Work

Platinum-group elements record both weathering changes and volcanic input through the Pliensbachian–Toarcian transition at Peniche, Portugal

Year: 2025

Type: article

Abstract: Large igneous provinces (LIPs) are thought to be the drivers of numerous Mesozoic episodes of dramatic environmental perturbation due to massive influx of volcanically sourced CO 2 and subsequent enhanced global weathering rates. Two such episodes studied here are the Pliensbachian-Toarcian (Pl/To) event, closely followed by the Toarcian oceanic anoxic event (T-OAE), both of which have been temporally linked to eruption phases of the Karoo and Ferrar LIPs (KFLIP). Here we present high-precision platinum-group element (PGE) data for the sedimentary succession spanning across the Pl/To and the T-OAE from the Toarcian Global Stratotype Section and Point (GSSP) at Peniche, Portugal. The concentrations of PGEs peak across both Pl/To and the T-OAE, and correlate with Hg enrichment and negative carbon-isotope excursions reported from these intervals. They are also positively correlated with siliciclastic content (e.g., Al, Zr and Ti) and weathering proxy variations from these intervals (i.e., 187 Os/ 188 Os and 87 Sr/ 86 Sr), although there are still enrichments in PGE/Al at both intervals. Pd/Ir and Pt/Ir ratios are slightly higher than in continental crust (~30–80 for Peniche samples and ~ 22 for UCC), but similar to basalts from KFLIP. These observations, together with Hg concentrations, 187 Os/ 188 Os and 87 Sr/ 86 Sr ratios, are best explained by elevated continental weathering and additional volcanic input. These results support the hypothesis that KFLIP eruptions were responsible for both Pl/To and T-OAE, and further show that PGEs are a powerful proxy for fingerprinting volcanism and weathering.

Source: Palaeogeography Palaeoclimatology Palaeoecology

DOI: 10.1016/j.palaeo.2025.113311