Role of High-Frequency Cycles in Analysis of Ancient Facies: An Example from Shelf-Crest Teepee-Pisolite Facies of the Guadalupian Section, Guadalupe Mountains and Subsurface of the Central Basin Platform, West Texas

Charles Kerans, David Fowler

Placing ancient strata within the high-resolution chronostratigraphic framework of high-frequency cycles is an essential step in evaluating basic facies interpretations and understanding the controls of high-frequency and longer term base-level shifts on deposition. A high-frequency cycle framework is also essential if estimates of facies geometry and continuity are to be quantified and scaled up for reservoir characterization and fluid-flow modeling.

Analysis of the fenestral-teepee-pisolite facies in the Guadalupian (Permian) section of the Guadalupe Mountains and in the Johnson Grayburg Unit was conducted to test the significance of constraining interpretations within a high-frequency cycle framework. Detailed outcrop mapping and subsurface correlations within the cycle framework support earlier interpretations that the fenestral-teepee-pisolite facies defines a strike-parallel linear topographic crest of depositional profiles, with gradual slopes both seaward and landward. More important, vertical and lateral stacking pattern analysis within the high-frequency sequence framework suggests that the best developed teepee-pisolite complexes occur above sequence boundaries during a period of increasing accommodation associated with he transgressive portion of a sequence. The common practice of placing sequence boundaries on top of thick fenestral-teepee-pisolite successions should be carefully reviewed.

Characterization of Grayburg reservoirs with prominent teepee complexes demonstrates that (1) the fenestral-teepee-pisolite facies forms a potential linear barrier to flow both laterally and vertically and (2) the productive section landward of the teepee complexes, as predicted by the shelf-crest model, points to potentially unexploited reservoir potential landward of the presumed updip porosity pinch-out.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995