Bottom water redox conditions and benthic foraminiferal morphogroup response in the Late Cretaceous Sverdrup Basin, Arctic Canada: Implications for Oceanic Anoxic Event 3

摘要

Oceanic anoxic events (OAEs) represent significant perturbations in the global carbon cycle and therefore studying these events is critical for understanding drivers of carbon burial and variable oxygen conditions under a Cretaceous greenhouse climate mode. Here we present whole rock geochemical and benthic foraminiferal morphogroup data from two localities in the Sverdrup Basin in the High Arctic of Canada to investigate bottom water redox conditions during the Coniacian to Santonian OAE 3 interval. Major element geochemistry reflects lithological change and is related to shoreline proximity. Evidence for bottom water anoxia in the Late Cretaceous of the Sverdrup Basin is lacking and benthic dysoxia was limited to the Coniacian interval at the basin margin. Dysoxic conditions were characterized by elevated Mo concentrations and small epifaunal trochamminid species adapted to tolerate low oxygen levels. Elevated total organic carbon (TOC) in the Sverdrup Basin was related to relative sea-level changes, with increased erosion and terrestrial organic matter flux during transgression that promoted primary production. During transgressions to highstands, the Sverdrup Basin may have acted as a minor sink of carbon due to increased organic matter flux, potentially contributing to CO2 drawdown in the Late Cretaceous. Our comparison of six records across the Sverdrup and Western Interior basins demonstrates that no distinct OAE 3 interval can be determined based on the timing of benthic dysoxia to anoxia, TOC increases, and carbon isotopic excursions. Instead, organic burial records are driven by local tectonics influencing transgressive/regressive phases that are accentuated in shallows seas. (C) 2020 Elsevier Ltd. All rights reserved.