Blake Nose stable isotopic evidence against the mid-Cenomanian glaciation hypothesis

Detailed multitaxon stable isotope (delta O-18 and delta C-13) data from Blake Nose (western North Atlantic) argue against a mid-Cenomanian glaciation event during the mid-Cretaceous greenhouse. Results generated are precisely correlated to sea-level changes inferred from European sequence stratigraphy using the twin delta C-13 excursions mid-Cenomanian event (MCE) Ia and MCE Ib. Microfossils analyzed (surface-dwelling to deep-dwelling planktonic foraminifera, benthic foraminifera, coccoliths) show remarkably consistent intertaxon delta O-18 and delta C-13 offsets; comparative scanning electron microscope and Sr/Ca analyses allow some delta O-18 data to be eliminated because of selective diagenesis. Across MCE Ia, the proposed interval of major glacioeustatic regression, the planktonic delta O-18 values are constant for each taxon. The absence of a mean seawater delta O-18 shift contradicts predictions for the mid-Cenomanian glaciation episode. The benthic delta O-18 records show significant fluctuations during MCE I, implying short-term variability in North Atlantic intermediate-water and deep-water circulation patterns and/or sources at that time.