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GEOL6358 Terrigenous Depositional System - Deltas part 1
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00:00 okay, We had Arbor Corti and break Delta's up into two parts.
00:08 not sure that I will stop where notes part stop, but,
00:14 we'll see how that goes. Eso talk about Delta's there. One of
00:20 I'm hesitant studio on these last couple years is do recommended readings, in
00:27 because there's been so many new lives part particularly on the accelerated program.
00:32 just don't have time to do much . But these air certainly some of
00:36 articles that I would suggest that look the references with the figures and if
00:44 a figure that intrigues you, that's reference that, you know, look
00:48 it. Most of those references that have taken figures from our in reading
00:55 . OK, uh, well, know, we we keep running into
00:59 same list of climate and tectonics and these other things that tend to influence
01:05 systems, and, uh, the are important. But all of these
01:13 come to play in different degrees to the setting deposition of setting of areas
01:19 interest and they interacting in some really ways. We talked about all the
01:27 ways that things influence important the things sentiment, water discharge and how that
01:46 this introduced to the standing body of is influenced by waves and winds and
01:53 . And so we're gonna trying to this together. And when we
01:59 ah, the one of the ways looking at Delta morphology or Delta classification
02:07 for many years been looking at the importance of sediment input, wave energy
02:16 marine energy. Okay, Now, it turns out, this transition here
02:24 river dominated to wave dominated is pretty . Individualism. We're gonna focus on
02:34 for, uh, um, much the lecture title dominated estuaries are already
02:42 bit of a problem. In well, we could always and the
02:47 of sand that would make this a dimensional diagram. Ah, and what
02:53 What we find is that Aziz Johnny so delicately put in that we've got
03:01 many models in too many Bird was many classifications. And that's really why
03:06 go back to this idea of architectural to reconstruct you're dealt of interest.
03:16 , um, one of his examples the difficulty that we have even what
03:22 with something as relatively straightforward as a year old hall. Issing Delta,
03:31 the Danu. Ah, first we see that in spite of having
03:35 time. So now it's just waves rivers. We've got a delta low
03:42 , a delta low here, a low here. And we now have
03:48 alone here. So we're dealing with regressive pulses of sediment. Okay.
03:59 . Where you gonna put it? , uh, it was put right
04:04 here, you know, kind of as someplace between river and weighed.
04:11 , you know, if I looked this, looks like a wave
04:15 Dealt if I look at this, looks like a river dominated delta.
04:19 this is already beginning to confuse And if you were just looking at
04:25 with respect, Teoh on exploration target either a few wells or a few
04:32 , it could be Louisville. It be a barrier island. It could
04:39 waived, dominated. It could be dominated or flu. Viel dominated.
04:45 , it's really hard to describe This is the kind of complexity in
04:50 real world that we do have to . Okay, now there has been
04:54 modification in, uh, 55 Ah, that seems to caught,
05:04 , people's attention point being used. that really is just a modification of
05:11 diagram of flu ville wave and But one of the things he did
05:17 , and this is just kind of , classifications, uh, scheme that
05:25 seem that important. It talks about and effects. So, for
05:31 if something were here and that's really of the problem with Galloway's diagram,
05:36 do you fit things in it would flu ville dominated, but wave influenced
05:49 title affected. Okay, here. there no times, he'll be flu
05:56 dominated, wave influenced or wave dominated viel influence. Now that in and
06:03 itself is not very useful, although does allow you is a shorthand to
06:10 something beyond flew via wave or tide . But it also suggests that there
06:18 be a way of quantifying, the variables that we see. So
06:26 look at what by most means is wave dominated delta. Okay.
06:33 and lets take make a geum or map of that delta. Okay,
06:37 we're looking at this, and so example, one things we see is
06:42 large area and, um, pro beaches. But they are mapped as
06:53 struggling. Okay, and then we some pro grading deposits here that are
07:05 as, ah, beach ridges, . And then we've got Ah,
07:15 is the upper floodplain. This area is title lower floodplain. So what
07:20 done is he's map the surface. specifically, map the surface deposits.
07:28 , if you do that and you plan metric Lee look and the relative
07:40 of surface face, she's that Air related River related, for example,
07:45 . Floodplain with river here. Wave . Uh, so here's our tattle
07:55 . There's flu ville in here and others is It's not quite broken
08:00 you know that these are the right . Flu ville. These were
08:06 You can end up saying, this is 62% tied dominated elements 25%
08:15 ill and 13% wait. So now have a way of quantitatively classifying the
08:24 River. Dealt can now, if problems with this and that it.
