ABSTRACT

The Sligo-Hosston depositional wedge occurs over an area of thousands of square miles of South Texas. The wedge thickens from its pinchout updip to greater than 1,000 feet thick downdip at the shelf edge. The wedge can be subdivided into three major time-equivalent parts based on quartz-sandstone and carbonate facies and interpreted depositional environments: Hosston, lower Sligo, and upper Sligo. The Hosston dolomitic quartz sandstone, dolomite, and anhydrite were deposited on an and tidal flat; the sandstone decreases and the dolomite increases in abundance upward in the Hosston. The lower Sligo is characterized by a number of cycles which consist of burrowed subtidal dolomite at the base and laminated supratidal dolomite and anhydrite at the top. The upper Sligo consists predominantly of subtidal skeletal wackestones to grainstones and thin oolite grainstones.

The vertical sequence described here indicates an overall transgressive trend to the Sligo/Hosston depositional wedge; however, detailed sections show that this transgression was accomplished by means of a number of progradational cycles each successive one of which was shifted landward of the previous one.

1. Publication authorized by Director, Bureau of Economic Geology, The University of Texas at Austin

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