Hydrocarbons in 60 northeast Gulf of Mexico shelf sediments: a preliminary survey
Abstract
Hydrocarbon results from gas chromatography of 60 recent sediment and 10 benthic algae samples delineate two distinct shelf environments in the northeastern Gulf of Mexico. Sediments off Florida (shell hashes and sands) have moderate amounts of lipids/total sediment (average 113ppm ± 80%) but low hydrocarbon levels (average 3.06 ppm ± 41%). Aliphatic hydrocarbons are dominated by a series of branched or cyclic, unsaturated C 25 isomers. The major n-alkane is n- C17. The n-alkane and isoprenoid patterns are consistent with a marine hydrocarbon source. Sediments closer to the Mississippi River (silts and clays) contain large amounts of lipids (average 232 ppm ± 53%) and hydrocarbons (average 11.7 ppm ± 55%) to total sediment. Aliphatic hydrocarbons are mainly odd carbon number high molecular weight n-alkanes, indicating a terrigenous hydrocarbon source. Isoprenoids are present in greater abundance than in sediments off Florida ( n- C17/ pristane and n- C18/phytane ratios ~2 to 3). Relatively large amounts of n- C16, together with an even distribution of n-alkanes in the range C 14-C 20 and a substantial unresolved envelope all point to a fossil fuel input to the Mississippi samples. Samples off the Alabama coast show intermediate characteristics.
- Publication:
-
Geochimica et Cosmochimica Acta
- Pub Date:
- September 1976
- DOI:
- 10.1016/0016-7037(76)90043-0
- Bibcode:
- 1976GeCoA..40.1005G