The identification of mono-, di- and trimethyl 2-methyl-2-(4,8,12-trimethyltridecyl)chromans and their occurrence in the geosphere

Stable carbon isotope compositions of isoprenoid chromans in Cenozoic saline lacustrine source rocks from the Western Qaidam Basin, NW China: Source implications

“…The identification of the MTTC compounds was undertaken by comparing the mass spectra with published mass spectrometry characteristics for MTTCs ( (Table 2), which is consistent with other saline lacustrine deposits [2,[5][6][7].…”

“…High concentrations of CO 2 can decrease the carbon isotope fractionation during carbon assimilation by primary biomass, resulting in the 13 Cdepleted MTTC compounds that may be produced by the microalgaes in this niche. Sinninghe Damsté et al [2] initially thought the δ-MTTC-producing biomass was located in the bottom water with salt leaking from the sediments, and, consequently, the non photosynthetic bacteria were ascribed as the biological sources of MTTC. As shown in Figure 4, the α-MTTC/δ-MTTC values are closely correlated with the gammacerane index, which indicates the influence of water column stratification on the distributions of various MTTC compounds.…”

“…aromatic terpenoids from higher plants, aromatic steroids, methyl-phenanthrene, alkylated naphthalene, and aromatic isoprenoids compounds), have been widely used as indicators of organic source, depositional environments and the thermal maturity of organic matter. In particular, a series of methylated isoprenoid chroman compounds (methylated 2-methyl-2-(4,8,12-trimethyltridecyl) chromans (MTTCs)) present in aromatic fractions, have been given considerable attention because of their application to water paleosalinity evaluation [1][2][3][4][5][6][7][8][9][10]. The MTTCs can be regarded as dehydroxy products of tocopherol.…”

“…Although methylated MTTCs are structurally related to tocopherol, they are unlikely to originate from tocopherol during diagenesis on chemical grounds [2]. Sinninghe Damsté et al [2] found abundant δ-MTTC in a stratified hypersaline water body, and initially ascribed non photosynthetic bacteria as the biological sources of MTTCs.…”

“…Sinninghe Damsté et al [2] found abundant δ-MTTC in a stratified hypersaline water body, and initially ascribed non photosynthetic bacteria as the biological sources of MTTCs. After further investigation, Sinninghe Damsté et al [6] provided an alternative suggestion of photosynthetic organisms in the upper part of the water column as the sources of MTTCs based on a molecular geochemistry study of organic matter from marl in the Oligocene Mulhouse Basin.…”