08:33 the biggest problem is it defines if like a snapshot at the surface
08:41 But if we were drunk, cross two here, I think you can
08:45 that there's a lot of differences with and that volumetric Lee this Delta is
08:52 but, uh that Titley influenced because along here, even though it says
09:04 title upper floodplain, you see clear that these air pro grading meet ridges
09:12 they're simply mantle by a thin veneer title settlements. Okay, so the
09:19 thing is, if we were looking rock burger and we just had a
09:26 , how would we look at the and course you can't. So
09:32 you look at the relative percentage of structures that are associate ID with
09:44 tide's and waves. And so this us back to those things that we've
09:50 talking about on A when we talked uni directional sedimentary deposits when we talked
09:57 Titley generated deposits and wave generated and now we've got a vertical section
10:03 plots over here. Now that doesn't that this section is the same
10:09 It simply means there's two different ways utilizing this more quantitative approach to classifying
10:19 deltas. This one here, the of sedimentary structures and looking at their
10:27 percent in the preserve don't take deposits a useful way of trying to go
10:34 and quantifying the type of delta. use of surface sediments is,
10:47 not very useful. If you went surface morphology, it might be a
10:54 easier, because at that point we have more evidence. The wave
11:02 This is a delta that should plot here. But the masking of wave
11:11 features with a tide dominated or Titley drape is causing the problem. So
11:21 see this and literature more, more are using it. I would not
11:25 it to classify modern Delta's based on . It is being, I
11:30 successfully used to classify vertical sequences of take sediments in the rock record.
11:39 , let's go back to thinking about variables again. Oh, here we
11:45 tides and waves and flew viel But we've also got some other things
11:51 we need to think about. For , the water depth and the shape
11:56 the Beth imagery or bottom slope. got the density contrast between the water
12:03 into the reservoir in the reservoir cell we can cut him, re raise
12:12 to think about they relative forces that impacting the settlement is inter scent of
12:20 basin. And so we're gonna talk buoyancy forces, frictional forces and inertial
12:27 And then, of course, tides waves. OK, so when we
12:31 that, what we're looking at in , is the relationship between the density
12:38 the river discharge versus the density receiving . And now we're back to something
12:42 started talking about earlier with the custom , uh so we have seen density
12:53 the river. Esma is less than . Basin of buoyancy is gonna be
12:59 . We're gonna have Homa picked a where it flows on top of the
13:06 and friction is is someone of important well. Um, for hyper
13:15 The river density is greater than the basin. So we're gonna have high
13:22 tights and this is called inertial And when they're the same, it's
13:30 type of inertial dominated. But this the area where we at least talked
13:35 Gilbert Tight Delta's So we've got Hypo and home will pick no flows.
13:43 so here, just examples of to pig Noel giving his hyper pick
13:52 Hi, Pope. Eternal giving a , floating and depositing from suspension and
13:57 elation. Okay, so when we at this high pope eternal, we
14:03 see a situation where we're going over bar. Okay, that's this bar
14:09 crafts bar front, and we are were sub critical flow. But it's
14:25 as we've got this water column up of freshwater increasing velocity until finally we
14:35 increasing. Frown number two supercritical. , in breaking up. Okay,
14:45 even though says you Max is about , um, there's some variations on
14:51 . What? Determining though the front is not the velocity, but rather
14:57 related to the dense in the metric , phone number. So we'll talk
15:03 that later. And then we have waves that are breaking lot of deceleration
15:08 sediment deposition here. Okay, if look at the surface, here's our
15:20 is that the water is expanding. a high density contrast, so there's
15:26 a whole lot of mixing. And we get this buoyant plume that continues
15:32 relatively unmixed, uh, and not wide. Okay, So what we
15:42 here is a plume, and the of these survey creates levies. And
15:55 we have a bar, crafts, bar, crest or crescent Rather bar
16:00 offshore two clays. Because this buoyancy to prevent the widespread dispersion of the
16:14 filled water, the bar channels and deposits are more or less restricted.
16:25 , so we get the what we're call later Bar Finger Sands.
16:29 And we can see this happening here the Miss Modern mouth of the
16:37 And what we're looking at is Boyett or I have picked up flow a
16:45 of mud and deep water. All things make the hyper picked of flow
16:53 likely. And of course, this gonna be where we have this continued
16:58 of the levees and bar finger Notice that the plume is relative,
17:11 little a lateral dispersion. Okay. that's again because of that type of
17:21 . Now let's go in the other . Let's look at a friction
17:25 Say where this is turns out to home a Vignal because the water there's
17:33 buoyancy here. Uh, the water is the same as the basin.
17:41 spreads out quickly. It's also a basin here, so there's a lot
17:51 frictional retardation, so the friction is the plume to widen very fast.
17:59 , so in those cases we have bar developed fairly close to the river
18:07 . And so it deposits that causes splitting, which then splits again in
18:12 . So we get. What's referred is a middle ground bar and a
18:16 of Byford occasions. Okay, and typical of something like that. You
18:22 a delta, the actor fly. Delta is forming from what I would
18:29 to be in the main Mississippi and it splits and splits and
18:38 So it's a friction dominated Delta with lot of by for cation.
18:43 so we had to really important types Delta's, both of which could be
18:48 . A picnic, uh, hyper , which could be hyper paint.
