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