Characterization, prediction and implications of compartments in a mixed carbonate–siliciclastic mass‐transport complex: The Cutoff Formation, Permian Basin, Texas

ABSTRACT Recent studies suggest that mass‐transport complexes can be vertically compartmentalized (i.e. contain multiple internal units or sub‐units), either by amalgamation of successive mass failures or by internal shear within a single failure event. While this compartmentalization has been documented in seismic studies, comprehensive characterization at the sub‐seismic (outcrop) scale is still lacking. Limited understanding of such complexity hampers high‐resolution modelling in the subsurface. This study utilizes the well‐exposed mass‐transport complex outcrops of the mixed carbonate–siliciclastic Cutoff Formation to characterize sub‐seismic compartment architecture, compartment lithofacies and deformation styles, as well as to explore how compartmentalization may affect rock properties. The studied mass‐transport complex has at least three stacked lithofacies units with significant internal deformation (i.e. compartments) that are bounded by extensive termination surfaces. A shear zone that formed along compartment boundaries further delineates the mass‐transport complex into multiple sub‐compartments. The available data cannot unequivocally distinguish whether the compartments were formed by a single or multiple mass‐failure events. Abrupt changes in lithofacies, microstructure styles and deformation fabric (linked to palaeotransport direction) could be used as recognition criteria in borehole data to identify compartmentalizations in mass‐transport complexes. The variability of compartment/sub‐compartment characteristics and their associated bounding surfaces can affect anisotropy and can form mechanical boundaries and hydraulic barriers/conduits in the subsurface. The ubiquity of mass‐transport complexes in the sedimentary record makes these deposits important factors in formation evaluation for hydrocarbon development, carbon sequestration, hydrogen storage and enhanced geothermal systems.