Carbon isotope chemostratigraphy and sea-level history of the Hirnantian Stage (uppermost Ordovician) in the Oslo-Asker district, Norway
Calner M, Bockelie JF, Rasmussen CM, Calner H, Lehnert O, Joachimski M (2021)
Publication Language: English
Publication Type: Journal article
Publication year: 2021
Journal
DOI: 10.1017/S0016756821000546
Abstract
We present a 13Ccarb chemostratigraphy for the Late Ordovician Hirnantian Stage based on 208 whole-rock samples from six outcrops in the Oslo-Asker district, southern Norway. Our data include the Norwegian type section for the Hirnantian Stage and Ordovician-Silurian boundary at Hovedøya Island. The most complete record of the Hirnantian Isotope Carbon Excursion (HICE) is identified in a coastal exposure at Konglungø locality where the preserved part of the anomaly spans a c. 24 m thick, mixed carbonate-siliciclastic succession belonging to the upper Husbergøya, Langåra and Langøyene formations and where 13Ccarb peak values reach c. +6 ‰. Almost the entire HICE occurs above beds containing the Hirnantia Fauna, suggesting a latest Hirnantian age for the peak of the excursion. The temporal development of the HICE in southern Norway is associated with substantial shallowing of depositional environments. Sedimentary facies and erosional unconformities suggest four inferably fourth-order glacio-eustatically controlled sea-level lowstands with successively increased exposure and erosion to the succession. The youngest erosional unconformity is related to the development of incised valleys and resulted in cut-out of at least the falling limb of the HICE throughout most of the Oslo-Asker district. The fill of the valleys contains the falling limb of the HICE, and the postglacial transgression therefore can be assigned to the latest part of the Hirnantian Age. We address the recent findings of the chitinozoan Belonechitina gamachiana in the study area and its relationship to the first occurrence of Hirnantia Fauna in the studied sections, challenging identification of the base of the Hirnantian Stage.
Authors with CRIS profile
Oliver Lehnert
Lehrstuhl für Geologie (Exogene Dynamik)
Michael Joachimski
Lehrstuhl für Geologie (Exogene Dynamik)
Additional Organisation(s)
Involved external institutions
Denmark (DK)How to cite
APA:
Calner, M., Bockelie, J.F., Rasmussen, C.M., Calner, H., Lehnert, O., & Joachimski, M. (2021). Carbon isotope chemostratigraphy and sea-level history of the Hirnantian Stage (uppermost Ordovician) in the Oslo-Asker district, Norway. Geological Magazine. https://dx.doi.org/10.1017/S0016756821000546
MLA:
Calner, Mikael, et al. "Carbon isotope chemostratigraphy and sea-level history of the Hirnantian Stage (uppermost Ordovician) in the Oslo-Asker district, Norway." Geological Magazine (2021).
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