Geochemistry

Sediment

Pristane

Geomorphology

Source rock

Mineralogy

China

Archaeology

Distribution (mathematics)

Developmental psychology

Carbonate

Geology

Phytane

Paleontology

Structural basin

Organic chemistry

Psychology

Mathematics

Geography

Environmental chemistry

Sterane

Marl

Mathematical analysis

Maturity (psychological)

Chemistry

Hopanoids

Hydrocarbon

Sedimentary depositional environment

Diagenesis

Organic Geochemistry

An unusual series of C22–C27 monounsaturated sterenes and C24–C30 tetracyclic terpanes (17,21-secohopanes) were detected in relatively high concentrations in an immature evaporitic marl sediment of the Jinxian Sag, Bohai Bay Basin, North China. The site of unsaturation in these novel sterenes is assigned tentatively to the D ring on the basis of mass spectral interpretation, which also distinguishes them from reported unsaturated sterenes. Other hydrocarbon biomarker or stable isotope characteristics are indicative of microbial (e.g. methyl hopanes), phytoplankton or higher plant (depleted δ13C values of isoprenoids and hopanes) inputs and an anoxic carbonate depositional environment (hexacyclic hopanes; tetracyclic terpanes). The hydrocarbon composition showed no obvious biodegradation and the relatively high concentration of unsaturated terpenoids (e.g. gammacerene) and low values of other established maturity parameters (Ts/Tm = 0.23; Ro = 0.44%; Tmax = 417 °C), are consistent with sediments of low maturity. The novel, low molecular weight sterenes and the tetracyclic terpanes may be early diagenetic products of microbial sources in a carbonate environment.

Distribution and significance of novel low molecular weight sterenes in an immature evaporitic sediment from the Jinxian Sag, North China