quote:
Originally posted by Tranquility Base:
Wehappy, anywhere there are non-zero paleocurrents there is going to be regional consistency so we can agree on basinal 3D topography issues. We all understand that - it couldn't be any other way. I'm talking about continent-wide consistency and that is where Chadwick claims the Paleozoic and Mesozoic differ from the Precambrian and Cenozoic. If there is no mainstream collection of data on this then that is a mainstream lack. Chadwick has done the global story and that is his conclusion. I can't find a mainstream gobal view. Can you?
Your source - Chadwick - does not agree with your conclusion state above...
"
the Mesozoic appears not to be under the influence of any prevailing continent wide vectorial forces."
"During the Paleozoic, in sharp contrast to Mesozoic, Cenozoic and Precambrian tendencies, clear and persistent continent-wide trends are normative. Sediments moved generally from east and northeast to west and southwest across the North American Continent. "
So the Mesozoic and Cenozoic are essentially identical to the preCambrian, according to Chadwick.
Chadwicks punchline appears to be this:
Paleozoic paleocurrents indicate the influence of directional forces on a grand scale over an extended period. Various authors have attributed the directionality to such things as "regional slopes," but it is difficult to see how this could apply to deposits of such diverse origins over so wide an area.
So it appears that Chadwick's central problem is his inability to incorporate the simple fact that the formation of Pangea dominated the sedimentary history of the Paleozoic. This is a singular event in Phanerozoic time, so
of course the sedimentary and paleocurrent data are unique. At no other time in the last 600 million years has a continental landmass existed adjacent to N. America. The collision formed mountains. The mountains eroded for hundreds of millions of years, shedding sediments. It should be no surprise at all that these sediments traveled downhill onto the N. American craton. At all other times, including most of the preCambrian, sediments and currents flowed from the center of the craton outward - leaving no continent-wide vector.
This appears to be another case of a Creationist applying the strictest, most outdated forms of gradualism and uniformitarianism to the geologic record, and coming up with a puzzled look on his face - as expected.
His finding that the Proterozoic paleocurrents are, overall, directionless on a continental basis is equally unsurprising. Even with a few pre-Pangea supercontinents thrown in, averaging data over a few billion years will zero out almost anything.