| 00:22 | We got it now. Okay. right, okay. We're back to |
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| 00:29 | coast, we've left the continental continental deposition systems. So we're gonna |
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| 00:36 | with war tides and tidal flats uh, and you may have recognized |
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| 00:42 | now that one of the important aspects each of these deposition systems um are |
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| 00:49 | characteristic types of processes and resulting bed structures and the like um characterizing. |
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| 01:00 | with rivers were pretty comfortable now with directional flow in water with alluvial |
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| 01:08 | We've added debris flows and cheap flood the aeolian deposits. We've added the |
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| 01:14 | of transportation by wind. And now gonna look at the effect of tides |
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| 01:20 | the title signature. Now, in , uh there is in all of |
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| 01:27 | systems, a wide variety of variables affect it. Uh and they're more |
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| 01:36 | less intuitive, but what I want focus on is the effect of tides |
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| 01:41 | tidal range. And he said that are almost as important even in tide |
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| 01:48 | settings. So if we look at global distribution of tidal range today, |
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| 01:56 | there's no apparent latitude control unlike, , weathering or climate, which we |
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| 02:04 | earlier. Um And what we're looking here is the spring title range. |
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| 02:10 | what we're looking at is basically I'm gonna subdivided eggs micro title. |
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| 02:18 | is less than two m mess a 2 to 4 m macro title for |
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| 02:24 | above. Now when you do that in the early seventies, uh Miles |
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| 02:32 | recognized as he was doing a contract the US Navy, that there seems |
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| 02:39 | be a variation uh between the types coastal systems that we get as a |
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| 02:47 | of tidal range. So when we're the micro tidal range, we get |
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| 02:52 | lot of barrier islands and tidal uh flood title deltas, uh not |
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| 03:00 | much tidal flats. Salt marshes as range increases, the tidal inlets become |
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| 03:07 | bigger, the title deltas become bigger the tidal flats and salt marshes become |
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| 03:13 | abundant Until finally, when you basically beyond about four m, you lose |
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| 03:19 | barrier islands and the associated fishes and basically have tidal flats, salt marshes |
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| 03:26 | subtitle sand shoals and ridges. Now people began to look at it more |
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| 03:34 | , they recognized that in reality we be thinking not just about tidal |
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| 03:40 | but effective wave energy as well. if you have higher waves, then |
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| 03:46 | tends to dampen the effect of And so if we look at the |
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| 03:51 | effects uh wave energy, we see we, we get a transition from |
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| 03:58 | are better called wave dominated the tide coastal aesthetics. And this is a |
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| 04:06 | diagram to kind of focus on because in wave dominated settings, think texas |
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| 04:15 | , we get these elongate barrier islands virtually no tidal flats. Uh When |
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| 04:21 | get to mixed energy, we get stubby barrier islands and a lot of |
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| 04:27 | flats. And when we get to dominated settings, we get no barrier |
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| 04:34 | . We get wide tidal flats and . Uh and I should have said |
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| 04:40 | in mixed tied the salt marshes are the dominant back beach feature, but |
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| 04:45 | get tidal flats as well. And when we get into tide dominated, |
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| 04:51 | , you're looking at inter title two tidal marsh. Now we get one |
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| 04:55 | thing and that is these linear title shows out here, whoops uh here |
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| 05:07 | we see him over here. I'm not gonna talk about those today. |
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| 05:12 | gonna focus on that portion of the dominated system. That's the tidal |
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| 05:20 | And he said that the sedimentary structures the title processes are going to extend |
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| 05:26 | the subsurface, into the subtitle. , when we look at titled velocity |
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| 05:38 | symmetry and asymmetry, if we think the water comes in and the water |
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| 05:43 | out during one title site, let's assume for a second that it's |
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| 05:50 | Dire. So it's gonna be a hour cycle and EB is going away |
