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GEOL6358 Terrigenous Depositional System - Day6 03-04-2023-Part1
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00:02 OK. Uh Welcome back, we OK. Uh We're back. Um
00:36 We talked about um introduction to delta processes. Uh The major constructional phases
00:44 the Mississippi delta, the modern the, and then the earlier Holocene
00:52 LA for delta, we talked about destruction of phase and the cycle of
01:04 construction and destruction uh as exemplified by uh of the abandoned Holocene delta
01:16 We then talked about how deltas can across the shelf. Which ones
01:22 which ones can't, how they would it and what happens when they get
01:26 the shelf edge. Uh And we that at that point, we have
01:31 least the potential for a lot of uh as well as sediment transport getting
01:38 into the deep water system uh thereby this shell. But I want to
01:44 uh today is to finish up on and uh look more specifically at those
01:51 and tide dominated deltas. So, let's see if we can I get
01:58 . Um Yeah, there we Uh So we've got wave at tide
02:06 river dominated deltas on uh uh Bill . Uh We've also got uh a
02:14 version by Ainsworth. And so, as I had mentioned a little
02:20 when we look at deltas, that of the problems is, uh they
02:25 only changed through time, but they can change rather quickly spatially. And
02:32 , well, I'm gonna go back the example of the Danube, uh
02:36 recognize that within a relatively short period time, let's say, uh 6000
02:45 or less, uh we've seen uh lobes. And uh in particular,
02:52 would refer you to boar and Gilson's on wave influenced deltas uh for uh
03:00 good general overview waved on the deltas general. Um Having said that there's
03:08 a lot of new papers too. , uh this is a good starter
03:14 . Now, when we talked about early concept of GEOM morph classification,
03:19 went from the river to wave dominated we can look at a uh a
03:27 of hypothetical of pro gradation of sequences um are ba basically combining idealized pro
03:40 of sequences in a river and waved system. Um And I I I
03:46 the main takeaway here is that although are pro grading coarsening upper sequences,
03:55 the river dominated delta is much more lithic. It's got a lot of
04:01 interbedded with that pooring upper sequence. those muds are largely not preserved in
04:09 wave dominated delta, they've gone They may be that pro grading mud
04:15 or that uh sub aqueous delta. talk a little more about that
04:20 but the muds have been wintered away the waves. And so we're looking
04:24 a frankly much more, uh, a barrier island strand plain analog.
04:34 , and in fact, as we'll in a moment, the wave,
04:38 the up drift portion of a wave delta really is appropriating strand lane.
04:44 really can't differentiate. Now, there's a lot of examples of waved
04:49 delta. Some are really big, Some are smaller. Uh A lot
04:54 the, the work has been uh by the Brazilians. Uh And so
05:00 a lot of waved doin deltas in . Uh also um some important ones
05:08 Mexico. Uh We've had the R one of the things you might notice
05:12 this point is that the morphology of wave doin A delta is rather different
05:19 this wave dominated delta. And so is a fair amount of variability even
05:25 that context of the NME wave doin . And when we look at the
05:32 , I think you can see that whereas the modern delta is here,
05:40 it wasn't long ago that the river coming out here and there's a delta
05:47 here and there may have been another here. And this is actually a
05:52 loa here. And then there's been lot of reworking. You could see
05:57 the waves reworking, particularly these older deltas Now, this is kind of
06:04 the Mississippi that is when we had uh lobes, a new lobe and
06:15 reworking of that lobe. One of big differences here is that there's much
06:20 wave reworking of the distal portions of abandoned lobe. When you map the
06:28 as a whole, though, it's a low bait Isopack. And
06:33 uh recognize that within that low bait , which is where, how we
06:38 of begin to look at these packages a potential field or reservoir point of
06:44 . Uh We need to begin to about how we might um disaggregated,
06:50 we might uh compartmentalize it, Uh So here, it's maybe 20
06:56 thick, OK. Uh But you also see it's on the order of
07:01 m long and it's gonna be elongated the direction or rather parallel to the
07:10 . Uh There's a nice study from upper Cretaceous of South Texas looking at
07:17 Isaacs and seeing how even within a river system over time. Uh There's
07:25 a lot of uh modification as well , the contour interval is about 20
07:32 . And so you can see some these things are much thicker than the
07:36 day delta and it ranges from what she describes as uh low bait to
07:44 much elongate and, and this is this model came uh that I showed
07:51 , I believe and, and it a lot of important nuances that really
07:57 picked up, uh, at least picked up by me. Um,
08:02 I first looked at it, first of all, it does have
08:06 abandoned delta in the modern de, . And the abandoned delta,
08:14 actually probably extended over to here. , in any case, the modern
08:21 is sitting in here. Ok. , and if you look at that
08:30 delta, the direction of longshore drift , is in this direction, um
08:40 portion is basically a strand plane grow out this way. There are no
08:48 or almost no muds in that up portion of the wave dominated delta down
08:54 . We have a spit that's pro . OK. And we also had
08:59 implication of that down here uh as in that older delta. OK.
09:06 So there's an asymmetry of the, delta between the up drift and down
09:14 portion of that delta. And, that was made explicit by Dominguez
09:20 and others in late nineties who had that. Um The Yeah,
09:34 I just got those mixed up Uh Yeah. OK. That's because
09:38 is upside down uh that the deltas their up drift side is basically a
09:45 plain and in essence what the river doing as it programs out, it's
09:52 the longshore current. And so it's kind of like a jetty. And
09:57 the sediment is piling up on the drift side of the jetty, it's
10:01 the mouth bar but still it's programing and intercepting that longshore drift.
10:07 what that means is the sediment that derived from the river is actually not
10:13 the upper portion of the delta. setting was derived from longshore drift someplace
10:20 . The only sediment that's being derived the river is the down drift
10:27 And that consists of a series of spits and muddy interbedded areas. You
10:36 , the sandy spits will uh form , a barrier between a kind of
10:42 a lagoon and then the lagoon barrier barrier. So that was really the
10:51 to recognizing this asymmetry. Now, Bottari and others did, they then
10:57 that and began to look at the of that. Now, symmetrical wave
11:06 deltas don't show that up drift and drift symmetry. They show an alternating
11:14 of sandy and muddy and sandy and clots that are related to floods.
