Evolution of Suprasalt Minibasins in the
Gulf of Mexico
Michael R. Hudec
Bureau of Economic Geology, The
The conventional explanation for minibasin subsidence is that it is driven by gravity—that minibasins exist because their fill is dense enough to sink into the underlying evaporites, expelling salt into the adjacent salt highs. This explanation is valid if the average density of the sediments is greater than the density of the salt, but it cannot account for subsidence of thin, less dense clastic sequences into salt. Seismic data show that many minibasins started sinking into salt when their siliciclastic fill was much thinner than the 1.5–2 km thickness necessary for compaction to invert the density contrast. For such minibasins, some mechanism other than gravity must be involved.
investigated mechanisms of minibasin subsidence using a 3,600-km2 pre-stack
depth-migrated 3D seismic dataset near the Sigsbee Scarp, northern
The specific cause of shortening that led to minibasin formation is currently unknown. The orientation of thrust structures is highly variable. Their pattern suggests that shortening was partitioned by flow boundaries defined at shallow levels within and above the salt sheet. If so, suprasalt processes may have been an important control.
AAPG Search and Discovery Article #90064©2006-2007 AAPG Distinguished Lecturers