C27–C30 neohop-13(18)-enes and their saturated and aromatic derivatives in sediments: Indicators for diagenesis and water column stratification

Environmental conditions in the South Atlantic (Angola Basin) during the Early Cretaceous

“…The presence of PMI and lycopane supports the conclusion that the sediments and/or water column were anoxic/euxinic during the Early Cretaceous. Lastly, the presence of 28,30-bisnorhopane in these (immature) sediments further indicates anoxic depositional conditions (Katz and Elrod, 1983;Sinninghe Damsté et al, 2014). The results are in agreement with Simoneit (1978) who, based upon a low Pr/Ph ratio and abundance of porphyrin pigments in one Aptian sample, proposed that the Aptian organic-rich sapropels were deposited under anoxic conditions.…”

“…Although the overall boundary between anoxic, intermediate and oxic surface waters in the Angola Basin, based on sedimentological evidence, was proposed to have been around 300-400 m palaeo water depth (Zimmerman et al, 1987), the presence of isorenieratane suggests that euxinic conditions episodically reached the photic zone (likely < 100 m water depth) in the Angola Basin during the Early Cretaceous (Sinninghe Damsté et al, 1993b;Koopmans et al, 1996). The presence of aromatic hopanoids supports the idea that the palaeowater column of the Angola Basin was anoxic and stratified during the Early Cretaceous (Sinninghe Damsté et al, 2014). Although we only investigated the free biomarker fraction and part of the total abundance of isorenieratene (derivatives) is likely sulfur-bound (Kohnen et al, 1991), the relative abundance of isorenieratane (as well as the concentrations of TOC and S) indicates that euxinia was the most intense in during the early stages of basin opening.…”

“…6), assigned from published relative retention times and mass spectra (Koopmans et al, 1996). Aromatic hopanoids, assigned from their relative retention times and mass spectra (Greiner et al, 1976(Greiner et al, , 1977Sinninghe Damsté et al, 2014), were also present in all samples. Similar to the series of n-alkyl and isoprenoid thiophenes in the apolar fraction, the aromatic fraction contained 2-alkyl,5-methyl-to 2-alkyl,5-pentylthiolanesas well as isoprenoid thiolanes (base peak m/z 87, 101, 115, etc.…”

Spatial extent and degree of oxygen depletion in the deep proto‐North Atlantic basin during Oceanic Anoxic Event 2

“…Based on our paleoredox proxies, we conclude that there were large spatial differences in the degree of oxygen depletion during the event (Figure ). Anoxia and euxinia were particularly severe in the southern part of the basin, where bottom waters were already euxinic before OAE2 (Figure ), in perfect agreement with the isorenieratene derivatives and other biomarker proxies [ Sinninghe Damsté et al ., ]. In contrast, the bottom waters of the northern part of the deep proto‐North Atlantic were not anoxic prior to and after OAE2, and were intermittently anoxic during a major part of the event (Figure ).…”

Factors controlling the petroleum generation characteristics of Palaeogene source rocks in the Austrian Molasse Basin as revealed by principal component analysis biplots

“…Accordingly, the 17α-diahopane which is normally correlated with oleanane (Li et al, 2009) is enriched only in the lower part of the Schöneck Formation ( Figure 7A). In addition, unsaturated biomarkers, e.g., norneohop-13(18)-ene and olean-13(18)-ene, can be identified based on retention times and fragment mass information (Curiale and Bromley, 1996;Sinninghe Damsté et al, 2014). The concentrations of tricyclic terpanes are generally low in all samples, because they are not readily released from the kerogen at this level of maturity (Seifert and Moldowan, 1978).…”