11:21 . Uh On the other hand, deltas in many places from the little
11:30 to the Big Danube. And uh part, some of the Nile major
11:36 have this solid black or largely solid uh pro grading strand plane. And
11:44 this is kind of a pattern of happens. Um You've got this
11:51 the levee is trapping the sand drift down drift. A flood comes
11:59 a mouth bar and some offshore those bars begin to prograde and merge
12:09 drift and then there's a little bit a bay head delta. I don't
12:14 like that term but uh a, , an area where sediment is coming
12:21 from the river that's between this offshore and also some pictures of that to
12:27 that more clear. OK. So are just some of the Brazilian waved
12:31 deltas, asymmetrical now, particularly big . But even the Rome, remember
12:42 talked about how if you only had small area of, well, if
12:48 trying to reconstruct that region, uh might think of it as a river
12:54 delta, a wave dominated delta, even a barrier island complex. So
12:59 look at this interpretation from the We've got a strand plane, then
13:04 got muddy distribute plane and then we've another strand plane or barrier island coming
13:10 more bee roos over here. Um And so, and this is
13:16 drift direction. Uh Well, it out that imagine you're looking at the
13:25 main mouth of the, the main of the uh Ni uh Nile
13:34 This is the updf side. It's all strand play. Look what happens
13:38 drifts. You've got this elongated barrier is trapping to form a lagoon and
13:48 plane here or just flip that and what you end up having is
13:59 big delta sitting over here and this simply the down drift portion of a
14:05 delta. OK. So, is just a strand plane complex or is
14:10 part of a larger delta? Uh These are actually to the same
14:16 . OK. So, uh that's importance of this regional view.
14:22 And the other thing to know is if the up drift side is basically
14:29 pro grading stram plane, then the drift side is gonna be this alternating
14:34 muddy, sandy muddy sequence. And that has a lot of implications
14:40 the reservoir heterogeneity of uh these waved deltas. And going back, that's
14:48 what was anticipated by this model here in the late eighties or mid
14:58 OK. So there was a lot insight in this model done strictly from
15:04 laws um that um has a lot implications for what we, how we
15:12 waved dominated deltas now. OK. let's look at one bulb of
15:19 the run as an example of waved delta. And we're gonna look at
15:26 portion right here. It was active about um Oh uh 2000, years
15:36 or more. Um I mean, less. And so we can see
15:41 it's pro graded downstream. And I would, I would also note
15:47 it's basically the sediment wedge is It's, it's eroding older stuff to
15:53 younger stuff, this pattern of kind down drift migration. Uh We see
16:00 , in the uh the Brazos River well. But the point is it
16:05 pro grading out And if we look it, let's uh look at
16:09 this is the strand plane truncated and are a series of sand ridges and
16:19 marshes. And these two, um me, let me go it
16:28 It's easier to see these two pores are indicative of the A strand
16:39 Um These cores here art from this here. And so we see again
16:49 different the same delta is in terms the vertical sequence just because of the
16:56 drift and down drift side. And would also add that the composition of
17:01 sands may well be different than the drift sands because the up drift sands
17:07 from longshore, drift up streams in . Uh Notice though here, the
17:15 the sands are also being derived from portions of the delta itself, but
17:23 still being derived from the up drift . So these sands down drift are
17:32 with that river. No sand up may have a completely different composition.
17:39 . Now, to give an example how that bar that's bar mouth and
17:45 bar, crete and forms, uh look at this example here from the
17:51 Washington Oregon Coast. Uh during a , we have a distributor mouth bar
18:00 . And then after the flood, have reworking of that well, uh
18:08 bar into swash bars, that is say the waves cresting on that bar
18:14 it to become emergent and begin to . So we've got flood and
18:21 Ok. Uh That's one of the we have to keep in mind that
18:26 the river in flood may, may completely unrelated to the waves and
18:33 And so there could be a significant between that development of the mouth bar
18:42 the formation and migration swatch bar. , uh this is looking at a
18:52 two cores in this area here. this is a core of one of
18:58 . Um Actually, it kind of like this. Uh These are those
19:10 down drift sides and this is a in one of the sandy ridges.
19:16 then this is a core in the and notice you've got this or what
19:22 would assume is this um like OK. So again, that
19:42 yeah, sorry. Here we've got core and the intervening March and that's
19:55 those cores are basically showing. Uh here we've got the mouth bar,
20:02 swash bars, they're beginning to migrate . Notice that the clone of sediments
20:12 moving down stream as well. And the up drift migrates in a high
20:20 , higher wave energy samp or situation , the down drift they accrete uh
20:28 they may well be a spacing of in between and then the next flood
20:37 . So let's look at how that happen. Here's the uh the
20:42 this clearly is the direction of longshore . OK? And here's your mouth
20:49 flood. And here are your squash and notice uh they're beginning to accrete
21:03 , they're moving on shore and now largely accreted and you got the sandy
21:10 an earlier sandy ridge and this intervening flat area. Ok. Uh Without
21:21 accretion at all, what little accretion occurring is uh occurring is sand up
21:27 . Ok. So that's what we're at as we look at this transition
21:33 symmetrical uh plumes to asymmetrical or even plumes where um the there's so much
21:46 energy compared to sediment supply uh that river simply just can't feel gray.
21:53 here would be an example of a plume. There's the river and it
22:01 which direction is the sediment moving. , it's just kind of moving offshore
22:10 uh in by diffusion. Here. the other hand, we have a
22:15 deflected plume and we have a very a deflected uh river. Uh This
22:25 looks like it's relatively low mud. if there was higher mud, you
22:31 , you'd have a little more down separation here. OK. So this
22:37 , my favorite um wave dominated del and one of the reasons is you
22:45 see very much the formation and transit of a former waved dominated delta here
22:59 the present way dominated delta here. . Uh That line that I just
23:07 is about 14:00 14:68 Christian er or uh so this basically has formed in
23:22 last uh 600 years prior to this was the uh main distributor.
