Most petroleum arises from the thermal alteration of organic matter in fine-grained
sedimentary rocks. The time–temperature conditions of petroleum formation have been …

Despite many investigations concerning the insoluble organic matter in sediments
(kerogen), its chemical nature and origin are only poorly understood. Here we report the …

The origin of the organic matter in carbonaceous meteorites remains controversial despite
extensive study1–4 over the past 20 yr. Motivated by the expectation that the patterns of …

Abstract THE Proterozoic aeon (2,500-540 million years ago) saw episodic increases in
atmospheric oxygen content1, the evolution of multicel-lular life2, 3 and, at its close, an …

Ocean anoxic events were periods of high carbon burial that led to drawdown of
atmospheric carbon dioxide, lowering of bottom-water oxygen concentrations and, in many …

Although the notion of an early origin and diversification of life on Earth during the Archaean
eon has received increasing support in geochemical, sedimentological and …

The determination of osmium content and isotopic abundances in geological materials has
received increasing attention in recent years following the proposal of Alvarez et al. 1 that …

Molecular fossils of biological lipids are preserved in 2700-million-year-old shales from the
Pilbara Craton, Australia. Sequential extraction of adjacent samples shows that these …

WATER (and hydroxyl, OH) plays an important part in determining the properties of minerals
and melts in the Earth's upper mantle. The main hydroxyl-bearing phases found in rocks …

Isotopic variations in oceanic igneous rocks provide important constraints on models of
oceanic mantle structure. Of particular interest is the global negative correlation between …