18:53 , this could also be home a , but basically friction dominated more sand
19:00 . Oh, buoyancy dominated more mud deep. Okay, Now, the
19:07 type inertial dominated, is where we , uh, fully dominated for this
19:17 deeper water. That is to there's not friction involved, but it's
19:24 , we don't have a lot of . So there is more expansion,
19:29 laterally and vertically. And it's gonna either home a pickle or hypertension.
19:37 ? And that is our so called type Delta. We get a kind
19:42 wider loon. A bar very quickly out. Okay. The problem here
19:52 that what this really is is deep . That's not Hi, hypo
20:03 Okay, uh, so is depositing in deporting these Air Force set.
20:09 we've talked about this a little We'll talk more later. This is
20:13 a low Custer and Delta. I have to be. Now. The
20:17 deltas can be friction dominated or inertia . They could be home. A
20:28 . Nall thinking the hyper pectoral. key here is there's a lot of
20:33 deposition in deep water. Okay, that's what we're getting here. Rapid
20:39 and DePorter. The other thing that can get in those settings is hyper
20:45 inflows, so notice we can get home. A pickle and hypo pickle
20:51 in different times as the sediment discharge , uh, in these home a
21:02 and hyper pickle settings. Now, work has continued on. Um,
21:11 these are models that show the extension the survey. Cleese levy the deformation
21:17 the Oh, I'm not gonna get this except to say that.
21:26 really. This is the first significant done about 40 years. And
21:31 if you're interested in the dynamics of mouths, go this article here
21:38 we're interested in the sedimentary environments, we're gonna look at the different
21:43 She's seven metric faces. If you channels, levies, then offshore.
21:51 we'll go through all of these. let's begin with Mississippi Delta because that's
21:55 only one of the largest deltas in world, and the largest drainage areas
22:00 one of the best study. uh, unfortunately, because it is
22:06 of the best that he can it was the first studied in
22:11 Too often we had tried to squeeze takes in the rock record into the
22:19 Delta More. Okay, uh, so we do clearly have a good
22:25 for it, but recognise were more in the elements that piece together make
22:30 felt a rather than the delta So if we look at right here
22:34 the river mail. Okay, we've the survey Quist, Samaria, levees
22:41 Grady into some bakeries levies. You've this presenting bar this in clues
22:51 rework, sand. So this is distributor Eri Melt Bar that goes from
22:58 to find her a proximal to distal then you've got a Siris of frontal
23:06 and or pro delta. Now, transition here basically going to go from
23:12 to mud. That's pretty simple. then displays are typically storm or flood
23:23 failures that introduced sand into a money . Okay, so here we're looking
23:31 some of the processes that are affecting This distributor email are particularly the upper
23:38 sitting here. It's affected by weight Louisville deposition and wave reworking. And
23:46 , in some cases, film. , um, up in this area
23:53 is all flu view related. so we can kind of compare the
23:59 or fix settings. Ah, with various processes that influence it in the
24:04 here is that the river Mel is by a mixture flu, veal input
24:12 wave reworking. Okay, now, , we just looked over here and
24:21 went from the distributor, Eri Mount to the pro Delta. All we're
24:27 at here, particularly It was A perfect inflow is the courses.
24:32 settles out first. So we're gonna from sand the month and then beyond
24:39 , we've got this young. which may be sandals. Okay,
24:44 that's straightforward. It gives us something pretty easy to visualize. Ah,
24:50 . The sandy fishies is considered san the pro Delta muddy face she's is
24:58 offshore. Play in this case would the, uh, shell.
25:05 And then we get pro grading Well, this isn't really very
25:10 Let's look at it a little First full, let's make the delta
25:15 of sandy face. She's and recognize it pro grades impulses. So we're
25:26 have not only con forms, but going to kind of ragged crying for
25:32 monetary causes that she exam. uh, showing that inter fingering in
25:41 on a Delta front is a term is used a lot of different
25:48 It usually refers to the sandy thinks an in this particular example, the
25:57 drop out pretty quickly and shallow water here the globe around in deeper water
26:03 . This is dogmatic, so we get too much into that detail.
26:10 you already know our have a sense how wave reworking can distribute sand.
26:18 , rework sand, different depths. so think of this is the pro
26:24 short face. It is when we into waves on me to Delta's
26:31 The other thing is, as we before, it is far too easy
26:36 correlate things, uh, with layer . Strategic pretty. You need to
26:41 to correlate the individual clown forms. we talked about this with the customer
26:48 Delta's, um, it's on Lee that you can get a better feeling
26:54 how Sands are or are not Okay, now, we've been looking
27:03 the Mississippi Delta for a long We've got bath metric maps going to
27:07 17 hundreds from the French, and as that is pro graded, we
27:12 these timelines and we see a zone of Sands. Uh, now we're
27:22 it something else. Tributary, Mount and Delta Front from Delta. The
27:30 is more than I can bear so just recognize all sand, mainly
27:38 , mainly mullet Notice. So the of that sand face. She's is
27:46 quite very okay. So depending on you took a cross section today,
27:53 79 verses 67 18 67 that would a rather significant difference in vertical
28:04 Okay, now here we've looked at idealize section, um, brain size
28:19 gamma ray sedimentary structures. Uh, is we're getting into some Bakley's ripples
28:28 the delta plane. Here's the bar . Here is an area that we'll
28:36 about in more detail later. But basically all sand amalgamated sand with writing
28:42 . And then we get down to area of inter bended sand in
28:50 The innovation when we get to the Delta. Okay, which is almost
28:54 mud. Ah, a lot of sands here. Oh, are the
28:59 that we talked about, Okay. sediment from appear, which is the
29:06 bar. Okay, now, these two different ways of showing a measure
29:16 here. We've shown the grain size on the extent of the description.
