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GEOL6358 Terrigenous Depositional System - Day3 02-24-2023-Part1
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00:00 They put okay there. Okay we're together. Alright guys um But I'm
00:34 turn off this light. Um I tried to update uh the readings uh
00:46 I tried to put them all in reading list then intermittently successful so that
00:53 see some readings that uh either I have P. P. D.
00:58 . For or I'm still looking So it's kind of a work in
01:02 but let's continue on from uh the systems of alluvial fans and lakes which
01:12 to be uh in closed areas and arid. Uh And and add to
01:19 the aeolian systems because they are genetically associated quite often. Now we were
01:30 in the only bus for a lot reasons uh controlling specifically. But their
01:35 aqua fers turns out their major climatic . So you wanna know something about
01:41 climates. And often we're looking at nurse and other the only deposits and
01:48 also we've got just environmental issues of and like so what do you need
01:56 new Orleans system? Sand supply continued of supply. So you're gonna find
02:02 associated with rivers especially glacial out wash deltas for your continue continuing to feed
02:11 sand to the coast beaches, particularly that are creating uh lakes particularly when
02:19 dry up and things of that But it's not just enough to have
02:25 sand, it's got to be available be transported. So what that means
02:30 non vegetated. It also means low take wet sand just doesn't move.
02:38 you want it to be dry. vegetated non injury. Did so you
02:44 want it to have developed a soil . Okay. Um On the other
02:49 , you could initiate movement by for reason destroying the vegetation. Uh So
02:56 we'll look at that a little And and lastly, you've got to
03:00 a way of transporting and depositing Uh So you've got to have a
03:05 of stand in the system and it to decelerate in order to have
03:13 Okay, so again, vegetation is of the reasons. Uh we'll look
03:20 other reasons why sands begin to deposit well. We've seen this before.
03:26 looked at it with respect to let weathering. And basically what I'm looking
03:32 here as we did earlier, or arid regions. And in particular the
03:38 high pressure systems and the polar systems that's where a lot of our desserts
03:44 . Uh Most Aeolian deposits are associated deserts. And so we've got the
03:52 and the tropical equatorial or rather the highs. We've got the uh the
04:02 Simpson desert. Um So these are of the areas where we have large
04:08 of of the only deposits, but also get them in some other
04:13 like, so if we look at Gobi for example. Uh just get
04:18 look for the Gobi up here or the mojave over here. Uh These
04:24 rain shadow deserts. Uh So we've another set that are less dependent on
04:31 . Uh we also have coastal Uh the Atacama sitting here, the
04:38 sitting here are associated with oceanographic conditions have cold air moving onto an
04:47 And it's basically the water, whether air evaporates as it gets onto warmer
04:55 , causing arid conditions. And I would just remind you, we
04:59 polar deserts. They're not shown in diagram, but the dry valleys of
05:04 antarctic our desserts. Uh desert doesn't , oh, it just means lack
05:11 precipitation. When you look at the of sand and in particular, sand
05:20 what we call herbs. Uh you that uh the active or partially active
05:29 seas today are a smaller subset of had been active in the past.
05:35 so that's the distinction between the dark here in the hatchet which are called
05:42 . And I would just point out couple of things notice there's a big
05:46 see down here in south texas. a big sand sea up here uh
05:51 the Nebraska sandhills. So there are lot of areas both in north America
05:59 really all over the globe where the sands were much more widespread during the
06:07 ice age. And then is the changed. What we saw in south
06:12 and Nebraska was basically, it got and warmer and so vegetation stabilized those
06:23 . Now they're stabilized until such time they're unstable. Ized. And so
06:29 are areas that are environmentally pretty So when agriculture comes in and removes
06:35 vegetation, uh it's an area where occur and you've got major soil erosion
06:41 . It's also interesting to note that these sand dunes were active, we
06:49 a lot of lakes and what are pliable plants like Death Valley. So
06:58 seen this kind of a seesaw alternating of climate change, particularly during the
07:05 and interglacial periods. Okay with respect the active and stabilized sand dunes,
07:12 respect to alluvial lakes drying up into . Now, when we talked about
07:24 fans and legs were looking at Moving, said to me,
07:31 uh, when we think about the system, when moving settlement, we're
07:40 looking at Aeolian, these are going at the same time, so it's
07:45 easier for me to separate them. clearly all these uh systems are going
07:53 at least potentially being being co equally in different basic fields. Okay.
08:02 , not all systems, not all deserts are the same, however.
08:07 if you look at the amount of , what are called aeolian sand
08:13 predominantly sand, uh, in large , it's only about 20% of all
08:18 desserts, a lot of the dessert basically stripped stripped bedrock. Uh but
08:26 variation is great. So for in the Simpson Desert in Australia,
08:34 Of the desert is covered with sand and the mojave, maybe 2%.
08:41 , and that's the reason in we are much more focused here in
08:48 US on alluvial fans and less than deposits because our deserts tend to be
08:54 for, we've got a lot of fans because we have the topography that's
09:01 lee maintained. If we go to , the Sahara, we don't have
09:06 tectonic topography. So we don't have alluvial fans, but we have a
09:11 of sand. Okay, so when look at deposition in deserts,
09:18 it's not just climate, but it's tectonic lee generated relief. That's going
09:24 be a factor. Now, when think about fluid transport, air is
09:32 fluid, so it's water. But we look at the differences, water
09:38 1000 times more dense than air and a result, there are a lot
09:46 different magnitudes of forces that are generated a grain of sand. Okay,
09:55 , buoyancy much greater in water, , momentum or impact much greater in
10:03 . Okay. And you don't need know these numbers except to recognize that
10:08 like momentum, which is related to , to grain impact is thousands of
10:16 greater with the aeolian sediment transport than Pflugerville. And as a result,
10:24 we get a little bit of a look at, let's say the shields
10:30 . This is really a variation of shield diagram where the fluid threshold.
10:35 , this blue line right here is essence that line of motion for sand
10:44 water. Okay. Um but with deposits, grain grain impact is so
10:54 greater that that critical threshold is significantly for a grain of sand. So
11:05 takes a lot less velocity to get moving in an aeolian cyst.
11:14 when it moves, it moves differently , um it rolls and creeps and
11:22 salt states and eventually gets up at suspension. So when we say
11:31 remember it's air is a fluid. It can get into suspension into the
11:37 atmosphere and trans be transported across the . We literally see Saharan dust coming
11:45 across into the caribbean, affecting coral and hitting uh North America.
11:55 now, what we don't see in inception emotion in air are the developments
12:04 the kind of ripples and dunes at initially that we think about.
