Geochemical fingerprints of glacially eroded bedrock from West Antarctica: detrital thermochronology, radiogenic isotope systematics and trace element geochemistry in Late Holocene glacial-marine sediments

• Published in: Earth-Science Reviews
• Main Authors: Pereira, Patric Simões, van de Flierdt, Tina, Hemming, Sidney R., Hammond, Samantha J., Kuhn, Gerhard, Brachfeld, Stefanie, Doherty, Cathleen, Hillenbrand, Claus-Dieter
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2018
• Subjects: Antarctic; The Antarctic; Antarctic Peninsula; West Antarctica; Amundsen Sea; West Antarctic Ice Sheet; Bellingshausen Sea; Pacific; Hobbs; Wrigley; Sulzberger Bay; Hobbs Coast; Wrigley Gulf; Antarc*; Antarctica; Hobbs coast; Ice Sheet; Iceberg*
• Online Access: http://nora.nerc.ac.uk/id/eprint/519931/; https://nora.nerc.ac.uk/id/eprint/519931/1/Simoes%20Pereira_et_al_ESR.docx; https://www.sciencedirect.com/science/article/pii/S0012825217305974

Geochemical provenance studies of glacial-marine sediments provide a powerful approach to describe subglacial geology, sediment transport pathways, and past ice sheet dynamics. The marine-based West Antarctic Ice Sheet (WAIS) is considered highly vulnerable to ocean warming and sea level rise that is likely to cause its rapid and irreversible retreat. Studies of its past response to climate change are hence essential for projecting its future behaviour. The application of radiogenic and trace element provenance studies for past ice sheet reconstructions requires surveying the geographic variability of geochemical compositions of glaciomarine sediments. In this study, we characterize the provenance of the detrital fraction of 67 Late Holocene marine sediment samples collected off the Pacific margin of West Antarctica (60°W to 160°W), including 40Ar/39Ar ages of individual hornblende and biotite grains (>150 μm), as well as Sr and Nd isotope and trace element composition of the fine-grained (<63 μm) sediment fraction. Overall, this approach allows differentiating West Antarctica into five source regions: the Antarctic Peninsula, Bellingshausen Sea, Amundsen Sea, Wrigley Gulf-Hobbs Coast and Sulzberger Bay. Minor geochemical variability is found within each individual sector due to local variability in onland geology. 40Ar/39Ar ages of iceberg-rafted hornblende and biotite grains record primarily Carboniferous to Lates Quaternary ages (~0 to 380 Ma), with a notable age peak of ~100 Ma, associated with plutonic intrusions or deformation events during the mid-Cretaceous. Permian-Jurassic 40Ar/39Ar ages are widespread in the Amundsen Sea sector, marking episodes of large-volume magmatism along the long-lived continental margin. Metasedimentary rocks and Late Cenozoic alkali basalts in West Antarctica cannot be detected using detrital hornblende and biotite 40Ar/39Ar ages due to the absence or small grain-size (i.e. <150 μm) of these minerals in such rocks. These sources can however be readily recognized by ...