TY - JOUR

T1 - Chitinozoan biostratigraphy and carbon isotope stratigraphy from the Upper Ordovician Skogerholmen Formation in the Oslo Region. A new perspective for the Hirnantian lower boundary in Baltica

AU - Amberg, Chloé E. A.

AU - Vandenbroucke, Thijs R. A.

AU - Nielsen, Arne Thorshøj

AU - Munnecke, Axel

AU - McLaughlin, Patrick I.

PY - 2017/11

Y1 - 2017/11

N2 - The end-Ordovician has received wide attention because it hosts major global events including mass extinctions, glaciations, significant sea-level fluctuations, and large-scale perturbations of the Earth's carbon cycle. Knowing the order and timing of these events and their components is crucial for understanding these environmental changes. Here, we use stable carbon isotope stratigraphy in combination with chitinozoan biostratigraphy to correlate the Upper Ordovician Belonechitina gamachiana chitinozoan Biozone. Its position has long been a matter of debate; some argue that it is of late Katian age and others that it is of early Hirnantian age. The Skogerholmen Formation from the Oslo-Asker District in Norway has been correlated with the lower-middle Pirgu Baltic Stage, hitherto believed to correspond to the international upper Katian Stage. Our study, however, reveals the presence of B. gamachiana, diagnostic of the eponymous Biozone, in the descending trend of a modest carbon isotope excursion in the lower part of this formation. This is strikingly similar to data from coeval end-Ordovician sections in North America, where the prevailing evidence suggests an early Hirnantian age for the B. gamachiana chitinozoan Biozone. This new correlation suggests that the lower Hirnantian boundary may be positioned within the Pirgu Baltic Stage.

AB - The end-Ordovician has received wide attention because it hosts major global events including mass extinctions, glaciations, significant sea-level fluctuations, and large-scale perturbations of the Earth's carbon cycle. Knowing the order and timing of these events and their components is crucial for understanding these environmental changes. Here, we use stable carbon isotope stratigraphy in combination with chitinozoan biostratigraphy to correlate the Upper Ordovician Belonechitina gamachiana chitinozoan Biozone. Its position has long been a matter of debate; some argue that it is of late Katian age and others that it is of early Hirnantian age. The Skogerholmen Formation from the Oslo-Asker District in Norway has been correlated with the lower-middle Pirgu Baltic Stage, hitherto believed to correspond to the international upper Katian Stage. Our study, however, reveals the presence of B. gamachiana, diagnostic of the eponymous Biozone, in the descending trend of a modest carbon isotope excursion in the lower part of this formation. This is strikingly similar to data from coeval end-Ordovician sections in North America, where the prevailing evidence suggests an early Hirnantian age for the B. gamachiana chitinozoan Biozone. This new correlation suggests that the lower Hirnantian boundary may be positioned within the Pirgu Baltic Stage.

KW - Baltica

KW - Biostratigraphy

KW - Carbon isotopes

KW - Chitinozoans

KW - End-Ordovician

KW - Hirnantian

UR - http://www.scopus.com/inward/record.url?scp=85021770853&partnerID=8YFLogxK

U2 - 10.1016/j.revpalbo.2017.06.008

DO - 10.1016/j.revpalbo.2017.06.008

M3 - Journal article

AN - SCOPUS:85021770853

VL - 246

SP - 109

EP - 119

JO - Review of Palaeobotany and Palynology

JF - Review of Palaeobotany and Palynology

SN - 0034-6667

ER -