12:10 there's just a lot of impact. so the grains are either creeping along
12:17 they're bouncing along. That's the main in which they move across a flat
12:23 and sometimes in the bouncing uh shown here, there's in in air
12:33 Uh this is causing more grains to , so it's more and more sand
12:41 put into the air by bouncing or . Uh Then the more and more
12:45 kind of kept in. Now the ation pathway is a function of the
12:56 and the velocity, relaxing momentum as function of velocity. So it's a
13:01 of the mass and the velocity, mass or grain size velocity of the
13:08 . And so we can think of more or less uniform path link or
13:17 distance or given grain size and wind . Now that in turn actually is
13:24 generating wind ripples. Uh when we at these wind ripples uh and one
13:31 the discussion questions uh from the next , guard the comparing aeolian ripples and
13:39 a quiz ripples. We find that ripples are the result of the bouncing
13:49 or rather the salt ation length. when the ripples where the, when
13:57 air kind of goes, jumps and this area here, the backside of
14:05 ripple is impacted much more than the side of the rippling. We see
14:12 here, what's happening is in the side we get relatively little energy in
14:20 backside, high energy. So when have higher energy we are preserving coarser
14:27 . Were transporting coarser grains in the , we're depositing finer grains. And
14:35 that actually gives us of course any set of rip eliminations. Okay,
14:47 the spacing here, as I said is controlled by salutation path link and
14:54 in turn mass of the grain or size and wind velocity. Okay,
15:03 so here we have that inverse Now let's compare it with Slovakia's ripples
15:10 a second. Um One of the that is characteristic of sub aerial or
15:17 ripples. What they're called is their two dimensional, they tend to be
15:23 crested. Sometimes you have these little for uh bifurcation. Okay. But
15:31 more important variation has to do with height and grain characteristics of the ripple
15:43 . We have thin inversely graded lamination very few visible forces. And that's
15:53 we're not looking at avalanches were just at that variation from high impact.
15:59 loaded on the other hand in we have thicker, inversely graded.
16:08 typically can go from low energy two to high energy three dimensional. They're
16:14 graded because it's grain flow down. four set. Four sets are fairly
16:20 . The other thing is we know we just don't get some a quiz
16:26 more than about 40.7 millimeters. That's gradation between hydraulically round 25. We
16:35 that with wind, wind can move up into granule size. Now you
16:43 think well that's not a surprise because has higher velocities. But the reality
16:51 that wind really can't move anything bigger granule size because we're not going to
16:59 uh gravel transported by went We can't gravel trance and do get gravel transported
17:09 water. Okay. Yes we know it can be 150 mph. The
17:15 is when we measure when we measured 10 m height. Okay. And
17:21 very quickly goes down to the two uh almost a hydraulically smooth contact uh
17:30 erin. And so if you see , you know immediately that it's not
17:36 its water or grafted if it's a . Now we also talked last
17:44 well last week about translate strap translated . Remember are those sets that are
17:54 by ripples migrated. But more uh we're particularly interested when we cannot
18:03 the four sets. When what we looking at is basically a first order
18:09 surface. With ripples. We can see the ripple four sets and therefore
18:18 we can recognize the difference between that set and that first order bounding
18:25 Okay, so although I use the translates strata for water and when generated
18:35 , it's mainly restricted to wind generated . Because there you can't you almost
18:44 can't see the four cents. So see what that might look like.
18:48 are translating strategy. Lamination is here's a one centimeter. Okay,
18:58 you look real closely you can see these are dipping down went. But
19:12 you mainly see is that forcing upwards . Okay, so this is what
19:21 translator wind uh ripple laminate would look . Okay. Uh here again we
19:29 we see very uh low angles but one's actually climbing but uh this is
19:39 you usually see. And and notice these lamination, these set boundaries are
19:49 parallel. Uh When you look closely can see some low angle inclinations but
19:56 they're pretty parallel. That's because those two dimensional dudes. I'm sorry two
20:04 ripples. And remember that one of characteristics of the two dimensional transverse metformin
20:10 that when you see it in dip , the set boundaries are so
20:20 These are sometimes called pinstripe lamination. , for obvious reasons, but pinstripe
20:27 is basically win drip or wind Okay, well these uh ripples can
20:39 on flat surfaces or dipping surfaces. they often form on the four set
20:49 a larger do. They're usually thin continuous, inversely great. What this
20:59 with the alternating fine, Coarse, course find courses that the permeability energy
21:07 can be like 75-1. It can 75 times more permeable horizontally than
21:13 So there's a lot of vertical Um They tend to be closely
21:22 They have lower permeability and lower These so these are not particularly permeable
21:30 porous uh types of lamination. Uh often see them formed by wind whipping
21:41 the slip face. So we've got almost vertical press Migrating across the of
21:52 uh four set. Now another thing see in terms of comparing severe
22:05 aerial or aeolian ripples and dunes is they do form distinct uh wave lengths
22:15 heights. Uh One of the big is that the Olean Olean dudes are
22:22 lot larger. Then the aeolian So let's look at some of
22:28 the aeolian dunes. And here's one little Barkan dune and white sands and
22:34 the wind ripples on the back side the do. So we're gonna look
22:42 where those occur and look at their preservation potential. The backside of a
22:49 does not have a lot of preservation because that's kind of the erosion side
22:57 the dune is migrating. Okay, we'll see Translating strata preserved but usually
23:07 on the top of the dude, on the 4th set. In
23:12 this is something I think I've shown uh when we look at four sets
23:20 this actually can apply in some as as several dudes, it's just more
23:26 and several dudes, we have ripple , we have rain fall out,
23:34 have grain flow or avalanche ng and we have reactivation surfaces. The reactivation
23:42 isn't so much a um deposit but it's a truncation that represents a
23:54 And so it's kind of a line that cross section. And this I
24:00 show uh there we got when grain fall or grain flow. All
24:07 this uh is sitting here um waiting be described. And this four set
24:17 top to bottom is going to basically multiple forms of sediment deposition.
24:26 now let me talk a little bit great fall. Um They are gonna
24:34 extremely thin, extremely laterally continuous uh are typically gonna be steep because they
24:43 to form on the and form on four slopes. Uh They're really hard
24:52 see. Okay, um Their porosity a little better than translating strata,
24:59 as we'll see in a second, nearly as predominant as grain flow.
25:06 in terms of preservation potential, they not real common. What is more
25:15 is translating strata and green flow. They're typically steep. They're sick,
25:26 says eliminations, I I should beds because of the thickest. Um
25:33 we'll look at the geometry and they be both inversely and normally graded.
25:40 tend to coarsen down the dip and have the highest permeability and porosity of
25:45 of the the strap, uh loosely Ferocity is 45%. In fact,
25:54 we look at probabilities, here's the of the interview deposits, which I'll
26:00 about the moment, but here's the of average probability of translate. And
26:08 the average permeability of grain flow. , so these are in darcy
26:15 this particular. Uh these are air ease uh in a Jurassic sandstone,
26:22 we're gonna see this time and time with ancient deposits as well as
26:28 There's a significant difference in the permeability the inter dune. The translate in
26:35 grain flow. Okay, so let's at the geometry of these grain
26:42 Remember these are those avalanche deposits and what we see if we look at
26:50 horizontal cut in here. Uh They're discontinues. That's because you're looking at
27:04 scallop of that, slow that little . Okay, so here, for
27:13 , these are green fall. Some them are translated but look how much
27:24 and discontinues these are. That is green plug. Okay, say it
27:37 . Uh No, that's uh the is from fly burger and this is
27:47 a cartoon from uh ralph Hunter. but it's the same view that is
27:56 say it's the horizontal slice. So looking at a horizontal cut of the
28:03 flow deposits. Okay, now fry has described the processes on the dune
28:09 the slip face. I'm not gonna it except to simply say the upper
28:15 is scour intention. The lower part deposition and compression. And then in
28:23 is just kind of a transition So scour compression, scour tension
28:33 compression in transition here. And they vary from this kind of a classic
28:40 look to literally a big slap And this is how they might look
28:49 when the, the dune is damp coastal dunes, especially uh there can
28:57 a lot more brittle deformation because the provides a little bit of the heat
29:03 the failure. So this is a from great great sand dunes. We're
29:13 at kind of an oblique view we're still looking at the dip
29:22 but now we're cutting it slightly at angle. So this is each of
29:27 is a grain flow deposit and you see how the scalar is occurring.
