Geochemistry of the Cambrian Sirius Passet Lagerstätte, Northern Greenland

Abstract

The lower Cambrian Sirius Passet Lagerst€ atte (518 Ma) consists of mudstones about 8 m thick located in the Franklinian Basin of North Greenland. We analyzed major and trace elements plus the S, C, Cu, Fe, Zn, and Mo isotope compositions. Factor analysis allowed the lithology of the mudstone to be broken down into variable proportions of two inputs, a dry felsic component and a hydrous mafic component (smectite or chlorite). Zircons U-Pb ages indicate multiple sources, the local Proterozoic basement of Northern Greenland (1250-2400 Ma) and Pan-African felsic magmas (620-650 Ma) from across the Iapetus ocean. Diagenesis involved the reduction of Fe, S, and Mo from seawater and pyritization. The Sirius Passet Lagerst€ atte formed in oxygen-starved muds inhibiting degradation of organic matter underneath a wellventilated water column. The chemistry of the samples, their very fine grain size, their apparent lack of graded bedding, and the age of zircons suggest that the Lagerst€ atte may represent wind-blown dust deposited on the continental slope.

Onychophoran‐like myoanatomy of the Cambrian gilled lobopodian Pambdelurion whittingtoni

“…This is supported by geochemical analysis (Le Boudec et al . ). However, the presence of narrow, irregular, horizontal burrows crossing many Sirius Passet fossils indicate the activity of a shallow burrowing, sediment‐ingesting infauna (Peel ), suggesting that the muds of Sirius Passet were not fully anoxic (Ineson & Peel ) or varied temporally.…”

The Sirius Passet Lagerstätte of North Greenland—A geochemical window on early Cambrian low‐oxygen environments and ecosystems

“…Thus, Budd (1995) was the first to acknowledge the challenge of resolving how the soft-tissue Sirius Passet fauna was preserved effectively in situ in an environment that hosted some trace makers. Finally, a predominantly oxic water column-but with a fluctuating oxycline-was inferred from the absence of iron and molybdenum enrichments that are typical of euxinic settings as reported by Boudec et al (2014). Finally, a predominantly oxic water column-but with a fluctuating oxycline-was inferred from the absence of iron and molybdenum enrichments that are typical of euxinic settings as reported by Boudec et al (2014).…”

“…Several elements of the Sirius Passet fauna such F I G U R E 1 The Sirius Passet locality in North Greenland. (c) The Sirius Passet locality at 82˚47.59′N 42˚13.54′W, east of JP Koch Fjord is marked with a star (modified from Boudec et al, 2014). (b) The eastern Franklinian Basin (modified from Ineson & Peel, 2011).…”

“…Although sea-level change is not welldocumented in the Buen Formation, an overall upward deepening trend in this part of the section is clear from the onlap pattern of basal Buen Formation quartz arenites (shallow setting) being draped by Transitional Buen mudstones (deeper setting) (Higgins et al, 1991). Previously, it has been suggested that Sirius Passet experienced dramatic variations in climate and productivity, since preserved zircons have shapes and ages consistent with aeolian influx (Boudec et al, 2014). While the development of anoxic conditions that intersect the depositional site may be associated with deepening, a change in primary production or sedimentation rates may also have led to increased preservation of organic carbon.…”

“…Since then, the subordinate presence of bioturbation (here evidenced by laminated mudrock, but see Kristensen et al, 2012, for definitions within bioturbation), in combination with seemingly autochthonous faunal components, has been taken to reflect a habitable setting that resembles the edges of oxygen minimum zones (OMZs) (Budd, 1995;Ineson & Peel, 2011). These authors also discussed a model where the geochemistry could reflect OMZ-like conditions, but reasoned that if such conditions facilitated soft-tissue preservation, both phenomena should be associated throughout the Phanerozoic Eon (Boudec et al, 2014). These authors also discussed a model where the geochemistry could reflect OMZ-like conditions, but reasoned that if such conditions facilitated soft-tissue preservation, both phenomena should be associated throughout the Phanerozoic Eon (Boudec et al, 2014).…”