CALL FOR PROPOSALS:

ORGANIZERS

  • Harvey Thorleifson, Chair
    Minnesota Geological Survey
  • Carrie Jennings, Vice Chair
    Minnesota Geological Survey
  • David Bush, Technical Program Chair
    University of West Georgia
  • Jim Miller, Field Trip Chair
    University of Minnesota Duluth
  • Curtis M. Hudak, Sponsorship Chair
    Foth Infrastructure & Environment, LLC

 

Paper No. 3
Presentation Time: 8:45 AM

THE PALEOECOLOGY OF THE COCONINO SANDSTONE DEPOSITIONAL ENVIRONMENT: THE CASE FOR AVAILABLE SURFACE WATER


BARTLETT, Rickey, Geology, Baylor University, One Bear Place #97354, Waco, TX 76798 and ELLIOTT, David K., Geology Program, SESES, Northern Arizona University, Flagstaff, AZ 86001-4099, Rickey_Bartlett@baylor.edu

The Coconino Sandstone is a well-studied eolian sandstone which was deposited in a huge desert erg or dune sea that stretched across present day Arizona, Colorado, New Mexico and Utah during the Permian. While the Coconino Sandstone contains no actual body fossils, it possesses a wealth of trace fossil evidence of various animals, from arthropods to large tetrapods, as well as environmental traces such as raindrop marks.

The classical sedimentological interpretation of the Coconino depositional environment has been that of a hyper-arid desert with no available surface water, with the primary input of water being supplied by periodic fogs. To a large degree, this interpretation was based on the lack of recognized inter-dune deposits within the Coconino.

The Namib Desert in western Africa has been suggested as a viable modern analog for the Coconino Erg. The Namib, however, is not a suitable analog for several reasons. The limited area of the Namib, its proximity to an open sea, the lack of a cold offshore current as a fog producing mechanism proximal to the Coconino Erg along with the size and metabolic requirements of the Namib fauna all combine to limit its suitability as a viable analog for the Coconino Erg.

New trace fossil evidence from a previously un-described locality in Grand Canyon suggests a relatively high concentration of organisms, both vertebrate and invertebrate, in a restricted area within the Coconino for an extended period of time. This locality, as well as others, provides sedimentological evidence for the presence of surface or near surface water within the Coconino Erg. This evidence includes well developed desiccation cracking and horizontal clay rich sediments associated with bounding surfaces. This new evidence, coupled with a re-examination of the Namib as a suitable analog, suggests that a re-evaluation of previous ideas regarding the environment in which the Coconino Sandstone was deposited is needed.

Meeting Home page GSA Home Page