29:33 , uh this is the grain flow almost perfect cross section. You see
29:44 the tongue that deposition lobe is pinching and draping in between translates strategy.
29:55 , so we've got at the toe this particular or set uh failure as
30:03 flow reworking by wind ripples. And is again what we're looking at
30:11 Uh This is in the ancient deposit those darker, coarsely coarser, inversely
30:18 grain flow deposits in that pinstripe variation grain of translating strategy. Now,
30:27 other thing that is common in aeolian or reactivation surfaces. Uh We've talked
30:33 these earlier where we gotta win reversal then erosion and deposition over here and
30:42 see that in the record by these ations. Here's another one. So
31:00 got transportation from right to left, truncation, left to right, then
31:08 reactivation. So the net motion is from right to left, but there
31:14 intermittent periods of reversals. Okay. we can see that here as well
31:20 those truncation and one of the things point out here, this particular zone
31:26 , these are reactivation surfaces. They're differentially cemented, which is beginning to
31:35 that as we look at these I'm sorry, as we look at
31:40 , surfaces as we look at uh pro grading yoli deposit, it's easy
31:47 visualize it being compartmentalized in terms of characteristics, with the horizontal flow being
31:57 greater and the vertical permeability because of complications. Okay, and again,
32:08 is just looking at some seasonal Yeah, again seasonal variations. Uh
32:22 we have rainfall, but here we grain flow and notice the kind of
32:28 intermittent areas of the the scholars. this is just a diagram. Look
32:38 at your leisure Iceland has a really way kind of compartment capitalizing and capitalizing
32:45 lot of different options of what's going . And in systems of uh the
32:54 justice example like sub deposits, we have superimposed bed forms superimposed, the
33:08 bed forms. Here we've got um grain ripple superimposed on larger dunes.
33:17 here we actually have mega dunes, huge. Some people might call him
33:24 draw, but they're basically a compound . Where this is one dune form
33:34 A wavelength of about four km. then we have these smaller dunes wavelength
33:42 about 600 m. So uh this 10 km. So this is about
33:51 km. So these are huge dunes their dunes on dunes. In
33:59 if you look at brain size and , um here are ripples that kind
34:06 form this and then here's a set dunes and here's complex dunes. And
34:16 we get these really big compound dues literally, you know, sea of
34:24 uh we call it a draw. it's not at all clear that that
34:32 is real. Okay. Um well Israel is we're going from simple dunes
34:40 the left to compound dude complex dune the right. So uh here we're
34:51 at those mega dunes that we saw and over here, we're looking at
35:02 of the other dudes. Okay. now one of the ways we describe
35:08 , they are typically elongated. Um what is the relationship of that to
35:14 wind pattern? If they're elongated parallel the wind or result and better said
35:22 direction, which is seen here is . Their longitudinal if they're right angles
35:28 less their transverse and if they're an there oblique. I use the term
35:35 a lot because that's what we mainly used to thinking of. But in
35:40 only assistant longitudinal dudes and bleak dudes much more common than we get
35:48 No particularly rivers because you don't have width to allow them to develop.
35:57 what I want to talk about is was common classification scheme that is based
36:06 whether or not the dens are formed uni directional wins or bidirectional wins for
36:13 directional winds. Uh We've got bark , we got kind of Barkan
36:21 transverse, two parabolic. Okay, those are the types and our type
36:31 , if you like, type locality be white sands. We also have
36:37 formed by multidirectional winds. These are dunes. Uh They're star dunes and
36:46 forms look kind of like this and there are linear or sheep dunes,
36:53 dunes rather and they actually vary in . So we'll talk about this all
36:58 these separately. Uh but this is the most common and useful way of
37:06 with dunes and notice that little dumb while they introduced those in just a
37:11 . Okay. Uh so what we're do, we're gonna go to white
37:14 and look at where this kind of classification was kind of first noticed.
37:19 if we look at white sands is between a couple of major uh horse
37:31 into Robin. Well, here's uh paso. So here it is up
37:39 . Now here's white sands. But notice there's a lot of areas like
37:46 . Um And so what we're looking here are combination apply a lakes and
37:52 and the reality is that much of , western texas and new Mexico and
38:05 were covered with alluvial lakes. Where alluvial lakes were the ones during the
38:11 period during negotiation. Okay. And lakes have been drying up and so
38:18 of them are just a little pliable . Now. Okay, if we
38:23 at one of them, that's lick for terra, that was this
38:29 right here. That's gonna continue to up into what is now a little
38:38 lake like lucero and then from that we get our present dune field.
38:47 , so white sands is formed from , the evaporating release the bulk of
38:58 sands is formed from reworked evaporates. specifically gypsum. So here's our little
39:10 lake areas was left of that huge lake. And here is the dune
39:17 . Now in reality, if if we were to go to the
39:23 we would actually find some quartz sand they're, the winds are blowing off
39:29 , walk out, blowing across holistic deposits. So they're getting sand,
39:35 tells part. But to the south the lake was a source, the
39:41 uh their white sands of chips. if we begin to look at that
39:49 , we begin to get domes parabolic transfers to bar camp. So we
40:03 to see a an aerial fe. tracked if you like. The aeolian
40:08 forms. Okay, so here's the there in areas closest to the
40:15 Their little mounds. Um they move quickly. You can see them down
40:21 here. They migrate faster than transverse of the sand that's coming from here
40:32 to pile up along these transfer These are sometimes also called bark annoyed
40:42 they're kind of custody. Okay, here's those transfer students. Strong
40:50 High supply center hi supply coming in the dunes over the dome dunes which
40:57 in turn bringing it in from the . There's a transition two from bark
41:09 ridge to bar cans. The sand is a little less. Now,
41:16 of the sand is being trapped within transverse dunes. Uh and so this
41:24 be an example of that transverse Here's the slip face and we can
41:33 how they're moving because they left behind track. Okay, so they're almost
41:47 star ripples. Okay, there's an dune area that separates the moving
41:58 It is which you don't see in . Eventually those slow moving bar cans
42:19 into parabolic dudes. And basically the is beginning to be slowed down by
42:28 and so the vegetation is kind of the tails slowed them down. So
42:36 basically getting slow moving parabolic dunes and lot of vegetated inter dune areas.
42:49 , so here is the resultant wind . Here's the direction of sediment motion
43:03 to say transverse high, highest lower supply, lowest supply of
43:12 So that's if you like our she's truck. And so it might
43:15 something like this. Uh We are velocity a little bit, but more
43:25 . Well, very important for the students is the bulk of the sand
43:32 getting crapped in the transverse dudes. see an increase in influence of
43:43 So don't well, source dome transfers parabolic transverse dunes. I slipped
43:57 reactivation surfaces. Okay, bark, . They're more three dimensional. So
44:11 gonna be more variation in the dip . Okay, These are more two
44:32 . These are more three dimensional and little dunes here, these are basically
44:37 dunes that are creating in the downwind . Those are the dome dudes.
44:48 , this is a picture of a dune and its avalanche. Ng,
44:54 , we know we see that here avalanche, more of it as a
45:02 . So we can see those The actual plain dead or grain fall
45:09 right here. And then you get pretty good idea, it's probably gonna
45:14 pretty soon as well. The entire of the slip face was reworked by
45:22 wind drill as well as the Yeah, so the grain fall doesn't
45:30 it quite to the bottom. So kind of have a vertical or rather
45:36 change from brain. Hello, mainly , the wind ripple at the bottom
45:46 what that suggests is that the wind will often be lower than the grain
45:59 and this grain fall it's intermittently So here we've got an example um
46:13 little section that I showed you a bit of rainfall in this age,
46:19 the bulk of it being rain flow then at the bottom translating strategy.
