Coastal dominance & catastrophic geology

JarThe point about Horner's quote, and the findings of sequence stratigraphy, is that 'valley accumulation, marshes, swamps and all other potential inland depository sites' are extremely minor contributions to the geo-col. Inland seas frequently had access to the open ocean, but I'll grant that genuimely closed inland seas may enable us to test our models.Swamps etc simply can't compete with river delivered sedimentation as we can see today. Remember that most of the strata on the continents are shallow marine deposits forme at high sea levels.

And yet mountains are worn away to nothing. We know from the grand canyon thread that there were periods of sever erosion of structure within the grand canyon.There is also the extensive record of ice age glaciers stripping places down several layers, taking away all deposited soils and scraping the rocks. Curiously this does NOT occur over water ... perhaps because ice floats. Wrong. Horner was primarily talking about the fossilization of coastal habitat dinosaurs - duckbills - that would be concentrated in coastal or around wet habitats around the world - so finding them in sedimentary deposits associated with coastal or wet habitats should be no great surprise to anyone.Horner tossed of an off-hand statement about OTHER dinosaurs that is the focus of your quote mining.

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We don't know whether they, or any other dinosaurs, also lived in inland areas, ...

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But he was talking about the appearance of fossils and not all inland contributions to the sedimentary column. AND he is talking about the KIND of rock formations that can capture fossil specimens.While many fossils were made due to being buried by swift moving waters and mud, that does not include all fossils and it certainly does not include places where all animals on the earth have happened to die but were NOT preserved.

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Deposition or sedimentation, which is what makes sedimentary rock and what preserves fossils, did not occur to a large enough extent in the inlands....

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... to cover fossils of duckbilled dinosaurs ... "or any other dinosaurs" Nice try. It is the deposition of layers on top of previous layers, no matter what the previous layer was or where the cover layer comes from. Lava and ash depositions inland are significant in some areas and have nothing to do with coastal or wet environments, yet they are part of the geoplogical column as much as wind driven sand and dust.Stuff collects in low points, as Jar pointed out, whether it is driven there by water, wind or other means. None of the above.It is due to the transportation of the rock on which the depositions land toward the subduction zones, so the deposition gets deeper with time from the mid-ocean ridge (where the new rock is "born") towards the subduction zones - that just happen to be near coasts. Perhaps as part of the {mechanism\process} that, I don't know, builds continents?Once you are a half kilometer from the coast there is minimal coastal effect, and even there it is transitory.
(image from Page not found | Cal State LA,
Page not found | Cal State LA)From Page not found | Cal State LA

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Sedimentary rocks are formed through a special sequence of events. the products of weathering are the typical materials from which sedimentary rocks are made, that is ions in solution, clay minerals and resistant minerals or unweathered fragments. These materials are eroded, transported, and sedimented. They are transported by mainly by rivers, but also by the wind, waves, currents, glaciers, gravity (mudflows, landslides), etc. Then they are compacted, dehydrated and often cemented.

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It's geology 150 rather than 101 ... but you get the idea.Can you point out where he says "coastal"?Enjoy.

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I don't know why RAZD chose to dispute this. The continents are a huge source of sedimentary material, and the closer you get to a continent the more significant the sediment accumulation will be.But continents are not the only source of sedimentary material. Life living in the waters above the sea floor are also a source of sedimentary material, and the most obvious example is limestone layers. The more pure the limestone, the more distant from continental shores it was deposited. In the case of the purest limestone, it was deposited by a slow rainfall of the skeletons of calciferous microorganisms living in the waters above over millions of years in a warm, shallow sea many, many miles from any coastline. And limestone layers comprise a significant proportion of the geologic column.As you noted, sandstone and shale layers form relatively close to the coastline, and that's what you're referring to when you say "ancient shallow marine deposition at lower sea-level".But a lower sea level isn't the cause. What you're really trying to say is that as sea levels rise and fall, and as regions experience subsidence and uplift, the shoreline will repeatedly march inland and then retreat. And wherever the shoreline goes, sedimentary layers of sandstone and shale will form in the waters nearby.But limestone layers represent a significant proportion of the geologic column, they are not coastal sedimentary deposits, and so coastal sedimentary layers cannot be said to dominate the geologic record. And that's true even of just the layers we have relatively easy access to.When you add to these layers those from mid-ocean that are much more difficult to access and much shorter lived, it can be seen that coastal sedimentary deposits represent only a small proportion of all sedimentary layers being laid down.About this that you quoted:

