The nature and location of gassy sediment sections in the continental shelf and slope in the northwestern Gulf of Mexico
In the northwestern Gulf of Mexico continental shelf and upper slope gassy sediments are a pervasive phenomena and an important consideration relative to engineering and acoustic activities on the sea floor. An examination of seismic data from over a thousand M.M.S. geohazard reports and core logs of 1,670 foundation boreholes drilled to an average subbottom depth of 125 m on the continental shelf and upper slope in the northwestern Gulf, has revealed that gassy sediment sections are most abundant near the Mississippi River Delta, in the sediment fill of buried stream channels that were eroded during the early and late Wisconsinan, and in Miocene and Plio-Pleistocene depocenters on the continental shelf and upper slope. Out of the 1,670 bore holes examined 1,158 (68%) contained indications of gassy sediments most of which is of biogenic origin. Large patches of gassy sediments exist, some exceeding 10 km in size but most are less than 500 m. The examination of 500 piston cores, up to 40 meters in length, taken on the mid and lower continental slope areas were almost void of gassy sediments as the result of the halokeiesis of allocthonous salt.