46:28 , now, one of the problems almost a problem, but one of
46:35 realities of dealing with the only deposits just like ripples and dudes in a
46:45 top is being cut off. So set that's preserved preferentially preserves the lower
46:54 . So we don't really know if got a set, let's say a
46:59 thing, We don't know if that a dune that was two m high
47:04 20 m high necessarily. Okay, here is that dune where the grain
47:14 couldn't make it to the bottom. that was probably a pretty large do
47:19 to suck. So if it's we're going to see when ripple deposits
47:28 preserved. If it's a little the grain flow deposits make it all
47:35 way to the bottom and grain float be preserved in that lower post
47:41 So the presence or absence of translating in these relatively thin sets is a
47:51 as to the relative size of the . Okay, so here's one of
47:57 sets. Okay, so a couple things to note, first of all
48:06 that there there's a difference in color the lower most tangential Portions of those
48:15 four sets. Okay, that is to the lower permeability of the translating
48:27 , the cleaner, wider uh color is more related to the grain
48:36 But but the question I was mainly about was what controls the thickness of
48:41 sense. I mean, these are sets and of course they're gonna be
48:48 sand dunes. So each of these a bounding surface. Okay. And
49:00 we go back to what we talked before these are climbing dunes except of
49:06 they're climbing sea burial dudes. And the angle of climb, which is
49:12 angle here um is a function of rate of trans relation versus the rate
49:24 deposition. Oops. Now, as increase the amount of suspended load relative
49:34 bedrock. We go from the little ripples by the way. This could
49:38 any kind to a high angle but the set we're here to
49:51 I have trouble. Well, you the idea uh can be no
49:59 well not much thicker than the height the dinner. In fact, usually
50:06 less. Okay, If you actually it. Supercritical climbing, then then
50:14 can actually see the whole doom We tend not to see that in
50:20 aeolian deposits. We do see an . We see it fairly commonly in
50:26 ripples less commonly in some Bakley's So let's look for a second at
50:36 inter dune areas. The dunes I'm sorry, the areas between the
50:42 , uh notice their vegetated or can vegetated. Uh We looked at him
50:52 . So one of the things that's of striking is that we actually see
50:59 these horizontal slices, remnants of the faces. That's what we're seeing
51:07 These are slip faces. And the reason why the erosion didn't go any
51:13 , because that's the water table. this is an area of high water
51:18 . And so the slip faces uh preserved because it's hard to move.
51:25 sand. It's also an area of deflation. Okay, so we tend
51:32 leave behind the granule size uh particles a deflation lag. We also see
51:43 unique type of sedimentary structure that's formed wind blowing over damp sand And these
51:51 called adhesion ripples. Okay, and show you a little more in a
51:58 . Uh Now you might have areas the water table fluctuates and it's low
52:08 dry rises is wet, so you get mud cracks for example, or
52:15 supply of lakes if it's more you tend to get a variety of
52:24 . But adhesion ripples are one. also get these little algal mats,
52:30 little microbial mats that form that are of stabilizing the surface. Now,
52:39 thing that's unusual about these adhesion ripples that they actually grow up drift,
52:52 like antidotes. I have never recognize in the field, I think that's
53:01 I'm not quite sure what I'm looking and I've seen other, I probably
53:05 seen him and didn't recognize it, the fact is um these are,
53:14 you recognize them are characteristic of wind wet sand so we can have inter
53:21 deposits that are dry, damp or . And I'm not gonna go into
53:28 uh just to know that you can of think about what the differences might
53:33 between completely dry and typically wet. that's discussed on these two diagrams here
53:42 uh I'm not gonna ask you to a lot about that other than the
53:47 to dry transition. Okay, what multidirectional dudes. Right? Um let's
53:58 with reversing dudes because that's the great dicks. Okay. And in the
54:05 sand dunes. Uh and this is a second case study. So I'm
54:10 ask you to think about the story white sands compared to the story of
54:20 sands. Okay. Uh because it's comparison. It's also a nice discussion
54:27 . You've got Large dunes. The is over 200 m thick. It's
54:37 large area of sand over 600 square of which about 70 square kilometers or
54:44 dudes. The remaining area that fringes presumably underlies the dunes is a sand
54:53 and very low Dudes like the great . It lies in a basin within
55:05 basin and range province. Now though source is basically the Rio grande River
55:13 more specifically kind of a mega ban came out of the san juan volcanic
55:31 . And so here's that. It called Rio grande san and like um
55:47 sands, it filled a large I mean the basin was filled by
55:55 large lake like Alamosa lake. Alamosa up leaving behind the custom and flew
56:12 deposits to be reworked into this large area. Okay. And as we
56:23 at that, we see this actually beyond here. But if we look
56:28 at this little Porsche, this is the main dunes are piling up where
56:36 piling up piling up against this pre basement is actually like this.
56:42 so we've got a source of set dens piling up. Now I'll go
56:53 to this little more second. But see within this pile of dunes we
56:59 different types of dudes. We got aeolian face. She's trapped. Similar
57:05 some ways to white sands. The here are not white because they're solicit
57:13 , you know? Re working mainly real deposits, the surrounding sand sheet
57:21 more widespread, thinner. Um a of evidence of re precipitation of carbonates
57:30 Ap writes a lot of root zones it's vegetated typically by ultra baited little
57:37 Doom's dome dunes and other types of uh that are associated vegetation, maybe
57:46 little ripples when it's going over standing of water. Okay, so that's
57:52 be fringing the whole area. That's sand sheet. Okay, over
57:59 Now, if you look at this , Barca known transverse parabolic stop.
58:16 . And alluvial fans over here. we see some of the same types
58:23 dune forms and white sands that we in over there in great sand that
58:28 saw in white sands. But their is different. Okay, in some
58:34 . So let's look a little more , let's look first of all at
58:38 transverse dude just got a cramp. and here we see these transverse students
58:52 of running like this. Okay, we look at the wind rose predominantly
59:02 from the west and southwest, but reversal winds from the east and the
59:13 drift, It's kind of little bit the north. So when we look
59:24 these, one of the things we kind of get the sense of
59:31 these transverse dens are kind of broken . The other thing that we see
59:44 that the wavelength of these transverse students getting smaller and smaller, shorter,
59:53 as we get on the flanks. here we kind of envision these climbing
60:03 . I mean not ripples, these dooms and look at them way down
60:18 , the height and therefore the thickness low and what we're looking at is
60:26 lateral shift based on the rate of supply set. Okay, where the
60:39 supply is highest. You get these transverse students forming on the flanks where
60:46 supply is waning. The transverse students getting smaller and smaller and we'll see
60:52 a moment they actually change in the cans laterally, just like we saw
60:57 the white sands changing downwind. the other thing we see are these
61:05 peaks here is a big slip face what that peak is. He is
61:20 wedge of sediment that is forming during reversal went seasonally reversal winds and so
61:34 are reversing dudes. Um this is a picture of how they form.
