Formations really do match detailed lab expts of sorting under rapid currents

Your post is a good example of someone gradually beginning to understand some bare rudiments of geology. A lot of this material is impossible to explain over the internet, especially without lots of diagrams, pictures and fieldtrips to moderns sedimentary equivalents. I'm glad you found a video to explain some of these basic concepts. Too bad they have to cloak it in the usual Creationist mumbo-jumbo to make it palatable for you. But if you sort through the propaganda, you might find some small glimmers of reality peeking through.Like this one:

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It turns out that this exactly matches the types of prograding patterns one gets at a beach...

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and this one:

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I can't emphasize enough that the three sub-beds of the 1000 foot thick Tonto group looks geometrically, and from a particle size, just like the facies ... at a beach.

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Now that wasn't so hard to figure out, was it? Modern shoreline environments do indeed create very distinctive sedimentary structures. These exact same structures are found in the Tapeats Sandstone, Bright Angel Shale and Muav Limestone: "Close up of the Tapeats at the same Verde River outcrop, showing crossbedding from underwater marine dunes that are interbedded with coarse flat bedded conglomerates from shore line wave deposits."More from the same site:
"Appearing as a browinish to light tan in color, it contains almost shaley sandstone up to coarse conglomerate. Much crossbedding occurs in the Tapeats, because it is a tidal marine deposit, and includes the deposits right up to the shorline, but not beach dunes or eolian deposits. The material for the Tapeats was derived from the underlying Precambrian granites and metamorphic rocks found in the region. It is easy to see how a pounding marine surf can separate out the constituents of such basement rocks, and form beach sands and highly winnowed tidal deposits." (source)Keep up the good work. More research like this will make it much easier for you to understand real world geology. All you have to do is learn enough to be able to seperate the outlandish claims from the real data. Sort of like with Humphrey's zircon/helium "research." He claims the data supports a young Earth, but closer examination has shown exactly the opposite.In this case, you've finally begun to understand a fundamental concept in sedimentology - the transgressive sequence.

This sentence of your reply illustrates quite clearly that you do not yet understand a prograding transgressive sequence.All three types of sediment are deposited simultaneously in a transgressive sequence. The shoreline at a particular place and time is the basal unit of the TS. It commonly contains conglomerates composed of the underlying sequence, and is always unconformable to it. At the same time the Tapeats sandstone is being deposited, farther offshore the tidal and beach sands grade into the silt and shale of the Bright Angel shale, just like passive margins today. Farther still, the water is deep enough and far enough from siliclastic sources to allow carbonate platforms to accumulate, like the South China Sea, for example.As eustatic sealevel rises, the entire assemblage migrates uphill. Shales are deposited on top of sand, lime mud on top of shale, while the new shoreline cuts into higher ground pC basement rock, creating more siliclastic source material for the whole system.There is nothing arbitrary about sequence stratigraphy. It is a well developed branch of sedimentology. It is quite useful in petroleum geology. Modern examples of transgressive sequences are common, and very well studied and understood. But not by any Creationists. You are being mislead again, just like the Paluxy mantracks, galacto-centrism, and the Gentry zircons and helium. Creationist propaganda peddlers who know some geo-buzzwords and are careful to show you only a small part of the picture can weave a believable tale around the Noah myth. As you learn more, you will become better and better at seeing through the deception.I am honestly not being condescending in saying that. I applaud your efforts to learn this material. You have made some real progress in the last year.

