Published in Organic Geochemistry
Glycerol dialkyl glycerol tetraethers (GDGTs) are membrane lipids of high molecular weight and include the isoprenoid GDGTs (iGDGTs) produced by Archaea and the branched GDGTs (brGDGTs) produced by unknown bacteria. Several indices have been developed to describe the relationship between GDGT distribution and environmental parameters: the TEX86 (te...
Published in Organic Geochemistry
We analysed leaves from 42 plants from the South African Succulent Karoo. Whole leaf δ13C values clearly differentiated 3 different populations, consisting of plants operating under obligate CAM (crassulacean acid metabolism), facultative CAM and C3 modes. In contrast, the leaf wax n-alkane δ13C data from these metabolic groups showed a broader ove...
Published in Organic Geochemistry
The environmental controls on leaf wax n-alkane distributions and associated interpretation of such distributions in geological archives have long remained rather enigmatic. Studies of contemporary vegetation often conflate changing environmental conditions and species differences between biomes, making it difficult to assess the extent to which va...
Published in Organic Geochemistry
The addition of biomass-derived black carbon or biochar to agricultural soils is attracting attention as a means for sequestering carbon and as a potentially valuable method for improving soil fertility. Recent research has shown, however, that biochar is not completely unreactive in soil as it potentially enhances microbial activity, adsorption of...
Published in Organic Geochemistry
A litterbag method was used for studying the variability in chemical and carbon isotopic compositions of four grasses during litter decomposition. After the 300d degradation, >90% of litter mass was lost for three C4 species (Setaria viridis, Eleusine indica, Amaranthus retroflexus) and one C3 species (Erigeron speciosus). The solid state 13C NMR s...
Published in Organic Geochemistry
Large amounts of solid bitumen occur in the Honghuayuan Formation of the Lower Ordovician (O1h) within the Majiang paleo-reservoir. Most of the potential source rocks and solid bitumens in the Southern Guizhou Depression are of high maturity (%Ro>2). Consequently, the yields of extractable organic matter (EOM) from the potential source rocks and so...
Published in Organic Geochemistry
Hopanoids are pentacyclic triterpenoids commonly found in soils and sediments and are used as biomarkers for recent or past bacterial communities. While hopanes are the ultimate degradation products of bacteriohopanepolyols (BHPs), only a few BHPs, such as 32,35-anhydrobacteriohopanetetrol (anhydroBHT), have been identified as early diagenetic degr...
Published in Organic Geochemistry
Upper Paleozoic natural gas in the Ordos Basin is typical coal-associated gas. Natural gases in Sulige, Yulin and Zizhou gas fields were systematically analyzed in this study. Based on the hydrogen isotopes of CH4, C2H6 and C3H8 components in natural gases, and combined with the natural gas compositions and carbon isotopes and fluid inclusions homo...
Published in Organic Geochemistry
Organic geochemical assessment of seep oil from the Upper Ordovician (Hirnantian) Boda Limestone and solid bitumens from the Middle Ordovician (Darriwilian) limestone formations in the Siljan Crater, Sweden indicates their generation primarily from peak oil window maturity, clay-rich marine source rocks that contained aquatic algal organic matter a...
Published in Organic Geochemistry
Past environmental changes were frequently accompanied by changes in fire regimes. However, the extent to which the residue of ancient fires (black carbon, BC) is abundant in Pleistocene palaeosols remains largely unknown, and whether, and to which degree its occurrence and composition relates to pedogenetic processes and palaeoenvironmental change...
