The Permian–Triassic boundary in central East Greenland: past and present views

Abstract

The latest Permian, Changhsingian fauna in East Greenland is a typical northern cool-water fauna, dominated by a low diversity assemblage of boreal brachiopods and lacking fusulinids, small foraminifers and fish. Continuous sedimentation across the Permian–Triassic boundary is recorded at the Fiskegrav locality, southwestern Jameson Land but the precise location of the boundary is disputable within an interval covering the uppermost few metres of the Schuchert Dal Formation and the lowermost 23.5 m of the Wordie Creek Formation. Based on palynological data the boundary is best placed 50 cm below the top of the Schuchert Dal Formation at Fiskegrav, in a monotonous interval of bioturbated, grey offshore marine siltstone characterised by a marked drop in the ä13C of organic carbon. ä13C of carbonate from brachiopods shows a temporary drop of 2‰, 4–5 m below the top of the Schuchert Dal Formation, while the ä13C of whole rock carbonate reaches a minimum in the lowermost part of the Wordie Creek Formation. Comparisons to the ä13C carbonate curves from the boundary stratotype section at Meishan, China are therefore highly subjective and allow the boundary to be placed within a 24–27 m thick interval in the topmost Schuchert Dal Formation and the lowermost Wordie Creek Formation, – here termed as the Permian–Triassic boundary interval. The lower part of this interval, below the palynological boundary includes a low diversity Permian-type fauna of two brachiopod and four agglutinated foraminifer genera. Above the palynological boundary, in the uppermost 50 cm of the Schuchert Dal Formation remains of the Triassic-type fish Bobasatrania occur together with agglutinated foraminifers, and at the base of the Wordie Creek Formation a more diverse, Triassic-type fish fauna with five genera is present. In the stratotype section at Meishan the first Triassic-type faunal elements appear above the negative ä13C anomaly in what is regarded as a topmost Permian mixed fauna interval. A similar situation may possibly exist in East Greenland so the old East Greenland issue of faunal mixing with Permian-type fauna in the Triassic may turn out to be a matter of having Triassic faunal elements in the Permian.