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Nature of healing phase gravity flows overlying mass failures in salt diapiric basins: a case study in the Thunder Horse area, Gulf of Mexico Salt Province, The
AlHussaini, Abdulrahman M.
AlHussaini, Abdulrahman M.
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2025
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2026-11-11
Abstract
Submarine mass failures (MFs) have played a crucial role in the deep to shallow stratigraphic evolution of the Thunder Horse basin. The MF and associated deposits form the foundation for intervening healing phase top fill (HPTF) deposition. The uneven surfaces of MF top surfaces create complex topography through which turbidites must navigate and emplace. These HPTF turbidites can form large reservoir volumes within traps, with the top seal created by the overlying pelagic shales that blanket these deposits or, in some instances, with a top seal created by younger overlying mass failures, and lateral and basal seals formed by the underlying mass failure. In addition, these types of deposits form complex overburden scenarios for well completions.
An examination of six distinct healing-phase top-fill deposits of different ages within the Thunder Horse salt basin at shallow depths (approximately 0–1200 meters) was conducted using 3D seismic data and well log analyses. This investigation concluded that the material nature of the underlying MF (in-basin or beyond-basin sourced), the thickness of the underlying MF deposits, and the size and degree of emergence of rafted blocks from the underlying MF strongly influence the thickness, spatial distribution and the architecture of the basal HPTF deposits. Overlying HPTF deposits occur at multiple scales from small-scale filling of detailed MF top topography to the large-scale filling over the gross area of the mass failure. HPTF overlying in-basin sourced mass failures appear to be sandier than HPTF deposits overlying extremely large and extensive beyond-basin sourced mass failures, the later of which may be large enough to redirect turbidites away from their pre-emplacement depocenters.
A detailed interpretation of the HPTF overlying MF10 reveals that it is composed primarily of two systems: (1) debris flows; characterized by low amplitude, mottled seismic facies, showing arcuate tractionally-formed scour marks, and sourced from local diapiric uplifts, and (2) leveed channel systems; characterized by moderate-to-bright amplitude, surrounded in some instances by moderate-amplitude levee aprons. Channels arrange from high-density, sinuous channel braided networks to low-sinuosity bypass fairways. Detailed examination of the HPTF10 systems shows three north-south oriented fan complexes, each off-lapping to more westward locations in older to younger stacks. Log data through the oldest and most eastward fan show significant sands developed in these high-amplitude fans. Salt diapirs confine and pond fans along the southeastern edge of the study area, and debris flows interact with fan deposits to create stratigraphic traps.
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