Temporal covariation of island arc Sr isotopes and seawater chemistry over the past 2 billion years.

The chemical compositions of island arc basalts (IAB) reflect contributions from the mantle as well as fluids and melts from the subducting slab. Addition of radiogenic seawater Sr to oceanic crust through hydrothermal alteration and subsequent subduction is often invoked to explain elevated Sr/Sr signatures in modern IAB. However, changes in the Sr/Sr of island arc magmatic rocks through time has not been investigated, limiting our understanding of the factors influencing the Sr budgets of arcs throughout Earth's history.

Isotopic clumping in wood as a proxy for photorespiration in trees.

Photorespiration can limit gross primary productivity in terrestrial plants. The rate of photorespiration relative to carbon fixation increases with temperature and decreases with atmospheric [CO]. However, the extent to which this rate varies in the environment is unclear.

The origin of carbonate mud and implications for global climate.

Carbonate mud represents one of the most important geochemical archives for reconstructing ancient climatic, environmental, and evolutionary change from the rock record. Mud also represents a major sink in the global carbon cycle. Yet, there remains no consensus about how and where carbonate mud is formed.

Nitrogen isotope evidence for expanded ocean suboxia in the early Cenozoic.

The million-year variability of the marine nitrogen cycle is poorly understood. Before 57 million years (Ma) ago, the N/N ratio (δN) of foraminifera shell-bound organic matter from three sediment cores was high, indicating expanded water column suboxia and denitrification. Between 57 and 50 Ma ago, δN declined by 13 to 16 per mil in the North Pacific and by 3 to 8 per mil in the Atlantic.

Neoproterozoic to early Phanerozoic rise in island arc redox state due to deep ocean oxygenation and increased marine sulfate levels.

A rise in atmospheric O levels between 800 and 400 Ma is thought to have oxygenated the deep oceans, ushered in modern biogeochemical cycles, and led to the diversification of animals. Over the same time interval, marine sulfate concentrations are also thought to have increased to near-modern levels. We present compiled data that indicate Phanerozoic island arc igneous rocks are more oxidized (Fe/ΣFe ratios are elevated by 0.