--> Abstract: Fabric Development in Phylloid Algal Bioherms, by J. Gournay and B. Kirkland; #90928 (1999).

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GOURNAY, JONAS and BRENDA KIRKLAND
The University of Texas at Austin

Abstract: Fabric Development in Phylloid Algal Bioherms

Phylloid algal bioherms of the Paradox Basin exhibit two end-member fabrics: 1) a phylloid algal biomicrite where algae appear to float in a mud matrix; and 2) a poorly washed phylloid algal packed biomicrite-biosparite with mud-filled thalli and broken thalli. These two fabrics are vertically, gradationally cyclical and laterally continuous. Each fabric type ranges in thickness from 0.3 to 1 meter. The variation in mud content, the lateral variation of fabrics, and the hummocky surfaces of the bioherms supports the suggestion that these bioherms were partially sculpted in response to current activity.

Within these bioherms, at least three different micrite events are present. Macro- and nannobacterial bodies, including microbial stromatolites, are present within some of these micrite events, but are absent in others.

Both microbial micrite and micrite cement were more important than isopachous marine cement in the early lithification of these bioherms. These micrites are key to overall bioherm formation and are directly responsible for early porosity preservation. Rapid lithification of these bioherms is inferred from the lack of bioherm derived material in flank beds and from the preservation of intact, 1 mm thick, mud-filled thalli.

Comparative studies between Paradox Basin bioherms and bioherms from the Holder (Virgillian), Laborcita (Wolfcampian), and the Hueco Canyon Formations (Wolfcampian) to the south, reveal consistent similarities with respect to cyclicity, microbial content, fabric development, and community.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas