Integrated characterization and failure mechanism for a mid-Pleistocene mass transport complex-dominant interval in the Mars Ursa Basin, northern Gulf of Mexico, USA

Abstract

The economic and operational risks associated with mass transport complexes (MTCs) in deepwater hydrocarbon exploration act as a principal motivation to investigate their depositional elements using industry data. There is a lack of extensive seismic and well data coverage that limits the understanding of the processes associated with the evolution of MTCs within deepwater sedimentary basins. This study leverages a unique integrated data set to evaluate the depositional character and potential failure mechanisms of seven identified MTCs preserved in a synkinematic mid-Pleistocene MTC-dominant interval that spans the hydrocarbon-bearing Mars Ursa Basin in the northern Gulf of Mexico. Through seismic interpretation and attribute extraction methods using a 3D prestack depthmigrated seismic survey, we have determined the kinematic indicators and preserved the morphodomain geometries of the identified MTCs. The MTC-dominant interval covers an area of 631 km2, a volume of 392 km3, and a maximum thickness of 549 m in minibasin centers. The interval is penetrated by 15 boreholes that provide stratigraphic and lithologic calibration of the morphometric analyses. The lithologic composition of the MTC-rich interval is claystone/mudstone-dominant with a few interbedded, thin sandstones. The identified kinematic indicators and geometric extent of the identified MTCs are a function of the local salt tectonics extrabasinal controls. The stratigraphic framework presented in this study constrains the timing of failures to a period of high sediment deposition related to a major increase of glacial input into the Quaternary Mississippi Fan. This study offers borehole-calibrated MTC morphometrics preserved in an MTC-dominant interval whose failure is triggered by local salt inflation, but ultimately it is a consequence of loading following increased sediment supply into the basin. The results from this robust data set build upon past integrated seismic-well studies that strive to improve the understanding of MTC processes and their implications in hydrocarbon exploration across salt sedimentary basins.