61:40 I think at this point, you can kind of follow that, recognizing
61:45 the potential for these reverse students is . But here we see him moving
61:53 this direction and is sometimes called locally chinese walls. So these are the
62:06 peaks due to reverse identify low preservation . But what has a high preservation
62:17 is that erosion surface? That's the surface. So we see these reactivation
62:24 that are representing periodic reversals in the . Now the other thing is when
62:35 uh and you can actually see it this image here. Notice the dark
62:41 , the dark line. Is that ? Okay, so that that reverse
62:49 peak, that little chinese wall is shadow and the slip face of the
62:58 dune is illuminated. So this is slip face. And then that's the
63:10 . Now when we look at take a look at this, it's
63:17 we have a secondary set of transverse and that's actually what we have.
63:26 forgot that this show through basically. you have reversing dues and you begin
63:31 get more and more multiple winds, begin to get these noses.
63:44 And that's what we're looking at This is the effect of bidirectional or
63:52 direction. Okay. And as we'll it's gonna leave a distinct pattern in
63:59 strata graphic record. Going back to wavelength of the transverse students look at
64:06 much smaller they are. See that . Okay. And then as we
64:14 down here, this, by the , is river great extreme. We
64:22 grade into Barkan DUIs separated by vegetated flats. Okay, now that river
64:37 here as the Medina River and the dunes are trying to get across
64:45 You actually see some dunes get across dry periods. But what it cannot
64:50 is get across the song increase of . So that's what having the old
64:54 stopped. And so here we've got Medina river, the main dooms and
65:02 of the sands that get across the supply is so low that we actually
65:10 bark can do and again go back white sands. Okay, the least
65:17 of sand supply. Slowest migration, amount of vegetation a little bit over
65:25 of some bark. And it's now we come back to the backside,
65:35 our sand sheet. Here's one of parabolic dunes that made it across the
65:45 . Okay. And we not only bar cans across the river, but
65:51 got bar cans down drift. Whereas white sands, we had dome dunes
65:58 , we have Barkan dunes and they're across this long sand sheet and their
66:12 actually are creating a type of longitudinal . But it's really just the vegetated
66:23 of these kind of isolated dooms that blow out. So this is more
66:30 a sand sheet phenomenon. Okay, we've got these parabolic or the sand
66:38 . Rather parabolic big to little trans little bar cans and small parabolic step
66:54 here. That's where we have our dunes. And when you get into
67:00 , there is no linear or transverse face. Okay. Uh it's just
67:08 dips are everywhere or better said the of the dunes are everywhere. And
67:15 see that in the topographic map shaded map. Okay. And what we're
67:27 at here is essentially like the end of sediment getting thicker and thicker and
67:39 more exposed to multiple wind directions and up into star dudes. And this
67:46 part of an auto cyclic process because the dune gets bigger, winds begin
67:54 whip around so we begin to get secondary wind direction, then a new
68:01 forms and that causes yet another wind . And so this is an auto
68:10 phenomenon that's occurring here. And we it particularly well developed in the Sahara
68:17 the libyan deserts where we see these look like brittle stars. Okay,
68:28 those are our startups. So between sands and great sands, we we've
68:40 the whole spectrum of sand dunes with exception. And these are these big
68:48 dudes. Remember that white sands and sands are restricted to a um really
69:00 half drop. Um Both some Yeah. And they have limited lateral
69:12 . Once we get to the we don't have that tectonic topography.
69:17 so we have this huge continent scale . Okay. And so we can
69:26 gradations from transverse to linear dunes. These things can be up to hundreds
69:34 meters. Yeah. Now there's two of linear dicks and, and I
69:50 here 20 m high a kilometer in , um are not the biggest,
69:59 what we're gonna see is these things from smaller linear dunes or safe
70:04 Simple dunes, the larger compound So there there's a gradation in
70:13 And if we look at a satellite , we see that linear aeolian bed
70:19 are most abundant on in the yet they're the least commonly recognized in
70:26 rock record. Okay, now, the general idea is that these are
70:38 dunes that are the result of two more directions of wind. Basically by
70:48 , they may have started from little will bark hands, but one arm
70:56 longer than the other and it Okay. Uh, and that seems
71:01 work. But there is another Maybe there's a heloc oil flow in
71:09 lower part of the atmosphere. It air to rise and deposit and then
71:19 down to a road. The problem caused effect. We know in fact
71:25 flow can be observed. But is the cause or the effect of the
71:31 dudes most argue it's probably the effect linear duties. And it's not the
71:39 likely cause having said that if it's model, which seems to be the
71:49 , what would the internal stratification B so when you go and you climb
71:54 these big news, uh, and dig into them meter or so you
72:02 see dips in both directions. And uh the general model or rather one
72:10 model is that they form packages. . And it might look something like
72:18 . Thanks. Now it's called the . No, I'm getting to Colonel
72:26 know that. He's an interesting Um there's a different model and that's
72:33 Hunter and Dave Rubin's suggested maybe they s symmetrically. That is to say
72:44 dominantly move in one direction. But a reversal, you know, just
72:52 reversing dudes giving a reactivation surface. this little red cap just didn't
73:05 Now one of the problems here, are in deserts during the middle of
73:11 . You can't cut dry sand, have to cart up gallons of water
73:15 wet the sand, cut it. we have very little information about the
73:21 structure of these dudes. Or rather had that until we got G.
73:28 . O. And what the ground radar showed. At least in some
73:33 these reflective of predominant, you need but they're trump by these reactivation
73:45 So in this area at least it like the linear dunes are results of
73:52 winds but one wind is stronger than other and they're actually migrate At,
73:58 know, maybe 10,15 cm a So in this particular example it looks
74:06 the Hunter model is a better model the linear dudes. Uh the problem
74:15 that when you when you begin to at these dudes, they sometimes had
74:26 . And as the dune is getting , it's getting more complex Now in
74:36 particular example is still showing net met migration but is getting larger and
74:46 complex. And so as it gets , the internal geometry gets harder to
75:00 . And this model here, that's model. This model based on field
75:06 um suggests that that's what we're getting other areas. We're getting a large
75:14 dune with the slip face and then rose into a mega. Do the
75:25 mega dude that has no slip face said it's mantle gold with smaller
75:34 So here's actually uh a cut and lower part, the earlier part was
75:44 concentric began to get s symmetrical and it gets more complex still. So
75:54 see these big linear dude are really their biggest r compound dudes. They
76:03 have a slip face. That's what see here. Yeah. And as
76:11 as the concentric versus asymmetric. this that's more The Bag. No
76:23 vs 100. Now, some of dunes are so large that they're actually
76:36 . That is they are dunes that formed under a different climatic condition.
76:44 from under modern wind conditions there basically of relief and so what's happening,
76:53 beginning to be reworked. And so lot of these linear mega tibbs are
77:01 reworked into these areas of filling the , we're bark annoyed dudes. And
77:16 this is the wind direction and here have these rework bark annoyed dudes that
77:23 filling in between and we kind of that here this is a different
77:28 But here are the bark annoyed dens in the troughs. Here are the
77:40 linear dooms with the traps in Now, in some cases, those
77:52 dunes show some very low amplitude long bed forms called Z bars.
78:08 They're under 10 m high. There m wavelength. They're mainly on sand
78:18 or introduced. Okay, so I'm gonna talk much about those, but
78:24 see the turn and they're mainly going be associated with these areas of low
78:32 of sedimentation. Okay, we're gonna it at that. Yeah. Now
78:42 you what, I'm gonna take a . Let's uh pause the reporting.
78:51 , one of the things that that out when you look at this picture
78:55 the owing deposits in in Toronto are lines and they're clearly bounding surfaces.