23:30 was abandoned. And I want you think about how this looks compared to
23:40 Mississippi Delta. When we look at abandoned loads and there we had
23:47 we went through that cycle of uh , reworking, flooding of the delta
23:56 . Here, it's just truncated. mean, there's virtually no subsidence
24:03 It hadn't been that long, but still virtually no subsidence and nothing but
24:10 . There's no subsidence in part because is a low mud area. Remember
24:16 had Fixed up to 60 m of that was beginning to compact when that
24:28 was abandoned here, you have almost blood. So when it's abandoned,
24:34 only thing that happens is you've lost sediment supply, the waves are still
24:39 in. And so you have OK. So I want you to
24:46 thinking about how these waves or rather these different types of deltas behave and
24:56 as a pro grade in their constructional and as they are Barmy destroyed uh
25:05 their in that is as they're when abandoned and go through the destruction
25:10 Both the geomorphology, the map view the geometry of the settings and how
25:17 might affect how you would recognize these out or subsurface. OK. Uh
25:24 another thing to note, if we at this portion of the delta here
25:32 was shown here. Uh I want to look at this area here in
25:42 little more detail. OK. Right , you notice there's, there's a
25:49 of little truncation actually seeing better here large. Now, this is largely
26:06 symmetrical wave dominated Delphin. So we're getting a whole lot of distinction uh
26:15 the up drift and down drift OK. Uh But having said that
26:21 , there's an interesting distinction going on between what they mark as green,
26:31 is a mouth bar system and which they describe as a uh uh
26:42 , it's basically a, a OK. Now, so let's look
26:47 that here. Here again, we it more schematically. OK. And
26:52 is how, how we mm this how we look at. Um I'm
27:08 . OK. Yeah, I don't you, all right. Um This
27:13 what happens. You've got a mouth formed and they call the element set
27:24 is then truncated or eroded and then on both sides. That's a measure
27:32 the asymmetry. OK. And so that happens, bye. Flood,
27:43 , flood, reworking. Each time a major flood and reworking event,
27:48 get this kind of dispersed zone between mouth bar and the ridges.
27:58 I think you could, if you about it, imagine how that would
28:06 if you had an asymmetrical delta where maybe this was the up drift side
28:14 this was the down drift side and began to have more separation in here
28:21 the swatch bars come on. it turns out that these mouth bar
28:32 complexes uh can be picked up in the subsurface as well looking at
28:40 attributes or time slices. Uh The thing is that when you look at
28:48 vertical sections in the mouth bar, more heterogeneous or more muddy. And
28:58 the downstream section of the lobe lobes much thicker and much more typical of
29:10 pro grading shore face as opposed to sands in an urine or distribution
29:18 OK? You can look at this your leisure. So here we have
29:24 example of a pro grading short face dominated delta. Um Galloway doesn't show
29:35 of an increase in grain size once become amalgamated in what I would call
29:42 a uh a delta front again. These are two different ways of
29:50 The same thing. Galloway tends to describe the uh vertical sequences as
29:59 be seen in a core. Uh And then the grain size would
30:04 shown separate. Uh And, and others tend to combine the two uh
30:11 use the grain size as uh changing this direction. So that the outer
30:20 of this is a grain size curve then the sedimentary structures are shown
30:27 Um all things equal. I prefer this type of, of uh example
30:33 , is the one that's done most uh in part, because it's easier
30:38 visualize how the grain size is changing the change in upper uh with the
30:44 in sedimentary structures. And we can here now that there really is some
30:49 going on within this zone here. we have it, for example,
30:54 here, uh shown again uh where is a series of those accreting cycles
31:04 uh pro gradation events in that program delta. In fact, here's that
31:16 core sitting here. And what we're at is we're looking at uh multiple
31:28 . OK. As we're uh looking and this pro grading sequence, there's
31:37 big discontinuity here. Um This, is associated with a uh I'm
31:46 this lobe set is associated with an lobe and then the newer lobe is
31:57 here. And here they do suggest been some subsidence between the older lobe
32:04 the younger lobe. Uh In there's very little but it's, it's
32:09 here for, for effect. And again, are those uh cross sections
32:17 we, we might have seen through . OK. So the main focus
32:24 is this is the pro grading Sandy . OK. So here we've got
32:31 river dominated and here we've got wave now, but Ari made the distinction
32:38 storm wave influenced and storm wave Uh conceptually, that's, that's not
32:47 all surprised because think of that uh triangular classification um as waves get
32:57 and more dominant or storm waves get and more dominant. Uh You would
33:01 a transition and the transition you see is um the decreased influence of the
33:14 and the increased influence of the So by the time we're here,
33:21 looking at a scrambling in between, looking at a river dominated. But
33:30 actually, I want you to imagine this is the up drift side of
33:38 wave dominated delta, what would the drift side look like? Really?
33:43 look like this or this? It's be those packets of marsh Bee
33:52 marsh sandwich, marsh sandwich. So I don't think I'll ask it
34:00 an exam, but I would ask to think about what that core might
34:06 like on that down drift side. . Now, the other thing I
34:11 you to think about is that destruction phase um the wave dominant deltas in
34:23 Texas and the Cretaceous uh provided a of background. There was some uh
34:32 look at what happens with say a strand plane sequence or uh let's say
34:39 dominate delta. Well, you begin , you wrote it and you continue
34:50 erode it. But what you're doing you're really just cutting down and truncating
35:00 system. You're not seeing a lot subsidence. So the section simply is
35:07 up, cut out. And you say you're getting an erosional transgression,
35:16 also get a lot of calcite cementation at that contact just below the.
