Positive europium anomaly at the Permo‐Triassic Boundary, Spiti, India

Abstract

A limonitic layer at the base of the Otoceras‐Ophiceras zone in the Lalung section in Spiti valley shows a significant positive europium anomaly with maximum Eu/Eu* = 1.9. This layer defines the contact between the earliest Griesbachian and the Permian Productus shale sequence. The layer shows a small cerium anomaly having the maximum value of (Ce/La)N = 1.4. The iridium concentration in this layer, at 73 pg/g, is only marginally above the levels found in the adjacent shales although higher than that found in the overlying limestones. Another horizon having 114 pg/g of Ir occurs 70 cm below this limonitic layer in the shale sequence. These observations have important implications, both for the terrestrial (mainly volcanic) and extra‐terrestrial impact hypotheses for the Permo‐Triassic transition which are discussed.

Catastrophic environmental transition at the Permian-Triassic Neo-Tethyan margin of Gondwanaland: Geochemical, isotopic and sedimentological evidence in the Spiti Valley, India

“…An exception to this observed pattern is the uppermost shale sample PB-1 that shows an REE pattern similar to the overlying ferruginous sample, 8b) that may be interpreted as a result of marine regression with turbulent sediment mixing at end-Permian and yet maintaining the geochemical conformity of the Spiti section.Although the Ce anomaly continues into the ferruginous layer, the absolute REE concentrations are ten times more enriched in it than the Late Permian shales showing a conspicuous positive Eu anomaly(Fig. 8b), identical to the patterns observed in few samples from other sections of Spiti valley(Bhandari et al, 1992). The Ce anomaly in the ferruginous layer is possibly due to adsorption of CeO 2 on Fe-oxyhydoxide phases.…”

Carbon isotopic evidence for terminal-Permian methane outbursts and their role in extinctions of animals, plants, coral reefs, and peat swamps

“…Some of these supposed shocked quartz grains have subsequently turned out to be metamorphic quartz grains (Langenhorst et al, 2005). An unusual positive europium anomaly in rare earth elements of the Permian-Triassic boundary near Spiti, India, has been attributed to an eucritic bolide impact (Bhandari et al, 1992), but a thick sequence of sandstone with comparable europium anomalies near Banspetali, India, has been interpreted as due to erosion of Archaean gneisses (Sarkar et al, 2003).…”

A Unified Theory of Impact Crises and Mass Extinctions: Quantitative Tests

“…On land, plant fossils and palynological data from several sites reveal evidence for a profound ecological disturbance at the K/T boundary. Late Cretaceous palynomorph assemblages commonly show severe reductions in abundance and diversity at the boundary, followed by a thin barren interval, and sudden rise in spore abundance — the so‐called fern spike [138], and increase in fungal spores [9].…”