δ13C chemostratigraphy in the upper Tremadocian through lower Katian (Ordovician) carbonate succession of the Siljan district, central Sweden; pp. 277–286

M Joachimski,R Wu,G Meinhold,M Calner,O Lehnert

doi:10.3176/earth.2014.31

Abstract

Based on delta C-13 data from two drillcores recovered from the Siljan district, we present a first continuous carbon isotope record of the upper Tremadocian-lower Katian limestone succession of central Sweden. New names for some isotopic carbon excursions from the Cambrian-Ordovician boundary through the basal Darriwilian are introduced. The Mora 001 core from the western part of the Siljan impact structure ranges through the Lower-Middle Ordovician, whereas the Solberga 1 core from its eastern part ranges through the Middle-lower Upper Ordovician. Upper Tremadocian and Floian units are extremely condensed and include extensive stratigraphic gaps. Multiple hardgrounds, sometimes with minor karstic overprint, imply recurrent periods of erosion and/or non-deposition. Like in other parts of Sweden, the Dapingian and Darriwilian succession is characterized by a relatively complete sedimentary record and low sedimentation rates. (Less)

Highlights

Over the last two decades, the strong potential of the δ13C record for regional and global correlation of ancient marine sediments has become more and more evident. Bergström et al (2009) compiled a generalized δ13C curve for the Ordovician System, which serves as a good overview of the period (Fig. 1)
Our goal is to study the Lower to Middle Ordovician carbon isotope record in Baltoscandia for comparison
We present δ13C data from two overlapping core sections, which could serve as a future δ13C standard for central Sweden

Summary

Introduction

Over the last two decades, the strong potential of the δ13C record for regional and global correlation of ancient marine sediments has become more and more evident (see Saltzman & Thomas 2012 for a summary). Bergström et al (2009) compiled a generalized δ13C curve for the Ordovician System, which serves as a good overview of the period (Fig. 1). 6; Fig. 2), shown in the lower part of the Ordovician δ13C standard compiled by Bergström et al (2009), to name some of the Lower Ordovician events (see Fig. 1; without rescaling of the events in relation to the stage slices) This helps to discuss the possible presence of some of the younger peaks in Swedish sections. We introduce and formally define the following names for significant isotopic carbon excursions (the age frame for the Tremadocian and Floian in terms of conodont faunas studied by Lehnert (2001) and correlated by Lehnert in Buggisch et al (2003, figs 6, 8). To North American and Baltic conodont zones; Fig. 2): COTICE: Cambrian–Ordovician Transition Isotopic Carbon Excursion, upper Cordylodus intermedius through C. angulatus zones, this positive excursion of more than 1‰ is followed by a low (‘Skullrockian low’) in δ13C through the upper Rossodus manitouensis

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Conclusion