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Modeling Strike Variability of Clinoform Surfaces; Last Chance Canyon, Guadalupe Mountains, NM

Sam Z. Scott

John A. and Catherine G. Jackson School of Geosciences; Department of Geological Sciences; University of Texas at Austin.

Austin, TX, United States of America

[email protected]

Our current understanding of clinothem systems is almost entirely based on 2-D schematic depictions of outcrop and seismic data. The Last Chance Canyon area of the Guadalupe Mountains is well known for its excellent exposure of seismic-scale mixed siliciclastic-carbonate clinoforms. Strike and dip oriented outcrop transects provide an opportunity for characterization of along-strike variability within the context of a sequence stratigraphic framework. Acquisition of ground-based LIDAR (light detection and ranging) has provided a high resolution (8 cm spacing) point cloud of the outcrop walls in which mapped surfaces may be distributed. Mapped surfaces can then be correlated across canyons and between areas of poor exposure. Correlative surfaces are then imported into three-dimensional modeling software to statistically generate surfaces between deterministic data points.

Mapping clinoform surfaces within the highly progradational Guadalupian 9 HFS reveals significant along-strike variability within the fusulinid wackestone/packstone facies. Mapped surfaces suggest sinuous clinoform fronts characterized by topographically higher areas of fusulinid deposition and lower areas of reduced carbonate deposition. Variable dips oblique to large scale dip direction indicate localized fusulinid accumulations were capable of developing subtle topographic highs. Adjacent lower areas contain a higher percentage of silt, sand, and siliceous sponge spicules­­­ and are punctuated by sandy fusulinid-rich turbidity deposits.­

Surfaces honoring mapped stratigraphic contacts have been generated in the highly progradational Guadalupian 9 high frequency sequence. Successful modeling requires integration of outcrop exposure, technology, and statistics, and is an iterative process. When significant, along-strike variability should be incorporated into reservoir models.

AAPG Search and Discovery Article #90060©2006 AAPG Foundation Grants-in-Aid