
88:37 | the first order bounding services which are sense and you can, I think |
|
|
88:45 | can convince yourself here, this is four sets a lot of suspended |
|
|
88:53 | Okay here again, we've got sets of the things to notice and and |
|
|
89:03 | hard for me to draw being left . No, that the bottom part |
|
|
89:12 | that set of ripples is Lighter than four set. So there's actually a |
|
|
89:21 | set formed by this river. The stuff probably is um organic material. |
|
|
89:30 | up here, look at what we , we see a ripple that is |
|
|
89:40 | that those ripples that were forming the Travis. So we actually see the |
|
|
89:46 | form here that formed across the out here. And the reason we see |
|
|
89:54 | is because its mantle with mud. that real dark stuff on the |
|
|
89:59 | that's mine. So we've got first bounding surfaces all along here. Then |
|
|
90:05 | have a mud drape Which if we draw the base of it would be |
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90:10 | second order bounding surface. And then the top of the mud rate, |
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90:15 | third order bounding surplus. Why? ? Because the mud drape basically says |
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90:21 | event is over that flood event that depositing all of this stuff and whatever |
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90:28 | can't see at the bottom ended with deposition of the Hence three Dimensions. |
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90:38 | , three dimensional bounding surface. here is a strike section and here's |
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90:45 | very clear that we're looking at Now they're small troughs because they're small |
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90:56 | . But if we took a picture horse green dooms that would actually look |
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91:04 | just bigger deal. So that's what looking at now the two D dunes |
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91:11 | tablet across strata. The three Dunes 12 across strata. And just |
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91:16 | kind of visually this is what it like when it zoomed is bent. |
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91:23 | is the trough that was filled with dipping set and if you truncate |
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91:36 | those troughs are cutting into other And so I guess what's called rib |
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91:48 | , which is what is going on and you can even get that in |
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91:56 | . Okay, so let's have another , so to speak. Let's look |
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92:02 | this particular exposure and it's certainly cross deposits. It's sand. It's variable |
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92:17 | it's coarse sand. So we can with that when when I kind of |
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92:25 | a in the outcrop. My first is to define the bounding services. |
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92:34 | I've got bounding surfaces here here here . Little fuzzy here, but there's |
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92:41 | here here, this one here looks this here. So I'm gonna start |
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92:53 | defining them both where they occur in G. On the trip. |
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93:12 | And there's in geometry. I'm thinking the cross sectional shape everybody and the |
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93:26 | . So let's start with thickness. Robbie, how would you describe the |
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93:33 | in thickness of the sets? Going bottom to top. It's it. |
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93:43 | , they're thickening. Okay. Um Okay so Hayden, how would |
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93:50 | describe the shape of the sets as go from bottom to top. |
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94:06 | okay, again, I don't like laminar. But uh there is a |
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94:12 | a term first of all uh as this is a dip section, flow |
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94:19 | left to rot. Let's go describe the lower stance or set boundaries different |
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94:29 | said this one. There's another one in here. Lower angle. |
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94:39 | Lower angle. Think about it in of this. Are they more like |
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94:48 | or travel across strata in dip Yeah. Yeah. Uh And the |
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94:57 | with tabular, Is there pretty much Jack over some distance? And so |
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95:07 | what do we say at top? , the top Which is called |
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95:19 | 12. Okay. Okay. So got several observations that we can |
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95:29 | We have sets that are on the of a few millimeters to Yes, |
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95:39 | mean thickening upward. All things equal higher bed forms. These are |
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95:52 | How do I know they're dunes? if no one at some point they're |
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95:56 | high to be ripples secondly, have told you. Of course Grant |
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96:00 | Okay, so we got dunes that getting all things equal. Again larger |
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96:09 | larger as we grow up the Now there's no obvious truncation to suggest |
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96:18 | are different flow events. So this probably one major flow event. The |
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96:27 | here. This is again down in . This is a first order bounding |
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96:40 | . What's going on here. What you say is going on at that |
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96:46 | surface? Is there a transition that can see, you may want to |
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96:58 | it here. So yeah, that's second order bounding surface. And |
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97:10 | Oops. Okay, why did you it a second order down the |
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97:21 | Because it's going from tabular to trough strata and therefore from two dimensional to |
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97:29 | dimension. Dudes. Okay, now third order is blow us in on |
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97:35 | of this. We don't know, it's pretty thick positive for an |
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97:39 | Okay, down with uh this transition tabular to trough, would you say |
