Carbon isotope composition of Upper Cambrian to Lower Ordovician carbonate in Korea, and its bearing on the Cambrian–Ordovician boundary and Lower Ordovician paleoceanography

Abstract

This study presents an example of locating Cambrian–Ordovician boundary in the lower Paleozoic carbonate succession in Korea using carbon isotope stratigraphy. The Yeongweol Unit of the lower Paleozoic Joseon Supergroup comprises the Upper Cambrian Wagok Formation and the Lower Ordovician Mungok Formation in the Cambrian–Ordovician transition interval. Conventionally, the boundary was placed at the lithostratigraphic boundary between the two formations. This study reveals that the boundary is positioned in the basal part of the Mungok Formation based on the carbon isotope stratigraphy coupled with biostratigraphic information of conodont and trilobite faunas. The δ 13C curve of the Lower Ordovician Mungok Formation shows a similar trend to that of the coeval stratigraphic interval of Argentine Precordillera ( Buggisch et al., 2003), suggesting that the δ 13C curve of the Mungok Formation reflects the Early Ordovician global carbon cycle.