Fill, Strip and Spill model of minibasin sedimentation, Mad Dog area, Gulf of
Mexico
Salt tectonism is the primary control on topography of minibasins in the Mad Dog
area of the southeastern Gulf of Mexico. However, modern maps of the salt surface
cannot be used to infer paleosediment transport direction or define locations of fill
and spill because of the dynamics of salt mobility. Stratigraphic relationships and 3D
seismic geomorphology are used in the Mad Dog area to illustrate how fill-and-spill
depositional processes occur within ponded-basin accommodation space. Two major
periods of salt movement have been documented that influence basin geometry and
processes, one occurring xxxxx and the other occurring xxxx., both resulting in
minibasin evolution from ponded, partly ponded, to bypass facies assemblage. During
ponding, the salt wall is sufficiently high, and the basin captures all sand-rich,
mud-rich components of the turbidity currents. However, during phases of partial
ponding by a topographically low sill, the process of ‘‘fill and spill’’ is not to form a
channel that cuts deeply through successive ridges and fills in successive basins, as
has been proposed by other authors. Rather, it is to overtop the obstacle (Rottman et
al., 1985) and instigate a process of flow stripping as a sheet flow and not as a point
source. MTCs occur both in ponded and partly ponded assemblages, but do not appear
to derive from minibasin flanks, and must have originated farther updip on the
continental slope. The partially ponded phase is followed by bypass and development
of a localized truncation surface formed by erosion of the upslope basin as the
equilibrium profile adjusts to the downslope basin. Muddy turbidites or hemipelagic
deposits drape the erosion surface of the minibasin. Large submarine canyons develop
only after basins have become filled.