DISTRIBUTION AND CHARACTER OF SOFT-SEDIMENT STRUCTURES WITHIN A PALEO-SUBMARINE MASS TRANSPORT COMPLEX AND RELATIONSHIPS TO OVERLYING AND UNDERLYING PALEO-BATHYMETRY, PERMIAN CUTOFF FORMATION, WEST TEXAS

Paleo-topography atop a huge (20,000 km²) paleo-submarine mass transport complex (MTC) controls the geometry and lithology of overlying deep-water siliciclastic strata (Permian Brushy Canyon Formation). Sedimentological and structural data collected within the Guadalupe and Delaware Mountains suggest the MTC was formed by multiple mass transport events (MTEs) of previously deposited carbonate turbidites.

Six "strato-structural" units were recognized and mapped and exhibit unique geometries, facies, and structural characteristics. Structures include variable-scale (mm- to decameter) folds, faults, cylindrically shaped complex deformation zones (CDZs), and lineations resulting from the intersection of cm-scale folds and faults with bedding planes. These structures are locally concentrated within MTE bodies. Blocks in MTE bodies contain previously formed mm- to cm-scale structures. Such blocks are several meters thick, with lateral dimensions of at least 10s of meters. Relationships with enclosing MTE bodies suggest multi-phase transport.

MTE bodies show a generally north-south transport vector and a pattern of waning volume and degree of deformation through time. Smaller MTE bodies near the top of the succession appear to be locally derived from intrabasinal highs, whereas lower, larger MTE bodies may have traveled from the basin margin. Structural style is dominated by shortening, which caused Cutoff thickness to double over a distance of 20+ km. Local highs on the Cutoff surface concentrated Brushy Canyon sandstone deposition within the intervening topographic lows.

Stratigraphically thick zones within the Cutoff have a higher density of folds, CDZs, and draped intervals than do thin zones, which are dominated by truncation surfaces. Cutoff thickness distribution does not appear to have a one-to-one inverse relationship with overlying Brushy Canyon thickness distribution; instead it modifies, and is influenced by, inherited underlying paleo-bathymetry that may have been created by older MTCs or tectonic movement. Distribution of variable-scale structures within the Cutoff suggests underlying paleo-bathymetric control and provides clues to overlying sandstone depositional patterns.