ABSTRACT: Depositional Environment Analysis of the Carrizo Sandstone, Nacogdoches County, Texas

GALLOWAY, CHAD A., and CHRISTOPHER D. SUMNER, Stephen F. Austin State University, Nacogdoches, TX

In the Gulf Coast region of Texas, the Carrizo Sandstone represents the basal formation of the Eocene Claiborne Group. The Carrizo Sandstone, a well-sorted, fine-grained quartz arenite, is composed of angular quartz weakly cemented with hematite and silica. Well-defined south to north cross-bedding, along with load structures and flaser bedding, are the dominant sedimentary structures of the Carrizo Formation in outcrops of northern Nacogdoches County.

Paleocurrent analyses indicate two general current directions: 0az and 320az. Cross-lamination orientation trends fluctuate from 305az to 45az. Paleocurrent data further indicate that the current direction shifts northwest as the outcrop is exposed to the west.

Deposition of the Carrizo Sandstone is interpreted as being part of a Gulf coastal transgressive sequence. Concave lenses of sandstone and fan-shaped cross-laminated deposits indicate that this section of the Carrizo Formation was deposited as a barrier island beach complex with associated washover fans. Variable directions of planar cross-bedded strata, from south to north, are the result of sediment deposited in a washover fan sequence. A source for the sand is difficult to determine because of the multicyclic nature of the quartz grains.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)