Along Strike Variability in a Mixed Carbonate-Siliciclastic Ramp Setting, Last Chance Canyon, New Mexico
University of Texas at Austin, Austin, TX
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 a superb opportunity for characterization of along-strike variability within the context of a sequence stratigraphic framework. Acquisition of ground-based LIDAR (light dectection and ranging) has provided a high resolution (10cm spacing) image of the outcrop wall in which along strike variability may be distributed within a modeled 3-D volume.
Measured sections and mapping of the strongly progradational Guadalupian 13 high frequency sequence of Last Chance Canyon reveals three orders reservoir-scale along strike variability. Regional variations in siliciclastic input along the Guadalupian shelf margin constitute the lowest order and may be influenced by persistent tectonic control of siliciclastic point sources. Higher order variability in volumetric proportions of facies in a strike direction persisting for less than one high frequency sequence are suggested to be influenced by subtle precursor topography. Field observations suggest variations in topography may be tied to a system of reentrants and embayments. Slope and toe of slope variability at the high frequency cycle scale may be an autogenic process characterized by slumping and debris flows and is the highest order observed