Geology- working up from basic principles.

In general, the change of depositional environment will happen relatively rapidly if the paleoslope is gentle. In such a case, the lithostrat unit approaches identity with the chronostratigraphy. For the purposes of this discussion you are on target.

Now you are getting the idea. It took me a while to find the following slide show, it is excellent. I found it googling "layer cake stratigrahy" a kind of derogatory term used by sedimentary geologists.It is only 27 slides and you go through left clicking your mouse. Pay careful attention to the rocks and depositional environments ("geologic habitats") shown in the 3 d diagrams. when you get to slide 10, pay careful attention to the bottom where you see the formation boundaries and the time lines.http://www.geology.wmich.edu/barnes/geos435/18_G435.ppsYou might find this short article of interest as well.Geologic Misconceptions: “Layer-cake” stratigraphy | Clastic DetritusOr this quote from Tanner (Geology Department, Florida State University You asked our YEC friend to show you somewhere in the real world where that experimental flume deposition occured. Have a look at the Gilbert deltas in Maine. Foreset/crossbeds from 10-25 degrees deposited in water. Check the photos out.I also know where an excellent one is near McCoy, Colorado. I'm going through there in a few days. I get some pictures.Maine Geological Survey: Maine ACF Edited by petrophysics1, : No reason given.Edited by petrophysics1, : typosEdited by petrophysics1, : another typo

Thanks Petrophysics1 and edge So if we focus on a single point and go down through the layers, then - barring some mechanism that mixes up the deposition process (like earth quake faults) - the layers lower are older than upper layers.If we take a core at any one location, the horizontal sample size is so small that it will be similar to a line going down from recent to old to ancient.If we take another core a mile away, we get the same relative relationship of the layers from young top to old bottom. We may also see similar layers to the first core, but at different elevations, and possibly (probably?) from different timelines.Timelines in cores could consist of volcanic ash deposits, as there are distinct "signatures" in the ash for particular eruptions and they do "fall from the sky" at the same time over wide areas. One of the things I noticed in this article on the Green River Varves:Indiana University Bloomington (click here if fails to load)

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The laminations in Green River oil shale consist of pairs of laminae, one being richer in organic matter than the other. ... The richest grades of oil shale are characterized by the thinnest laminae because the organic matter compresses more than the mineral fraction of the rock during burial.

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Bradley also notes that larger-scale variations displayed by these laminated rocks suggest correlations with astronomical cycles including the 11-year sunspot cycle and the 21thousand-year eccentric orbital cycle of the earth which lends further evidence that the paired laminae are indeed varves, or annual units of sedimentation. Units of laminated oil shale are laterally very persistent. Individual laminae within certain units of oil shale have be correlated in drill cores over distances of 100 kilometers.

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So in this one case we have (a) a strong horizontal pattern, and (b) a cyclic pattern matching the solar cycle. The latter being of interest in terms of correlations of age dating systems (see Age Correlations and An Old Earth, Version 2 No 1). The long term seasonal variations could be another correlation to add to that thread (although I may need to use other "rhythmites" with strong seasonal evidence, such as pollen.I would think these 11-year cycle correlations could make it easier to track the oil rich layers.But this is getting off the topic - the law of superposition. I think it has been fairly well demonstrated that no matter the horizontal pattern, that the vertical pattern still demonstrates the validity of the law of superposition.

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Sediments that were carried all the way to the front of the delta cascaded down into deeper waters, forming the sloping foreset beds on the delta front. The foresets are inclined in the general direction of sediment transport and delta growth, and are typically composed of sand or mixed sand and gravel (Figures 7 and 8). Figure 8. Close-up of foreset beds in marine delta south of Erskine Academy, South China, Maine.

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And I would (previously) have assumed that the layers were tilted after formation instead of formed at these angles with the sediment running (pouring?) downslope as the delta formed. So those layers could be older to the left and younger to the right, even though the right end is lower than the left end?So the law of superposition holds for any vertical core through those deposits, but the timeline\age will be different for the same depositional environments ("geologic habitats") for a core 5 or 10 feet to the right.Maine low bush blueberries, yum. Lived in Castine ME for a (too short) while. Cool stuff. Heh. Using subjective evidence and guessing ... making up stuff you know. Enjoy.

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This is exactly where our YEC friends become confused. They think that comparing the time of deposition of the lower part of the lamination on the right with the upper part of a lamination on the left refutes superposition. As if no geologist ever noticed this before...Anyway, each lamination is essentially a time-strat unit, a compositionally uniform deposit occurring essentially instantaneously. And, as it turns out, the real comparison is one lamination with another - superposition holds.At the same time, each 'bed' which contains laminar elements overlies another 'bed', also with laminar elements, and is younger. Supersposition holds again. Correct (now), this is a primary depositional feature. Very common in current-laid sediments. Correct. However, keep in mind, that in this type of deposit the laminations are usually deposited quickly enough that age difference in the geologic record cannot really be resolved. Coarser-grained deposits such as these can be laid down very quickly. Yes, even though the actual ages might be very slightly different. They are the same bed.By the way, your 'core' example is a very good way to describe this to the lay person.

Regarding the picture you included in your post. When I first looked at it, I thought to myself, "not eolian", before I read the caption. Do you think our YEC friends could tell us why?

Hi,Thanks very much for this comment. It help me to think about my ideals.Apart from that, you also can ref more resources at: Performance evaluation phrasesTks again and pls keep posting.Edited by hdblue, : No reason given.Edited by hdblue, : No reason given.Edited by Adminnemooseus, : Spam treatment to link.