Neogene evolution of deep-water Nd isotope values at Walvis Ridge ODP Sites 1262-1264

Author(s): Thomas, D. J.; Via, R. K.
Author Affiliation(s): Primary:
Texas A&M University, Department of Oceanography, College Station, TX, United States
Volume Title: AGU 2006 fall meeting
Source: Eos, Transactions, American Geophysical Union, 87( Fall Meeting Suppl.); American Geophysical Union 2006 fall meeting, San Francisco, CA, Dec. 11-15, 2006. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0096-3941 CODEN: EOSTAJ
Note: In English
Summary: We present new Nd isotope records from Walvis Ridge ODP Sites 1262-1264 spanning the past 24 million years to complement published benthic foraminiferal δ13C and Mg/Ca data in the investigation of the Neogene evolution of Atlantic thermohaline circulation. The new Nd data indicate that deep water εNd(t) values from ODP Site 1262 decrease from "11.0 at 11.8 Ma to "12.1 by 10.6 Ma, followed by a further rapid decrease to "13.3 by 7.3 Ma. This decrease parallels the Nd isotope decrease contained in Fe-Mn crust records from the northwestern Atlantic, however the decrease at ODP Site 1262 (4755 m water depth) occurred nearly 6 million years earlier than the corresponding changes any Atlantic crust record or sedimentary sequence shallower than 2700m water depth. The combination of these data sets suggests a change in deep-water mass stratification beginning ≈10.6 Ma. A potential cause of the rapid decrease in Site 1262 Nd isotope values and the change in deep-water mass stratification is the onset of deep-water convection in the Labrador Sea. However, an increase in the delivery of very nonradiogenic Nd via glacial mechanical weathering must have accompanied this change in deep convection to produce the characteristically low Labrador Sea Nd isotopic signature. Both the onset of deep convection in the Labrador Sea and an increase in glacial delivery of more nonradiogenic Nd to the region of convection can be explained by overall climatic cooling during the middle and late Miocene.
Year of Publication: 2006
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; C-13/C-12; Carbon; Cenozoic; Deep-sea environment; Isotope ratios; Isotopes; Leg 208; Marine environment; Metals; Nd-144/Nd-143; Neodymium; Neogene; ODP Site 1262; ODP Site 1263; ODP Site 1264; Ocean Drilling Program; Paleo-oceanography; Rare earths; South Atlantic; Stable isotopes; Tertiary; Thermohaline circulation; Walvis Ridge
Coordinates: S271100 S271100 E0013500 E0013400
S283200 S283200 E0024700 E0024700
S283200 S283200 E0025100 E0025100
Record ID: 2007070721
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