At 09:53 PM 11/30/97 -0600, bpayne@voyageronline.net wrote:
>More than one lithology was cut by the 1982 mudflow at Mt. St. Helens.
>Ancient solid rock was also cut.
OK, 2. there is limestone, shale, sandstone, conglomerates etc at the Grand
Canyon
>
>> The Grand
>> Canyon has many different lithologies. The situation at Spirit Lake is quite
>> different from the Grand Canyon.
>
>Correct, in scale only. I understand several hundred cubic miles of
>water would be impounded behind the Kiabab Uplift if it were not cut by
>Grand Canyon. This natural dam would have trapped water as the Flood
>receded. A breach in the dam would have eroded out rapidly and allowed
>the impounded lake to discharge within perhaps a few weeks, cutting
>Grand Canyon catastrophically.
>
>Question, Glenn. If the Canyon eroded slowly (over millions of years)
>as it is doing today, where is the delta? The delta at the mouth of the
>Colorado River looks pretty puny on the aerial photos I've seen. You
>have to not only account for the volume removed from the Canyon, but
>also the upland plateau material removed from between the mesas. Where
>is it?
There are two places. The older is:
"Upper Paleocene to Middle Miocene fluvial-deltaic rocks in
the Los Angeles and Ventura basins were deposited by a Colorado
paleoriver prior to 300 km of dextral displacement on the San
Andreas fault. During the late Miocene, movement on the fault
and associated rifting in the Salton trough rerouted the
paleoriver into the proto-Gufl of California."~Jeffrey L. Howard,
"Paleocene to Holocene Paleodeltas of Ancestral Colorado River
Offset by the San Andreas Fault System, Southern California,"
Geology, 24:9(Sept. 1996):783-786, p. 783
And the younger is the sediments in the Imperial Valley (I forget the name
of the valley just north of the Baha Gulf). The present day delta is merely
the present day extension of the total delta system which includes the
sediments in the valley just north of Baha California.
>
>I still have a little crow left, if you want a slice to be chewing on.
>
>I think between the two of us, we can pin him this time, Art.
If you do, I like my crow barbequed. :-)
glenn
Adam, Apes, and Anthropology: Finding the Soul of Fossil Man
and
Foundation, Fall and Flood
http://www.isource.net/~grmorton/dmd.htm