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| 05:57 | the land flood is towards the So, as we visualize the time |
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| 06:03 | velocity as it coming in, it , it hits a maximum, so |
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| 06:10 | going out because it accelerates, it a maximum decreases back zero. That |
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| 06:20 | in the flood direction. Plan a , this is a long time. |
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| 06:30 | in this particular type of title a long time horizontal stops, the |
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| 06:39 | velocity is an increasing uh uh no is zero. It increases as we're |
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| 06:51 | and then stops again. Um that's type of title range, it's very |
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| 07:00 | this is easy to visualize and it . Uh And it also forgets that |
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| 07:06 | is some critical velocity above ways you transport center and let's just think san |
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| 07:14 | means we're gonna have sand going offshore on shore stop. Now, in |
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| 07:22 | we could modify that and we typically to have a setting that is f |
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| 07:31 | that is more velocity going offshore than . Okay. Now that might seem |
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| 07:40 | because it seems like there's got to the same amount of water coming in |
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| 07:45 | out bays will fill with empty. But what we find is that when |
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| 07:52 | in estuarine and title settings, the begin to, some tides begin to |
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| 07:59 | themselves into different areas. So there dominated channels and flood dominated channels. |
|
| 08:11 | um these don't have to balance out any one place. Okay, um |
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| 08:17 | there may be areas where there's such velocity asymmetry that there's no onshore transport |
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| 08:25 | offshore, that means it's gonna be to be balanced by another place, |
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| 08:29 | it's onshore transport in the offshore. we'll see where that might happen. |
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| 08:37 | the kind of classical view of sedimentary , associated tides, herringbone cross |
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| 08:45 | So the idea is that when uh tides go out um they're gonna go |
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| 08:54 | in this direction and then in and and in etcetera. Now, the |
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| 09:01 | here is that the frequency of these strata is a title cycle. |
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| 09:10 | uh so here we've got hearing bunk strata. Here's a first order |
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| 09:19 | here's another one, another one, one, etcetera. Now, if |
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| 09:28 | took that literally, as we were about it before, that's uh |
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| 09:35 | Onshore, offshore, onshore, all of that occurring in five |
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| 09:42 | Well, that's not the case. we're looking at are periods of time |
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| 09:50 | the dunes were being transported on flood dominant in offshore. So, |
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| 09:58 | variations entitled basic symmetry can move And in fact, when we look |
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| 10:06 | this particular example here, see these lines right here. That's actually one |
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| 10:15 | cycle. That's either a diurnal or internal cycle. So we're looking when |
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| 10:24 | look at herringbone cross strata as an , we're really looking at Alternations of |
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| 10:33 | intervals of time and flood dominant intervals time. So let's go to a |
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| 10:38 | flat and see what it might look . Uh wet ripples. It's actually |
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| 10:43 | a bad start. Uh Those ripples flooded during the high tide and then |
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| 10:50 | become emergent during the dropping tide and ripples that were active during the high |
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| 10:58 | then become draped with mud on the water and then that muddy ripple becomes |
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| 11:06 | activated. Okay, so this is to give us a hint as to |
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| 11:10 | the types of sedimentary and biogenic structures be in our title flats. So |
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| 11:17 | again is our title Asymmetry. And just take the extreme case where they're |
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| 11:29 | regression. We've got SAm not sad and the same Jolie movie when that |
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| 11:40 | velocity exceeds the critical threshold velocity. usually in a in a tidal flat |
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| 11:49 | standing and we're usually looking at, see about a very as we get |
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| 11:54 | deeper water. So we get sand . And these are tidal red |
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| 12:00 | Now, here's a case where unlike herringbone cross travel, individual ripple individual |
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| 12:08 | mud couples represent a single title So I'm gonna be and it'll be |
