Sigsbee Abyssal Plain Research Articles

A reconnaissance study of the Sigsbee knolls of the Gulf of Mexico

The positions and bathymetric profiles of three distinct knolls on the Sigsbee abyssal plain and seven knoll-like structures to the south-southwest on the continental rise are presented. These knolls, some with total surface relief of over 400 m, extend the region of reported knolls some 200 km farther to the south-southwest. The positions of all knolls reported to date are seen to trend approximately along an azimuth 15°. The occurrence of discrete ooids and oolitically coated pellets in the sediments obtained from an interknoll position on the continental rise is offered as proof of the occurrence of submarine slumping from the Campeche shelf. Chemical work performed on small black particles obtained in one core from a knoll indicated that these materials were of high molecular weight (> 500) and dominantly aliphatic hydrocarbons. The sediment veneer on the flanks and tops of the knolls differs from that of the abyssal plain; the former contains a much thicker interval of grayish-orange foraminiferal lutite.

Rate of Salt-Dome Growth: GEOLOGICAL NOTES

Small hills, 10-20 km. across, rise 150-350 m. above the Sigsbee abyssal plain in the Gulf of Mexico The abyssal plain received a thick layer of silty gray lutite during the Wisconsin sea-level lowering where as the knolls are covered primarily by foraminiferal ooze and calcilutite; thus they stood above the abyssal plain for the period of time exceeding that required to deposit their sediment column. By extrapolation beyond the maximum C l4 date in cores from the top of the knolls, at least 200,000 years is estimated as required for deposition of the top-capping sediments. At least 20 structures are present, called the Sigsbee Domes, and as investigated by the seismic reflection profiler, most do not reach the ocean floor, and are judged to be piercement salt domes. Each of the buried domes underlie small knolls on the sea floor; the observed rate of distortion calculated above for a knoll 200 m. high is about 1 m. per 1000 years or 1 mm. per year.