Ultra-depleted hydrogen isotopes in hydrated glass record Late Cretaceous glaciation in Antarctica.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 36071035.
- Also identified by DOI 10.1038/s41467-022-32736-9 and PMC identifier 9452555.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The Early Jurassic Butcher Ridge Igneous Complex (BRIC) in the Transantarctic Mountains contains abundant and variably hydrated silicic glass which has the potential to preserve a rich paleoclimate record. Here we present Fourier Transform Infrared Spectroscopic data that indicates BRIC glasses contain up to ~8 wt.% molecular water (H<sub>2</sub>O<sub>m</sub>), and low (<0.8 wt.%) hydroxyl (OH) component, interpreted as evidence for secondary hydration by meteoric water. BRIC glasses contain the most depleted hydrogen isotopes yet measured in terrestrial rocks, down to δD = -325 ‰. In situ <sup>40</sup>Ar/<sup>39</sup>Ar geochronology of hydrated glasses with ultra-depleted δD values yield ages from 105 Ma to 72 Ma with a peak at c. 91.4 Ma. Combined, these data suggest hydration of BRIC glasses by polar glacial ice and melt water during the Late Cretaceous, contradicting paleoclimate reconstructions of this period that suggest Antarctica was ice-free and part of a global hot greenhouse.