29:33 , here we have two different If we were to take these set
29:38 infrastructures, moved him into here, we get this here The reason I
29:43 that is because there are different ways showing a measured section. Remember that
29:51 we're getting it from core, we to create this from this grain size
30:00 . But way use this more often we're doing measure sections in the
30:05 And the one thing I would caution against is that when you're Ewing,
30:11 measure section feel there's a tendency and to draw. This is a weathering
30:17 , and that's actually the best way draw it in the field because something's
30:23 resistant because of segmentation. Ah, not necessarily because of grain size.
30:29 , what I would suggest you do the field is measure a weathering profile
30:34 sedimentary structures, but also be measuring size. And then you can construct
30:41 measure section for your report any way like. Um, now the weather
30:47 profile often is related to grant but my point here is that not
30:58 . Okay, so this is a grading Delta Front family and notice the
31:05 Delta Front now is referring to all this sandy zone. So that's why
31:11 confusion comes in. Um, we a coursing up towards sequence. The
31:18 are also thickening. Upwards were ah, decreased amount of shale increased
31:25 of san her sandstone etcetera. so let's look at the offshore
31:32 Basically, this is the shelf, that's an area where muds may be
31:38 from time to time. But there's of depositions so slow that is completely
31:43 today, cakes as we get into disco pro Delta that there's a distinct
31:49 here. The first thing you see are preserving the sedimentary record. I
31:56 so sedimentary land, the structures, lamination Zen Betty. Now the reason
32:03 that is actually related to this being river dominated delta. Because what you're
32:09 is the evidence of the freshwater mixing the brackish water and a decrease in
32:17 observation. Okay, we didn't see in the muddy spore shin of a
32:22 grading strand play or a pro grading island. When we were into that
32:28 portion, Uh, we still had lot of our tradition. Bob probation
32:34 a river dominated delta is damping down of the stressful environment of these Alternations
32:44 fresh water plumes, saltwater, brackish and what we're seeing now. Are
32:53 sands that air coming in here? if we look carefully, they are
33:00 . Now, in reality, they're all great for better said they're not
33:05 greater. These are a lot of air hyper pick knives that are either
33:12 deposit. Well, that are flood that have come in and in some
33:17 , their settlement coming down from But where the coarser sands particularly down
33:23 this area here. They're part of frontal displays that we've been talking about
33:29 well preserved. Okay, is we higher up, We're getting less
33:37 We're getting wave generated sedimentary structures. that is this here, this is
33:47 , candidate. More like a sway . Betting there's a mud rapes saying
33:52 century we were in here. Now getting more sand. We're getting these
33:59 so called ball and pillow structures. what this is recording is that sand
34:07 been introduced into a muddy ah hype . McClay Ah, and that
34:18 as it comes in, just kind sinks into that fluid mud.
34:25 so that's very typical again of a delta. Okay, on Muddy Del
34:31 deposits now when we get up into let's say what he's called here,
34:36 tributary mouth bar. Uh, we're packages, probably coast that's in.
34:47 we could even think that Third order second order sequences there sequences of sedimentary
34:53 in here, uh, the beds thickening and their coursing is they go
35:00 . Uh, not quite sure what going on here, but I'm sure
35:04 interesting. Uh, so now we're a lot of preservation and primary seven
35:11 structures. Uh, although there now is actually a surprising amount of observation
35:17 this setting. Ah, which is don't completely understand why I don't understand
35:24 the no technology of this setting very , but it's not uncommon to have
35:30 intubation here. Now, I want to think about how this vertical sequence
35:38 similar to and different from the pro shoreline. Okay, Um, there
35:49 by information out here in Fairmount, there's really not there's a lot out
35:59 , but the bottom ation is low and actually has shown is low
36:07 I'm not quite sure why that that , but, um, look at
36:12 change in sedimentary structures. Look, the absence of mud, and that's
36:21 quite true. There's some innovated but this is a way dominated
36:27 And so muds are selectively removed from near shore setting and moved offshore on
36:34 show. Four downs, More downs . In fact, remember that transition
36:41 away dominated delta to a ton. mean, wave dominated estuary to a
36:47 dominated estuary. Okay, we had change from basically, wave dominated low
36:56 of plays to something with the higher plays. Okay, so certainly the
37:02 of play and how the clay impacts sedimentary structures is something to think
37:10 Okay, Now, if we looked the river dominated dealt Oh, that's
37:16 , what can be thought of his sand? We've got the pro grading
37:23 sequence Clearly is finer as you go . You can have a subspace lays
37:32 out through here. So basically, is the clean sand, the so
37:40 distributor Mount Bar, Then it pro out in the distance and then pro
37:48 . Okay, Of course. The is here. That you Okay,
37:54 , as that pro grade C remember, the plume stays narrowed.