Another lightbulb turns on over TB's head. That is precisely what happens in a transgressive sequence. Although you might find that the deepest water lime muds to the west are still accumulating as the highest altitude Tapeats sands are forming to the east. That makes the middle of the Muav in the west contemporaneous with the bottom of the Tapeats in the east. At the farthest advance of the shoreline, there would be no shale or lime above the sandstone, but in the Cambro-Ordovician, the shoreline advanced across the entire PangeaI to Gondwanaland, leaving no strandline in N. America.If you traced an individual bedding plane from east to west, you would find conglomerates unconformably overlying the pC basement in the east, grading to shoreline and tidal facies shallow water dunes, grading to slightly deeper water sand waves and point bars, grading to deeper sand, silt and shale beds interleaved by storm action, grading to deeper silt and shales (we would begin to call this the Bright Angel Shale at some arbitrary point) with storm turbidites mixed in, grading to more and more limey muds until the lime content is high enough to call it the Muav Limestone. The entire bed just described is deposited at the same time. All three formations of the Tonto Group were deposited simultaneously on any single bedding plane, but it took tens of millions of years for the transgression to advance from west to east across the N. American continent. That makes it a time-trangressive formation. The Tapeats in the west is 50 million years older than the Tapeats in the east. The Bright Angel Shale in the west is younger than the Tapeats directly below (law of superposition), the same age as some of the Tapeats to the east, but older than the Tapeats farther to the east. The individual beds do not follow the same angle as the tops and bottoms of the overall formation, they are inclined down to the east relative to the overall formation (sort of like very large scale, regional cross-bedding). Each bed of Muav in the west grades imperceptibly into a Bright Angel shale to the east, and inclines down to the east, and grades into a Tapeats farther east at a still lower level in the overall Group (but a higher absolute altitude at the time of deposition). That is how superposition is maintained.Do you see now how hard this is to describe in words? If you tell us what sedimentology texts you have read, I'm sure one of us could give you the exact page numbers where this is described, complete with very helpful diagrams, cross-sections, pictures, and maps. This is all standard sedimentology - covered in the 2nd year of most geology programs. Sorry, but you don't, as shown by your responses here.
But you are making rapid progress just in the last few days, as shown above from your newly found understanding of time-transgressive formations. Of course we do. Time-transgressive sequences are, in fact, being formed today. How do you think sedimentologists have come to understand all this stuff? If you go to practically any passive margin today, you will find modern river delta deposits on top of shallow water silts on top of deep water shales. This is called a prograding delta. It is not the same thing as the Tonto trangressive sequence because the shallow water deposits are on top. It is formed by a different combination of sea-level, sediment supply, tectonic, and subsidence parameters. Again, all of this is standard sedimentology. You repeatedly claim to have read the standard geology texts, so how could you have missed this? Can you name a standard geology text you have read? We could then point out the pages you need to read again.

As I re-read some of your posts, TB, I find some more clues indicating where you are confused about some essential concepts in sedimentology.Line-by-line, let's review: We have several problems here:
1. The Tonto group is not a "facies", it is a large accumulation of many, many facies.
2. The 3 formations within the Tonto Group are NOT seperated by bedding planes, as should be clear by now from my explanations in previous posts.
3. Your assumption that this is "essentially by definition" reveals a lack of understanding of what constitutes a formation, stratum, facies, and/or bedding plane. I have seen closer to 45-50 million years. Saying that the Tonto Group represents the passage of "70 million years" is an oversimplification. At any one location, the 3 formations may span something like that time interval (I haven't checked the actual data in any specific loacations), but the 70 Mya it took in western Arizona occurred earlier than the 70 Mya of depostion in southeastern Utah. Exactly. The Muav in the west is older than the Tapeats in the east. This is evident both by the law of superposition (the bedding planes are inclined), and by index fossil assemblages. Nope. The Law of Superposition remains unbroken. My fellow geologists do not assign any "gaps" to the Tonto, I believe it is considered a continuous record of tens of millions of years of deposition in any given locality. At DIFFERENT localities, the time intervals may not be contemperaneous, however. Just to be clear, time-transgressive sequences are being formed today. A modern prograding delta deposits at least 4 main types of sediment:
1. Freshwater meandering delta channels, oxbows, swamps, etc.
2. Nearshore sands, in the form of beach, tidal and shallow water sand waves
3. Slightly deeper water silts
4. Deep water shales (clay-sized particles)All of these are deposited simultaneously today. The top surface of the delta, beach, and offshore ocean bottom represent the top of a potential bedding plane that might be preserved in the sedimentary record. This bedding plane extends unbroken from the land out to deep sea. The sediments grade imperceptably in many cases along this bedding plane from sand to silt to shale.If you look under ground, you find that today's beach sands are being deposited on top off finer grained shallow-water sediments, and the shallow water sediments overly deeper water shales, and so on. In the past, the delta was farther inland, so going down into the ground is like going back in time (superposition again), and into a sedimentary environment formed in deeper and deeper water.This simple picture can be complicated by things like subsidence, sea-level change, sediment starvation, etc. The Mississippi River delta right now is subsiding rapidly, for example. That means river floodplain sediments are being reworked into, and overridden by, beach sands as the shoreline retreats. Most of the sediment load of the river that normally would replenish the delta is bypassing the floodplain as a result of Man's intervention. What you "don't see" is a reflection of how limited your knowledge of mainstream geology is. Time-progressive formations are not a new or surprising phenomena to geologists.

