Opening of a trans-Pangaean marine corridor during the Early Jurassic: Insights from osmium isotopes across the Sinemurian–Pliensbachian GSSP, Robin Hood's Bay, UK

Abstract

The Hispanic Corridor represents a significant phase of continental reorganisation of the Early Jurassic that eventually provided connectivity between the western Tethyan and eastern Pacific oceans along the Central Atlantic rift zone. Although the initiation of this marine corridor profoundly impacted oceanic circulation and marine faunal exchange patterns, the timing of its formation hitherto remains poorly constrained with estimates spanning both the Hettangian and Sinemurian.The Sinemurian–Pliensbachian Global Stratotype Section and Point (GSSP) at Robin Hood's Bay, UK, comprises a succession of well-exposed, immature organic-rich sediments, only previously characterised by strontium, oxygen and carbon isotope geochemistry. New Re and Os isotope profiling indicates substantial variation in seawater chemistry at this time. Initial osmium isotope data become increasing unradiogenic (0.40 to 0.20) across the boundary, providing evidence for a continual flux of unradiogenic Os into the oceans during the latest Sinemurian. The initial unradiogenic 187Os/188Os values indicate the occurrence of low-temperature hydrothermal activity associated with the formation of the Hispanic Corridor during the breakup of Pangaea. Therefore, combined with biogeography and faunal exchange patterns, the Os isotope data demonstrates that connectivity between the Eastern Pacific and Tethyan oceans initiated during the latest Sinemurian. As a result this study better constrains the timing of establishment of the Hispanic Corridor, which was previously limited to poorly defined biogeography.