About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

Oklahoma City Geological Society

Abstract


The Shale Shaker Digest XII, Volumes XXXVI-XXXIX (1985-1989)
Pages 236-246

Brachiopod Biostratigraphy and Biofacies Analysis of the Marble Falls Formation (Pennsylvanian) of Central Texas

Edward Ernest Dihrberg

ABSTRACT

The purpose of this investigation was to establish a biostratigraphic framework for the Marble Falls Formation (Pennsylvanian) of central Texas. The Marble Falls Formation is a sequence of fossiliferous limestones and shales that crop out along the northern periphery of the Llano Uplift. The Marble Falls Formation is divided into two members: a Lower Member which is Morrowan in age, and an Upper Member which is Atokan in age.

Brachiopods were collected from numerous measured sections and other fossil collecting localities in the Marble Falls Formation. Also, brachiopod collections made by University of Texas students were borrowed and utilized in this study. After an exhaustive literature review, the brachiopods were identified as completely as possible. Of the 55 species collected, only 7 undoubtedly occur in both the Upper and Lower Members. This indicates a major faunal change across the Morrowan/Atokan boundary. Biostratigraphic evidence suggests that the oldest Morrowan strata and the oldest Atokan strata are in the eastern part of the study area. This supports the idea that both members were deposited as part of an east to west transgression.

This study also attempted to determine the environmental preferences of the brachiopods by relating biofacies to lithofacies. Cluster analysis was done to identify the biofacies, but only one community (the Desmoinesia-Spirifer community of the Lower Member) was recognized. Using the lithofacies scheme of Johnson (1983), it was shown that the vast majority of brachiopods were collected from Johnson's spicular facies and skeletal facies. These facies represent deposition in quiet water, muddy substrate environments. In the Lower Member these environments occurred in a low-energy, shallow platform interior. In the Upper Member these facies accumulated in the quiet, semi-restricted areas between algal buildups and calcarenite shoals. Morphologic characters of many brachiopod specimens also indicate adaptations to soft-substrate conditions.


Pay-Per-View Purchase Options

The article is available through a document delivery service. Explain these Purchase Options.

Watermarked PDF Document: $14
Open PDF Document: $24