1000m transgressive sequences take a long time to form. Your request is nearly unreasonable. The fact that modern transgressive sequences are universally thin (often tens of meters since the LGM of 40kya) should be a clue that 1000m in five days is not feasible.Here are some of the numerous examples of modern transgressive sequences:Woods Hole Coastal and Marine Science Center | U.S. Geological Survey
"A Continuous Holocene transgressive sequence recorded in an 8-M core taken from northern Chesapeake Bay
A complete sediment sequence that records the Holocene sea level rise, beginning about 8000 yr BP, is well preserved in an 8-m sediment core (RR98-9)..."
"We identified three distinct lithofacies (C, RE, and OE) in core RR98-9. Lithofacies C, a basal channel deposit, is preserved in the lower 50 cm. it is a massive, dark greenish gray (SGY 4/1), moderately sorted, coarse-grained pebbly sand with common wood -fragments. These channel sands were deposited before about 7800 yr BP. Atop lithofacies c is lithofacies RE, whose base is marked by an oyster bed. Lithofacies RE is approximately 320 cm thick and is characterized by dark gray (5Y 4/1) to dark greenish gray (5GY 4/1) muddy sand to sandy mud, with scattered oyster beds J15 to 40 cm-thick) and common woody organic layers. Filled burrows are well preserved in the upper loo cm of this lithofacies. The lithology, shell and organic debris, and burrows suggest that RE was deposited in a restricted estuarine environment, probably a sand flat or tidal channel. Lithofacies RE was deposited during the interval of 7800-3740 yr BP. The youngest lithofacies preserved in this trangressive sequence, lithofacies OE, is about 410 cm thick and is composed of massive to diffusely laminated, slightly sandy (trace to 10%) clayey mud."
Notice the fining upward character of the 3 facies, indicative of transgression.http://www.sci.qut.edu.au/...rch/geopsed.htm#plaeogeographic
Third abstract down on the right side:
"The onset of Tertiary sedimentation was marked by the deposition of a regionally widespread transgressive silisiclastic unit known as the Gobernador Formation, which was deposited under continental conditions in the south-southwest of the basin, changing to coastal marine conditions in the east-northeast. Over most of the area, this quartz-dominated sandstone unit is overlain by marine shelf mudstone, but to the north-northeast part of the study area, the Gobernador Formation passes vertically to the transgressive bioclastic limestones of the masparrito Formation."
"The thickness of the Gobernador Formation varies from 12 m to 220 m..."
So a transgression that spans the whole Teriary can accumulate a pretty significant thickness.http://www.gl.rhbnc.ac.uk/palaeo/2palynology.html
"The Nanggulan Formation has been shown to be a transgressive sequence containing a series of stacked rising sea level sequences. These sequences may be comparable to the cycles (third order) from TA 3. 4 to TA 4. 1 or from 43. 0 Ma to 36.0 Ma. These sequences support palynological zones. The coastal plain setting (lower unit) changes upward into brackish or marginal marine, then into shallow marine (lower part of middle unit). The palaeoenvironment then shifts into deeper marine, characterised initially by gravity flow deposits and finally by deep water, fine-grained, volcanics and marls."

I think you are forgetting that the designation "Cambrian" is determined by the fossils, not the other way around.The concept of time-transgressive rock formations is not new. The understanding that rock units are often time-transgressive is an integral part of geology. Ummm... no else here is buying your fantasies about rapid formation of hundreds of feet of limestone and other rocks. Chemically, it is impossible, as has been pointed out to you already. Geologically, modern anologs show precisely what is expected - the 1000meters of the Tonto Group requires a lot of time and a slow average rate of transgression. The long time scale is revealed in every detail of the rock. But your sources have carefully glossed over the details:
YEC-faslifiers such as well-sorted, well-rounded mature sands in the Tapeats and other Cambrian sandstones; extensive bioturbation, burrows, trilobite fragments and fossils; the complete and utter lack of any land animal or plant in the basal unit of the Tapeats; and many, many more.It looks like we are moving to the fingers-in-the-ears stage of the lesson plan, gents. It's about time to pack it in. Chalk up another in the list: Cyclothems, galactocentrism, helium diffusion in zircon, Paluxy mantracks, and now transgressive sequences. Did I miss any?

I think it might help to share the videos and Creationist tracks you have been relying on, TB.Here are some links that might be similar to what you have been referring to:http://www.geology.ref.ac/...hault/fusion/stratification.htmhttp://www.geology.ref.ac/berthault/fusion/new-approach.htm What do your paleocurrent indicators say about that? I thought you said all paleocurrents point to the southwest in N. America? If the depositional current is coming from the west, then the whole model falls apart - the source of the sediments is now downcurrent from their resting place. Do Julien's flume experiments show conglomerates, then sands, then shales flowing against the current (back to the west)?I think edge is constrained by an expectation that the flow regime modeled for the Flood should bear some resemblance to what is physically possible. If you look at the drawing in the second link above, you will see that Flood waters advancing along the surface from the West to the East, with a return flow along the bottom back to the West that carries the sediment into the Tonto Group strata. At least this model has the currents going in the right direction.
But if you can't see the problem this model has, well... we have a lot more work to do.

Poor reading skills again, TB. One of those TSTs I cited for you was 220m thick. This is a common occurrence in these threads, TB. You skim our carefully prepared posts to find what you want, then ignore the rest. The Sauk transgression lasted until the early to mid Ordovician, IIRC, so the eastern part of the Tonto might be that age. Again, it requires a profound lack of geological background to be unaware of the existence of time-transgressive formations. Nonsense. The flume experiments generated very thin laminations, not 1000 meter foresets. The exact opposite is true. Modern transgressions of short duration produce thin TSTs, long duration = thick TSTs. You have produced no data, field studies or theoretical explanations of how Julien's flume studies apply to anything other than the very specialized parameters he studied... extremely rounded grains, bimodal grains size distributions, laminar flow, flat bottoms, etc.So far, we have a persistent pattern of obvious objections raised to the conjecture that the Tonto is Flood produced. With your limited background in gelogy, TB, you do have not the knowledge to address these problems, and I can understand your reluctance. But you could at least acknowledge that these problems exist, yet you continue to believe that your Creationist sources have discovered a huge gaping hole in the sciences of sedimentology and stratigraphy.Look at Berthault's drawing again... you ignored my reference to the obvious hydraulic error, how about noticing the presumed current velocities?Do you see the Muav being deposited in water moving at <.5m/s, and the BA Shale deposited at .5 m/s ?That is wrong. If you look at the Hjulstrom diagram in your sedimentology text, you will see that .5 m/s is sufficient to transport 5mm pebbles. Silt and shale will not be deposited. The ironic thing is that Berthault's website has a poorly labeled Hjulstrom diagram as figure 12 (new-approach). If you look closely, you can see the bottom line showing the velocity at which a particluar grain size begins to be deposited. It shows small sand grains requiring less than 1 cm/sec for deposition. Yet Berthault's scenario requires these sands to be deposited at 50 cm/sec. Errors of this magnitude are a good explanation for how Creationists can delude the gullible. GIGO.Berhault's entire thesis is a plausible sounding (to the less knowledgeable) collection of pseudo-science dressed up with references to actual science (like Julien's flume studies). Examining the details reveals how flimsy it is, just like Humphrey's zircon/helium paper. So far you have ignored all such examinations. Sometimes I wonder if you will even read this post all the way to the bottom... are you still paying attention?

Again you ignored most of my carefully detailed argument. The part you responded to, you got wrong.Berthault's page shows the BA Shale being deposited in water moving at 50 cm/sec, not 1 cm/sec. It shows the "fine to coarse sand" of the Tapeats being deposited at .5 to 1.5 m/sec. Using your Hjulstrom diagram, you should easily see that "fine sand" requires a maximum of .005 m/sec to .02 m/sec for deposition to occur, and "coarse sand" implies .05 to .2 m/sec.The part you got wrong is still unanswered - BA shale and silt deposited at .5 m/sec (not LESS THAN .5 m/sec) according to Berthault, while Hjulstrom says those grain sizes need less than .005 m/sec.Berthault's entire thesis seems to be based on mistaking .5 CM/sec (from Hjulstrom) for .5 METERS/sec.Still no comment on Berthault's ridiculous hydraulics? Or Austin's west-to-east currents that require the sediments to move upcurrent back to the west?