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| 12:15 | or two a day. Okay, with asymmetrical ripples, I'm sorry. |
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| 12:23 | asymmetrical title ASymmetry uh We may network the critical velocity to get sand uh |
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| 12:36 | so we're only gonna get sand positive it's moved in the larger flood dominant |
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| 12:43 | . So one title cycle might be one title written might uh might be |
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| 12:53 | or two pairs of sense. The result is that we get this alternation |
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| 12:59 | sand and mud. It's difficult mudflats tidal flats uh stand here is darker |
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| 13:07 | buddies can't break. Now this is to as mixed betting. Hetero with |
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| 13:14 | bedding but Alternations of but saying and here there's a coming down here that |
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| 13:22 | been filled. Um So we see combined effects of the title and the |
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| 13:33 | opportunities here. So we can actually nick's betting into um a gradation of |
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| 13:44 | and mud. Uh and it starts almost all sand, which is little |
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| 13:51 | of clay in the ripple drip, troughs to virtually all mud with little |
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| 13:58 | ripples and in between wavy bedding with or less continuous uh sand followed by |
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| 14:07 | and love. So what we're doing we're looking at the increase as we |
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| 14:10 | from bottom to top, uh increased of sand over mud. That could |
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| 14:16 | due to increase title a cemetery. the most typical reason. Uh And |
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| 14:22 | also see uh that that is we're follow this as we go from lower |
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| 14:28 | flat to the upper title flat. let's look at these in more |
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| 14:32 | Let's look at the uh pleasure And here we've got three dimensional |
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| 14:40 | Okay, actually two dimensional top down with three dimensions. Um and we |
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| 14:47 | the mud trapped there. And so would be an example of these little |
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| 14:54 | of mud intermittently caught and sandwiched within sandy matrix. Okay, so that |
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| 15:05 | be the sand, sandy portion of tidal flat. You look at wavy |
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| 15:14 | . Uh The idea is that you've ripples but they're completely covered uh with |
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| 15:23 | at slack time. Think of that I showed of the ripples covered with |
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| 15:29 | . Okay, And so they're gonna like this. They're gonna be basically |
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| 15:36 | bands of sand. Okay, separated continuous bands of mud and wavy. |
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| 15:43 | , that just refers to the fact we are flooding the ripple surface. |
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| 15:49 | we're actually reporting um the top of ripple, giving it a wavy look |
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| 15:56 | . These are sometimes called starred There's not enough to have one ripple |
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| 16:01 | another. And so here it's almost mud and we can see uh intermittent |
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| 16:11 | in here and it's almost wavy Now. In reality there's just gonna |
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| 16:21 | this variability, This vertical variability in of hedonism betting here, we're seeing |
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| 16:29 | boroughs where sand has been deposited in borough Phil here, we have predominant |
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| 16:36 | here, we got mixed sand and . Here's a ripple has been very |
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| 16:42 | sand. So, this is a title flat statements now in the case |
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| 16:54 | these little mud, sandy layers and this would be an example of more |
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| 17:01 | less uh way they bedded the thickness the mud and or sand varies depending |
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| 17:15 | the magnitude of the tidal range and perceptive that each one of these sand |
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| 17:24 | couplets is a single title site, means either one day or half a |
|
| 17:31 | . Let's further imagine that we look the range of tides over a lunar |
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| 17:40 | . So it's gonna be maximum when sun and moon are reliant. Those |
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| 17:44 | gonna be your spring tides, your spring tides and then when they are |
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| 17:50 | each other, that is the gravitational of the sun of the moon, |
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| 17:54 | tidal range is the least. And we have a higher Spring tide in |
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| 18:00 | lower Spring Tide. So we see over a 28 day period or |
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| 18:05 | uh we are looking at variations in magnitude of the velocity because the higher |
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| 18:13 | tide the greater velocity. Well, turns out that that title variability can |
