Systematic Lithologic Characterization of Neogene Mass-Transport Deposits, Mississippi Canyon of the Northern Gulf of Mexico, U.S.A.

Abstract

Few publications have attempted systematic lithologic characterization of Mass Transport Deposits (MTD’s), usually as a byproduct of field development. While the principal motivation for further understanding these slope failure deposits are driven by the economics of deep-water hydrocarbon exploration, the geoharzards related risks of tsunamis and shallow gas also provide a stimulus for research. The Mississippi Canyon of the Northern Gulf of Mexico is one of the few basins with the necessary density of seismic and well data to effectively investigate the variable lithology throughout a MTD–rich continental margin.

The proposed hypothesis evaluates: 1) differences between attached and detached MTDs in the Neogene Northern Gulf of Mexico through seismic analysis, 2) areal variations of MTD external dimensions in relation to depositional age throughout the northeastern and northcentral Gulf of Mexico, and 3) differentiation between sand-prone and shale-prone MTD’s in relation to associated regional structural and depositional trends through integration of well-based information and seismic characterization.

This study attempts lithologic calibration of MTDs in Pleistocene–Miocene strata of the study area through integration of seismic observations and lithologic related information extracted from logs, mud logs (cuttings), pressure, and available core data to further constrain the distribution of MTD types, lithology, and geometries throughout the study area. Work is focused in supra-salt basins that have the highest seismic data quality.

Initial seismic to well-ties and biostratigraphy underpin the primary stratigraphic framework throughout the survey. Focus of analysis nicely constrains an interval between GBDS chronostratigraphic units PS (70 Ky, Late Pleistocene) through PTA, PAB, PL1, PGa to PB1 (4.45 Ma, Early Pliocene). Numerous erosional features and unique internal seismic anomalies are observed within mapped seismic packages. Working interpretations reflect a variable of seismic responses to the presence of sand and shale (constrained by wells) with contrasting geometries of the MTD geobodies. Comparison of different seismic facies within MTDs can improve understanding of seismic character and related lithologic facies, while also constraining potential uncertainties related to reservoir quality and seal integrity. This approach can stand as an analog for similar areas with much less well control, such as Mexican part of the Gulf of Mexico deepwater.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018