Research about Mid-Atlantic Outer Continental Shelf

USGS1981

Update 2, February 1981: Outer Continental Shelf oil and gas activities in the Mid-Atlantic and their onshore impacts: A summary report, November 1979

The level of activity of oil and gas exploration on the Mid-Atlantic Outer Continental Shelf (OCS) has remained constant, with two drilling rigs operating during the period from June through December 1980. Gas flows in two wells were announced in November, but neither has been shown to be commercial at this time. A third lease sale in the Mid-Atlantic Region, Lease Sale 59, is scheduled to be held in December 1981. The proposed sale area is in deeper water, seaward of existing leased tracts. Recent drilling results and preliminary geophysical investigations indicate a greater potential for resources in this area than in the two earlier lease sale areas on the Mid-Atlantic OCS. Onshore impacts from OCS exploration during this period have remained minimal at the two support bases serving the Mid-Atlantic Region.

Mid-Atlantic Outer Continental Shelf↗

USGS1979

Hydrocarbon geochemical analyses of Mid-Atlantic Outer Continental Shelf sediments: an environmental assessment

Concentration levels of hydrocarbon in 122 composite mid-Atlantic shelf surface sediment samples have been examined during the second year (1976-1977) of the Bureau of Land Management environmental assessment program. The objective of this study was to establish baseline concentrations and provide data for the "natural variability" curve for the mid-Atlantic region. Concentration levels ( μ g/g) have been determined for the total lipids recovered by liquid column chromatography, and hexane-soluble fraction (aliphatics) benzene fraction (aromatics) as resolved by gas chromatography for each composite sediment sample. Several geochemical parameter values were also determined among which were: 1) n-alkane odd-even ratio; 2) isoprenoid alkane/ n-alkane ratio; 3) pristine/phytane ratio; 4) pristane/n-C 17 ratio; and 5) phytane/n-C 18 ratio. Summary analyses of the concentrations and geochemical 18 parameters are included in this report. Surface sediments examined from the mid-Atlantic shelf contained very low concentrations of resolved aliphatic hydrocarbons, less than 5.0 μ g/gm sediment, and very low concentrations of resolved aromatic hydrocarbons, usually less than 1.0 μ g/gm sediment. Mass spectral analyses of selected hexane eluates confirmed the presence of a series of normal aliphatic alkanes ranging from to n-C 16 to n-C 31 as well as the isoprenoids pristane and phytane. A series of three hydrocarbon peaks in the n-C 20 to n-C 21 range were tentatively identified as n-C 25 unsaturated, branched homologs, The aromatic fractions contained a number of polynuclear aromatics including phenanthrenes, methylphenanthrenes, fluoranthene and pyrcne, benzofluoranthene, and alkyl benzenes. Data accumulated in the second year of the program, coupled with data from the first year's investigations (Miller et al., 1977), have provided the basis for establishing a preliminary natural. "variability curve" for the hydrocarbon concentration levels and distribution in these selected mid-Atlantic shelf samples. This curve shows the seasonal variability noted in both the aliphatic and aromatic hydrocarbons in these samples.

Mid-Atlantic Outer Continental Shelf↗