The geochemical data presented in this paper are first measurements of hydrocarbons (hexane fraction n-C15 to n-C34 and fatty acids, n-C10 – n-C26) using solvent-extraction procedure, high-resolution gas chromatography (GC) and GC-mass spectroscopy and isotopic ratios of organic carbon, nitrogen and sulfur in the sediments from Gulf of Cariaco. All the data are consistent for near-shore ocean sediments, with marine and non-marine sources for the organic matter.
The distribution of hydrocarbons reveals a resolved and an unresolved complex mixture of alkanes and cycloalkanes. No isoprenoid hydrocarbons (pristane and phytane; except for stations 5 and 31), were present. The CPI (20-32) was over 2.0 (station 5 with CPI = 1.57) and probably reflects a predominantly allochthonous biogenic source.
The GC and GC-MS data of fatty acids indicates homologous series whith maximum n-C14 (me-myristate) or n-C16 (me-palmitate) and n-C24 (me-lignocerate) or n-C26 (me-cerotate). The values of the CPI suggest a terrestrial biogenic input (plant wax). Pigments (chlorins and carotenes) were also detected in 68 to 90% of the FAME fraction, with CH2Cl2 solvent.
These geochemical data suggest that the organic matter in these sediments are derived from mixed autochthonous and allochthonous sources, which can be correlated with isotopic data (δ13C = -19.0 to -22.0‰, δ15N = 0.1 to 3.1‰; δ34S = -19.1 to -29.3‰).