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| 18:26 | recognized by the range in thickness. so if you we're unemployed geoscientists looking |
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| 18:39 | work, you could count those one one, measure the thickness, I |
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| 18:48 | do it if I were you. literally somebody did. And so they're |
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| 18:54 | and thinning and thickening and thinning. looking at a title cycle from Nip |
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| 19:01 | spring. These are spring tides. are nip tides Spring me and we |
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| 19:10 | see it in the thickness of the of four sets. Okay, we'll |
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| 19:18 | to that in a moment. But not just the thickness of these tidal |
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| 19:22 | mites, it's also the thickness of four sets of a dune movie. |
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| 19:29 | . In fact, we can look uh individual daily tides spring neat And |
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| 19:40 | longer term cycles ranging all the way to 18 years. So there are |
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| 19:46 | astronomic variations in the title range that be actually recognized in title cycles. |
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| 19:55 | here, for example is one uh uh brazil. Now, I'd rather |
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| 20:01 | brazil formation in Illinois. Okay, literally you're looking at the variability in |
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| 20:07 | tides. So here's the thickness, are the deep tides. Now, |
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| 20:14 | second thing that happens when the tides is that we get a falls in |
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| 20:25 | direction of larger scale don't particularly dunes they stop and then there's a reverse |
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| 20:32 | . And so when that happens, when there's a reverse flow, it |
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| 20:41 | off a little bit of that doom then it's reactivated. So we have |
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| 20:50 | reactivation service and so reactivation surfaces are during title cycles as well. Now |
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| 21:05 | didn't think of those as we have as being flood pauses or the |
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| 21:12 | but in fact originally reactivation services were unique to title deposits. Then we |
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| 21:19 | reversing dunes and then we realized even flood deposits, um we get reversing |
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| 21:27 | services. So this is one title and it's and it's a good thing |
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| 21:35 | spend a little time because it looks at the dominant Direction of motion. |
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| 21:43 | got four sets and ripples and then slack tide and then a reversal and |
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| 21:51 | slack time and what this does, results in a title bundle. And |
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| 21:58 | title bundles are extra actually important for title deposits. So let's just say |
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| 22:10 | flood doesn't matter. So during the tide, we've got dunes migrating and |
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| 22:16 | got little ripples down here during slack , we have deposition, but we've |
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| 22:21 | a mud rate and it's gonna be in the lower parts of the |
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| 22:28 | Then we got reactivation, this is away and we have what's called an |
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| 22:33 | cap and then we have um uh and it starts all over. |
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| 22:41 | so here we have a uh title title Dude, that is pro grading |
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| 22:59 | here then it's truncated, that's the service. And then there was an |
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| 23:07 | cap over here but you don't see now then that den was reactivated all |
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| 23:14 | way to here and then it was and here's the cap. Okay, |
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| 23:27 | there's no mud in this particular example it's a high enough velocity that mud |
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| 23:32 | able to settle out. So in lower parts, higher energy parts of |
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| 23:37 | title flat and into the subtitle region gonna get these title bundle but without |
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| 23:43 | mud drapes. So what we see in essence what's shown here. |
|
| 23:52 | so recognition these title bundles is And so here's one, here's one |
|
| 24:06 | those are a little hard to see spots but where we get the best |
|
| 24:15 | is in the lower parts which is the mud is deposited and and notice |
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| 24:22 | the thickness is very so we can spring neep tide, well see spring |
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| 24:34 | neep tide fluctuations based on the the dune travel, which is a |
|
| 24:40 | of how long we had a high . So here's one of those paddle |
|
| 24:46 | , here's a mudcat and This is title one and notice hell is thick |
|
| 24:56 | then thins thing is sick again. , if we look down in here |
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| 25:03 | the toe, we actually have the of seeing a double mud drink because |
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| 25:11 | on that title cycle we had activation mud then reversal in mud activation in |
