The Archean-Proterozoic transition is characterized by the widespread deposition of organic-rich shale, sedimentary iron formation, glacial diamictite, and marine carbonates recording profound carbon isotope anomalies, but notably lacks bedded evaporites. All deposits refl ect environmental changes in oceanic and atmospheric redox states, in part associated with Earth’s earliest ice ages. Time-...

Reconstructing vegetation at hominin fossil sites provides us critical information about hominin palaeoenvironments and the potential role of climate in their evolution. Here we reconstruct vegetation from carbon isotopes of plant wax biomarkers in sediments of the Nachukui Formation in the Turkana Basin. Plant wax biomarkers were extracted from samples from a wide range of lithologies that inc...

Stable carbon isotope analyses have shown that South African australopiths did not have exclusively frugivorous diets, but also consumed significant quantities of C4 foods such as grasses, sedges, or animals that ate these foods. Yet, these studies have had significant limitations. For example, hominin sample sizes were relatively small, leading some to question the veracity of the claim for au...

The globalization of food production and distribution has homogenized human dietary patterns irrespective of geography, but it is uncertain how far this homogenization has progressed. This study investigated the carbon and nitrogen isotope ratios in the scalp hair of 1305 contemporary Japanese and found values of -19.4 ± 0.6‰ and 9.4 ± 0.6‰ (mean ± SD), respectively. Within Japan, the inter-reg...

Several stable isotope ratios have been measured in human skeletons to determine prehistoric diet. These include the isotopes of nitrogen, sulphur and strontium, which have been used to assess the importance of marine foods in human diets. The systematics of these isotopes in food chains are imperfectly understood, whereas that of carbon is quite well-known. Stable carbon isotope ratios (i.e., ...

The best-documented example of rapid climate change that characterized the so-called 'greenhouse world' took place at the time of the Palaeocene-Eocene boundary: introduction of isotopically light carbon into the ocean-atmosphere system, accompanied by global warming of 5-8 degrees C across a range of latitudes, took place over a few thousand years. Dissociation, release and oxidation of gas hy...

The natural abundance of stable carbon isotope values (δ13C) of organic matter of marine macroalgae collected from Taiwan and its offshore islands (Penghu Islands) were analyzed in this study. These values ranged from -10.5 to -29.5‰. The highest δ13C value came from green algae (-10.5‰), Ulva pertusa while most algae exhibited values in the -14 to -19‰ range. On average, the δ13C values of red...

Microcosm experiments were conducted to quantify carbon isotope fractionation during aerobic biodegradation of n-alkanes (from C3 to C10) and monoaromatic hydrocarbons in unsaturated alluvial sand. In single compound experiments with n-alkanes, the largest enrichment factor was obtained for propane ( 10.8 ± 0.7‰). The magnitude of the enrichment factor decreased with increasing number of carbon...

The molecular orbital model of hyperconjugation was utilized in rationalizing some long range interactions in carbocations. Conveniently such interactions can be detected by measuring secondary · kinetic deuterium isotope effects. Hilckel's 4n + 2 rule can be extended to interactions between the cationic center and pseudo-:n: orbitals of CH3, CH2 and CH groups respectively. Thus, in analogy to ...

The Palaeocene-Eocene thermal maximum (PETM) is characterized by a global negative carbon isotope excursion (CIE) and widespread dissolution of seafloor carbonate sediments. The latter feature supports the hypothesis that the PETM and CIE were caused by the rapid release of a large mass (greater than 2000Gt C) of 12C-enriched carbon. The source of this carbon, however, remains a mystery. Possib...