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Upper Ordovician stratigraphy of the Stora Sutarve core (Gotland, Sweden) and an assessment of the Hirnantian Isotope Carbon Excursion (HICE) in high-resolution

Gunnarsson, Niklas LU (2023) In Dissertations in Geology at Lund University GEOR02 20222
Department of Geology
Abstract
The Hirnantian Isotope Carbon Excursion (HICE) is a major anomaly in Earths global carbon cycle at the end of the Ordovician time period, at ca 445 Ma. The anomaly is intimately associated with substantial cooling of the global climate, expansion of continental ice-sheets and the Late Ordovician Mass Extinction (LOME). The present study investigates the Upper Ordovician to the lowermost Silurian sedimentary record, with particular emphasis on carbonate microfacies and carbon isotope stratigraphy of the Hirnantian Stage, based on the recently drilled Stora Sutarve core from southern Gotland. The lithological record has similarities with both the East Baltic and Swedish successions and includes the Kahula (including 13 bentonites), Hirmuse,... (More)
The Hirnantian Isotope Carbon Excursion (HICE) is a major anomaly in Earths global carbon cycle at the end of the Ordovician time period, at ca 445 Ma. The anomaly is intimately associated with substantial cooling of the global climate, expansion of continental ice-sheets and the Late Ordovician Mass Extinction (LOME). The present study investigates the Upper Ordovician to the lowermost Silurian sedimentary record, with particular emphasis on carbonate microfacies and carbon isotope stratigraphy of the Hirnantian Stage, based on the recently drilled Stora Sutarve core from southern Gotland. The lithological record has similarities with both the East Baltic and Swedish successions and includes the Kahula (including 13 bentonites), Hirmuse, Rägavere, Paekna, Jonstorp, Loka, Motala and Kallholn formations and spans the Sandbian to the Aeronian stages. Several δ13C excursions have been identified in the core; LSNICE, GICE, Moe excursion, HICE and possibly the Late Aeronian CIE. The Hirnantian Stage and the HICE is entirely confined to the Loka Formation in the core. The Loka Formation constitutes a lower limestone unit (Skultorp Member) overlain by a more argillaceous unit (informal ‘upper member’). Both units yield abundant brachiopods of both the Hirnantia and Edgewood-Cathay faunas. This formation is interpreted as one cycle of transgression-regression bounded by hiatuses at the lower and upper boundary, inferably glacially induced. The HICE includes a slowly increasing rising limb, a peak and plateau, which is truncated at an unconformity at the upper boundary of the Loka Formation. Based on the dense sampling four clusters of δ13C values help to define significant changes in the HICE trend that may facilitate global correlation of the succession and the herein interpreted sea-level change. (Less)
Abstract (Swedish)
En avsevärd anomali i jordens globala kolcykel, känd som Hirnantian Isotope Carbon Excursion (HICE), finns dokumenterad i lagerföljder från Hirnantetagen, i slutet av Ordovicium för cirka 445 miljoner år sedan. Anomalin är kopplad till den samtida globala nedkylningen, bildande av inlandisar och ett massutdöende – Late Ordovician Mass Extinction (LOME). Denna studie undersöker lagerföljder från övre Ordovicium till lägre Silur i en nyligen upptagen borrkärna från södra Gotland. Särskild vikt läggs på beskrivning av kalkstenen och kolisotopstratigrafin i Hirnant-etagen. Borrkärnans lagerföljd har likheter med såväl baltiska som svenska lagerföljder och inkluderar Kahula (inklusive 13 bentoniter), Hirmuse, Rägavere, Paekna, Jonstorp, Loka,... (More)
