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ABSTRACT: High-Resolution Sequence Stratigraphy of Lower-Middle Guadalupian Outcrops, Western Guadalupe Mountains, Texas and New Mexico

W. M. Fitchen, M. E. New

We describe parts of three third-order depositional sequences and their associated system tracts within seismic-scale outcrops of the Lower-Middle Guadalupian Northwestern shelf-to-Delaware basin transition. These sequences are well exposed along a 20-km dip-oriented transect in the western Guadalupe Mountains, Texas and New Mexico. Systems tracts are defined on the basis of lithofacies distribution, stratal geometry, and bounding (stratal termination) surfaces. These Lower-Middle Guadalupian sequences record (1) carbonate platform retrogradation, basin margin erosion, and sediment starvation followed by platform aggradation and progradation (lower San Andres Formation-Cutoff Formation; transgressive and highstand systems tracts), (2) major basin infill by terrigenous cla tics bypassed over the underlying lower San Andres highstand carbonate bank and development of a shelf-margin-restricted carbonate bank and coeval base-of-slope apron (Brushy Canyon Formation, Cherry Canyon Tongue, and basal upper San Andres Formation; lowstand and transgressive systems tracts), (3) progradation of a mixed carbonate-terrigenous clastic bank (upper San Andres Formation; highstand systems tract), followed by subaerial exposure of the highstand bank top, and (4) deposition of interbedded terrigenous clastics and carbonates in a shorezone that onlaps the subaerial exposure surface at the top of the upper San Andres Formation highstand bank (lower Grayburg Formation; lowstand and transgressive systems tracts). Systems tracts developed in response to the interaction of rate an direction of change of relative sea level; timing, rate and location of terrigenous clastic supply; and depositional topography.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990