38:01 not only does the plume Stay The sand I Selous Ice impacts Danny
38:13 . Well, it's the idea of bird foot delta in a bird foot
38:19 and ice impacts. Now, this an example of a Delta system that
38:27 originally was misinterpreted, and this was as a tributary system and later reinterpreted
38:39 a distributor system. Okay, major difference in interpretation, but what
38:47 want to look at here we kind have that bird foot look. But
38:55 pause thick pods and shallow pods, that seems odd. Okay, but
39:04 turns out if we were toe ice the modern bird foot delta. But
39:09 get her paws, we get areas thick and thin sands. Okay,
39:22 , the sand isil is of this and pods aren't that on case?
39:35 Here's our are thinking for some of things were over sand over 100 meters
39:41 , and others three. And we about that earlier that that was
39:45 And the reason is kind of like self settlement information that we saw with
39:51 pillow That is that you got this pro grading seaward depositing sediment over the
40:03 Pro Delta must. Okay. And are water saturated, really wet.
40:11 there's also so much coming in from east. As we load those
40:20 you get a dye parent company and can even begin to get up lift
40:26 some of the older but still But and so we get a uplift
40:33 . Now, it's gonna start to over here, and we got actually
40:37 withdrawal here. So look at the thickened and under thickened muds because of
40:45 rising die appear okay, Very Very thin game. So when you
40:55 at these things, uh, these all plays, okay? Of
41:06 The bar finger sands thickened and then ls you put in a core here
41:17 years they put that corrine 300 m that die appear kept pushing it up
41:29 pushing it up until 100 m of , where it was extremely for at
41:38 was, uh, elevated in 20 . That is a huge rate of
41:45 period. Uplift and shale die peers important features in a lot of
41:52 and not just the Mississippi butts. *** Delta of the Orinoco Delta areas
41:59 trended and these are major features for have a lot of mud.
42:05 Now the other thing is happening with modern Mississippi. To complicate the story
42:10 that that soft sediment information is not dive gear up lift, but we
42:15 are getting folded. No, here some of those fault. He's a
42:23 thrust faults honor, And they these here, our little growth falls.
42:35 are associated with doctor Google it. then offshore, we get zones of
42:42 pulling apart extension. We've got mudflow . We look at each of
42:53 We got a little die. Appears also up here, and we got
43:01 great big slumps and falls. now what we're looking at in
43:12 these are mudflow gullies and mudflow Okay, They great into these sig
43:26 pro grade A Schimmel packages. Here's pro gradation. This is not so
43:31 failure is simply the off flapping, grading, short face, natural face
43:42 from Delta. And then there's the re entrance, which are large
43:47 Some of what your film. So haven't unfilled failure here, and we
43:53 filled failure here, and some likes in here we're gonna have a
44:02 And here's the summary Can. so this is what it kind of
44:08 like. Here are those extension algo here is a mudflow gully going into
44:19 lobes. We get a lot ah, mud, Vince, by
44:22 way, and we get some larger that are associated with faulting as
44:30 Okay. And notice your hair of die peering up lifts there are controlling
44:37 thickness of that sandy facings. All is occurring on a 1/5 of a
44:46 slope you don't need steep slopes toe mud fail, especially if that mud
44:55 water saturated and is exposed to Luethi and the cycle gloating of hurricanes
45:01 other big storms. We really began notice this when we had a
45:09 I think it was Camille. It Rig that after the storm that came
45:16 , it was gone. He was eight miles down here. You can
45:24 when we began to look at these as geo hazards. But we also
45:30 them as sedimentary l'Ours Okay. And cover a lot of that pro delta
45:39 shell Delta front. Up to 40% been reworked by some extent. We
45:46 . My either the gullies were the . So on side scan, this
45:55 what those gullies would look like. , this is the source broken
46:04 Okay, Uh, and this is of the Lopes I'm Seriously,
46:15 yeah, and these are pressure Okay. And here's the extension with
46:28 things. So we're gonna look at , and we're going to see these
46:32 only in Mother's same in Sands or to policy. So these features are
46:39 small examples of what we're going to on the slope and fan as larger
46:47 mass transport deposits. And he said they are important to recognize their easily
46:54 falling the, uh, shelves seismic . Okay. And you really want
47:04 be able to recognize these Aziz, start thinking about the word of such
47:09 platform. Okay. Now, the come complex are complication there said is
47:20 the modern delta lobe of the Mississippi just a little piece of the mid
47:25 Mississippi Delta. Okay, there's all of abandoned areas. So we're gonna
47:36 on the modern and then see to extent is an analog or is different
47:44 saying the older parts of the So here we've got the modern
47:51 Okay, here it is in 18 is basically Siris of PSA burial levies
48:01 channels. So what's happened is that Delta has fleshed out mainly backrub ass
