Climate and ocean circulation patterns during and after the early Maastrichtian cooling event

Author(s): Haynes, Shannon J.; MacLeod, Kenneth G.; Martin, Ellen E.
Author Affiliation(s): Primary:
University of Missouri at Columbia, Department of Geological Sciences, Columbia, MO, United States
University of Florida, United States
Volume Title: Geological Society of America, 2014 annual meeting & exposition
Source: Abstracts with Programs - Geological Society of America, 46(6), p.274; Geological Society of America, 2014 annual meeting & exposition, Vancouver, BC, Canada, Oct. 19-22, 2014. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7592 CODEN: GAAPBC
Note: In English
Summary: An early Maastrichtian increase in benthic oxygen isotope values (δ18O) in the equatorial Pacific and South Atlantic Oceans indicates a brief (∼1-2 million year) cooling event at c. 71.5 Ma. Here, we use neodymium isotopes (εNd) from fish debris (microfossil tooth, scale, and bone fragments) to make inferences about intermediate and deep water formation and circulation patterns across the early Maastrichtian cooling event. Correlated shifts in εNd values at widely spaced sites could indicate a change in the location of bottom water formation, whereas the absence of an εNd shift could indicate cooling in the region of downwelling without requiring a change in circulation patterns. Cooling in many regions appears to correlate with changes in εNd values that are consistent with an increase in Southern Component Water (SCW). Anomalously high εNd values are reported during the early Maastrichtian cooling event at a site 525 on Walvis Ridge, but this excursion does not fit the SCW model. For Site 525, the early Maastrichtian shift was attributed to local volcanism with the correlation to widespread δ18O and δ13C excursions apparently coincidental. At Site 525 we confirm anomalously high εNd values during the early Maastrichtian cooling event, but also observe a 2-3 εNd unit decrease 30 m above the cooling event. Further, even late Maastrichtian values at Site 525 remain ∼2 εNd units above expected SCW values, but typical SCW values are found in late Maastrichtian samples in deeper sites from the northern flank of Walvis Ridge. To test whether the εNd value anomalies recorded on the top of Walvis Ridge are local and to search for a record of Southern Component Water along the bathymetric barrier between the Southern Ocean and the South Atlantic, we are analyzing samples from Site 516 (Rio Grande Rise) as well as increasing sampling density at Site 525, and Site 463 (mid-Pacific Mountains, equatorial Pacific Ocean). In addition we are analyzing spot samples from the North Atlantic Ocean, South Atlantic Ocean, and Caribbean Sea.
Year of Publication: 2014
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; C-13/C-12; Carbon; Cretaceous; DSDP Site 463; DSDP Site 516; DSDP Site 525; Deep Sea Drilling Project; IPOD; Isotope ratios; Isotopes; Leg 62; Leg 72; Leg 74; Lower Maestrichtian; Maestrichtian; Marine environment; Mesozoic; Metals; Mid-Pacific Mountains; Nd-144/Nd-143; Neodymium; North Pacific; Northwest Pacific; O-18/O-16; Ocean circulation; Oxygen; Pacific Ocean; Paleo-oceanography; Paleoclimatology; Paleoenvironment; Rare earths; Rio Grande Rise; South Atlantic; Stable isotopes; Upper Cretaceous; Walvis Ridge; West Pacific
Coordinates: S290415 S290414 E0025908 E0025907
S302000 S261000 W0351500 W0381000
N212101 N212101 E1744004 E1744004
Record ID: 2015031512
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States