Integrated biostratigraphy and carbon isotope stratigraphy for the Upper Cretaceous Kanguk Formation of the High Arctic Sverdrup Basin, Canada

摘要

Considerable Late Cretaceous research has focused on Cenomanian to Turonian organic carbon-rich deposits associated with oceanic anoxic event (OAE) 2. Less is known about changing paleoceanographic conditions after this event, especially in the Arctic region. The Upper Cretaceous Kanguk Formation, composed of organic-rich shale and mudstone deposited in the Sverdrup Basin of the Canadian Arctic Archipelago, was investigated at two localities on Ellesmere Island, Canada. This study provides an Upper Cretaceous stratigraphic framework for the Arctic region by integrating chemostratigraphic, lithologic, and benthic foraminiferal biostratigraphic data. The potential influence of global transgressive-regressive cycles and positive carbon isotope excursions in the Turonian to lower Campanian were recognized in the Kanguk Formation at both sites by utilizing carbon isotope stratigraphy-based correlation to carbon isotope reference records. The presence and absence of OAE 2 at the Kanguk Formation base in distal and proximal settings, respectively, demonstrate the diachroneity of the lithological boundary between the Kanguk Formation and the underlying Hassel Formation. Two foraminiferal biostratigraphic zones are proposed and correlate to assemblages across the Arctic region: the Turonian to late Santonian Evolutinella boundaryensis zone and the late Santonian to Campanian Verneuilinoides bearpawensis-Glaphyrammina spirocompressa zone. The biostratigraphic zonal ages are constrained by correlations to chemostratigraphic data. This research refines the stratigraphic framework for the Upper Cretaceous of Arctic Canada, improves our understanding of the paleoenvironmental dynamics of the Late Cretaceous Polar Sea in relation to global transgressive-regressive cycles and OAEs, and can be utilized to understand relative timing and gaps in the sedimentary record.