Trace elements and Sr and C isotopic signatures in late Neoproterozoic and earliest Cambrian sedimentary organic matter from siliciclastic successions in the East European Platform

Abstract

Sedimentary organic matter deriving from tubes of sabelliditids, vendotaenids, sapropelic films and kerogens was extracted by acid processing from Upper Vendian siliciclastic successions in the East European Platform. Elemental composition obtained by instrumental neutron activation analysis (INAA) displays the increasing cobalt (Co) concentration from 1 ppm at the bottom of Upper Vendian succession to about 800 ppm in the uppermost part near the Precambrian–Cambrian boundary. This distribution is recorded in all studied successions and is not related to resistant minerals that survived acid treatment. The enrichment in Co and other metals in the sedimentary organic matter is inferred to be caused by the bloom of cyanobacterial microbiota, and bonding of metals in decaying sedimentary organic matter during pre-burial bacterial reworking and post-burial early diagenesis in a low energy, stagnant depositional basin during Kotlin times. The positive Ceanom in probable benthic sabelliditids, and the exceptional preservation of sedimentary organic matter from Kotlinian strata, indicate the anaerobic conditions during their sedimentation. Clear correlations between 87Sr/86Sr, δ13C and Co imply the secondary isotopic signatures of Sr and C in sedimentary organic matter deriving from a restricted epicontinental marine basin.

Palaeontologic and biogeochemical characterization of the Cyrtograptus lundgreni event in the black shales of eastern Mid‐Sardinia, Italy

“…The suggestion that organic matter (organisms) might have absorbed these elements during their life cycle (and preserved after death and fossilization), is being assessed for the time on the basis of analytical data and palaeobiological observations made within a stratigraphically constrained succession. Some authors (Felitsyn et al . 1998) remark that the SOM may have become enriched immediately after death, but before burial, by anaerobic cyanophyte bacteria, though, in the case under study no traces of organic lamina or films were found that could be referred to algae and cyanophytes, unless they occurred indistinctly within the kerogen.…”

“…Integrated geochemical and palaeontological approach is frequently adopted for studying stratigraphic successions of major interest, like the bio-radiation in the Neoproterozoic Á Lower Cambrian transition (Bartley et al . 1998;Felitsyn et al . 1998).…”

Nd isotope composition of the Ediacaran and earliest Cambrian phosphorite nodules and Fe sulphide from the East European Platform

“…More details concerning the stratigraphy and composition of the studied successions are presented in numerous publications (e.g. Strauss et al 1997;Felitsyn et al 1998).…”

Early Ordovician molluscs with preserved colour pattern from the Timan-Pechora Basin of Russia

“…Thus, unusual preservation of Timan-Pechora molluscs reflects low subsidence temperatures, something that is a general characteristic of the Late Proterozoic -Early Palaeozoic strata of the East European Platform (Felitsyn et al 1998), and minimal tectonic deformation of fossil-bearing strata.…”