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"Although rare today because of the overall lowstand of sea level, epeiric seas were widespread in the past during highstands of sea level, such as the early and middle Paleozoic, and for many times provide the only record we have of the marine realm."
http://www.geosc.psu.edu/~sling/ORDOVICIAN/patz_summary.html

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He's absolutely right. Frequently such layers are the only record we have of the marine realm. They aren't the only record that was formed, and they aren't the only record that was preserved and survives until today, but because of accessibility they're the only record we have.About this from you following message to RAZD: That's precisely what happened. Upland regions are areas of net erosion, while coastal flatlands and nearby offshore regions are areas of net deposition. The fossil record of land animals is almost exclusively of those that inhabited low lying coastal regions. Sea-level cycles make by far the most significant contributions to stratigraphy that is preserved in easily findable places, which is just another way of saying that these types of layers dominate what we find because we're looking on continents, which is where such layers are preserved, and because they are the most likely type of layers to be preserved. The fate of most mid-ocean sea floor is subduction, and it is rarely preserved in places where the ordinary person can find it. In other words, it isn't one of the common layers seen at road cuts and canyons. You really shouldn't make a throwaway line by a paleontologist in a popular press book the basis of a geological claim. It isn't that Horner is wrong, but the context is wrong and it is causing you to reach conclusions he never intended.--Percy

What I was rejecting is the implication that these were due entirely to coasts, on reading again I would say that as long as these include transport of material from anywhere inside the continent that this list is partial and under certain conditions, but incomplete in total.What I was also rejecting was the idea that the depth was directly proportional to the distance from the coast was due soley to the coast as a source - ignoring the effects of the transport of the ocean bottom towards the coast from new bottom created at the mid-ocean ridges.The model was, and is, too simplistic and incomplete.It is my understanding that most deep sea deposition is due to organic life by-products - both as waste and as dead material.Occasionally some material from continents is deposited - sand storms in africa, volcanoes and the like - and some comes from more point sources than coastlines - such as river deltas. But usually these do not reach far from the continents, and fail to explain the deep sea deposits or the difference in depth with distance from mid-ocean ridges. These materials have signatures and can be identified in deep sea cores. These types of signatures would also show up in ancient sediment that has been converted into rock.

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Sedimentary deposits have two qualities that are very relevant to TB's argument: depth and extent.Regarding depth, the contributions from nearby continents is enormous, and a general rule is that sedimentary deposits accumulate at a rate inversely proportional to their distance from a continent. In general, close to continents, continental contributions to sedimentary deposits far outweigh organic contributions. The great depth of coastal sedimentary layers is due to this reason.Mid-ocean sedimentary layers, usually referred to as pelagic, accumulate far more slowly than sedimentary layers near continents. Even after a journey of a 100 million years from a mid-oceanic ridge, the depth of accumulated sediments would probably be in the neighborhood of only a kilometer.So whether or not TB has listed all the possible contributions to coastal sedimentary deposits, while he exaggerates by saying they dominate, they are extremely significant with respect to depth, and of course when doing geology on continents they're almost exclusively the only kind of layers you'll find, so of course they dominate the kinds of layers that get studied, which is the "looking under the lamppost" effect you mentioned earlier.But coastal deposits are not very significant with respect to extent, not by a long shot. Mid-ocean sedimentary layers, though much thinner, far exceed coastal deposits in extent, even though they are subject to slow but continual destruction at subduction zones.As near as I can make out, TB's argument appears to be that the absence of upland sedimentary deposits is because his postulated cause of coastal deposition, periodic sea-related catastrophes, do not reach far inland. His proposal ignores the fact the upland regions are areas of net erosion, not deposition, and hence almost never create significant sedimentary deposits. And his belief that the layers were formed rapidly a few thousand years ago ignores what we know about what floods look like, ignores the evidence of slow deposition, ignores radiometric dating, and ignores magnetic sea floor striping, to name evidence which come mind at the moment.--Percy