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| 25:29 | reversal in mud. And so we here we get a little bit of |
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| 25:37 | reverse motion preserved in that baseball So let's just call the double mud |
|
| 25:44 | . Ok, and here you actually the ripples, This is one title |
|
| 25:54 | . Okay. Uh they not only wider, that is to say the |
|
| 25:59 | progress farther in the direction of but they get deeper as well because |
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| 26:06 | getting larger. So the dunes get higher and transport farther in the spring |
|
| 26:15 | . So, here's an example again we looked at the title bundle, |
|
| 26:20 | its thickness and recognize we're looking at cycles now within a single site within |
|
| 26:27 | single title bundle, we can actually the effect of the rise and fall |
|
| 26:35 | the stage, the increase and decrease velocity in both the flood in that |
|
| 26:40 | . So this is a single title and this is the bundle deposited during |
|
| 26:49 | flood and then draped during the uh . Now this graph here, it |
|
| 26:59 | the uh velocity and the asymmetry of velocity. Okay, the blue is |
|
| 27:15 | the elevation, maximum velocity is actually high water here and it accelerates to |
|
| 27:25 | to minimum velocity over here. So think not so much about elevation, |
|
| 27:33 | think about the lost the increase and gonna be a critical velocity. You |
|
| 27:39 | to get to some kind of velocity about here before you can reactivate and |
|
| 27:45 | that sand movie. And then you to get the deposition of angular four |
|
| 27:58 | as this dune is growing. And the velocity increases even more you get |
|
| 28:03 | more suspended sediments, you're beginning to tangential four cents. And as the |
|
| 28:10 | is that the creep, the peak we're actually getting on cave four |
|
| 28:22 | And then as it begins to you begin to get raping until finally |
|
| 28:28 | stops altogether. So we can look the shape of the four sets and |
|
| 28:35 | something about where the magnitude of the velocities and the change in title velocity |
|
| 28:42 | the time. And we can see in here. Now we use the |
|
| 28:54 | inclined hetero with thick strap and it's descriptive, it's not generic um the |
|
| 29:03 | , elliptic strata, the mixed betting we normally think about with tidal flats |
|
| 29:09 | to be relatively horizontal or low, they could be inclined and they're inclined |
|
| 29:16 | example, in the play drapes of , they can also be inclined in |
|
| 29:25 | clay drapes of santa paws. I river deposits, we've already talked about |
|
| 29:31 | importance of play drapes being baffles for upper part of the black bar. |
|
| 29:40 | they tell you is an intermittent mud deposition regimen in the point bar |
|
| 29:46 | flood non flood in the paddle It's peak floods, uh, peak |
|
| 29:55 | like slack, lost it. so here would be some of those |
|
| 30:02 | drapes, draping dune deposits in a system. And remember I said earlier |
|
| 30:10 | this example was not uh, a series of 12 hour or 24 hour |
|
| 30:20 | cycles. Look at the mud drapes and here. Yeah, each of |
|
| 30:32 | mud drapes is in fact a flood . So these dudes didn't migrate very |
|
| 30:41 | in a single day, uh, other settings, they can migrate great |
|
| 30:48 | . But now we're beginning to actually again that for in a high dominated |
|
| 30:57 | , it's migrating in a flood dominated for a while, in an ev |
|
| 31:04 | setting for a while and intermittent, is on these flood cycles were getting |
|
| 31:12 | rapes at least partially preserved. Now, once we get to a |
|
| 31:20 | , we can talk about tidal we didn't, but as those rivers |
|
| 31:24 | closer and closer to the ocean, if there's a tidal range, then |
|
| 31:30 | gonna replace some of the flood generated by tide generated drapes. So a |
|
| 31:38 | river may be sufficiently impacted by tides that's what's causing the drapes on the |
|
| 31:47 | . By now, let's look at north sea, the north sea tidal |
|
| 31:53 | were kind of the place where we first time understood title flat environments and |
|
| 32:01 | of the things that Miles Hayes noted that when you have a large in |
|
| 32:06 | mint like this with the shelf out , the tidal wave, that high |
|
| 32:17 | system coming in is being squeezed into more and more narrow in vacant. |
|
| 32:24 | because of that, the wave is so the height of the wave is |
|
| 32:33 | as it goes into this more and narrow these days. The the other |
|
| 32:42 | though, is that the way lights increasing because of the way the attenuation |
|
| 32:49 | is getting wider and wider. So the combined effect of increasing title manage |
|
| 32:59 | velocities and decreasing when he fights. that suggests is we're going to see |
|
| 33:05 | transition from waiting dominated the tide dominated . And that's exactly what we |
|
| 33:12 | And this is a good model to because this is at a large scale |
|
| 33:18 | stand bodies will change from right 48 around too elongated idol show and associated |
|
| 33:31 | plants. So let's look at one right here with jade and let's look |
|
| 33:39 | the Thank you again within a and what we're looking at, uh |
|
| 33:49 | Uh, I don't see anything. are title channels and here, for |
|
| 34:03 | , is what it looks like Uh, with the channels and |
|
| 34:10 | muddy upper sand class to sandy, , muddy, upper out of flat |
|
| 34:18 | lower sand out flat. Yeah. at the bottom or up and even |
|
| 34:26 | types uh, Bonner's and more specifically of trace falls that you will get |
|
| 34:34 | on where you are. And uh of them that's pretty common. It's |
|
| 34:39 | nickel. And this is a cross of where it has a U. |
|
| 34:48 | burrow. And this is uh critter burrows down. So that's uh the |
|
| 34:56 | of era Nikola. This is trace is not an uncommonly found trace |
|
| 35:04 | And there are others as well. what we see then is a |
|
| 35:14 | The mix the mud don't watch. here we have and and next somebody |
|
| 35:29 | the lower part of this because all , you know what Is gonna have |
|
| 35:37 | will in fact be titled one down as you get up into here. |
|
| 35:44 | we're getting more blood. So what be expected that transition? It didn't |
