Sequence stratigraphy, chemostratigraphy, and facies architecture of the Marble Falls Formation (Morrowan-Atokan), Central Texas

Stephanie Wood
The University of Texas at Austin, Jackson School of Geosciences, Bureau of Economic Geology Austin, Texas, United States of America
[email protected]

The Marble Falls Formation (Pennsylvanian, Morrowan-Atokan) is a carbonate unit that was deposited to the northwest off the Llano Uplift paleobathymetric high. Outcrops of the formation are well-documented (e.g., Winston, 1963; Namy, 1969; Kier, 1972; Erlich and Coleman, 2005), yet a larger-scale model has not been created using modern sequence stratigraphic methods. Newly available subsurface data including core and chemical analyses will be used to gain a comprehensive understanding of lateral and vertical facies relationships and to ultimately create sequence-and chemo- stratigraphic interpretations for the formation.

Initial analyses of core and thin sections have identified fourteen distinct basin-to-platform interior facies, including black shales, burrowed spiculites, algal grain-dominated packstones, and foraminferal mud-dominated packstones. Examinations of these packages support previous interpretations of a major regression at the top of the Lower Marble Falls, resulting in an exposure surface present in most of the cores. This regression was followed by the ultimate drowning of the carbonate platform, evidenced by deepening upward profiles in the Upper Marble Falls and deposition of the Smithwick shale (Erlich and Coleman, 2005).

Facies correlations interpreted in conjuction with chemostratigraphic data will improve previous interpretations of the unit’s depositional history to form a unified regional model. Because the Marble Falls was deposited during the Pennsylvanian icehouse climate, this project will supplement our understanding about changes in the stratigraphic record resulting from glacio-eustatic fluctuations. This study will also serve as a sedimentological and facies analog for middle to late Atokan shallow- to deep- water carbonates present in the Permian Basin.

AAPG Search and Discovery Article #90157©2012 AAPG Foundation 2012 Grants-in-Aid Projects