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TROUTMAN, TONY J., University of Texas at Austin, Dept. of Geological Sciences, Austin, TX

ABSTRACT: Reservoir Characterization, Paleoenvironment, and Paleogeomorphology of the Mississippian Redwall Limestone Paleokarst, Hualapai Indian Reservation, Grand Canyon Area, Arizona

The top of the Mississippian Redwall Limestone represents a second-order sequence boundary that karstified during 5 m.y. of subaerial exposure. Former tidal channels, deltaic channels and extensive paleokarst systems are present. The paleokarst is characterized today by numerous vertically oriented breccia pipes and horizontally oriented areas of collapsed paleocaves. This paleokarst system represents an important analog for reservoirs found in paleokarst.

The study will characterize the spatial distribution and magnitude of the karst features using three-dimensional exposures of the paleokarst. Fracturing, hydrologic base level and climatic factors exert control on karstification. Characterization of the paleocave systems as vadose, phreatic, or flank-margin caves may allow prediction of the spatial distribution of these features and their relationship to surficial paleodrainage systems. The relationship between the type of karst system that originally formed and paleoclimate may be important in predicting patterns within paleokarst. Comparisons of the distribution of paleokarst features will be made with modern day karst systems that most closely match the Redwall paleoclimate.

Distribution of porosity and permeability within the paleokarst system will be examined on a range of scales. The study may provide further information on the effects of paleokarst on secondary porosity and may provide insight into why some paleokarst features become flow barriers, while others act as flow conduits. The Redwall represents an excellent opportunity to study paleokarst that will improve the predictability of subsurface paleokarst distribution and characteristics.

AAPG Search and Discovery Article #90909©2000 AAPG Foundation Grants-in-Aid