|
| 35:51 | they wait. And then let's take . So we would expect that transition |
|
| 36:00 | in time. Now, George clients that we could look at the base |
|
| 36:07 | the stand to the mud or rather top of the sand as being a |
|
| 36:14 | of the tidal range. So, here we go. Um high tide |
|
| 36:22 | up to uh vegetated area and uh tide comes down here or sent the |
|
| 36:34 | they're saying down below is what so we try to interpret um tidal |
|
| 36:42 | uh the top is pretty clear. where you go into from muddy intertidal |
|
| 36:50 | to vegetative super top, but down , it's not quite clear. And |
|
| 36:57 | fact, take a look at this which looks very similar for uh this |
|
| 37:02 | from an Exxon group and this is name. People say you should be |
|
| 37:09 | to um but here and it's a , strong way transgression regression transfers. |
|
| 37:21 | Except here, what's pro grading out a mud flat and then the caesar |
|
| 37:27 | me and and flooding it and then breaks out again. The good. |
|
| 37:36 | is? Well, according to this is some time yet. According |
|
| 37:47 | this, that's Lord. Yeah. , the reality is that this is |
|
| 38:02 | be transitional from lower sand flat to standing system. And so it's not |
|
| 38:11 | clear cut as you might expect. having said that the vertical sequence and |
|
| 38:18 | the title signature is rather clear. here we see a series of transgressive |
|
| 38:27 | sequences uh as you might see. it actually did say, I think |
|
| 38:33 | uh I think it's the cretaceous uh , so ridiculous, friend. And |
|
| 38:44 | can see how it changes. You predict where the pleasure betting would |
|
| 38:50 | Uh There's ripple, laminated sandstone pleasure it sounds labor that it says taking |
|
| 38:58 | sandstone, shale with little sandstone streets ship. So this is exactly what |
|
| 39:04 | would expect in a finding upwards. grading sand flat or my I'm flat |
|
| 39:12 | mixed sand and mud and it basically goes back to that sequence. We |
|
| 39:18 | here. Now, what I haven't is what's shown here is being really |
|
| 39:23 | important and here to uh have a . So the title flat is in |
|
| 39:33 | the champs, but the reality is some cases the channels form that's a |
|
| 39:40 | of the side of flat. So need to know what the channels look |
|
| 39:43 | as well. So this is a tidal channel within in the North Sea |
|
| 39:50 | notice the vegetated areas up here. the marsh Super Tyler. So this |
|
| 39:59 | a these are meandering channels and if were to cut a cross section through |
|
| 40:05 | , you're gonna find that you typically hills and armored mud balls of the |
|
| 40:10 | based hallway where the gravels. we don't have any gravel sorcerer, |
|
| 40:15 | eroding muddy title plants. So the is saying you've got a shelf and |
|
| 40:21 | say, but last this is a all. It's a time of three |
|
| 40:28 | ball and its pro grading in response high and low water levels and velocities |
|
| 40:40 | tidal cycles. So you're gonna have grapes. That's gonna be typical of |
|
| 40:45 | . Here's a meandering uh title channel you can see one more side, |
|
| 40:57 | could infer what it would look like we got down there and trenched it |
|
| 41:03 | we can actually see what it looks in the light to see deposits where |
|
| 41:08 | have these declined trump building it Now, some of these others can |
|
| 41:22 | some of these channels can be quite say that this is actually a couple |
|
| 41:29 | years. But uh they need to larger than that and like a river |
|
| 41:35 | bar as a mad meander, they'll the abandoned become. So there's a |
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| 41:44 | of lateral migration that is seen cutting the what? So here's the channel |
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| 42:01 | . This is the base of a champ. This these are mudflats |
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| 42:09 | So the title channels and this is you like um the baseball channel ravel's |
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| 42:22 | down below we've got the large burrows are whirling animals that live in the |
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| 42:28 | bottom thinking crabs. And so here have these crab borrows and here we |
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| 42:36 | the channel deposit. And when we at it more carefully, it's basically |
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| 42:41 | grain shell. And when we look that show one of the things, |
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| 42:45 | know, there's articulated plans with them if you look at the orientation of |
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| 42:53 | degree, um some of it is made up, thomas cup spec |
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| 43:03 | okay. Uh the orientation can tell something about how those tail fragments were |
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| 43:11 | . If you have scale fragments that moved by water. So they're basically |
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| 43:19 | reworked. What happens is they're gonna predominantly concave down because if they're concave |
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| 43:26 | that's unstable and it flipped the stable is gonna be concave death if they're |
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| 43:34 | , including concave up, that means were just bio attributed in place. |
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| 43:39 | we also see that from this So we know here that these are |
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| 43:44 | clan bags that were living in the not being transported actually by the champ |
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| 43:50 | kind of winnowed by the removing of sand and mud. Okay now here |
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| 43:57 | got title channels in a macro title U 9m Spring Touch. And the |
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| 44:07 | . The lower sand flats had these unit bars of ripples. And I |
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| 44:19 | this only to tell you if you're given the choice, do not work |