48:09 deposits. And so what was They now crevasse. Play is part of
48:18 delta plane. Okay? And we that in this particular example, it
48:24 around 18. 40 and we can that profess grow. And one of
48:31 things, though you might notice, that if you look at the areal
48:38 between 22 46 it's about the But look at all the water that's
48:48 in 71 into the present today. , well, will it be that
48:55 , uh, this delta has grown , but now it's beginning to be
49:05 . Okay, there's a lot of area here. Those marshes are
49:16 Okay, not a good sign. , now we can begin to see
49:25 each of these crew Bess plays has documented for the most part. And
49:30 that's what's filling in much of the park of this long term. Distribute
49:39 . So this is just a example how you can think about elongated channels
49:50 the fleshing out of a vast This is in settings where usually it's
49:57 title and low wave INGE. I'll that you might think, Well,
50:03 can the Mississippi be low? Weigh in energy? Well, the short
50:11 is because the all the mud that deposited in front of the Mississippi Delta
50:18 the pro Delta provides a wide, platform. Members about 0.2% um,
50:26 degrees rather the damp of the So we actually have a interesting feedback
50:33 by which sediment that's two, causing and forming a shallow delta front.
50:42 Delta, in turn, dampens the energy, which allows Maurer of the
50:47 to comfort. Okay, so that has dampened its own wave energy.
50:54 , so it is a low wave which he dealt and we'll see that
50:57 differ, find different settings. So look at one of these two of
51:03 crevasses, really. We're gonna look on inactive crevasse that was here,
51:09 that was that had formed a vaz over here and then it was abandoned
51:18 this for Vaz play, which is here. So we're gonna take a
51:27 of sections. A is true here kind of perpendicular to the,
51:35 river or ready Parallel to the river to the distributor Eri. And then
51:42 gonna take a section B which goes the main river in across parallel to
51:51 tributary. Okay, so here's that well here. Here's the major distributor
52:00 and here is a pro grading curve play. I'll add some shoes Sam's
52:15 , uh then right about here it's and we begin to see a transgression
52:28 And what's happening is we're reworking the because a large for still accumulating center
52:36 notice there's some oyster reefs along We'll come back to those animal So
52:42 had a active and then an inactive . Now, here the delta front
52:52 a little complicated, but in what we're looking at is too for
52:58 place here. This is the older , and this is the new
53:07 okay. And so this is still . So we don't have any of
53:13 abandonment face. She's but notice we've got some oyster reefs back here
53:22 what those are is they're developing along high areas that were the channel margins
53:38 little channel levies of the distributor Eri Forster's will grow and money environment if
53:45 got ah, hard substrate release of in this little higher and less
53:51 And so that's where we see these leaves, Uh, and the same
53:56 Galveston Bay as well. Okay, what we've got is a coursing up
54:01 sequence, and then this case Marsh okay. And you can think of
54:10 is Bay Pro Delta Delta Front distributing , and in some place in here
54:18 be a channel. It's just like delta, because it is It is
54:23 little delta that's forming by a breach the natural levee. Okay. And
54:33 , Dad, dramatically, we're looking , uh, here's a lady coming
54:38 and I have said It's cut. a levy coming through. We haven't
54:44 too much about levees. Basically, gonna do this until they're cut by
54:49 channel. And so there's that channel on. Then display. We're gonna
55:01 at those play depositing the channel can big and with or it can be
55:09 . Oh, this bubbly. this is the mouth bar. This
55:14 pro grading crevasse, lobe coursing This is the channel finding upwards.
55:25 if we look at Levy, remember way Saw this when we talked about
55:33 , uh, flow of your Levees can begin to pro grade into
55:39 Jason area one of two ways, by migrating laterally, in this case
55:45 be left to right or by growing , In which case, the distribute
55:49 begins to become the main course. so we're looking at a larger and
55:54 river. Okay, so this is displaying. Now it's cut Sudden intrusion
56:07 lobes, in some cases, a . Okay, so what we see
56:16 looking at, they face, she's these deltas are the coursing up recycles
56:24 up There is nothing really big until get a channel finding upwards and then
56:32 uppers again, going into a bay . Okay, uh, so we
56:37 expect to see ah, these coursing finding up for sequences, especially in
56:47 in this area here. So it look at a cross section.
56:52 and actually, let me let me here first when we looked at this
57:02 tributary channel. Here's the big The big channel is gonna be finding
57:14 . That's the main tributary. The play is gonna be coarsening, and
57:24 the crevasse Channel is gonna be finding . So we've got a small
57:31 a big channel. And then we this filling into the bay. So
57:38 province channels air these small finding a sequences. And they are bacon.