79:03 . Um and if there were ripples the subsequent environment, we're not calling
79:09 order bounding surfaces. Um The problem as useful as is the concept of
79:19 subdividing these little architectural elements into bounding . The Aeolian community. Does it
79:26 backwards from the some community. for water, Their first order is
79:36 biggest bounding surface or second big is order is the smallest. Okay.
79:43 so uh the only thing I will in the only defense is they actually
79:48 the came up with the idea of surfaces. First. Okay, so
79:53 gonna talk about scooper regional surfaces which basically all over the whole basis unrelated
80:04 individual doing migration. Then we're gonna the first order, which is the
80:12 of big complex dunes. Second the migration of smaller dunes and third
80:22 truncation due to reactivation services. So see what that might look like.
80:28 these first order dunes, there's two ways they could afford. One is
80:36 to horizontal, water speaking and that occur, but a different way is
80:45 doomed migration. Okay. Um one the reasons why people began to think
80:53 this is that the water table. Well, merry friends. Uh
81:03 The idea is that the water table horizontal. Therefore these Stokes type uh
81:12 surfaces should be horizontal. Well, problem is the truncation czar, not
81:20 . Okay, most cross strata has removed by erosion is does migrate.
81:25 this is the second possibility. that they're basically inter doomed boundaries due
81:37 migrating strategy. And the key is a cord through here. We actually
81:47 that here's the inter dune deposit and previous did So, virtually all of
82:07 first order deposits are related to migrating now probably should have shown this
82:15 This is the idea for water tape in the direction of flow and truncated
82:26 direction of flow climbing dunes, they're be inclined some angle of climb and
82:39 there's any kind of sin you are , there's the inter dune deposits are
82:44 to be this continues laterally, whereas water table would be continuous laterally.
82:53 if you like. An easy way checking is to look at the lateral
83:00 of these inter doomed deposits. So one example, notice their deposit their
83:08 out down dip and they're pinching out long strike. So it's clear that
83:16 this particular case these first order bounding are not water table. In
83:25 the water tables rarely the case except the super uh cycles. So going
83:32 to look at the entrada. These here, at least some of these
83:41 gonna be first order bounding surfaces. might look like this. And so
83:55 we've got a laterally discontinuous inter doomed . This is based on the entrada
84:05 , uh And you can see look at the lateral discontinuity in
84:12 Okay, and Saca is a term use more typically with marine setting marginal
84:22 but it can be marginal lake as , particularly if it's an evaporative
84:28 Okay, so now up here, are laterally continues. These may well
84:38 water table control but these laterally discontinuous and deposits are definitely due to dune
84:48 . So this is the laterally discontinuous her title. Inner dune deposit and
85:00 is the packaging that we get like . Okay, now the reality is
85:12 the water table does change and it's uncommon for either the water table to
85:22 or sand supply rate change. In , if you think about it,
85:30 they're connected. If the water table dropping, why is it dropping?
85:35 dropping because maybe it's getting more arid exposes more sad. So sediment supply
85:43 be coincident with dropping water tape. look at this system right here here
85:52 have pretty high water table. The left we get some dunes there.
86:03 gonna be uh bark annoyed. Maybe uh loss of introduced space. But
86:12 we move up the system we're getting and more dune, less and less
86:23 until finally we're getting a system that all do the inter dunes are
86:32 We've gone from what we would call wet system to a dry system.
86:38 . We've actually gone from something that like white sands to great sands.
86:44 let's think about that idea of a versus dry in system here, our
86:55 doom areas. But these aren't simple . This isn't your everyday bark.
87:08 this is actually a complex draw. as this thing migrates, it's gonna
87:14 us a larger bounding surface. And this might be what that dune
87:28 or earth looks like sand sheet rating the central portion in the back system
87:36 system. Okay, literally, now looking at a large region that has
87:45 topographic room to migrate laterally. Now white sands could do that. It
87:52 doing that great sands can't thanks. here we have a pre Cambrian
88:01 we've got these small simple dunes with dune areas, we're getting more and
88:09 dune development, maximum growth and then begins to die down into a sand
88:18 . Sand supply is decreasing. Maybe change. Okay so we've got the
88:27 of er growth or mega sand sea , maximum growth destruction back to sand
88:37 . Okay, so this is what might look like at the time it's
88:43 maximum growth and then eventually dies. this would be the backside. Um
88:54 . Yeah this would be the backside sediment supply is decreasing so it's gonna
89:00 sand sheet. So let's look at bounding surface as that complex dude migrates
89:21 . And now here here's that complex here are the individual migrating down
89:40 They're moving up the back side and the front side. Yeah. And
89:47 they move down there's a bounding it represents the migration of a single
90:00 . That's these right here, this that single due migrating down.
90:09 And that truncation on the back side the top side. That's that
90:16 First order bounding circles separating the Draw a complex. Do Now we
90:30 second order bounding surfaces that represent the wind migration of these simple dudes.
90:48 then what's happening in here? Those reactivation services. Okay, that's what
90:56 are. Okay, So First Order Order 3rd. Okay, so if
91:08 were to ask you to compare a true 3rd order bounding surface of the
91:16 deposits with Sophocleus deposits in your You should be able to do
91:23 It might require a little fall between and the exam, but think about
91:29 these different bounding surfaces are showing. , all right. Now, if
91:42 look here, what happens if you have simple dudes like this, that
91:53 be more analogous to a smaller Like white sands. Their if their
92:01 dune deposits, we might call these order in third. But if it's
92:10 compound dude, you're gonna have simple moving, moving down between the
92:25 I find this confusing and I've had think about it a while. Um
92:32 it has to do with are you a system that's predominantly accumulating simple dunes
92:42 compound dunes. Okay, and that's of what this says here.
92:51 Simple set compounds set. And so you look at this, if you
93:01 at this, it should be more . Okay. And then these super
93:16 . These are our regional surfaces that driven by tectonic or climate change.
93:24 trunk hates the whole base. so here we have a wet system
93:34 sands, high water table here we a dry system. Great sand dave's
93:42 water tape. Okay, wet system sand accumulation is due to a rise
93:52 the water table. Dry sand, cohesive above a deep water table accumulation
94:01 aerodynamic processes really. So what So of the distinction is, how is
94:09 thing preserved a wet system? The table rises a dry system. You
94:18 have to somehow stop the doom from and then let it be stabilized.
94:26 , let's look at this wet One of the ways of having the
94:31 table rise is a rise in sea . I did a lot of work
94:37 California, looking at coastal dues where rise in sea level resulted in the
94:45 preservation of those deposits. But we also have a rise in sea level
94:50 an enclosed basis. It could be climate gets wetter or it could be
94:59 subsidence and it's simply, it's It's not, it's the relative rise
95:06 water tape that allows the preservation. any of these three models are
95:16 would allow a wet system to accumulate white sands. It's mainly due to
95:28 because it's a wet system. just keep this okay, dry
95:37 It can accumulate the above the water and it just needs to have something
95:45 it now in California. This coastal dunes or migrating inland and then they
95:56 capped by a soil during the uh periods, they're being driven by periods
96:06 sediment When sea level was dropping, had doing accumulation, sea level rise
96:16 to preserve it and then we had more humid climate that preserved the dune
96:24 by soil formation. So it's it's separate story. I don't have time
96:29 get into but soil accumulation and vegetation stabilize the dunes, they can become
96:40 and once they're vegetated and soils have over, they're no longer active.
