--> Abstract: Reinterpretation of the Angular Sets of the Black Dragon Member of the Moenkopi Formation, Southeastern Utah, by S. P. Baker; #90987 (1993).

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BAKER, SHAUN P., Department of Geological Engineering, Geology and Geophysics, Michigan Technological University, Houghton, MI

ABSTRACT: Reinterpretation of the Angular Sets of the Black Dragon Member of the Moenkopi Formation, Southeastern Utah

An angular unit of alternating sandstone and siltstone is present within the Black Dragon Member of the Moenkopi Formation in the Island in the Sky District of Canyonlands National Park and in the Orange Cliffs of Glen Canyon National Recreation Area in south-eastern Utah. These dipping units have been previously interpreted as isotope foresets and structurally tilted strata. The purpose of studying the dipping units is to establish the depositional environment or the structural origin of the angular sets, and the facies relationships with underlying and overlying units. This in turn will aid in defining the stratigraphic position of the TR-1 unconformity, which has been placed by some at the top of the angular sets.

Based on field studies of the Black Dragon Member during fall of 1992, the angular units appear to be lateral accretion sets of atidal channel facies, as indicated by the structure and lithology of the alternating sets. The angular sets have a sigmoidal appearance in which the angular beds gradually become horizontal down-section. The dipping units unconformably overlie the Hoskinnini Formation and/or the white Rim Sandstone, and are overlain by horizontal beds of similar lithology which truncate the angular sets. The alternating siltstone and sandstone units contain current ripple laminations, current ripple cross-stratification, oscillation ripple laminations, mudcracks and lodecasts. Paleocurrents indicate a north to northwest flow direction and are generally parallel to the strike of the angular sets.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.