Compartmentalization and grain-fabric alignments in mixed carbonate-siliciclastics mass-transport deposits: the Cutoff formation, Permian Basin, Texas

Abstract

Mass-transport deposits (MTDs) comprise complex, multi-scale deformation that renders them unique compared to sediments of other depositional origins. The topics of this research entail compartmentalization (outcrops) and grain-fabric modifications (thin sections) in MTDs developed during the emplacement processes, which can significantly impact formation heterogeneity and anisotropy. Our research emphasizes on (1) the recognition criteria of sub-seismic MTD compartments and (2) qualitative and quantitative characterizations of grain-fabric alignments, both of which utilize the well-exposed Cutoff MTDs in the Permian Basin, Texas. Our study shows that sub-seismic compartments in MTDs can be predicted from the intersegment contrasts of lithofacies, deformation types, and deformation orientations. Using these recognition criteria in conjunction increases the likelihood of identifying MTD compartments. Thin section analysis over 29.000 elongated grains (predominantly sponge spicules) reveals that grain-fabric alignments in MTDs are heterogeneous in multiple scales, and are likely controlled by grain lengths (with constant aspect ratio) and matrix types. The results of this study contribute in the following fields: (1) identification of sub-seismic MTD compartments, which can serve as barriers or conduit to fluid flow, (2) anisotropy prediction of petrophysical (e.g., permeability) and mechanical (elastic moduli) properties, (3) the kinematic of MTD evolution during emplacement, including the origins of MTD compartments and the prediction of paleotransport directions.