Application of biological markers in the recognition of palaeohypersaline environments

Abstract

In this study the saturated and aromatic hydrocarbon fractions of a marl sample from a Messinian (late Micoene) evaporitic basin located in the northern Apennines, and four oils, Rozel Point oil (Utah, USA; Miocene) and three seep oils from Sicily (Messinian), have been studied by GC with simultaneous FID and FPD detection and by GC-MS. All samples show characteristics which might be linked to hypersaline conditions prevailing during the time of deposition. Some of these characteristics are: a very low pristane/phytane ratio (22) and gammacerane and a series of extended hopanes and/or hop-17(21)-enes maximizing at C₃₅. The aromatic hydrocarbon fraction of all samples is dominated by organic sulphur compounds of which 2,3-dimethyl-5-(2,6,10-trimethylundecyl) thiophene is the most abundant compound. The suggestion of Meissner et al. (1984), that the source rock of Rozel Point oil was deposited under hypersaline conditions in a playa-like system, is supported by the organic geochemical characteristics of this oil.