Carbon isotope chemostratigraphy and sea-level history of the Hirnantian Stage (uppermost Ordovician) in the Oslo–Asker district, Norway

Abstract We present a ? 13 C carb chemostratigraphy for the Late Ordovician Hirnantian Stage based on 208 whole-rock samples from six outcrops in Oslo–Asker district, southern Norway. Our data include Norwegian type section and Ordovician–Silurian boundary at Hovedøya Island. The most complete record of Isotope Carbon Excursion (HICE) is identified coastal exposure Konglungø locality where preserved part anomaly spans c. 24 m thick, mixed carbonate–siliciclastic succession belonging to upper Husbergøya, Langåra Langøyene formations peak values reach +6 ‰. Almost entire HICE occurs above beds containing Hirnantia Fauna, suggesting latest age excursion. temporal development Norway associated with substantial shallowing depositional environments. Sedimentary facies erosional unconformities suggest four inferably fourth-order glacio-eustatically controlled sea-level lowstands successively increased erosion succession. youngest unconformity related incised valleys resulted cut-out least falling limb throughout district. fill contains HICE, postglacial transgression therefore can be assigned Age. address recent findings chitinozoan Belonechitina gamachiana study area its relationship first occurrence Fauna studied sections, challenging identification base Stage.