96:45 like those fixed dunes we see like the sand sheet in southern uh
96:55 coast for the Nebraska sandhills. I'm gonna skip this for a second
97:04 just imagine that we've got a dry . Water tables down here someplace but
97:17 supply of set up as we increase sediment supply. The dunes get
97:26 The wavelength you're beginning to fill in finally the dens coalesce and all this
97:39 is the dinners are getting bigger because increase in supply. Okay, now
97:48 what's happening as we go get to super saturated center, 100% sand cover
98:01 news. That's the Great Sand Okay, if we look at a
98:09 Sandhu system, this is the white . Okay. And they're gonna have
98:21 inter doomed deposits. These inter dunes gonna be dry interview deposits.
98:32 In that zone from here to hear going from under saturated, no aeolian
98:50 meta saturated were beginning to get dunes . That was the parabolic dunes and
98:57 our transverse dunes. Now we could from a web system to a dry
99:08 by simply increasing the sediment supply. can also do it by dropping the
99:16 tape. So we're seeing the wet in deposits rating up into truncated interviewing
99:29 of a dry system. Okay. sand sheets. Again, these big
99:38 surfaces, they're covering the entire mike, tectonic, maybe herb
99:47 Um but usually regional changes in sea climate, tectonics, etcetera. And
99:57 are some of the characteristics. And let you look at those later.
100:00 this is the truncation first, 3rd. Okay, so I want
100:10 finish with three reservoir studies. He deposits are good reservoirs in locally and
100:19 fantastic aquifers. Okay, let's look the 10 sleep and swallowing the north
100:25 in southeastern us. And uh guns the North Sea. So here's the
100:36 and permian intensely. And in particular that in the pennsylvania there's a lot
100:45 inter bedded marine and non marine Remember also that's when we had Pennsylvanian
100:56 and regressions. So we've got basically and it still Esther extend here in
101:04 upper. But in this particular example gonna take a portion of that transgressive
101:10 system, marine, non marine. . And that non marines system is
101:23 ill. So we've got marine transgressions form marine carbonates in Dolomites regressions to
101:36 aeolian deposits kept by transgressions in the and marine deposits again. So we're
101:44 from high stand to high standard. are actually sequenced boundaries that would be
101:49 essence a super surface. Okay. it is a type of power sequence
102:01 transgressive regressive transgressive cycles. Okay. , within that surface we see other
102:13 surfaces as well. So we're gonna this para sequences into a variety of
102:22 . Okay, so here it is surface. And let's take this some
102:26 . We've got what he calls first bounding surfaces coming down here and they're
102:39 up into second order bounding services, in turn are broken up into 3rd
102:54 bounding services. So let's see what looking at here would be a simple
103:03 grading. Do truncated my system Okay, now that could be
104:18 Okay, back to um So if look at this simple cross set
104:30 we get first order bounding the If we look at the more complex
104:38 see some higher order surfaces. So look at the simple first here's first
104:47 In in four cents. And it's . Water table is rising. So
104:56 we get it preserved. Okay. finally the sea level transgressive. Why
105:02 the water table rising? Because sea was rising intel eventually it transgressed.
105:11 , so here we got that first . But now we got second
105:17 And so what this tells me, that the dunes or compound dunes that
105:25 say there were oppressions. But the that was climbing consisted of smaller dunes
105:45 down the face of the larger So the second order, I mean
105:53 still over here, they mega do climbing in the smaller dunes, we're
106:17 down the face. That's second And then in here these little packets
106:29 3rd order packets and that's reactivation. that's really what we're looking at right
106:36 , we're looking at a packet. these little lines here Or 3rd order
106:48 services. Okay, that's what those their package like this. Now,
107:02 already suggested that these bounding surfaces are flow baffles. There are changes in
107:13 . Okay. In fact, we look at the great sand dunes
107:20 remember I said that we've got this migrating in that direction, in these
107:29 migrating in this direction. Yeah. there's a computer program where you can
107:39 create Packages across straight in three dimensions on assumptions as to bet forms.
107:48 that's what we've got here. We've dead forms and this is the pattern
107:58 she would get. Thank you. what we've got in here is we've
108:05 taxes of bed forms again. So we're gonna call them flow units thousands
108:12 feet wide, 10 : 50 ft . And those are those first order
108:21 which are related to the compound dues top of those. The four sets
108:31 these migrating secondary, simple dudes. what we saw here, Those simple
108:42 are migrating generating second order bed forms then those simple dunes are being truncated
108:55 reactivation services and seasonal reversals. So we were to imagine these dunes being
109:06 , let's say annually by annual changes direction, then we would have yet
109:12 set of bed folks here. And so what we see is that
109:21 the 10 slate was first developed, just drilled vertically but as it began
109:29 be depleted, they began to look and closer at the permeability or slow
109:38 and they began to increase the well and horizontal drilling. Okay, because
109:45 looking at this complex zone and then within the three third dimensional reactivation
109:55 Okay, uh we're actually getting and are two different sources but they're from
110:02 same units. We see changes within package and the change is from wind
110:14 or translate strata on the bottom part that package. two grain says grain
110:22 , but it's more grain flow in upper part. And so basically primary
110:36 and we began a series of field with increased horizontal drilling. Taking advantage
110:46 these smaller and smaller flow packages. , now, the second area,
110:56 major uh aeolian reservoirs are, is Norfolk formation in the Norfolk formation is
111:05 onshore, offshore a Mississippi Alabama Okay. And it's locally 600
111:18 Uh a thick. They think. , I think so, yeah.
111:24 . And so uh if we look the dip meters here. Low,
111:33 steep, no stay. Uh It's up into, In this case three
111:44 faces, faces of the aeolian Startup maximum earth development devise. Uh
111:57 just gives you a sense of the . The source of sediment here is
112:06 the it's a Triassic deposit, it's the Appalachians and it's being deposited on
112:14 of salt. So we've got salt and then aeolian deposits above the
112:27 In terms of environments. We've got , sands and aeolian deposits. The
112:33 sands are thin rims here. Aeolian dune is mainly here. Alluvial fans
112:41 flew viel and marine carbonates, shale salt. Okay, look something like
112:52 . So here's our alluvial fans, mountain fronts, aeolian sands and
113:02 Okay, now we've got fields within areas and this is an area of
113:10 . And introduce, we're gonna ignore short face. We're gonna ignore aeolian
113:14 fan. So one suggestion we got cans, bark and oil bridges,
113:23 transverse. Okay, that might. then she'd stand beyond that.
113:30 well this is kind of like the sands. Uh, but then if
113:36 begin to look at wind directions based four sets, this is a big
113:44 . And so it's likely that there's lot of variability of doom type and
113:51 what's inferred here. We've got Barkan, star dunes linear,
114:03 Okay, Star dunes again. And we can expect that these fields of
114:08 north, we are going to have styles of the only accretion, in
114:18 , when we get down into this here. Uh, the interpretation is
114:26 dudes compound well oblique uh, Davis by internet and the general deposition is
114:45 to the west, suggesting that there's analogous to what was described in the
114:52 in Algeria. Now, one of interesting things is that if you look
114:58 the gross packs, you're kidding, linear accumulations, uh, 800 to
115:11 ft thick, which is of comparable scale to the Namibia dudes.
115:26 as we'll see in just a part of that is due to the
115:29 of the dudes. But part of is these dudes are sinking due to
115:37 of the underlying soft. So we've salt deformation that's accentuating the thickness of
115:45 dudes. Now in other dunes, interpreted a similar geometry as barkin.
