Triple-oxygen isotopes of stony micrometeorites by secondary ion mass spectrometry (SIMS): Olivine, basaltic glass and iron oxide matrix effects for sensitive high-mass resolution ion microprobe-stable isotope (SHRIMP-SI).

Rationale: Micrometeorites are extraterrestrial particles smaller than ~2 mm in diameter, most of which melted during atmospheric entry and crystallised or quenched to form 'cosmic spherules'. Their parentage among meteorite groups can be inferred from triple-oxygen isotope compositions, for example, by secondary ion mass spectrometry (SIMS). This method uses sample efficiently, preserving spherules for other investigations.

Brief communication: New method for measuring nitrogen isotopes in tooth dentine at high temporal resolution.

Objectives: Nitrogen isotopes (δN) are widely used to study human nursing and weaning ages. Conventional methods involve sampling 1-mm thick sections of tooth dentine-producing an averaging effect that integrates months of formation. We introduce a novel protocol for measuring δN by multicollector secondary ion mass spectrometry (SIMS).

Fine-scaled climate variation in equatorial Africa revealed by modern and fossil primate teeth.

Variability in resource availability is hypothesized to be a significant driver of primate adaptation and evolution, but most paleoclimate proxies cannot recover environmental seasonality on the scale of an individual lifespan. Oxygen isotope compositions (δO values) sampled at high spatial resolution in the dentitions of modern African primates ( = 2,352 near weekly measurements from 26 teeth) track concurrent seasonal precipitation, regional climatic patterns, discrete meteorological events, and niche partitioning. We leverage these data to contextualize the first δO values of two 17 Ma individuals from Kalodirr, Kenya, from which we infer variably bimodal wet seasons, supported by rainfall reconstructions in a global Earth system model.

Lifetimes of interstellar dust from cosmic ray exposure ages of presolar silicon carbide.

We determined interstellar cosmic ray exposure ages of 40 large presolar silicon carbide grains extracted from the Murchison CM2 meteorite. Our ages, based on cosmogenic Ne-21, range from 3.9 ± 1.

Globally asynchronous sulphur isotope signals require re-definition of the Great Oxidation Event.

The Great Oxidation Event (GOE) has been defined as the time interval when sufficient atmospheric oxygen accumulated to prevent the generation and preservation of mass-independent fractionation of sulphur isotopes (MIF-S) in sedimentary rocks. Existing correlations suggest that the GOE was rapid and globally synchronous. Here we apply sulphur isotope analysis of diagenetic sulphides combined with U-Pb and Re-Os geochronology to document the sulphur cycle evolution in Western Australia spanning the GOE.