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97:49 | increasing or decreasing velocity as we go straight up section, We're increasing. |
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97:57 | , we're going D-3 d. And also increasing the height of the bed |
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98:03 | . All of this is occurring during flood a river. So I suggest |
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98:10 | this is actually the rising limb of flood hydrographic as the water is getting |
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98:19 | and the velocity is getting higher, dunes are getting two dimensional dunes are |
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98:26 | higher until they grade into three dimensional . I didn't hire yet. That's |
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98:31 | lot of information that you can do reconstruct the flow conditions of these bed |
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98:39 | . Okay, again, ripples are ripples. Okay, that is a |
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98:50 | army knife uh about this much call six centimeters, maybe 10 centimeters. |
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98:59 | is this uh form by ripple, ? It's too big. So this |
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99:07 | to be do uh but let's play game? Oh and also it's the |
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99:14 | direction left to right. It's clearly oriented. But let's play that game |
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99:20 | uh defining the bounding services. Okay if we got dunes at the bottom |
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99:47 | do you think we have up here here? Yeah so we go from |
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99:58 | to rips. We go from thick to decreasing set thickness within the |
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100:09 | So that suggests maybe water depth is and maybe velocity is decreasing. Not |
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100:17 | sure yet. But uh second thing looking at is by the way there's |
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100:22 | bounding surface down here and there's a of a zone here that I would |
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100:27 | as a bottom set. Now if look at these bottoms here there's some |
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100:35 | of suspension but basically a lot of is pretty straight and then we get |
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100:42 | ripple cross laminate. Mhm. So lower part tabular cross stratified dues. |
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100:53 | the upper part though. And maybe can see a little more clearly now |
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101:00 | got ripples. And You think those are two D. or three |
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101:11 | Three D. Because they're pinching out in deep section. And then finally |
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101:19 | got thick mud rate. So again order. Second order. First |
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101:29 | And down here I suspect that's another order because I think this is pretty |
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101:36 | one flood packet. Yeah. Now you had a core uh you could |
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101:49 | tell a similar story. The only you wouldn't be able to tell for |
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101:54 | is whether or not. And and had never really quite said it or |
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102:01 | tabular or not based on this. are pretty parallel sets are pretty constant |
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102:08 | . So I would say tabular. . The fact that this is kind |
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102:13 | horizontal, this is what makes you it may be tap water, but |
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102:18 | sure you know what to do. , and these are four cents. |
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102:23 | still have a first and now, know here That these are ripples and |
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102:30 | even in core you can see there three D ripples. So this is |
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102:36 | order and then this mud is gonna a third order downing surface. So |
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102:42 | can make a lot of these distinctions poor. Now one of the games |
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102:51 | play is trying to reconstruct flow depth set thickness of dunes, We know |
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103:00 | dunes are at least seven cm We know that they usually scale to |
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103:08 | measure of flow depth. one of problems is we rarely get a complete |
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103:16 | of the doom. There's always almost always some truncation. So we |
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103:23 | , alright, the the height mean of the dunes of the the sense |
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103:31 | is typically rather of the dune height typically some fraction of the septic, |
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103:39 | sorry, the set thickness is some of the dune height 2 - three |
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103:47 | as high. And so if we that we can maybe try to predict |
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103:54 | hide and from that, so So here we've got two m uh |
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104:07 | Um almost three, let's say, call it two m in height is |
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104:12 | complete heights because uh we haven't seen truncated. So that suggests that the |
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104:18 | on top was on the order of m above the point bar at this |
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104:29 | , which again actually is pretty pretty for this. Uh The problem is |
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104:36 | been a lot of work more recently dune hide versus flood depth and there's |
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104:43 | lot of variability and so lot of within scatter and variability as we get |
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104:54 | higher and higher flood depths. So range of uncertainty is pretty high. |
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105:02 | so don't you will see people trying reconstruct flow depth. Sometimes it's a |
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105:11 | it's the only thing you got but the very potential errors in those |
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105:20 | And then God forbid you're trying to flow depth to predict Haley of |
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105:27 | hydrology and sediment transport and add on . Oh, yeah. And I |
