Abstract
The lower Cambrian Lagerstatte of Sirius Passet, Nansen Land, North Greenland, is one of the oldest of the Phanerozoic, exceptionally preserved biotas. The Lagerstatte evidences the escalation of numbers of new body plans and life modes that formed the basis for a modern, functionally tiered ecosystem. The fauna is dominated by predators – infaunal, benthic and pelagic – and the presence of abundant nekton, including large sweep-net feeders, suggests an ecosystem rich in nutrients. Recent discoveries have helped reconstruct digestive systems and their contents; muscle fibres; and visual and nervous systems, for a number of taxa. New collections have confirmed the complex combination of taphonomic pathways associated with the biota and its potentially substantial biodiversity. These complex animal-based communities within the Buen Formation were associated with microbial matgrounds, now preserved in black mudstones deposited below storm-wave base that provide insight to the shift from late Neoproterozoic (Ediacaran) to Cambrian substrates and communities. Moreover, the encasing sediment holds important data on the palaeoenvironment and the water-column chemistry, suggesting that these animal-based communities developed in conditions with very low oxygen concentrations.
Highlights
The Sirius Passet fossil biota is the most remote, one of the least well-known and, to date, one of the least diverse of the major Cambrian Lagerstätten
During the early Cambrian, Sirius Passet lay on the northern margin of Laurentia, at a palaeolatitude of around 15° S (Fig. 1a) (Cocks & Torsvik 2011)
This segment of the Greenland–Canada margin is commonly referred to as the Franklinian Basin (Higgins et al 1991; Trettin et al 1991); it accommodates a succession of Ediacaran– Devonian age extending from Kronprins Christian Land in eastern North Greenland, westwards to Ellesmere Island and the Arctic islands of Nunavut, Canada (Fig. 1b) (Higgins et al 1991; Trettin et al 1991; Blom 1999)
Summary
During the early Cambrian, Sirius Passet lay on the northern margin of Laurentia, at a palaeolatitude of around 15° S (Fig. 1a) (Cocks & Torsvik 2011). The boundary is well exposed adjacent to the Sirius Passet locality, where the upper part of the carbonates is deeply fretted by karstic erosion, with deep grykes, vadose fissures and accompanying shallow phreatic tubes, all of which are infilled by millet-seed quartz arenite. This lithology is seen as a thin sheet overlying the Portfjeld Formation regionally and passing upwards into black mudstones and siltstones of the basal Buen Formation (Fig. 2). These are taken to represent low greenschist-facies metamorphism, which has influenced the presentation of the taphonomic detail
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