35:23 the, and the reason for that that during the transgression, that erosion
35:29 transgression formation of that wave rave there's typically a lot of uh gravel
35:36 , including shell material and that shell is dissolved and repre it just below
35:45 in the top of whatever it is being truncated. And that could
35:51 concretions or it could be an actually consistent. Uh And it can certainly
36:01 as a, a um majors top in terms of that better sort of
36:10 material uh potential reservoir downdraft. here's one of the tricks though,
36:17 is the best reservoir in this grading sequence? It's in the upper
36:24 face. What is the first to removed if you just are dealing with
36:32 , the your face. So you preferentially removing your best reservoir and you're
36:42 beginning to bioturbated it as is being . So we've got a, a
36:55 between the transgression that just be it a transgression and subsides that at least
37:05 the potential of that oh uh that face, high permeability potential reservoir to
37:17 . And so we kind of see issue here. We, this would
37:20 an example of what we talked about a uh pro grading or uh short
37:28 where, where we've got uh these and we've got transgression, regression,
37:36 regression. And, and let's look what that looks like as one
37:45 Ok. Um These are pro grading and so it's basically the a portion
37:57 here one of the shazam. And this is a, a programing event
38:06 each of those has the potential for and vertical changes in reservoir quality.
38:14 . And eventually we can get down individual beds within those deposits.
38:27 All right. Yeah. Um So let's look at what's happening down
38:36 . There's a lot of stories to told from here to hear.
38:44 Uh Here, of course is the he still here. Is that narrow
38:52 uh plume. Uh Here's the sediment to fly a bay and coming out
39:01 there, that sediment we can see the finer material is being dispersed down
39:09 and the course material is also hugging coast. We have a zone right
39:14 here. Uh That's actually Nier We'll come back to that in just
39:20 moment. But what I want to on is that when we look at
39:28 satellite imagery, we realized that there sediment being dispersed all the way down
39:37 Mexico from Mississippi. OK. when we look at this portion of
39:45 down drift delta plain, it's called sheer plain. We see that it
39:50 of a series of distinct Shane, are basically uh referred to linear sandy
39:59 separated by mud flats. OK. so this is an example of what
40:06 they look like on earth. Uh a little, you can, you
40:11 kind of see the strand plane pro if you took a cross section through
40:19 , uh, it would look like . So we've got little sands and
40:27 . Now, one of the important here is notice that this sand is
40:33 , it basically does not extend offshore we kind of predicted for that down
40:49 portion of I'm, yeah, the drip portion way do a delta is
40:55 just right here and it's surrounded by . And the reason it's truncated is
41:03 it's formed by the reworking of a sands or a muddy uh programing title
41:19 . And so it's a transgressive feature on the back March and it's winnowing
41:32 the, the finer material leaving behind a little sandy ridge and then there's
41:41 pro gradation that flows. Ok. this basically is a, reflects a
41:48 of time when you, you have pro grading sediment supply and a shut
41:55 of sediment supply and reworking. you might think that's flood, non
42:01 , but in reality, these are in time that it reflects more the
42:11 of the up drift delta, the drift Paleo Mississippi delta. Ok.
42:20 when we look at that, we've a, a delta here and we're
42:32 right here when this delta is we get a lot of mud down
42:39 . Now, what's gonna happen when shifts here? Well, you know
42:47 story of how that delta will be and it'll begin to subside. I
42:56 repeat that. But what's gonna happen this area? You've shut off the
43:01 shore grift of sediment. But, so it's going to begin to
43:07 So now that it's shifted over you have abandonment over here in that
43:16 flat, which had progra it out now eroding as well. And so
43:24 gonna give you that thin strip of . The sheer now the delta come
43:31 over here. It's close. The is coming along the the coast and
43:41 pro grading again. So those same that we saw with globe abandonment or
43:48 say, formation, abandonment, abandonment back and forth, left and
43:55 is causing cooperation, reworking, reworking of the down drift in your
44:02 . Ok. Ok. Um We that in a lot of major
44:09 Um I saw it on the uh on the uh the delta uh Yukon
44:17 . Uh This is the plane, is the, the modern delta at
44:22 . Um And you can see that little better here. These cheers are
44:32 older. The youngest Chiers are only about here. And so we have
44:42 abandoned river courses coming down here from Yukon as well. So we this
44:51 drift sheer of muds and interbedded really . Cheers or sand ridges is a
44:59 feature in, sorry. Pardon Uh large muddy deltas that now
45:10 we've looked at this transition. Uh this is looking at some of
45:21 I'm sorry, the Isopack that we get. Uh I wanna focus.
45:29 we're gonna leave the effective wave domination look at the role of tide.
45:37 among other things, just notice the in ice pack shape. OK.
45:43 going to these elongated zones. And does his finger like. And
45:56 is this both the modern? Did you take bird delta and these
46:08 tide dominated deltas at first blush have kind of a similar digitate is a
46:19 as we'll see, they're totally different . Now, we alluded to
46:26 In fact, we described this uh where we looked at a, an
46:32 , a tide dominated estuary. Uh saw that V shaped funnel, we
46:39 that meandering to straight portion upstream and saw the transition or rather the intermixing
46:48 river dominated processes and wave and tide processes. The tides being the dominator
46:58 we sold it as the river influx relative to the marine influence. Uh
47:09 get a shift and we get pro mud flats and we get accreting and
47:19 . Uh uh well down stream accreting vertically accreting uh tidal ridges as
47:29 Ok. So this would be an of a high dominated built here.
47:39 And you can kind of see why on people wondered is it really even
47:44 delta? Uh But it is, is. Ok. Uh This is
47:48 Fly River, which is uh one the, the main examples. Uh
47:54 so uh we're gonna look at present title processes and how high dominated deltas
48:06 both in the modern and in the en uh ancient environments. And one
48:15 to remember is that these things evolve into another. A tide dominated estuary
48:23 common during a rising sea level. sea level is stationary, then the
48:29 can begin to prograde and it transforms from a tide dominated estuary to tide
48:37 about delta. So where are our tidal ranges? Well, they're down
48:45 in uh uh Indonesia and uh Australia in, here in Korea. Uh
48:54 got a lot up in the Bay Fundy around uh UK, et
49:05 And here are the major rivers, sorry, major river deltas. The
49:12 in black or solid are tide dominated . So we've got them here in
49:23 macro tial area in Australia. We've them here in the macro tidal zone
49:27 the Gulf of um California. we got him here in the
49:33 the Amazon. It's just a locally dominated area that's a, a that's
49:43 from the geometry of the shelf. , here's the Amazon with this big
49:49 , here's the, with the big , the fly, uh and the
49:54 Sea. OK. Um All we'll skip this story right now.
