Bounding surfaces (disconformities) of regional extent (super bounding surfaces) have recently been recognized and described from a number of eolian sandstone units in the western United States. These surfaces are a potentially important tool for sub- dividing and correlating eolian sequences, leading ultimately to a better understanding of how such sedimentary bodies evolve. However, features diagnostic of super bounding surfaces formed by climatic, tectonic, eustatic or endogenic causes have yet to be fully recognized and documented. The best way to document such features and to understand how they form is to study their occurrence in a modern sand sea that is known to have experienced episodic eolian deposition. The Gran Desierto sand sea in northern Mexico is an excellent example of a sand sea that been strongly affected by changes in the regional tectonic, eustatic and climatic environment. These changes have resulted in an episodic deposition of eolian sand, separated by long periods of stability and non deposition or erosion. This study will undertake filed investigations of relations between sand bodies of different ages and regional-scale bounding surfaces formed by dune and sand sea migration, sea level change, and interruption of sand supply due to climatic and other factors. Criteria for the recognition of super bounding surfaces of different origins and more precise models for the formation of super bounding surfaces will be developed on the basis of these investigations.
