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PS Distribution and Character of Soft-Sediment Structures within a Paleo-Submarine Mass Transport Complex and Implications for Reservoir Geometry Prediction, Permian Cutoff Formation, West Texas*


Robert Amerman 1, Eric P. Nelson 1, and Michael H. Gardner 1

Search and Discovery Article #50012 (2005)

Posted August 15, 2005


*Poster presentation at AAPG Annual Convention, Calgary, Alberta, June 19-22, 2005.

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1Colorado School of Mines, Department of Geology and Geological Engineering ([email protected])



Paleo-topography produced by a huge paleosubmarine mass transport complex (MTC) controls the geometry and lithology of overlying deep-water siliciclastic reservoir strata (Permian Brushy Canyon Formation). Sedimentological and structural data collected across a 6-km transect 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, 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 dimenstions of at least 10s of meters. Mesoscopic complex deformation zones may indicate the presence of macroscopic structures.

MTE bodies show a generally north-south transport vector and a pattern of waning volume and degree of deformation through time. 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. As the geometries and cumulative thicknesses of all MTE bodies controlled depositional patterns in overlying sandy sediment gravity flows, the distribution of syn-sedimentary structural features within a slump and slide complex may provide a tool for predicting sand body geometry and lithology.




  • There were a minimum of six, and probably at least eight, MTEs in the study area based on significant variations in lithology, style, and intensity of deformation, regional truncation surfaces, orientation of structures, and presence of drape facies.

  • The dominant transport vector for the MTEs is generally N–S with a secondary ENE-WSW component, based on orientation of mesoscopic fold axes and lineations.

  • The dominant structural style is contractional, based on presence of folds, reverse faults, and contractional overprinting of extensional microstructures.

  • Contraction may cause Cutoff thickness to double over a distance of 20+ km. Local highs that concentrate sandstone deposition within the intervening topographic lows result both from MTE body geometry in the six strato-structural units and from topographic control by underlying units.

  • MTE bodies exhibit a pattern of waning volume and degree of deformation through time.

  • CDZs are concentrated in areas of increased stratigraphic thickness.

  • Deformation is ductile to brittle; occurrence of fluidal deformation is localized, reflecting differences in carbonate lithology and rheology.