50:01 here's an example. Uh P me the Gulf. Uh a yeah,
50:10 delta plane wide mud flats, funnel distributors and these elongated veg mud flats
50:26 into elongated subtitle bars, subtitle chan . Ok. Uh So here we've
50:35 the, and, and delta and turns out that it's somewhat misleading to
50:45 about. This is the tie dominated . This is actually the modern Thai
50:53 delta today. This is the abandoned . And what we're looking at is
51:02 drift accretion. Here's an accreting but all of this here here,
51:09 have that old delta and here's an older. We've got a disconnect.
51:17 we begin to look at the whole plane. It turns out that much
51:23 what we think about as the wave . I'm sorry, the tide dominated
51:32 are these elongated estuaries, some of are completely disconnected. Now, these
51:38 slightly connected still, but you can they are not as dominant. We
51:47 particularly see that with the Ganji So much of the here is the
51:53 act of Delta. OK. This the abandoned delta. There's still sediment
52:03 down here. But the title influence is much different than the title influence
52:16 . So this is abandoned, this active and again, when I say
52:23 , there's still sediment coming out. is not because you hear, but
52:33 have a very different morphology of the flats and rivers. If we look
52:42 that abandoned river, it's basically tidal channels So here we actually
52:50 what I would argue is an a that has formed on the abandonment of
52:59 Ganji tide dominated delta. Now, still see sediment coming out and I'm
53:06 come back to this later. But area here is typical uh both of
53:20 thi dominated deltas. But this surface morphology here uh tends to be
53:30 typical of the abandoned plane, abandoned plane. OK. Uh Here we
53:37 again, active delta, abandoned the , active delta, abandon delta.
53:53 . Here we've got reworking of the front into barrier islands and a lot
54:03 channels all along it. Here. we have the pro grading delta.
54:12 , we even see it with the here's a modern or it's a tie
54:20 mixed Hyde river delta. And here have down drift mud and sediment reworking
54:33 bearing that abandoned Ali or no. , in a purely fluvial system,
54:46 getting here and then we're gonna have delta mouth or the trip mouth bar
54:51 right here. Yeah, that's, know, it deep and it,
54:57 , it gets deeper and deeper until hits the mouth board in an
55:04 Mount bar is still way over but we're actually getting shallow channel in
55:14 showing way upstream of the, the and that is because of the landward
55:26 influence. So we have a net appreciate in this zone here because of
55:38 tide and the decrease in tidal a energy now they'll change in a
55:45 But the long term effect is to this accretion significantly upstream of the river's
55:57 . Let's look at the Colorado The Colorado river comes down here and
56:04 it takes a little bit of a and it forms what's sometimes referred to
56:09 an inland delta as it gets into , this a distribution fluvial system is
56:15 it is. But notice that here's salt Sea, the salt and sea
56:23 largely filled around The early 1900s. a big flood ended up diverting the
56:37 and flooding this region, the flood on what was called the All American
56:42 . So they were siphoning off water irrigate the agriculture in this area
56:50 Uh The river tried, the river change its course, eventually got it
56:54 come back here and it presently goes Mexico and enters in the Gulf of
57:07 to form this tide dominated delta. , the only problem is this delta
57:16 presently beheaded and it's beheaded. Not because the river itself was diverted,
57:29 the water was diverted. Uh This the decrease in water with time to
57:40 1960. There was a little bit a spurt here but basically zero water
57:45 flowing down to the Delta. It's being diverted for irrigation most for the
57:52 . In fact, there's a what is returned is so salty to Mexico
57:57 there's a desalinization plant at that spot try to freshen up the water.
58:02 the Mexicans continue to complain to us they're not getting their share of the
58:08 river water. We're complaining to them real bravo and our share of that
58:15 to the River Grande such as international . But we clearly show that this
58:23 system now is defunct. The good is we can at least look at
58:31 you like the relic tide dominated And what we see offshore are these
58:40 tidal sandbars? They're out in We see this big elongated bar here
58:50 this one here. It was the flats on either. So now if
58:58 draw a cross section through here, can kind of envision how that V
59:07 upper end of the Gulf of California would look like before I do
59:13 Let me just remind you that these those Tidal bars. This is the
59:21 that would be right here because this the main one that separates uh the
59:27 major distributors. And then as we further offshore, we see these smaller
59:36 , linear sand bars. Ok? here's the flooding, the transgressive flooding
59:44 the bay. Here's our alluvial Uh We've got she and pro delta
59:55 that are then begin to be interspersed these subtitle deltas. We've got mud
60:05 that are beginning to come on shore we have these distribution channel fills,
60:15 you. So we've got, if like four major faces to flat,
60:23 I'm gonna call it pro delta linear ridges and estuaries. We pretty much
60:38 what tidal plants look like. But about these rene distribution channels in the
60:46 title sandwich? Ok. Well, they're, they're pretty different and,
60:53 , and that's, this is really of the criteria that we use uh
60:58 reconstruct these systems. The distribution channels have an erosional base. They are
61:11 to slightly finding upwards until they're And there's a series of events that
61:22 that channel as it programs, it up. The linear title ridge is
61:32 pouring upwards system until it's a emerges become a title slap. And of
61:43 , it's punctuated by that uh muddy . Uh The sands get thicker as
61:54 get near the top. Yeah. these are our two in members.
