Re: Article in Natural History Magazine

David Yeamans, CST-7, 5-8832, dryeamans@lanl.gov (dryeamans@lanl.gov")
Tue, 30 Sep 1997 12:59:59 -0600


>Very likely in recent geological time
>>"reservoirs" due to damming of the river by basalt flows have been a
>>fairly common occurrence.
>
>It's the ponded water from these that may have been involved in cementing
>the colluvium near the Little Colorado.

The shield of travertine on the south shore near Elves Chasm below the
Redwall _may_ be evidence of ponding. I can't think of another mechanism to
explain it. Suppose that carbonate-rich water exudes from the redwall at a
point source such as Elves Chasm or Tapeats and falls into low-pH water such
as might be present in a lake on the Colorado. Viola`, we have CaCO3
dropping out of solution and acreting itself in shelves such as are seen in
the area described and in limestone caves in the Guadalupe Mountains of New
Mexico. One such form is called Coat Tables, and marks the surface of ponds.

PBS aired a program written by a group of geologists from Iowa or other
east-of-the-crick state. The main professor was such an experienced boatman
after two trips that he took his own boat down the canyon and when it got
into trouble, he "jumped out of the boat to save the boat." Anyway, perhaps
this fellow can show us evidence of ponding.

Dave Yeamans

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