115:56 , okay, so what's interesting here that similar geometries two very different
116:08 Multi dune oblique, linear versus and or simple dune, transverse. I
116:23 know that. And and you both be right, but we know more
116:32 we did in 1988 about the patterns linear dudes. So when I see
116:42 , I wonder if maybe this isn't aren't actually linear dish. We'll have
116:47 leave that for somebody else's decide. what is clear when we get and
116:54 at the Norfolk in terms of stratification look at from ability and ferocity.
117:02 , there are different types of deposits are non reservoirs and reservoirs.
117:18 Inter doom not really wet. Inter . That's even worse. Sand sheet
117:25 dune slip face, toast ratification. , that looks pretty good. So
117:31 first thing we see is that there a variation in the permeability and porosity
117:38 on the type of strap, not what we thought before. Inter doing
117:44 stuff. Face good. Now, we look at it more closely,
117:50 doomed, bad translating. Yes, . So so grain flow good.
118:01 , so the translating is variable. the the other thing we see is
118:10 the type of cement seems to be factor in determining the relative permeability for
118:16 gift for austin. A light cement flow. Right, cement good.
118:24 seems not intuitive. Clearly die genesis addition to primary porosity and permeability is
118:33 a role. Yeah, the You got your highest most permeable aeolian
118:46 where you have chloride grains coding the clays, coding the greats. This
118:55 not only the northland but in the sea as well. Okay. And
119:01 of it is the chloride is associated evaporate deposits, sodium chloride.
119:11 It turns out that if we look the lower part of the Northland,
119:19 doesn't matter if you've got dunes or , low permanent building. If you
119:26 at um I'm sorry, the upper . If you look at the lower
119:34 , even the inner dunes are pretty . And the doom slip face is
119:45 good. So what's happening, I'm . Um where we don't where we
120:00 discontinuous plays, We get four soul . Okay, Whereas up here we
120:11 more continuous clay drapes. We get courts overgrowth. Okay, so the
120:20 is do you have or it's over , which is typical of the upper
120:33 ? Or do you have no courts typical of the Lord's own? You
120:38 no ports over grows where there's continuous . The chloride prevents the ports sand
120:47 being exposed to the silicon rich Where you have discontinuous or uh clay
120:57 a light, there's enough of that course to allow the ports overgrowth to
121:06 to grow. Okay, and here have the Norfolk here we have these
121:19 parts. Okay, uh this is tight, lower porous. What is
121:34 about the lower zone that seems to allow those or it's over the over
121:45 to occur? Well, this is another example of saying the same
121:51 If you've got almost 100% overgrowth, have almost no loss of ferocity,
122:01 with poor housing. Didn't have no . Look at this go to
122:09 So we talked about that last Here are those continuous sports are play
122:17 of the courts. Here's where it's in the free attic zone. That
122:28 below the water tape, you've got rich marine waters allowing the precipitation of
122:43 genetic law. Right, clay. it's being thickened in part because it's
122:51 into the salt. So the linear are sinking, they're being saturated by
123:02 waters in the free attic zone. have continuous play cups down here
123:13 above the free attic zone. You've a couple of things. You have
123:21 different type of play for me or I? And because you're above the
123:30 attic zone, you've got more sand motion. It's dry sand. The
123:38 overcoats are being abraded. So you the abrasion of what clay overcoats were
123:48 , which means you've got more of ports exposed above the water tape.
123:57 , So you could have um, porosity up in here. But low
124:05 is because of the clays. our virus ilife. You've got good
124:15 austin credibility here. Low porosity, low porosity, permeability here.
124:24 so even with the clays in the zone, Lorelei. So you've lost
124:30 premier building and if the sand was motion, you got poured cement.
124:40 this is just kind of a I'm not gonna go into it,
124:44 I pretty much have told you what need to do. Okay, last
124:49 study north slope again, uh, the permian, we're looking at large
124:59 controlled basins that our fault bound. got thing false here, Alluvial
125:16 rivers, aeolian deposits marine here, got aeolian and here we got
125:33 okay, if we look at the fa she's remember we talked about little
125:40 , we've got shallow lancastrian flu ville flat. Inter dune. Think of
125:49 as wet. Inter do dry inter Aeolian do. And these are the
125:54 sedimentary structures. Uh And we got pretty much the same thing here.
126:02 now. What we're doing. We've the dune form. This is kind
126:08 the inter dune area. We've got blue translating strata, not like
126:21 Partner, darker brown. We worked ripple and then grain flow and green
126:33 flow and grain fall. I'm Uh grain flow is in uh grain
126:41 dominated grain flow, rainfall at the . Okay, eight. Now,
126:49 this trance as this large dune we're only getting the lower part
126:58 So we're getting almost no grain Instead, we're getting a lot of
127:07 strata and reworked translate. Strap a bit of rainfall. Green floor,
127:17 kind of looks like this. There's be We're not looking at the details
127:21 here like we did earlier. But we see is that the grain flow
127:28 we have it is great wind rippled . Not very good. We've seen
127:35 before here though for the first they're suggesting that some of the wind
127:41 sand can be reworked by winnowing and a deflation. So they actually suggest
127:50 this is a third type or if like really 1/4 type of fourth
127:57 And let's see, I'm gonna run ahead for a second. Here's the
128:11 rippled, here's reworked, wind here's green flow. Okay, wind
128:17 down here. Reworked up here. little up here. So when we
128:24 the north with the north, say you take the translate and divide it
128:36 good and bad translate, you're probably this reworked to translate strata Norfolk.
128:44 never been recognized. Okay, Inter dune translating. We're seeing the
128:59 thing. The purpose. Yeah. when we think about the big
129:07 let's go back to here. The strata is due to uh is associated
129:15 dunes, different dunes formed from different . We've got bark, hands and
129:23 annoyed, which are really the best they're the simplest linear dunes are potentially
129:30 worst because of the straddle complexity. dunes aren't very good at I.
129:38 the first thing we see is that things equal, bach annoyed and transverse
129:43 better than linear or star having said , we do get reservoirs in both
129:51 are some linear reservoirs starred in Okay, bark annoyed reservoirs. Simple
130:05 complex. So these all of these various reservoirs of various complexity.
130:16 Sacha, inter dune sand sheet, complex, two simple barkin.
130:28 so we see parallels at the larger and the finer scale within the
130:37 we received these variations and that's what looking at here in here.
130:48 interesting. The translating strata down in are not as good in part because
130:59 I said, they were finer more poorly sorted, I mean more
131:04 packed, but they also tend to cemented by calcite. So we got
131:11 semente shin and the Sascha's and the dunes are cemented as well. So
131:19 me just summarize the aeolian reservoirs are good, especially where you have clay
131:30 , high initial frosty permeability, secondary complications. A lot of bounding
131:37 a lot of heterogeneity introduced for reserve uh translating strategy for inter bedded,
131:48 aeolian for and even in good you get water coming leaders some fields
131:55 recovery factors in some of the enhanced recovery methods and these are Aeolian
132:05 same thing. Okay, so I'm gonna go into these uh that's really
132:12 of a petroleum geology, rather petroleum question. But what I want you
132:21 have gotten from this is that there different types of dunes which differ in
132:27 gross packages and within that there are levels of bounding surfaces which reflect compound
132:39 , simple dunes and then reactivation And then between those reactivation surfaces.
132:47 set variation between grain flow to Okay, all of these have to
132:57 affect the variability in permeability and they how you develop an aeolian reservoir and
133:09 time why you have to go to and tertiary and horizontal drilling.
133:16 okay, so let's we can stop recording now and then
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