57:47 have an erosion surface that made very hell laterally continuous. It is
57:56 probably more like this. Here's a this tributary channel. More widespread.
58:08 , now, here's a crevasse mouth complex. We saw that multiple Corvus
58:17 an abandoned curve, s playing the , etcetera. Okay, so we
58:23 look at how this distribute Terry was the filling of what was the
58:35 This everything. The left of that and below that line, we're basically
58:41 bay or floodplain deposits in this case . And they were filled with curve
58:47 play deposits, media channels or mount . Okay. And so again,
58:55 , multiple, maybe like this. , uh, caressed melt bars and
59:13 chance. And then the big Okay. Uh, so this is
59:17 it might look like. Uh, Blaker best played for best play coursing
59:25 . Ah, here's a large Eri Channel, as this here.
59:33 , I don't have any small grass , but that's OK. So let's
59:40 at that distribute, Terry, That is beginning to take over. We
59:48 a this trip take over here and is starting toe come down this way
59:55 get bigger and bigger. So now biggest it's gonna get. Now there's
60:02 sub angriest levy graze into some very living and particular case. The levy
60:10 growing. The settlement is filling in bay. We don't have any crevasse
60:15 you on here. So we're going , uh, bay mud interdistrict terry
60:23 to slightly brackish marshes to eventually fresh swamps and notice how that natural levee
60:35 getting larger and larger is that Terry is getting bigger and bigger.
60:41 this particular case, the bay filled first brackish, then fresh water
60:51 Okay, We took it core This is what we'd see who's increasingly
60:58 levy deposits associated with that growth of levee. This particular one has nothing
61:04 do with lateral migration. Okay, we see that as a channel
61:15 it fills in the bay with levy and over bank deposits and professed
61:23 But what about some of these other ? There's a lot of what are
61:34 abandoned channels in a abandoned river courses abandoned delta plane. So where do
61:46 fit in? That there's depending on you count them. There is seven
61:51 eight. They think that modern bird ah has only been around about 500
61:59 or so. So by avulsion, channels have been switching over a long
62:07 of time. The year old Okay, now this idea of of
62:17 and shit lateral shifting of the ah mouth, there is the delta
62:25 nothing new. And if you go the Hong here on ho or Yellow
62:30 , look how laterally extensive. The are all coming from an avulsion mode
62:40 about here. Okay, The real and then the lotion mode. Here's
62:47 may be here. The real question , why do they ship that pretty
62:53 . It's just it just this was long to go. And in the
62:57 has shifted. But we saw that in rivers as well. Why?
63:02 an apex here. This is actually of like a mega fan, but
63:07 with mega fans, this is a from constraint confined to unconfirmed fund.
63:15 , move again. There's something else on here to cause this shifting its
63:21 and what it is is the distance the back water effect. Okay.
63:27 a backwater. Fact is, when , uh, I say have a
63:32 in sea level. Oh, we're any river. You've got a river
63:38 in here. You got flat surface . The back water effect is the
63:46 of the lower part of the river is influenced by the base level.
63:54 , extend beyond the area of title beyond the area of freshwater saltwater.
64:01 it's that area there that tends to stable. And so that tends to
64:09 where the shifting tends to occur. that area is a function of the
64:20 of the channel. The slope of channel tends to determine the length of
64:31 backwater. Um, these are and it's also functional. Go channel
64:41 . So how deep and how state that these are the combinations for the
64:49 Delta, the Amazon. It's I'm not gonna get into that
64:54 except to say that the back water increasingly is being recognized for controls of
65:01 shifts of rivers in Delta Systems. the point here is that that Delta
65:08 extends so far River that we often think of it as a Delta,
65:14 example, that they lion that area title influence title effects up in here
65:24 . Um, the things that we associate with the Delta Sen logically are
65:34 controlled by that backwater leg. And so, using backwater equation,
65:46 we can look at no measured versus back water depth and that equation works
65:53 well, Okay, But no, is a long scale. So you're
65:57 at, ah, factors and maybe or minus two or three times a
66:06 . All right, so let's look the edge of flying. The actual
66:09 is a river that really wants to the new Delta or the new Mississippi
66:16 , just like they were older rivers , in the 19 sixties, the
66:27 Fly river almost completely beheaded the Mississippi as a devotion event. And your
66:35 it didn't is they would score of have been busy trying to build a
66:38 prevent that from happening. Now the is completed. It almost destroyed the
66:43 . But now long has completed an . A significant portion of flood water
66:49 diverted down through the answer Fly Oh, Baton Rouge and New Orleans
66:55 have a fresh water supply. what that has resulted in actually resulted
67:02 of the filling of a large Forget the stand. And now the
67:09 of actually turned deltas filling in at flight the actual flying delta and wax
67:18 delta. Yeah. Now, if look, look at the edge of
67:24 , that's remember, that's this one . It started off as a series
67:29 little emergent loads, but these lobes coalesced too far larger. This tributary
67:41 in their vegetative. Okay. And as we look at the growth of
67:46 actual fly delta, we see that little bars became bigger bars. And
67:54 the bigger bars became amalgamated to eat bigger bars. So I see a
68:01 , um, bar growth and noticed the bars extra graded, both seaward
68:10 extended extremes as well. So we a bar system, this book program
68:27 ALS, downstream and upstream. So we've got that first little no,
68:37 know, they begin to get bigger bigger and bigger. This is kind
68:45 false. Section with secondary channel through , the locus of Amalgamated.
