Salt tectonics, stratigraphy, and gas hydrates assessment of pliocene-to-holocene sediment gravity flows at Mississippi Canyon 118 (mc-118), Gulf of Mexico

Methane hydrates on continental shelves are the subject of extensive investigation, both as a potential energy resource as well as a possible contributor to global climate dynamics. Gas hydrates occurrences in the Gulf of Mexico are typically found in association with petroleum systems, and present a natural laboratory to examine the complex interplay of salt tectonics, sedimentation, and hydrate formation and dissociation.;The complexity of the factors controlling gas hydrates occurrence, stabilization and disassociation in the Gulf of Mexico motivate us to conduct a comprehensive geoscientific investigation, at OCS-Block MC-118 in the Gulf of Mexico, to provide better understanding of these compounds in complex geologic settings. OCS-Block MC-118 is located 128 miles southeast of New Orleans on the middle slope in ∼2600 ft of water.;Integrated tectono-stratigraphic interpretation at MC-118 using 3D seismic, well logs, piston cores and biostratigraphy reveals an area dominated by allochthonous salt and its related structures. It also shows a dynamic fluid flow system and a series of mass transport complexes in muddy Quaternary sediments.;Structurally the area is divided into three domains based on their structural styles. These structural domains are genetically-and-kinematically related to the salt structure and extend beyond MC-118 boundaries. The salt structure is part of a larger regional structure, eastern Gulf of Mexico, which involves some amalgamation between small-scale salt canopies and salt diapirs although collectively they appear mostly disconnected.;A Pliocene (3.13-4.95 Ma) third-order genetic stratigraphic sequence, the focus of this study, is as much as ∼3600 ft thick within the mini-basins and contains: muddy mass transport complexes; sandy slope fans; muddy turbidites and condensed sections; and transitional facies flanking the salt structure that collectively have ponded and wedged external geometries. The other part of the stratigraphic analysis, which is focused in post-Pliocene sediments, indicates two large muddy-rich mass transport complexes floored and capped by sequence boundaries and maximum flooding surfaces. Their genesis is explained as a series of retrograded slope failures caused by slope instability associated with salt tectonics rather than the common gas hydrates disassociation hypothesis.;Qualitative geophysical analysis reveals a dynamic fluid flow system composed of: pockmarks, chimneys, patches, and bottom simulating reflectors (brs). These acoustic elements appear in response to a vertically focused thermogenic-and-biogenic gas migration through an effective structural network composed of normal faults and fractures.