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105:33 | to estimate channel slope. It results a very wide range of estimates. |
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105:45 | I said, trough cross stratification, shape is the same. The only |
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105:52 | is scale and dunes. Well, are really big dudes in very coarse |
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105:59 | gravel, except here, these are . See this big chunk here |
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106:09 | we're looking at amalgamated channels and you can't tell where the base of one |
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106:16 | is. These are at least this here is probably 1/5 order bounding |
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106:21 | The base of the channel. So we get channels depositing on top of |
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106:27 | other, the lower part of the field typically is the one highest |
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106:33 | So we may well have 1st, , 3rd, 4th and 5th quarter |
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106:41 | surfaces in that amalgamated channel field. , so that's kind of what we're |
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106:46 | at here. I'm not gonna bother this, but this clearly is is |
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106:52 | dune. We talked about that. here we have the trough cross strata |
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106:59 | more sandy dudes as opposed to more debts. And here, one of |
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107:08 | favorites here, we actually have that point preserved the crest. And then |
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107:15 | have all sorts of ripple uh cross . We've got the two D. |
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107:24 | overlaying by three D. Ripples. , we could go through the same |
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107:29 | saying what we could do with a on. That's what um According to |
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107:44 | , the height of the dunes scales flow depth. I've already said. |
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107:50 | iffy. Uh But here are the in dune height and spacing in what |
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107:57 | call again, the very large are gonna be unit bars and probably do |
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108:05 | and do not scale with water And so this type of stuff in |
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108:14 | was before our recognition that these larger are really different types of bed |
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108:22 | Okay. Uh And here we have Dunes here and three d. Dunes |
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108:34 | their superimposed by the larger features excellent this. Oh, there's some little |
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108:45 | dudes down here, you can't really well uh which are unit bars. |
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108:51 | , so we've got unit bars, on the unit bar um the flow |
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108:58 | oops, The flow direction is kind coming like this. We can tell |
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109:03 | flow direction by looking at the the of the dude's unit bars are often |
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109:12 | an angle to flow direction. So you're looking for evidence of flow |
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109:18 | stick to the dudes, not the bars and also not the ripples because |
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109:23 | ripples are too easily modified by float . Okay, so down here, |
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109:34 | most likely is a unit bar with dunes on top. Okay. And |
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109:45 | probably is something like this where we a point bar. We've got these |
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109:50 | bars with the dunes down here and they as an aggregate form a point |
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109:59 | or sometimes called the compound can. when we look at the sediment deposited |
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110:10 | that point bar, we're gonna see and dunes and unit bars in flood |
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110:19 | , defined by migrating flood packets. what we're gonna anticipate when we look |
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110:25 | river deposits. Now, this particular deposit, these are this is a |
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110:32 | note, the fine grain, this the trinity. This is the |
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110:36 | santa's little coarser grained. And these are are gonna be unit bars. |
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110:46 | , With little dunes in between. gonna dig a trench right here and |
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110:55 | is the unit bar crest. This Roxana Herrero masters student and this is |
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111:04 | deposit of that migrating unit bar. . And so it's about a meter |
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111:17 | . And as we go back it's something like 100 m wavelength between that |
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111:26 | the next unit bar. Now unit have been described a lot on graded |
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111:35 | and that's in part because they're easily access. So here is a unit |
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111:41 | that's been pro grading, it's about meter thick, Not unlike what we |
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111:46 | actually a little lower that, but notice there are reactivation services and we |
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111:55 | see that unit bar broken up into . And that's because unit bars will |
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112:05 | pro grade so far during a single . And then there may be mud |
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112:11 | , there may be modification. the bar pressed and then it's reactivated |
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112:18 | the next event. So what happens what appears to be a very laterally |
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112:25 | cross stratified set is really broken up reactivation services, which could be mud |
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112:31 | and therefore affects the lateral permeability. vertical permeability is a lot more variable |
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112:40 | the bottom and top are often separated finer grained material. Uh Here we |
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112:49 | what are probably unit bars in the river with dunes on top of So |
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112:59 | scales, uh 100 50 m here here, 10 m high, we |
