96-7 Quantifying the influence of Diapir Relief on Deepwater Geomorphology Using Quaternary Analogues in the Deepwater Gulf Basin

Session: Twenty-Seven Years of Advances in Understanding Salt-Sediment Interaction: A Legacy of Katherine A. Giles

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Halokinetic Sequences (HS) and Minibasin Tectonostratigraphic Sequences (MTS) are sequences recognized in salt basins which form due to the interplay between sedimentation rates, diapir rise rates, and minibasin subsidence rates. Outcrop and seismic investigations show that the geometry of a sequence is controlled by the qualitative ratio of sediment accumulation to salt movement but have not yet explored quantitatively how salt topography and slope relative to an adjacent minibasin influence HS/MTS morphology and the behavior of nearby submarine systems. This study uses public bathymetry and seismic data visualized in open-source GIS and seismic interpretation software to quantify diapir relief and distance to depositional system axis across the deepwater Gulf Basin. Proto-HS and proto-MTS are interpreted adjacent to studied diapirs and integrated with bathymetric and geomorphology data to understand how salt bodies impact adjacent depositional systems. Initial results show that intrabasinal mass transport deposits (MTDs) can occur near salt bodies with >450m relief relative to the adjacent minibasin floor. They were found within wedges that thin towards the diapir with roofs ranging in thickness from 490 – 1,300m.  In contrast, the majority of studied deepwater channels occurred near salt bodies with relief less than 450m relative to the adjacent minibasin. Within proto-Hook HS/Tabular Composite Halokinetic Sequences (CHS), adjacent diapir roof thickness was relatively consistent over the diapir, under 500m thick, and the distance from edge of salt to adjacent depositional system axis was over 2,000m. Within a diapir-influenced proto-Wedge HS/Tapered CHS, the adjacent diapir roof thickened towards the minibasin, was greater than 500m thick and the distance to adjacent depositional system axis was less than 2,000m. When observed within a minibasi- influenced proto-MTS, diapir roof thickness varied and distance to depositional system axis ranged from 4,000m to 10,000m. Our results support the application of HS/MTS to interpret salt-sediment interactions. Quaternary variations in diapir roof thickness and distance to adjacent depositional system axis appear to match salt-sediment interactions predicted by HS/MTS theory. Our data further constrain the conditions under which diapir-derived intrabasinal MTDs may occur and how far they may extend into the adjacent minibasin. These modern quantitative values are critical for applying HS and MTS theory to outcrop and subsurface data when interpreting ancient depositional systems, basin evolution, and paleogeography.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9588

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