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| 44:24 | mud flats. It's a god awful . Les and these people are literally |
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| 44:31 | along a flat surface sink in. when you see somebody who did a |
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| 44:36 | of work on much less take your off. Um that takes six. |
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| 44:45 | here we see this kind of channel , it's about three m deep and |
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| 44:53 | turns out it migrates at different rates what we're seeing is that and I'm |
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| 45:03 | gonna go into detail this something interesting later. But as it migrates, |
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| 45:10 | it's the rainy season, then you a lot of brain off at low |
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| 45:17 | and what it does, it tends give you this. Uh He ruined |
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| 45:23 | service. So we're getting a cycle is actually not a bring neat cycle |
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| 45:32 | actually a monsoon rainy dry site, an annual site. So we're getting |
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| 45:41 | annual cycle based on the fact that it migrates in the rainy season it |
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| 45:48 | a different pattern than when it migrates the dry season. Okay. And |
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| 45:53 | can tell you something about the climate the time and you know, said |
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| 45:58 | climate is important. And this is an example here we have auto |
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| 46:04 | Um Let me Andrew. And then the time we get down here we're |
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| 46:14 | here's which low here here, here . Well, it turns out that |
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| 46:23 | the problem. One of the reasons can't tell what being what the paleo |
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| 46:29 | range was is because we don't know what's being preserved. Uh Each of |
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| 46:38 | is a variation of annual and monthly daily tidal range for the lobes. |
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| 46:48 | . And so uh here's um mean water means spring, low water mean |
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| 46:58 | low water. So all of this inter title at some point. And |
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| 47:04 | of these channels are really big. going back to those channels upper down |
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| 47:15 | , the channels commonly man in. when they're crossing the mugs, they're |
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| 47:22 | an estimate. Um the mud's just lend themselves to me Andrew. It's |
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| 47:31 | lot easier to cut laterally if you're . So you do see uh straight |
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| 47:38 | me Andrew to me. And and actually saw that in those Alaska |
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| 47:45 | I forgot to mention them. so this channel. Now imagine um |
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| 47:54 | north sea uh these channels between behind barrier. So we got from this |
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| 48:03 | where it's tied dominated. Now we're into mixed dominated. Okay, this |
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| 48:09 | gonna be intermediate. And uh if look at those and this is the |
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| 48:19 | um idle deposits over period of years. What this means is that |
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| 48:30 | is how much has been removed or , this is how much of this |
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| 48:36 | back area is actually titled channel deposit not title flat deposit. So if |
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| 48:46 | take a cross section here, look much of the section uh is channel |
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| 48:59 | . Uh the sand flats are mudflats are here are mixed flats and |
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| 49:12 | mud flats are here. So these the tidal flat deposits, but all |
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| 49:20 | this, these erosion surfaces and that their in our title channel deposits. |
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| 49:36 | you see that here as well, can see, I think a little |
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| 49:40 | uh the inclined hetero elliptic strata and much of the title flat has been |
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| 49:54 | . So here's, here's a simplistic that works. Uh It tells us |
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| 49:59 | about the vertical sequence of the mud . It also tells us something about |
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| 50:09 | laterally migrating channel bars. Wait Okay, And notice this title channel |
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| 50:20 | here goes to subtitle. So when get that lower sandy Porsche, some |
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| 50:29 | in there, it's gonna become but there's no good signature necessarily for |
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| 50:37 | . Um We we look at tidal and most of the work has been |
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| 50:48 | in macro title areas, fairly large range, but they're typically in invade |
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| 50:56 | where the wave energy is not very ? Will paul Bay is a |
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| 51:01 | The North sea is sheltered from waves most times because of that wave |
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| 51:11 | But imagine that we've got a a flat system that is open to the |
