Abstract
Debate continues about the nature of the Cretaceous–Paleogene (K–Pg) mass extinction event. An abrupt crisis triggered by a bolide impact contrasts with ideas of a more gradual extinction involving flood volcanism or climatic changes. Evidence from high latitudes has also been used to suggest that the severity of the extinction decreased from low latitudes towards the poles. Here we present a record of the K–Pg extinction based on extensive assemblages of marine macrofossils (primarily new data from benthic molluscs) from a highly expanded Cretaceous–Paleogene succession: the López de Bertodano Formation of Seymour Island, Antarctica. We show that the extinction was rapid and severe in Antarctica, with no significant biotic decline during the latest Cretaceous, contrary to previous studies. These data are consistent with a catastrophic driver for the extinction, such as bolide impact, rather than a significant contribution from Deccan Traps volcanism during the late Maastrichtian.
Highlights
The Cretaceous–Paleogene (K–Pg) mass extinction at 66 Ma is the most intensively studied of the ‘Big Five’ crises to have affected life during the Phanerozoic[1,2,3,4,5,6,7,8]
We suggest that the K–Pg extinction in Antarctica was as rapid and severe as that seen at lower latitudes, with no evidence for significant precursor extinction events during the latest Maastrichtian, which can be related to the onset of Deccan volcanism or climatic instability
The primary data for this study comprises 46,000 benthic molluscan fossils from 377 individual sampling stations accurately located within a series of detailed measured sedimentary sections through the Lopez de Bertodano Formation (Fig. 1; Supplementary Figs 1–4)
Summary
The Cretaceous–Paleogene (K–Pg) mass extinction at 66 Ma is the most intensively studied of the ‘Big Five’ crises to have affected life during the Phanerozoic[1,2,3,4,5,6,7,8]. The extinction led to a fundamental restructuring of global ecosystems and the rise of modern taxonomic groups[7,9,10,11] Despite this interest, debate continues as to the duration of the crisis as well as the relative contributions of the bolide impact at Chicxulub[1,4], voluminous eruptions from the Deccan Traps large igneous province[12,13], and dynamic climate instability during the preceding Maastrichtian stage (72.1–66 Ma)[6,14]. The depositional environment of the Lopez de Bertodano Formation is broadly transgressive; the lower portion has been interpreted as relatively shallow water, outer estuarine facies[28,29], with a low-energy, marine shelf facies forming the remainder of the succession[27,30] We address these debates on the timing and intensity of Antarctic marine extinctions with a detailed analysis of marine diversity trends during the Maastrichtian to earliest Paleocene B70–65.6 Ma We suggest that the K–Pg extinction in Antarctica was as rapid and severe as that seen at lower latitudes, with no evidence for significant precursor extinction events during the latest Maastrichtian, which can be related to the onset of Deccan volcanism or climatic instability
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