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113:08 | get some pretty big uh features in . Yes. Now everything I've said |
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113:18 | this point is uh related to lower regime, transverse bed forms increasingly, |
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113:28 | seeing evidence of upper flow regime bed uh like anti dunes chutes and pools |
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113:38 | cyclic steps. Now the transition from to plain bed to anti dunes is |
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113:48 | what are called humpback dunes. And basically dunes that are beginning to be |
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113:55 | . And so their gradation all. at some point you begin to get |
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114:01 | this, there's no angle described So finally we get nothing but minor |
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114:16 | . And and so let's look at upper player bed reading a ripple. |
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114:26 | look at that transition where we've gone dunes to humpback dunes to planer |
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114:35 | Okay, well, the planter they're usually in birthday graded because its |
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114:43 | carpet. And one of their characteristics that there is a parting linea ation |
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114:55 | at at the bedding surface and that reflecting that parallel linea ation of the |
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115:05 | grains I showed earlier. So when break these parts, you see this |
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115:10 | life. Okay, So parting radiations characteristic of upper floozy place, your |
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|
115:19 | . Yeah. Uh And then that's dip section usually adversely graded. And |
|
|
115:26 | again a picture of parting linea ations . Now here we've got our in |
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115:38 | beds upper floor regime less than a high wavelengths pretty long. Desa |
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115:49 | Okay. Hello conditions uh pretty high of phase And individual grains parallel to |
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116:04 | flow. And at least in the part of the upward cleaner beds. |
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116:10 | have these low angle bed forms or depositing flat rains increased velocity. |
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116:23 | lose those bed forms and we get implications in cross section. The individual |
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116:33 | are moving as a carpet, the are interacting, there's a zone collision |
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116:46 | graze in the Salvation. In that of collection results in the capture grains |
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116:54 | migrated up to the that was not pressure. They can't move laterally, |
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117:05 | start down. They have to. in verse three. Now, let's |
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117:20 | as we go from that planter bed the antidotes. And again, you'll |
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|
117:25 | it mainly on beaches. You do cross section here, you see that |
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117:31 | beds are dipping like this, but flow of the water actually is like |
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117:42 | . So the bed form is migrating and I have not seeing these real |
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|
117:52 | . But here is an antidote dipping float and and those when you start |
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118:05 | at it more carefully. There are low angle truncation and kind of little |
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118:15 | . So planer too. And he not unusual assemblage easily overlooked. I've |
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118:24 | them more times than I want to . Now a second place where you're |
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118:30 | to see him in the field is a sand flat and were braided stream |
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|
118:36 | you got ripples that are being cleaned . And this is an example of |
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118:41 | type of anti do cross stratification that will get in the great sand dunes |
|
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118:46 | the river. And this is a of some of the sand deposits from |
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118:56 | Medina River at low flow. And can see how the upstream Migrating bed |
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119:04 | giving upstream migrating or upstream dipping four okay. Um This is just a |
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119:13 | 30 showing the breaking way, throwing upstream migration afloat. And these are |
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119:23 | some examples of what it would look without going into details. But this |
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119:30 | what the cross section in. Thank Michael. It's almost like it's trough |
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119:38 | stratified, but these aren't angled. other way of distinguishing it from 12 |
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119:44 | stratification. Look at the dip century playing so this, you can honestly |
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119:53 | be tabular unless you saw it over . In case of this might be |
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120:00 | story here. Clearly not okay in again, but oh, in this |
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120:17 | exclude in the case of the river , you basically go once you determine |
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120:34 | this is an anti, you know it's now in some cases you have |
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120:42 | program information like this may break down to, but at the beginning of |
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120:56 | you either have to know that this an upstream or you have to have |
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121:09 | associating uh flow indicator. That's good you. Right again, just more |
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121:21 | the same. Um I include this because this is a peel that was |
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121:29 | from hurricane harvey deposits on the on the buffalo bile and one of |
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121:37 | students was doing their masters on And this is the first time I |
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121:42 | recognized upper floor regime. Anti dunes a flu viel deposit that wasn't a |
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121:52 | flat. This was just a good point bar. But the appeal brought |
