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

Abstract

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.