Your post to edge, being entirely an argument from authority, does nothing to correct my apparent misunderstanding of how Berthault can posit shale deposition at a current velocity of 50 cm/sec. Until you correct my understanding of sedimentology, I will continue to think that Hjulstrom's diagram shows Berthault's claims to be "idiotic".Humphrey's work has been shown to be equally idiotic in another thread here (which you have not responded to, BTW), although not for the reason originally claimed by Joe and myself. We are not perfect. Feel free to demonstrate using facts and equations, rather than vague argument from French authorities, that Berthault's work does not belong in the idiotic category as well. So far you have avoided Hjulstrom like the plague. Are you afraid to even LOOK in your sedimentology text?When YOU look at Hjulstrom's diagram, how do YOU think it works?

So the Eocene is now a possible Flood deposit? The Middle Eocene Gobernador Formation, up to 220 meters thick, is a continental sandstone, like the Tapeats.
It "is overlain, over most of the area, by marine shelf mudstone known as the Paguey Formation", similar to the Bright Angel Shale. The Paguey is up to 2200 meters thick (PAGEY, Formacin)If you want a nearly modern passive margin transgressive sequence, look no farther than Southern Australia:
Can't find what you are looking for? | Department of Industry, Science and Resources
Read the lithologic descriptions of the major groups here:
Can't find what you are looking for? | Department of Industry, Science and Resources
This sequence is thousands of meters thick. Sands overlain by mudstone overlain by carbonates. The carbonate deposition continued right up to the late Miocene (about 8Mya) in the cross-section shown. I do not know what is occurring farther inshore, but the overal pattern is identical to the overall pattern of the Tonto.Insisting that it continue to the present day is unreasonable gradualism again... Why should today's eustatic conditions be identical to the Cambrian? If we find evidence of very large impacts in the past, but no comets hitting this week, do we conclude the evidence for past impacts is invalid?

I've only repeated it about a dozen times. And in the field. None of this has been any suprise to geology since about 1600 in a general sense, and about 1912 to 1932 in a specific, experimentally verified sense. That is a very intelligent and relevant question. It is one of the few times you have allowed yourself to consider the possibility that geologists may have already addressed the issues you have raised.Therefore it deserves a careful and well-researched response. Naturally, it will also be a rather complex and detailed response. It would help if you told us which geology texts you own so that we can refer to diagrams and page numbers as needed.Part of the problem here is that you (and Berthault, possibly) have been proclaiming the death of the Law of Superposition when you have actually been presenting evidence against the Law of Original Horizontality (sediments are deposited in strata that are not far from horizontal, and parallel or nearly parallel with the surface on which they are accumulating).
When presented in intro geology classes, the two laws are presented as universally true. What Berthault and Julien (and Bouma (1962), Schmincke et al.(1973), Bailey and Weir (1932), Kuenen (1966), and Ball et al. (1967)) have shown is that under the right conditions, Steno's second Law (Original Horizontality) does not apply - thus the concept of time-transgressive formations, strata and beds.Perhaps you could get a head start on the detailed careful response mentioned above by researching what you think might be useful ways to determine a time-stratigraphic unit. Can you find or deduce any on your own?

There's a lot of imprecise and ill-informed language in your posts, TB. No, superposition refers only to a point. At any point, as you have already agreed, the lower layer forms before the higher layer. Original Horizontality IS violated in a prograding (or a transgressing) sequence. The lower layer at point Y is formed after the higher layer at point X. Actually, most strata and formations are assumed to be diachronous, or time-transgressive. Only someone with a kindergarten understanding of geology would make a blanket statement about the age of a stratum indicating its entire length. This does not follow logically. In Berthault's scenario, what causes the flow rate changes? Is it not the increase in water depth as the Flood migrates across the land?
Are you claiming that the lime muds, shales, silts, sands, gravels, cobbles and house-sized blocks of the Tonto can all be deposited simultaneously in the same flow conditions (like Julien's flume) WITHOUT any transgression?In gradual inundation, are not the sediments sorted "hydrologically" - coarse grained sediments are deposited near-shore in high current conditions, and fine grained sediments are deposited off-shore in low current conditions?Unless your answers to the questions above are different from what I expect, your 2 scenarios are NOT qualitatively different. The real difference is that one violates the observed behavior of sediments in moving water. Berthault's flow velocity of .5 to 2 m/s is too fast to allow anything smaller than 7 to 60 mm gravels and cobbles to deposit.
You have not been able to even remotely refute this simple fact.I am a little disappointed at your weak attempt at researching chronostratigraphy. Is that all you can come up with?