En avsevärd anomali i jordens globala kolcykel, känd som Hirnantian Isotope Carbon Excursion (HICE), finns dokumenterad i lagerföljder från Hirnantetagen, i slutet av Ordovicium för cirka 445 miljoner år sedan. Anomalin är kopplad till den samtida globala nedkylningen, bildande av inlandisar och ett massutdöende – Late Ordovician Mass Extinction (LOME). Denna studie undersöker lagerföljder från övre Ordovicium till lägre Silur i en nyligen upptagen borrkärna från södra Gotland. Särskild vikt läggs på beskrivning av kalkstenen och kolisotopstratigrafin i Hirnant-etagen. Borrkärnans lagerföljd har likheter med såväl baltiska som svenska lagerföljder och inkluderar Kahula (inklusive 13 bentoniter), Hirmuse, Rägavere, Paekna, Jonstorp, Loka, Motala och Kallholn formationerna och sträcker sig från Sandby-etagen till Aeron-etagen. Flera δ13C-anomalier har identifierats i kärnan; LSNICE, GICE, Moe-anomalin, HICE och med viss osäkerhet den sen-Aeronska CIE. Hirnant-etagen och HICE är begränsad inom Lokaformationen i borrkärnan. Loka formationen består av en lägre kalkstensenhet (Skultorpledet) och en övre enhet med högre lerhalt (ej formellt namngiven). Båda enheterna innehåller brachiopoder av Hirnantia- och Edgewood-Cathay faunan. Formationen tolkas som en lagerföljd avsatt i en transgression-regressionscykel med glacialt formade erosionsytor i formationens nedre och övre gräns. HICE består av en långsamt uppgående trend följt av en topp och platå. Platån är trunkerad vid en erosionsyta vid formationens övre gräns. Den täta provtagningen tydliggör fyra trender i kluster av δ13C-värden. Klusterna framhäver signifikanta förändringar i HICE, som kan underlätta global korrelation av lagerföljder och havsnivåtolkningarna i denna studie. (Less)
Please use this url to cite or link to this publication:
author
Gunnarsson, Niklas LU
supervisor
organization
alternative title
Övre ordovicisk stratigrafi från Stora Sutarve kärnan (Gotland) och en högupplöst studie av Hirnantian Isotope Carbon Excursion (HICE)
course
GEOR02 20222
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Hirnantia fauna, carbon isotope stratigraphy, Hirnantian, Baltoscandian basin, Loka Formation, Upper Ordovician, Sweden
publication/series
Dissertations in Geology at Lund University
report number
649
language
English
id
9112553
date added to LUP
2023-03-17 14:38:11
date last changed
2024-04-17 03:42:12
@misc{9112553,
  abstract     = {{The Hirnantian Isotope Carbon Excursion (HICE) is a major anomaly in Earths global carbon cycle at the end of the Ordovician time period, at ca 445 Ma. The anomaly is intimately associated with substantial cooling of the global climate, expansion of continental ice-sheets and the Late Ordovician Mass Extinction (LOME). The present study investigates the Upper Ordovician to the lowermost Silurian sedimentary record, with particular emphasis on carbonate microfacies and carbon isotope stratigraphy of the Hirnantian Stage, based on the recently drilled Stora Sutarve core from southern Gotland. The lithological record has similarities with both the East Baltic and Swedish successions and includes the Kahula (including 13 bentonites), Hirmuse, Rägavere, Paekna, Jonstorp, Loka, Motala and Kallholn formations and spans the Sandbian to the Aeronian stages. Several δ13C excursions have been identified in the core; LSNICE, GICE, Moe excursion, HICE and possibly the Late Aeronian CIE. The Hirnantian Stage and the HICE is entirely confined to the Loka Formation in the core. The Loka Formation constitutes a lower limestone unit (Skultorp Member) overlain by a more argillaceous unit (informal ‘upper member’). Both units yield abundant brachiopods of both the Hirnantia and Edgewood-Cathay faunas. This formation is interpreted as one cycle of transgression-regression bounded by hiatuses at the lower and upper boundary, inferably glacially induced. The HICE includes a slowly increasing rising limb, a peak and plateau, which is truncated at an unconformity at the upper boundary of the Loka Formation. Based on the dense sampling four clusters of δ13C values help to define significant changes in the HICE trend that may facilitate global correlation of the succession and the herein interpreted sea-level change.}},
  author       = {{Gunnarsson, Niklas}},
  language     = {{eng}},
  note         = {{Student Paper}},
  series       = {{Dissertations in Geology at Lund University}},
  title        = {{Upper Ordovician stratigraphy of the Stora Sutarve core (Gotland, Sweden) and an assessment of the Hirnantian Isotope Carbon Excursion (HICE) in high-resolution}},
  year         = {{2023}},
}