62:01 you like the dominant sandstone faces of tide dominated delta. And we see
62:09 in, in the ancient uh as . Here's a sand ridge or sand
62:14 that different people uh have interpreted but interpreted as le or sand ridge course
62:22 from bottom says, here's the transgressive , stone bottom set bar slope,
62:29 crest, the bar crest until it's is gonna have the most uh reworking
62:39 both tides and waves. And you're have in here, things like a
62:44 bundles, reactivation surfaces, et Oh OK. This was originally interpreted
62:52 a pro grading sandwich. Uh but people began to look at it in
63:00 detail, they realize that these are elongated features from river sources in this
63:08 . Ok. Mohawk is a significant . It's been studied a lot in
63:15 because it's tide dominated, but in because it's a humid source area.
63:21 , what does that mean? first of all, it's in the
63:24 of Moha of uh moan straits. it's got very low wave issues.
63:33 not much fetch. On the other , it's an area where the tides
63:38 accelerated as they come through the So it's got a high wave,
63:46 high tides, but low wave it's in a humid drainage area.
63:52 so you tend to have rainfall all round, which means you don't have
63:58 hydrologic flood and non flood cycles. That means you tend to have no
64:05 . You know, remember levees are when the flood overs spills the
64:10 You don't have displays. You don't a lot of avulsion. Ok.
64:15 the climate in the source area uh a major impact on the pluvial and
64:27 processes uh downstream or in the system , and downstream. I don't know
64:34 I was gonna do there. We it. OK. So this is
64:37 it look looks like in terms of the green on the left is the
64:46 as the uh red on the Uh That's a false color image or
64:53 infrared. But basically we've got these um dis tributaries. Um They're all
65:05 active and in part because remember what said about lack of floods, you
65:10 to have lack of, of uh all shows. Uh You do get
65:15 switching due to bar accretion. Uh you get a lot, you have
65:21 lot of these deltas, I a lot of these distributors continue to
65:25 active as they're progra offshore. You a wide delta plane uh and you
65:32 these little triangular shaped mouth bars. those mouth bars started here and then
65:50 become elongate. And as this these will become, these will merge
65:56 become elongate as well. So up here, we've got a distributor channel
66:09 here we still got channel, but little bit of lateral migration or bar
66:18 . And here we're getting a pro up bar formation case. Now,
66:29 we look at this, there's actually referred to as a sub aerial delta
66:36 , there's a zone of deposition and delta front way out here. And
66:46 a lot of these delta males are disconnected from the channel. Some are
66:54 next to the channel and some are offshore. And so this has to
67:01 with the tides that are forming this in during which the sediment is pro
67:11 . There was a lot of work on describing the transition from the offshore
67:17 river dominated deltas. The wave forget about the from wave dominated is
67:27 shore face. High wave energy, grained sediments moved offshore and down the
67:38 delta. Over here, a lot mud, it's a low gradient offshore
67:46 it begins to fail. Uh by uh in the pro delta river diving
67:56 we get less and less mud because more and more wave energy. We
68:02 that increase steepness of the shelf or near shoulder. Now, there's a
68:07 here, a radiant pro delta means wave attenuation. And so wave energy
68:19 getting progressively less as the as the programs. On the other hand,
68:25 we have removed the fine grain we increase wave energy. So there's
68:32 feedback between the relationships of the sediment offshore and the amount of wave
68:46 Now, when we looked at the Delta, it it was different,
68:49 had a very flat surface until about m, almost 20 km offshore and
68:56 it was steep. Uh that has do with the dynamics of ice.
69:02 not gonna get into that, but turns out that that is much more
69:10 of a high dominated delta. Uh being um this is the moca right
69:21 in the moa if you were to uh the depth and distance, this
69:30 the Mohawk delta been meaning to do for Yukon and I keep forgetting to
69:34 it. Uh So if we yeah, sediment across the shelf.
69:42 gonna see that the tides are pushing lot of that sediment offshore. And
69:49 gonna be one of the characteristics of Thai Doin deltas this zone of bypass
69:57 that is forming this broad flat. here's the Mekong dealt. OK.
70:11 Now, these black ridges are like cheers beach ridges and it, it
70:20 has that um morphology that is of Laird uh channels. Fact, the
70:39 shape looks a lot like the but it, it's rather different.
70:46 the if you draw a cross section here, you would see a very
70:53 kind of delta and delta and what have now cheese. Oh No,
71:12 not cheese. What you say. oh See, it is kind of
71:23 book out um coming in and down front that Yeah, what else?
71:47 , I've got a quick example. . Um Now the point here it
71:55 to enlarge that is that the delta actually formed changed as it filled in
72:10 early stage, which is around It was like the, it was
72:20 Thai dominated do in its later It actually became much more of a
72:28 bait, dealt with the effective waves much greater. And what that means
72:38 that if you were to try to the early maha, it would have
72:45 right here if you were to plot later moha, it plants over
72:54 So this delta has changed through time though it hasn't changed its location.
73:02 . So what's happened? Actually, don't remember, but I can tell
73:06 what I think happened. And that that that transition from rising sea levels
73:13 sea level, high stand meant that 25,000, from 6000 to 25,000,
73:21 still had the tides being the main , sediment supply was having trouble establishing
73:32 pro gradation, sediment supply finally was to allow that delta to prograde more
73:43 waves became the dominant process. So the transitions are numerous. The
73:54 of deltas from shelf edge deltas rising level to bay head, deltas and
74:03 , wave dominated estuaries. Pro grading into mid shell, shallow deltas,
74:09 shelf deltas, shelf deltas. What story. But it's important to think
74:17 those transitions. OK. Now, do you look for in, in
74:26 ancient or a th dominated delta or that the diagram of workers if you
74:38 to try to quantify the relative impact relative importance of waves, rivers and
74:47 because almost no delta is an end . All of those, those three
74:56 impact them to different amounts when you at the signature of the sedimentary
75:02 So what are the, is the of tide generated deltas and tide generated
75:09 ? Well, uh ring costs. Tangential four sets and reactivation surfaces,
75:23 lithic strata and double mud drapes and rhyth mites I mean, those are
75:29 things that you would would see. , you know, here would be
75:35 ripple and doom scale pros strata. bone Prosta remembering that that's not formed
75:43 a flood a cycle, but by of time, blood dominant om uh
75:54 sigmoid contacts. Uh That's basically our bund. OK. We've seen that
76:02 of course, if you recall that bundle uh can be eroded to form
76:10 reactivation surface. So, reactivation surfaces form during the subdominant flood cycle.
