Originally posted by blitz77:
quote:
I got some information from this site
But when the juncture between the Redwall Limestone and Muav Limestone is reached, a 200million-year gap appears. The sign posted here by the National Park Service reads:
AN UNCONFORMITY
"Rocks of the Ordovician and Silurian Periods are missing in Grand Canyon. Temple Butte Limestone of Devonian age occurs in scattered pockets. Redwall Limestone rests on these Devonian rocks or on Muav Limestone of much earlier Cambrian Age."
This supposed unconformity is puzling for several reasons:
The two limestone strata "seem" conformable in most places. Both are nicely horizontal, and there is basically no evidence that 200 million years of erosion and tectonic disturbances separate them.
In some places, the two limestone strata intertongue or interfinger, such that by moving vertically one flashed back and forth in 200-million-year jumps.
In both limestone strata, one finds layers of the same micaceous shale containing the same fossil tubeworms, suggesting near-simultaneous deposition.
In one place, the two limestones clearly grade into one another, with no separation at all.
Continuing from where the above quote left off:
quote:
Anyone who walks down the Canyon trails can see that the evidence for a 200-million-year hiatus between the Mississippian and Cambrian limestones is shaky at best. With the accuracy of geological dating through the use of contained fossils at risk, one would expect many professional papers dealing with this situation. Instead, the geological literature says little. One of the few papers mentioning the "unconformity" states that the contact between the two limestones displays ripples 2 feet from crest to trough, as one might expect with a true unconformity. Such ripples do not seem to exist. (Waisgerber, William, et al; "Mississippian and Cambrian Strata Interbedding: 200 Million Years Hiatus in Question," Creation Research Society Quarterly, 23: 160, 1987.)
Comment. Aha, this paper was written by scientific creationists, who have an obvious ax to grind. There's surely nothing to it. However, the senior author is a consulting geologist, and the paper is replete with photographs and diagrams. And you can always go see for yourself! It is the interpretation of the data that is in question. Where is the error?
Reference. Puzzles in the stratigraphy of Grand Canyon can be found in ESR1 in our catalog: Inner Earth. For details, visit: here.
The "here" is:
http://www.science-frontiers.com/sourcebk.htm
The implication is, that there has been an interpretative error made, and that the mainstream geology explanation can be found in one of the books the site sells (fair enough).
Perhaps this information can be tracked down without having to buy the book. The books do look to be rather interesting, if you have the inclination and the money.
Will try to do further on-line research.
Cheers,
Moose
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BS degree, geology, '83
Professor, geology, Whatsamatta U
Old Earth evolution - Yes
Godly creation - Maybe