68:54 uh, and now they're growing both and pro grading downstream, low fusion
69:04 refusing. We're getting more and more developed. Distribute Terry channels now,
69:11 . And some upstream growth. the best of these studies is actually
69:18 by Exxon geologists, including Dr Wilner's . And this is what the wax
69:24 looks like. And if you break up, it consists of a whole
69:29 of little lobes that put together for loads that eventually meld remain to form
69:36 delta itself. And the little lobes basically those early lobes we saw in
69:43 actual flying delta that amalgamated to form larger features. Now they're called
69:53 The positive ice packs. Okay. here, they kind of go around
70:00 . So what is a jet Well, we're going to go back
70:03 the idea of a jet and that coming in with sediments. This is
70:12 situation where there's not a lot of . The course load stuff is deposited
70:21 , suspended load here with these little bakeries levies and then not much deposition
70:30 . Okay, Looks a lot like , this is notice is very
70:37 okay? And the because it in sound of erosion and bypasses where the
70:48 develops, this is where the bed is deposited. This is where the
70:53 lovers and so here we have that word growth. An amalgamation for both
71:01 that low on the back is actually as the channel is developing and filling
71:12 scoured Channel. Okay, so you little growth and que Now,
71:28 these things were broken into these distribute , the mouth of which has a
71:34 breaks up into a lot of So these little lobes amalgamate before the
71:42 complex, and these load complexes now of May to form the delta.
71:49 we've got hoping to these little lows grading seaward and then also filling in
71:59 okay and becoming amalgamated. And here have the chance. Okay, so
72:06 is kind of a rough example what look like. And one of the
72:20 this counterintuitive is that the back side this load was actually erosion. Whereas
72:28 we have normal pro grading finding We have upstream bed form creation that
72:35 saw earlier, and that's also where channel is being too past it.
72:42 , now, I don't expect you be able to reproduce this on
72:50 but I do want you to think how the real simple model that we
72:59 he's gonna break down on outcrop and be related to these jet type
73:08 And as we'll see later on this , well, something similar to that
73:15 in submarine fans in submarine. fans. OK, eso here we
73:23 the channel Sands Sharp based Mount Bar into gradation. So our mouth our
73:34 aren't always going to be just pro forcing uppers. They may have a
73:40 your emotional tar grating into the And that's what is being referred to
73:52 . Okay. And that, in , is related to this transition that
73:58 see with the increasing, uh, and velocity and then the crescent.
74:07 got erosion here and deposition here. , now, let's see. We
74:15 just a little time left. let's look at this Delta love
74:22 Ah, lot of distributors radiating Okay, that is the left push
74:30 . And unlike the modern Bird it is referred to as low beta
74:36 . It has a lot of distributive breaking up with a lot of segment
74:43 put along the shoreline. And so we get is not a single Chris
74:52 tick melt bar, but rather a delta front. Rather cool. A
75:02 of mount bars. Okay, so having much broader she like loan because
75:15 the multiple entries of seven. And so here we have a sheet
75:24 delta front. There's a sheet uh, sandstone. Now compare that
75:34 the Burfoot and compare the ice Apax foot. I feel like Okay,
75:46 first very different. Okay, but other thing is, you know,
75:53 our Burfoot versus our sheet. um, let's think about the
76:04 Okay, This is 2 m. is 10 m. Okay, So
76:15 bird foot delta, as it progres , might be 80 m there or
76:24 . Remember? Is pro grading into deep water, at least when mothers
76:28 starting to be deposited. The low delta eyes pro grading into shell
76:38 And it's gonna be about 20 m less. Okay, so not
76:45 uh, are there some differences Well, we can talk more about
76:49 , perhaps later, but this is straightforward, but it is a deep
76:57 muddy delta. Okay, this is earlier Mississippi, and they have had
77:07 much mud, but it is programming shell. Okay, so it was
77:13 low bait, and it had a , uh, surface morphology. A
77:22 distribution of distribute Terry's different thicknesses, processes. This is an inertial
77:34 Okay, this is a buoyancy. . That friction. Buoyancy.
77:41 Okay, so that's what we're going stop right now. Uh, it's
77:47 a good time. Teoh. Break lunch. Let me, uh
77:55 Um, let's see. I'm going stop that recording. Um, I
78:05 that you're tired, but I really to finish DePorter. So let's take
78:09 45 minute lunch break. Let's be around 12. 30 ish.
78:16 So I will see you guys in 45 minutes. Okay.
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