Systematic lithologic characterization of Pleistocene mass-transport deposit, Mississippi Canyon of the Northern Gulf of Mexico, USA




Gutierrez, Mario Andres

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Few publications have attempted lithologic calibration of mass transport deposits, (MTDs), usually in the course of field descriptions. While the principal motivation for further understanding these slope failure deposits are driven by the economics of deep-water hydrocarbon exploration, geohazards related risks of tsunamis, and shallow gas, which also provide a driving concern for these deposits. Such risks can be mitigated and prevented by in depth analysis of slope stability and failure. The Mississippi Canyon of the Northern Gulf of Mexico is one of the few basins with sufficient density of seismic and well data to effectively approach constraining lithology throughout a MTD–rich continental margin. The proposed hypothesis evaluates: 1) geometric extents of morphodomains in relationship to depositional age throughout a specifically identified MTD by identification of kinematic indicators, seismic characterization, and well log calibration, 2) the potential extrinsic and intrinsic failure mechanisms of an identified MTD and their relation of their roles with the Attached & Detached MTD categorization of Moscardelli & Wood (2016) through seismic characterization, and 3) differentiation of potential sandstone and shale prone distributions of an identified MTD within the morphodomains through well log calibrated seismic characterization. The Northern Gulf of Mexico is a data-rich study area, with over 500,000 wells drilled and numerous surveys of high quality seismic reflection data. The Gulf Basin Depositional Synthesis (GBDS) Project at the UT Institute for Geophysics compiles this well related data (logs, lithology, biostratigraphy, pressure, etc). For this study, a large 3D seismic survey is located in the Northern Gulf of Mexico (TGS - Mississippi Canyon Revival) is available for high quality imaging and interpretation. This study will integrate observations of lithologic and seismic characterizations of the identified Pleistocene the Ursa MTD through integration of seismic observations (focused in the supra-salt, which have the highest seismic data quality) and lithologic related information extracted from logs curves and mudlogs, to further constrain geometric parameters and lithology throughout the study area in Mississippi Canyon, Gulf of Mexico. Initial well-ties and biostratigraphically defined surfaces constitute the primary stratigraphic framework throughout the survey. The focus of analysis constrains an interval between GBDS deposodes PS (.17 MA, Late Pleistocene) through PTA (0.5 Ma), PAB (1.33 Ma), PL1 (2.8 Ma), to PGa (3.1 Ma, Early Pliocene). Erosive features and a large distribution of internal seismic characteristics are observed within identified geobody. Working interpretations reflect a variance of seismic character responses to kinematic indicators that define three domains (Headwall, Transitional, and Toe) and direction of mass wasting of the MTD geobody. The lithologic calibration of the Ursa MTD will improve understanding of seismic character and lithologic implications in relation to seal/reservoir quality uncertainties and failure mechanism source. Additionally, this approach provides an analog to other similar areas with much less well control, such as the southern Gulf of Mexico. It can also serve as a predictive tool throughout this less well understood part of the Gulf of Mexico.


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