Deep-water formation in the North Atlantic during the latest Cretaceous

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Author(s): Martin, E. E.; Rostami, M. A.; MacLeod, K. G.; Haynes, S.; Poulsen, C. J.; Vande Guchte, Andrew
Author Affiliation(s): Primary:
University of Florida, Department of Geological Sciences, Ft. Walton Beach, FL, United States
University of Missouri Columbia, Columbia, MO, United States
University of Michigan, Department of Earth and Environmental Sciences, Ann Arbor, MI, United States
Volume Title: AGU 2017 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2017; American Geophysical Union 2017 fall meeting, New Orleans, LA, Dec. 11-15, 2017. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Global cooling during the late Campanian-Maastrichtian (78 - 66 Ma) has been linked to changes in ocean circulation. In the North Atlantic, both Northern Component (NCW) and Southern Component (SCW) Waters have been proposed as primary deep water sources in the Late Cretaceous. Neodymium (Nd) isotope records alone do not distinguish between these two alternatives because of similar initial εNd values. To provide additional resolution on deep water sources, we compiled an integrated dataset of Nd isotopes from fossil fish teeth, C and O isotopic records, and benthic foraminiferal assemblages from seven northeast (NE) and northwest (NW) North Atlantic DSDP, ODP and IODP sites with estimated paleodepths >2000 m. In the NE, deep water εNd values are ≈-9.5 throughout the latest Cretaceous, while values at NW sites are slightly higher (≈-8.5) in the Campanian and then decrease to ≈-10 during the Maastrichtian. Although coverage is limited because many sites were below the CCD, distinct patterns occur in the stable isotopic data. NE δ13C values are ≈1.7 ppm throughout while NW δ13C values increase from ≈1.2 ppm in the Campanian to ≈1.9 ppm in the Maastrichtian, and the increase is correlated with a shift to higher % benthic epifauna. These data suggest formation of oxygen-rich/nutrient-poor NCW in the NE Atlantic during the latest Cretaceous. Decreasing δ13C and increasing εNd values from north to south are consistent with flow of NCW into the NW Atlantic during the Campanian. In contrast, lower δ13C in the South Atlantic and εNd values that are similar at high northern and southern latitudes, but separated by regions with both higher and lower values, are inconsistent with flow of SCW into the North Atlantic. The shift to lower εNd values, higher δ13C values, and abundant epifauna in the NW Atlantic during the Maastrichtian may indicate formation of a proximal deep water mass analogous to modern Labrador Sea Water that introduced nonradiogenic εNd from weathering of old shield material. To support our proxy-based interpretations, we compare them with Late Cretaceous simulations performed using NCAR CESM1.2 to investigate the sensitivity of deep water formation in the North Atlantic to atmospheric CO2 and paleogeography. Together our data and models support the notion of North Atlantic deep water formation in the Late Cretaceous.
Year of Publication: 2017
Research Program: DSDP Deep Sea Drilling Project
IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Climate change; Cretaceous; Deep Sea Drilling Project; Integrated Ocean Drilling Program; International Ocean Discovery Program; Mesozoic; North Atlantic; Ocean Drilling Program; Paleoclimatology; Upper Cretaceous
Record ID: 2018074687
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States

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