Evidence for gammacerane as an indicator of water column stratification

Abstract

Abstract-Anew route for the formation of gammacerane from tetmhymanol is proposed; in addition to dehydration and hydrogenation, sulphurisation and early C-S cleavage are shown to be important in the pathway of formation, especially in marine sediments. Evidence is twofold. First, relatively large amounts of the gammacerane skeleton are sequestered in S-rich macromolecular aggregates formed by natural sulphurisation of functionalised lipids.

Geochemical application of tricyclic and tetracyclic terpanes biomarkers in crude oils of NW China

“…The gammacerane precursor is tetrahymanol (XV) found in hypersaline palaeoenvironments in Green River shale (Henderson and Steel, 1971). More recently, gammacerane is commonly considered to be of tetrahymanol origin which occurs in saline waters (Fu and Sheng, 1989;Sinninghe Damste et al, 1995;Yu et al, 2011).…”

Paleosalinity significance of occurrence and distribution of methyltrimethyltridecyl chromans in the Upper Cretaceous Nenjiang Formation, Songliao Basin, China

“…Because only some samples in the dataset have a Pr/Ph value <0.8, the Pr/Ph ratio in this study is taken as suggestive of redox conditions. Gammacerane is widely regarded as an empirical indicator of paleosalinity, and possibly a marker for photic zone anoxia (ten Haven et al, 1985(ten Haven et al, , 1988Moldowan et al, 1985;Sinninghe Damsté et al, 1995;Schwark et al, 1998), as it is considered to originate from tetrahymanol in bacterivorous ciliates living at the boundary of an enhanced salinity water layer, with an upper layer of less saline water. Salinity stratification implies circulation restriction and possibly temperature stratification, which in turn causes an enhancement of redox stratification in the water body.…”

Paleoenvironmental reconstruction of the Late Santonian Songliao Paleo-lake

“…Based on the δ 13 C values of hopanes, Wang et al (2015b) proposed that chemoautotrophic and methanotrophic bacteria were abundant during the deposition of K 2 n 1 + 2 . Gammacerane is generally considered to be derived from tetrahymanol, which originates from a type of bacteria-consuming ciliate living in the interface of the chemocline, and therefore, it is widely regarded as an indicator of a stratified water column and possible marker for photic zone anoxia (Sinninghe Damsté et al, 1995;Peters et al, 2005). The presence of gammacerane in samples from Lower K 2 n 2 indicates that the water column was stratified and the depositional environment was likely anoxic, and agrees with the relatively low Pr/Ph values.…”