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121:59 | the variations in permeability, which is in brain size and emphasize these low |
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122:08 | plantations and dip to our right to flow, left and right. That's |
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122:17 | I'm saying. They're probably, they're more common. And I realized, |
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122:23 | think most people realize He's just six . Uh, and again, more |
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122:33 | notice here we're beginning to get prior dippy upstream, but we're going to |
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122:42 | bigger scout as flow velocity increases. begin to go any due to choose |
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122:52 | . Uh, this is one of friends working on alluvial deposits. These |
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122:57 | playing beds are pretty thick. That a little surprising. But then we |
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123:02 | into this and this was actually the time in the field. See |
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123:11 | Uh, and if the student has to, if you're dipping up |
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123:17 | the clothes, right. This is large, y'all want to build and |
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123:27 | we're looking at is something more like . We're going beyond the interview, |
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123:36 | into chips and pools. Yeah. . So this is if you |
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123:47 | uh, as different people define There's more of the same escaping. |
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124:03 | , and here we have unstable No anti dams the suggestion here is |
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124:21 | they can migrate their stable, they're saying you'll never see this almost always |
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124:29 | to be unstable and they will give these wasn't shaped packets of sex dipping |
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124:38 | strength, the cool larger sour uh . Uh so regular doom anti that's |
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125:06 | sequence we see. And this is of what you're looking any news coming |
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125:16 | that uh, and I'm not gonna into this more except this is just |
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|
125:26 | to show how you can use the of set boundaries and bounding surfaces to |
|
|
125:34 | um different types of upper flow regime in this feature here. This is |
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|
125:43 | sea floor and these are migrating literally measure erosion deposition by repeated metric |
|
|
125:56 | Look at these seven waves that are flow regime and look at what they |
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|
126:02 | like. Uh, and here is a cyclic step interpreter. So we |
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126:11 | these upper flow regime type structures even on submarine fans, in certain places |
|
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126:22 | fans, not everyone, but particularly we're going from and find axial flow |
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126:32 | a jet flow is beginning spread out the fan from the channel to the |
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|
126:38 | . We tend to get these and what I show here. That is |
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126:46 | large scale horse brains ships and foods accepts this case. Okay, so |
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126:58 | me end by reiterating that we can different packages based on they bounding |
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127:15 | So yeah, 1st and 2nd order , we could start at the other |
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|
127:23 | and say we've got a very large meander built the big Neanderthal. It's |
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127:32 | 600 individual channels. Our 5th order services within the channel we have flood |
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127:47 | of metal bars that are free. the fifth order bottom there is increasing |
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128:00 | downstream creating that will be each of . Also is 1/4 order. That |
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128:14 | order package bounds either single or multiple and talk more about this. The |
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128:28 | absence of these is the unit bar gonna determine whether not blood Package will |
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128:39 | bound by 3rd or 4th. And then within that we've got the |
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128:48 | order package please. Uh 1st and I don't like I'm like recessed Because |
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128:58 | really wanted to see 1, 3. So we got, when |
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129:06 | started down services, cassettes, packages concepts feature basically process go back |
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129:17 | Now this to end. Uh let say when you're measuring a section of |
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129:26 | a lot of logging up from the sometimes use a shorthand or what we're |
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129:35 | at capital S capital he B four . But I'm gonna call it problem |
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129:54 | we don't distinguish between two and sure four. Oclock its really low |
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130:11 | cross strap broad channel scours the massive could be because understand or or typically |
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130:28 | we lost and we can do the thing gravel. Is it Matrix |
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130:35 | Class supported. Will actually use this we talk about and this is just |
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130:44 | for general, a little different but beginning to get closer to a, |
|
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130:54 | kind of common shorthand about describing, , core in sections with uh, |
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131:03 | shorthand gets complicated. You don't need read this but just recognize there is |
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131:08 | least a template that's available or dealing measure sections. Okay, so that's |
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131:19 | for this morning. We can check , uh, recording down and it's |
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131:27 | for lunch. So it's 11:30. about 12:30 to come back? |
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131:40 | Thank |
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