--> Abstract: A Dynamic Model For Formation Of The Tepee-Pisoid Facies In The Permian Reef Complex Guadalupe Mountains, New Mexico, by B. L. Kirkland, J. L. Banner, F. L. Lynch, and W. B. Ward; #90928 (1999).

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KIRKLAND, BRENDA L.1, JAY L. BANNER1, F. LEO LYNCH1, and W. BRUCE WARD2
1Department of Geological Sciences, The University of Texas at Austin, Austin, TX
2Earthworks, West Reading, CT

Abstract: A Dynamic Model for Formation of the Tepee-Pisoid Facies in the Permian Reef Complex Guadalupe Mountains, New Mexico

Tepee structures of the Guadalupe Mountains are a hybrid facies containing both depositional and syndepositional diagenetic components. Their formation is a dynamic, multistage process and their analysis may provide information about climate, sea-level change, and diagenesis.

Important features of the facies are association of tepee structures with cross-formational fractures, micritic pisoids with tilted geopetal structures at the base of tepee zones, walnutoid pisoids and fibrous zoned cements near the top of tepee zones, erosional truncation at the top of tepee zones, and very fine to medium grain size siliciclastic infill in the core of the tepee. Banded marine cements between fenestral fabric blocks comprise approximately 40% of the outcrop surface and can be correlated between tepee structures within a horizon. Normal marine fauna occurs at two tepee localities.

A model for formation of these structures must encompass processes such as lithification, fluid flow, and sea level change. Blocks of centimeter-scale bedded fenestral packstone were lithified very early and initially deformed by polygonal fracturing. Micritic pisoids formed in pools between these juvenile tepee structures. Subsequent displacive precipitation of thick bands of marine cements further tilted tepee flank beds. The large volumes of these cements suggests high fluid flux. Walnutoids and banded cements formed in pools fed by the same fluids. Siliclastic sediment fills the main conduit and is mineralogically different from the sandstones both above and below the tepees.

The cementing fluids may have been density-driven brines from the inner shelf. At times normal-marine waters from the basin may have flowed through the fractures, perhaps in response to tidal pumping, climate change, and/or high-order sea-level change.

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