TB, I think you are comparing apples to oranges here: I disagree strongly with the unneccessary dichotomy here. Vertical sorting in a prograding lamination/crossbed is a standard part of conventional sedimentology. Julien's flume work shows exactly what sedimentologists have known for decades. It shows how cross beds and other laminations build out along the direction of current. Julien has repeated the earlier work done by the half a dozen other researchers I listed in a previous post.
Julien's work does NOT show vertical facies changes, and it does NOT show that the superposition of crosscutting relationships is violated. The alternating layers of fine and coarse sand in the flume would be classified as a single facies of laminated sands or crossbedded sands. Several such layers can be seen in this photo: The top middle shows a series of crossbed sets that truncate previous sets. Each of these is composed of laminated fine and coarse sands. Each individual crossbed set is strongly diachronous - that is, the laminations at one end were formed at a different time that those at the other end. To translate this to Julien's work, several of these laminations would be forming at the same time, and a lower one might form after an upper one at a different location in the same crossbed set. Julien's flume layers represents the formation of a single set of laminations comparable to the laminations in a single crossbed set.Each time a set of crossbedded laminations intersects another set at an angle, it truncates it. This is a crosscutting relationship. It shows that all of the truncating laminations formed after all of the truncated ones. The photo of the Tapeats sandstone above shows several crossbeds that crosscut. From the few clear truncations visible, it might look like the dune sets that formed the crossbeds migrated to the left, thus the strata is older on the right, younger on the left. Each flat layer of conglomerate truncates the sand laminations below it, thus each conglomerate layer is younger than all the sand beds below it (and younger than the previous conglomerate below the sand crossbeds). There are several such sequences visible in the photo.Nothing in Berthault's website show any evidence that such crosscutting relationships have been found to violate superposition, despite his many claims of having done so. For his scenario to be correct, the flat-lying conglomerate layers above must all form at the same time, yet the crosscutting relationships of the crossbeds clearly show this is impossible.A vertical facies change is what constitutes a trangressive sequence. Sand overlain by silt overlain by shale overlain by limestone. Nothing in Berthault's website or Julien's flume experiments constitutes a vertical facies change. The alternation of fine and coarse sand is a single facies - laminated sandstone. The velocities in Julien's flume cannot deposit shale or lime mud or even coarse silt, so no facies change is possible. Even the conglomerate/coarse sand/fine sand visible in the photo above could not all be deposited by the same flow velocity. Even that limited micro-facies change from beach conglomerates to underwater sand dunes requires a significant change in current velocity. About 50 cm/s is low enough to begin the deposition of the smallest conglomerate, but that is high enough to erode a med/coarse sand. Not until velocity falls to about 1 cm/s would the fine sands be deposited, by which time the conglomerate would have long since dropped out.Your claim... "In Julien's experiments you do not need migration to get vertical sorting" ... is true only WITHIN the facies.In your last post: Actually, the exact opposite is true. Most formations are recognized and even assumed to be diachronous unless proven otherwise. Your geologic knowledge appears to remain at the cartoon/kindergarten level. Even the intro level geology texts cover the diachronous nature of most strata.

Imagination is a poor substitute for actually looking at rocks and sediments. The alternating bands of fine and coarse sand that result from your illustration are called "laminations". No one would confuse them with cross-bedding because a crossbed is composed of many individual laminations. It is the change in grain sizes that makes the horizontal laminatons visible. A line drawn through the surface of deposition would indeed cross the individual laminations, but would not leave a crossbed unless deposition was interrupted or changed in character. An interruption leaves a change in grain size at an angle to these laminations. Without any interruptions or changes, the time boundary is not even visible. Only the horizontal laminations have sufficient contrast to be visible.As I explained previously, these laminations are very common, and frequently intersect each other in a sequential manner to form crossbeds. The sequence is apparent by examining the cross-cutting relationships between each set of laminations.Other forms of laminations are also possible, and I wouldn't be suprised if Julien re-created then in his flume experiments. Think of the horizontal laminations as the simplest configuration possible. Under a different set of conditions, rippled laminations might form, for example.