Strontium isotope stratigraphy of the Gabbs Formation (Nevada): implications for global Norian-Rhaetian correlations and faunal turnover

摘要: The Luning and Gabbs formations in west-central Nevada, USA represent a Late Triassic shallow marine sedimentary succession with global significance (the Formation was candidate for the basal Jurassic GSSP). Typically, Norian–Rhaetian stage boundary is placed at contact between formations, Rhaetian–Hettangian Triassic–Jurassic boundary) within Muller Canyon Member of Formation. However, use different biostratigraphical index-species schemes successions Tethys Panthalassa, two largest ocean basins time, makes precise correlation problematic. Here, we compare 87Sr/86Sr measurements well-preserved carbonate shell material from Nevada to well-known biostratigraphically constrained record Tethys, where negative excursion noted across boundary. Our new data reveal comparable trend, sharp drop Nun Mine Formation, suggesting position higher succession, not as previously defined. Relating using isotopic signals useful tool estimating rate faunal turnover comparison succeeding mass extinction. If correct, this biostratigraphical–chemostratigraphical suggests that current index groups Panthalassic should be changed.