![]() These were used as inputs and "targets" for numerical modeling to simulate the features. One goal of the field program was to acquire adequate data to characterize seafloor mass gravity flow features and deposits. The fieldwork also included a program of navigated deep piston-cores and box cores, along with video observations from an ROV. These were used to plan a comprehensive program of bottom surveying with an autonomous underwater vehicle (AUV). Maps of mass gravity flow features, sources, and flow paths were developed. To accomplish these goals, there was extensive use of previously collected seismic exploration data that included seafloor bathymetric images and shallow reflection amplitudes. The goals of these evaluations were to: 1) catalog the varieties of mass gravity flows that have occurred in the past, 2) understand the causes of these events, 3) characterize the kinematics (e.g., speeds, dimensions) of these flows, and 4) portray the relative magnitudes of the spatially dependent exposures to possible future events. Accordingly, a multidisciplinary team conducted an evaluation of these features as part of an overall study of geohazards. There are many seafloor features on and near the base of the Sigsbee Escarpment that were formed as the result of mass gravity flows. ![]() The unprecedented detail of the data sets in the Mad Dog and Atlantis field areas allows a detailed kinematic model to be developed for the Sigsbee Escarpment, and an improved assessment of the geohazards. Deeper seated slumps may be related to retrogressive failure facilitated by internal overpressures. These dip slope conditions control the slumping in the shallow-seated slope failure portions of the escarpment at both the southwest Mad Dog and northeast Atlantis field areas. We differentiate among fault systems and slope failures of different origin and relate these differences to seafloor geomorphic provinces and variation in the geometry and movement history of salt.īoth normal faults in the supra-salt section, and seaward dipping beds above the frontal salt monocline, can provide pre-existing and preferential failure planes for slumping at the escarpment front. There are two primary modes of slope failure on the escarpment face: shallow-seated, small-scale slumping, and deeper-seated, amphitheater-shaped failures. We show that these differences are due to a combination of salt morphology, supra-salt stratigraphy, and faulting. On the seafloor, bathymetric data show distinct domains characterized by contrasting seafloor textures including dramatic differences in the style of seafloor slumping. Exploration 3D, high-resolution 2D and 3D seismic data, autonomous underwater vehicle data (bathymetry, side-scan, sub-bottom profiling), piston cores, boreholes, and remotely operated vehicle observations all provide information regarding the seafloor and subsurface geologic setting, and, in particular, the role that salt tectonics plays in creating, or modifying, the observed geologic features. Understanding the role of salt tectonics, and its control of the shallow geologic setting of the Sigsbee Escarpment, is critical to evaluating the shallow geohazards of these fields. The interaction of salt and sediment at the Sigsbee Escarpment controls the geohazard environment at the Mad Dog and Atlantis fields development areas.
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