δ 13 C chemostratigraphy in the upper Tremadocian through lower Katian (Ordovician) carbonate succession of the Siljan district, central Sweden (original) (raw)
Related papers
Estonian Journal of Earth Sciences, 2014
Based on δ 13 C 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.
2014
Based on δC data from two drillcores recovered from the Siljan district, we present a first continuous carbon isotope record of the upper Tremadocianlower Katian limestone succession of central Sweden. New names for some isotopic carbon excursions from the CambrianOrdovician boundary through the basal Darriwilian are introduced. The Mora 001 core from the western part of the Siljan impact structure ranges through the LowerMiddle Ordovician, whereas the Solberga 1 core from its eastern part ranges through the Middlelower 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.
Facies, 2010
The Katian (Upper Ordovician) facies succession of the Siljan district, central Sweden, records some of the most prominent environmental changes in the Ordovician of Baltoscandia. These changes include two separate phases of major sea-level drawdown that were of basinwide and presumably global importance. The Wrst regression and lowstand terminated an entire generation of carbonate mud mounds (the Kullsberg Limestone) and resulted in the formation of polymict carbonate conglomerates (Skålberg Limestone) belonging to the Amorphognathus superbus Zone. New stable isotope data from the Amtjärn quarry shows that this is immediately after the peak of the Guttenberg Carbon Isotope Excursion (GICE), which reaches a 13 C peak value at 3.3‰ in the uppermost Amorphognathus tvaerensis Conodont Zone. A second major regression and sea-level lowstand is manifested by palaeokarst morphologies in the Slandrom Limestone, which formed close in time to the comparably minor Waynesville positive carbon excursion in the basal Amorphognathus ordovicicus Conodont Zone. The widespread exposure associated with this latter lowstand terminated carbonate production in much of the basin, and, during the subsequent Xooding, organic-rich, graptolitic shale formed across most of Baltoscandia. The two corresponding sequence boundaries are amalgamated at the top of truncated carbonate mud mounds in the Siljan district, resulting in a pronounced Middle Katian hiatus in the immediate mound areas.
GFF, 2018
The Komstad Limestone forms a distal part of the widespread 'orthoceratite limestone' of the Baltoscandian continent. In this paper, we present an integrated conodont biostratigraphy and carbon isotope stratigraphy for a major part of this formation and address its significance for evaluating Middle Ordovician correlation and overall stratigraphy. Four conodont zones are distinguished, including the Lenodus antivariabilis Zone, Lenodus variabilis Zone, the Yangtzeplacognathus crassus Zone, and the Eoplacognathus pseudoplanus Zone. Carbon isotopes have previously not been published from the Komstad Limestone. The data herein show that carbonate strata may retain a comprehensive pristine δ 13 C signal despite relatively strong thermal influence during diagenesis (Conodont Color Alteration Index 4-5).
Estonian Journal of Earth Sciences
The largely covered Middle Ordovician succession in the classic geological Röstånga area in northwestern Scania has not been studied for some 80 years. A new drill core through a succession ranging from the lower-middle Darriwilian to the lower Sandbian has provided a unique opportunity to investigate the graptolite biostratigraphy and the δ 13 C org chemostratigraphy, and clarify their stratigraphic relations, through this ~90 m thick interval, which is developed within a black shale facies. The lithology, biostratigraphy and chemostratigraphy are closely similar to those of the coeval strata in the Fågelsång area, southcentral Scania, including the presence of the Fågelsång Phosphorite, which was previously unrecorded in the Röstånga area. The new data are particularly important in providing evidence of the relations between graptolite biostratigraphy and δ 13 C org chemostratigraphy. The Fågelsång3 and Röstånga2 drill core successions are currently the only Darriwilian sequences in the world where these relations have been well established.
Lethaia, 2009
A core drilling (Andrarum-3), from the classical locality at Andrarum, Scania, southernmost Sweden, penetrated a 28.90-m-thick Cambrian succession. The core comprises dark grey to black, finely laminated mudstones and shales with early concretionary carbonate lenses (stinkstones or orsten ) and a few primary carbonate beds. The middle Cambrian (provisional Series 3) part of the core comprises 17.35 m, whereas the Furongian Series (upper Cambrian) part covers the remaining 11.55 m. Nineteen trilobite and two phosphatocopine genera are present in the middle Cambrian, whereas the less diverse Furongian interval yielded four trilobite and three phosphatocopine genera. Other, less frequent, faunal elements include conodonts ( s . l .), brachiopods, sponge spicules, bradoriids, and coprolites. Trilobites and phosphatocopines were used to subdivide the core into seven biozones ranging from the Ptychagnostus atavus Zone to the Parabolina spinulosa Zone ( P . spinulosa Subzone). Carbon isotopic analyses ( δ 13 C org ) through the core show two important excursions, the negative DrumIan Carbon isotope Excursion (DICE) in the Pt . atavus Zone, and the Steptoean Positive Carbon Isotope Excursion (SPICE) beginning near the first appearance of Glyptagnostus reticulatus and extending upward into the Olenus and Agnostus ( Homagnostus ) obesus Zone. The DICE displays a peak value, in the samples at hand, of -30.45‰ δ 13 C org in the lower part of the P . atavus Zone. The δ 13 C org values increase through the overlying L . laevigata and A . pisiformis zones and display peak values of c . -28.00‰ δ 13 C org in the lowermost Furongian Olenus wahlenbergi and O . attenuatus subzones. Thereafter the values decrease significantly through the O . scanicus Subzone. Both isotopic excursions have been documented from several palaeocontinents, but never before from Baltica. Moreover, for the first time these excursions are recorded from organic matter in an alum shale setting. The recorded shift of +1.50-2.00‰ δ 13 C org is approximately half the magnitude of the SPICE documented from other regions. This discrepancy may be related to temporal variations in the type, origin, or diagenesis of the organic fraction analysed. ᮀ Biostratigraphy , Cambrian , carbon isotope stratigraphy , DICE , SPICE , Sweden , trilobites . Per Ahlberg [per.ahlberg@geol.lu.se], Niklas Axheimer [niklas.axheimer@geol.lu.se], Mats E. Eriksson [mats.eriksson@geol.lu.se], Birger Schmitz [birger.schmitz@geol.lu.se], and Fredrik Terfelt [fredrik.terfelt@geol.lu.se],