76:18 title cycle hetero lithic strata. Uh . But having said that we can
76:28 them in any environment that's alternating fast slow. So what we'd like to
76:38 is also bidirectional transport, particularly when have the ripples for sure.
76:44 But hetero xstrata are common, but are also, as we see,
76:49 find them in the deep deep sea well. Uh Double mud drapes are
76:54 part of the title bundle story. we're looking at tidal bundles, we're
77:03 at reactivation surfaces. We're looking at mud drapes. These are, that's
77:08 part of the tidal sedimentation story. finally, those idle couplets thanks related
77:20 that would be the inclined hetero lithic . OK. Go oh, hang
77:29 . Uh do something here. Well, I just uh forgot to
77:38 something. Um Let's just go to . Ok. Here are here is
77:47 pro grading tidal ridge or pro grading be pro grading mouth if we look
77:57 this, we see we can look a general package in here and that's
78:05 bed set. And within the bed , we see transitional faces. That's
78:21 that we're going to describe our show another moment. So we have these
78:29 that are progressing out. These are sandstone rich facies, these are the
78:36 rich faces. It's and eventually it to cease to prograde and the mud
78:49 or hetero lithic species began to take . So, what are those?
78:54 , that's what somehow got super composed faces five, which is this
79:04 thick sequences, sandy bars on the of the grading tide dominated delta.
79:17 , and we're gonna go from five 4 to 3 to 2 to
79:26 So three and 2, I'm four and 3. Uh You're going
79:34 cross strata to hetero lithic straddle and I'm sorry. Yeah, down
79:46 we're getting isolated thick cross strata. down here we're getting a hetero lithic
79:53 again. Ok. So I wanted try to explain that a little
79:59 but here's face. She's wanted two strata. Here's five, your best
80:12 And in the Middle three and relatively thick sands and hetero lithic
80:24 And so here's how those bars, look as a form of set and
80:35 bars themselves are separated by periods of bar degradation. And so when we
80:43 to look at those pro grading mud of that costing up, which be
80:54 , uh imagine that you were looking that mud draped surface. So
81:03 we basically took that grape surface, it out and looked at how continuous
81:11 mud was. What you would see that it's pretty continuous on the lower
81:18 and it gets more and more discontinuous the upper part. So what is
81:23 is the continuity of that baffle that barrier that gets more and more discontinuous
81:33 you get higher and higher up on program set. Yeah. So this
81:43 kind of a useful summary for these title bars. We see them in
81:54 , tide dominated estuaries and tide dominated . The tide dominated SWS are typically
82:02 . The deltas are typically regressive. what do you get in these regressive
82:11 ? Right. Well, you get stacking. First of all, that
82:18 the lower bar and I'm gonna have , here's the bar. So this
82:30 the, the bars and sea level rising. What that means is the
82:45 sets are preserved and the bars aren't up to the surface, they're being
82:56 because it's an estuary still, it's by Landward oriented paleo the title generated
83:09 it's pretty well, the sands are well sorted. The bars tend to
83:14 a little thinner and the bed sets a little thinner and you get the
83:23 low angle sigmoidal trough or cross the . But so how would that differ
83:33 a system where you've got sea level . Well, look at the top
83:45 the bar, the top of the tends to be eroded. Uh You're
83:55 more fluvial or basin where paleo currents because the river processes are, are
84:03 dominant. Uh The sediment in the is more poorly sorted. You get
84:09 pro gradation stacking, the bars are . You get a lot of trough
84:15 tabular pros strata related to the increased of the fluvial system. OK.
84:25 let's look at some case studies and there are several in Venezuela. Um
84:34 has many giant fields and many of are wedged just south of Columbia.
84:47 in what is basically a a for that formed during the collision and,
84:55 deformation. Oh South America. So have a, a series of thrust
85:09 that are forming a, an elongate , uh all along Venezuela from west
85:17 east. And we've got a fluvial that's an axial drainage system depositing,
85:30 in the Mara basin with pluvial and sediments into the open marine. So
85:38 a cross section, we kind of how that would be both a transgressive
85:49 a regressive system. So this, the way down here would be the
85:55 where we think the the tops of bars would be preserved if it's a
86:02 dominated system. And it is, then these areas here would be where
86:08 uh more regressive systems would be. this is a description of the reservoirs
86:20 right here. OK. Uh Here's tide dominated deltas and here's our rene
86:27 complexes and our proximal, the distal sandwiches. Those sandwiches being down
86:40 It depends. So, and here have, here's the are a series
86:48 channels and these are inter channel uh flats. These are the channels coming
87:02 like this. And then in here have these tidal ridges and mouth
87:18 And this is one interval with the sand and san channel sitting in
87:31 And we can see we've got kind an elongate low associated with this particular
87:39 channel would be this with you. , it turns out if going back
87:45 the max notice how these melt many of them are sitting at the
87:52 of that sub aqueous delta but are to the tidal flat in other,
88:00 a rene channel that continues offshore, are sub aqueous levies and then here's
88:07 mouth box and here's the same scale system for the Orinoco or rather
88:28 And, and if we go back those estuaries in the Amazon, we
88:37 that the channels are coming out, elongated and they had this kind of
88:50 or shoe like bar Some distance offshore this case, 20 km offshore
89:10 very different. I mean, very to those elongate bars. They had
89:23 mohawk, the scale is different, is two km that's 20 km,
89:29 it's the same process. And so we have are these linear ridges better
89:40 you like the tales of these mouth . And this is a vertical section
89:50 cores showing what those linear sand ridges like bursting upwards. OK. Here's
89:59 of the core. Uh This is lowermost part and here that's going from
90:09 delta hetero lithic to sand. And this is the part that been here
90:22 this is from in Spain. Uh is from um Venezuela and this is
90:35 summarized by Galloway, I think Galloway of ripped a lot of what he
90:43 uh based on this particular model. it's, it's also takes into account
90:50 models. So we're beginning to see similar these things are and how different
90:57 are from the chin where we have channels, a gratings and then finally
91:08 in the band of. And this is kind of the alloys look
91:14 , it looks awfully similar in part I think it's probably based on,
91:18 this work. So when we think the title sand ridges, we think
91:24 coarsening upward sequences. When we think rene channels, we think of somewhat
91:31 but finding upper sequences. So if we go back here, we're
91:38 call this grossly finding upwards. Whereas it's upwards. And so we've got
91:56 channel complex. Here's another one here here. We have a grading
92:04 Stan Bridges as this as this basin Philly. Now, if we continue
92:15 that same basin, here's a cross . We have folded mountains that are
92:21 that for basin, it continued to a basin into the mayo.
