Downwind Changes within an Ancient Dune Sea, Permian Cedar Mesa Sandstone, Southeast Utah

  1. K. Pye3 and
  2. N. Lancaster4
  1. R. P. Langford1 and
  2. M. A. Chan2

Published Online: 8 APR 2009

DOI: 10.1002/9781444303971.ch8

Aeolian Sediments: Ancient and Modern

Aeolian Sediments: Ancient and Modern

How to Cite

Langford, R. P. and Chan, M. A. (1993) Downwind Changes within an Ancient Dune Sea, Permian Cedar Mesa Sandstone, Southeast Utah, in Aeolian Sediments: Ancient and Modern (eds K. Pye and N. Lancaster), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303971.ch8

Editor Information

  1. 3

    Reading, UK

  2. 4

    Reno, Nevada, USA

Author Information

  1. 1

    Bureau of Economic Geology, University of Texas at Austin, Austin, TX 78712, USA

  2. 2

    University of Utah, Salt Lake City, UT 84112, USA

Publication History

  1. Published Online: 8 APR 2009
  2. Published Print: 27 MAY 1993

ISBN Information

Print ISBN: 9780632035441

Online ISBN: 9781444303971

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Keywords:

  • downwind changes within ancient dune sea, Permian Cedar Mesa Sandstone, southeast Utah;
  • Permian Cedar Mesa Sandstone, southeast Utah R.P. Langford and M.A. Chan;
  • stratigraphic sections along wind-parallel transect within upper part of Permian Cedar Mesa Sandstone;
  • sensitivity of aeolian deposition to changes in climate and other influences;
  • dune size and dune forms;
  • bioturbation abundance;
  • Cedar Mesa Sandstone;
  • non-aeolian deposit abundance;
  • ribbon-like trace fossils in Permian Caspar Sandstone in Wyoming;
  • downwind changes in deposition

Summary

Stratigraphic sections along a wind-parallel transect within the upper part of the Permian Cedar Mesa Sandstone illustrate changes relative to the downwind erg margin. Six phenomena may help to define the erg margin: bioturbation, wide inter-dune areas, abundant sand sheets or zibars, abundance of non-aeolian facies, smaller and different types of aeolian dunes, and an increased abundance of erosion surfaces. Each phenomenon responds differently to stratigraphic and palaeogeomorphological changes. Bioturbation varies stratigraphically rather than laterally, and may respond to climatic or water table controls rather than to changes in position within the dune sea. Dune spacing and the sizes of each type of dune do not show much stratigraphic or lateral downwind change. The proportions of different dune types change regularly as the abundance of large-trough cross-stratified sets decreases downwind. The proportion of sand sheet deposits increases regularly downwind. Grain size decreases regularly downwind but does not indicate position relative to the erg margin. Non-aeolian facies increase towards the erg margins, but can also form a significant proportion well into the dune sea. Erosion surfaces increase in frequency at the downwind erg margin from one per 17 m of section in the five upwind sections to one per 9 m of section and offer the most dramatic indicator of marginality.

The consistent average grain size at each section indicates that the sources of aeolian sand did not significantly change either in position or in sand composition throughout the periods of deposition.

Individual deflation surface bounded stratigraphic units do not change in grain size upward, implying that (i) periods of erosion were not long-lived, or (ii) the sand supply was shut off during periods of deflation, either due to removal of the supply or through a change in the transporting wind direction.