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| 51:24 | with big storm waves that can come . So at that point we can |
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| 51:32 | begin to reconstruct the effective waves and on this title system. So this |
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| 51:40 | a Cambridge or division title flat Uh I forgot where it was. |
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| 51:47 | think South America. Not sure. this is the paddle flat secrets and |
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| 51:54 | into the subtype. And let's look it here, go easy to |
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| 51:58 | Um We have this dominated by muds we're getting more sandy deposits and sand |
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| 52:10 | getting the point where at this point inversions of sand on the floor. |
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| 52:24 | , The tidal range here was on order of 15. And in reality |
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| 52:34 | have wave effects care that are forming the Now I just said early |
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| 52:48 | well it's their damping waves but we're getting wave induced features down here and |
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| 52:57 | highly in this feature up here. , we need the same thing in |
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| 53:05 | title flat. Um And one of questions might be, are there variations |
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| 53:12 | geologic time. Well, there are more importantly, what I didn't point |
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| 53:21 | that first map that showed the variability tidal range and said there's no latitude |
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| 53:30 | , right? What's controlling is the of the ship in the coastline? |
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| 53:35 | thing that controls title amplification is the of the show. So it's those |
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| 53:43 | in basements that are causing these lateral in. But again, we've got |
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| 53:51 | sand flat, which one is lower as this case squash bars, they're |
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| 53:59 | coming across strata, but they are induced features. In fact, we |
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| 54:05 | from there we go from super tidal , dicks, flat, sand |
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| 54:11 | Now we're getting into subtitle saying uh then as we didn't even farther |
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| 54:21 | we're gonna get, well actually this , we're getting title bars in |
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| 54:27 | We're getting some title sam richards on sand sheet. So we took a |
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| 54:37 | section over there, It might look like this. So, this is |
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| 54:46 | , a pretty good bottle. This show the effect of the uh the |
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| 54:53 | time crease. It's not unusual. drop down into a higher energy setting |
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| 55:01 | exactly what we say here. See bars right here, his white and |
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| 55:08 | they're very exposed down below. That's marsh bars that were getting down in |
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| 55:19 | as well. Now we eventually get tidal sand ridges. I'm not going |
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| 55:27 | get into those right now to talk about talk about shelf, but one |
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| 55:30 | the important things that we're still it's that we're still getting idle |
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| 55:37 | So we can see here, you riding mixed bedding types itself. |
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| 55:48 | skip. So if you look at verdict statements in this section, we |
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| 55:57 | from the margin to the court of course in the upwards is in a |
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| 56:03 | down native setting and then we go sans and the defining of. And |
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| 56:14 | each of these sequences we have characteristic . I'm not gonna go into those |
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| 56:20 | to say that different types of fossils found at different portions. Well, |
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| 56:28 | last example and it's gonna be a brief example. Um it turns out |
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| 56:33 | if you're in Libya, um about third of your oil production comes from |
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| 56:38 | spot. Here's right title. Some we've got stands and sandbars within the |
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| 56:58 | and best reservoirs. You're here sometime . How many buildings are here? |
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| 57:10 | are not a lot of blood That's what's following in the president mark |
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| 57:17 | in the section. So tidal flat title coastlines are actually pretty straightforward. |
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| 57:28 | you look at four or five it's easy to see the commonality and |
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| 57:34 | it's easy to fit that into a and we'll contrast that with wave dominated |
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| 57:41 | in the next election, which we're do in just a couple of minutes |
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| 57:44 | gonna take a break. It's uh 45. Let's come back at |
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| 57:49 | |
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