92:27 here's the fats again. We still a river coming in here.
92:38 we're into the heavy oil belt of uh Venezuela. Here's the paleo
92:45 Here's the fold and thrust belt here this is what's referred to as
92:50 as a or art. Yeah, a arch. Orland arch, I
93:00 . Or what is it, what's it called? Can you remember
93:04 you've got loading and then you've got , an arch that forms by the
93:11 . So you got this arch on one side of the for basin and
93:18 got the fold and thrust belt on other side, say it again and
93:25 , it, there's a name for arch which is a structural arch.
93:34 anyway, I forget its name. isn't a structural geology but it,
93:41 is topographically high. And so we're some rivers flowing into there as
93:46 The main river, the axial river the mayo is coming here and there's
93:54 big v shaped trough is causing tidal in the mayo in the western,
94:04 sorry, the eastern part of Venezuela well. Ok. So if we
94:08 at that area, the paleo geography something like this, there's kind of
94:15 tide waved dominated delta here, going a tie dominated delta here and notice
94:24 got some barrier islands here that we with the maximum uh tidal amplification and
94:34 wide tidal flats here. So These two large fields, heavy metal
94:49 Uh And uh this one is more a tide dominated delta. This one
94:58 more elongated Estan chance. And if look at the Isopack, that's what
95:06 look like. Um And what we is in yellow, we have sandy
95:19 channels, green, muddy, contributory . Why Rene Baout dos?
95:33 And if we look at this, . Ok. Yeah, let's go
95:40 more. Uh I'm sorry. Uh is All right. These are three
95:51 reservoir units. So what we're looking is a progressive change with time in
96:00 fields. Early on, you're looking a basically a sandal, the distal
96:11 of sandy braided stream or braided river . I little with time, it
96:22 a tide dominated delta and as it to, with time, it becomes
96:33 tide dominated delta and urine complex with lot of shade. So we grade
96:42 amalgamated braided streams to meandering streams, influenced mouth bars to and climb meandering
96:51 of tidal influence. OK? From sandwich portion to a muddy portion.
97:03 it turns out 65% of the oil from that lower system, down
97:13 which was is largely in the fluvial , But 35% of that oil is
97:21 uh heavy oil I should add is here in more tie dominated delta
97:32 And I'm just gonna paraphrase this. best production is coming from the fluvial
97:39 portion. The upper delte dominated portion is pretty good in the very top
97:49 that torsion uh is pretty poor. , if we look at the modern
98:00 , basically, we've, we've what looked at in the, in,
98:04 the previous two examples in this is pale Orinoco blowing down this Orland basin
98:15 the Iliac to the Miocene to the scene implies to see said long lived
98:25 system because it's structurally controlled in those parameters are keeping it in the same
98:36 . Now, if we look at the late Miocene to the Picene,
98:43 turns out that we've got a transgressive that's tide dominated a tide dominated system
98:56 a tide dominated delt system. In words, this system going from my
99:04 pliocene is going, we see transgressive regressive cycles. So we're looking
99:17 if we looked at a wave dominated system, we see waved dominated estuary
99:24 wave dominated delta. Now, if look at the modern delta, we
99:39 both tide dominated and more wave dominated in laterally adjacent. And this happens
99:52 the paleo or as well, we areas that were predominantly tide dominated,
100:01 are going from tide dominated estuaries to dominated deltas and laterally evil waved dominated
100:12 that were going from waved, dominated to waved dominated deltas add that system
100:22 into the press. So within the , we've seen significant changes with time
100:35 the legacy on and in, in development of reservoir faes, particularly in
100:47 title ridges and estuary channels, uh allowed major giant oil oil fields not
100:58 fall just as in sign if we to far, go farther upstream.
101:03 that same system, we would Pardon me? Alluvial fans, here's
101:15 river. There are these high dominated pro grading up here. We've got
101:28 fans coming in merging with that ax . This is kind of analogous to
101:39 you might get in the the end the uh Himalayas turns out these Louisville
101:47 are have amazingly high porosity and permeability there are oil fields right here.
101:58 had deleted that as a case study because of time. It turns out
102:03 should have just moved it here. we've got oil fields within this Orland
102:10 . With this being the arch, a cross section basically arch. And
102:25 the face she is from Alluvial fans deltas and then by the time we
102:34 in the my scene uh rated deltas to dominate deltas as well. So
102:51 seen All of this change in one , but over a long period of
103:00 . And yeah, this is in just a second. Um If this
103:10 Colombia and Venezuela, there's a big area here like Cabo is right
103:25 This is both a compression and trans uh series of thrusts that occurred as
103:38 plate boundary. As the Caribbean Plate migrated um to the west relative to
103:45 South American Plate. He formed this this basin in this arch Trinidad sit
103:56 here. In fact, some of sediments uh from the paleo or had
104:03 caught up within the uplift. This trend there. But we see paleo
104:13 , pardon me? Uh in this and thrust belt in Trinidad um that
104:20 part of this axial system. So deposit and then, well,
104:28 So that's a continuation of this. . Um It's no uh time to
104:41 . Uh We've got deltas to It's let's plan on getting back at
104:46 . OK. And we can stop
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