Paleogene deepwater mass composition of the tropical Pacific and implications for thermohaline circulation in a greenhouse world

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doi: 10.1029/2007GC001748
Author(s): Thomas, Deborah J.; Lyle, Mitchell; Moore, Theodore C., Jr.; Rea, David K.
Author Affiliation(s): Primary:
Texas A&M University, Department of Oceanography, College Station, TX, United States
Other:
University of Michigan, United States
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 9(2). Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027 CODEN: GGGGFR
Note: In English. 48 refs.; illus., incl. 2 tables, sketch map
Summary: The Pacific Ocean likely exerted the greatest marine influence on climate during the greenhouse interval of the Paleogene. The first step toward assessing the role of Pacific deepwater circulation in global heat transport is a comprehensive reconstruction of deepwater mass composition and circulation patterns. We present new deepwater mass Nd isotope data from ODP Leg 199 Sites 1215, 1217, 1219, and 1221 to augment the existing coverage provided by ferromanganese crust and fossil fish debris data. The new data corroborate the notion that the Pacific Ocean operated in a bimodal pattern with deepwater sources in both the Southern Ocean and North Pacific for much of the early to middle Paleogene. In addition, the data indicate that there was little to no influence of Atlantic waters on the deepwater composition of the tropical Pacific. The available deepwater Nd isotope data provide refined constraints on the geographic and depth range of influence of both a Southern Ocean and North Pacific deepwater mass. From ∼65 to ∼45 Ma, the deep tropical Pacific was the mixing location of deep waters sourced from the Southern Ocean and the North Pacific. The Southern Ocean deepwater mass extended from ∼1800 m to abyssal depths. Until 53.6 Ma it circulated northward in the western Pacific at least as far as the paleolocation of Fe-Mn Crust CLD01 (∼5°N paleolatitude) and in the eastern portion of the Pacific as far as Site 1215 (∼10°N paleolatitude). A North Pacific deepwater mass extended from at least ∼2400 m to 2900 m water depth from ∼65 to 54 Ma, south to Shatsky Rise (paleolatitude ∼10-15°N), and possibly as far as Site 1215, 700 km to the south of Shatsky Rise Sites 1209 and 1211.
Year of Publication: 2008
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Cenozoic; Chemical composition; Climate change; Deep-sea environment; Equatorial Pacific; Greenhouse effect; Isotope ratios; Isotopes; Leg 199; Marine environment; Metals; Nd-144/Nd-143; Neodymium; North Pacific; Northwest Pacific; ODP Site 1215; ODP Site 1217; ODP Site 1219; ODP Site 1221; Ocean Drilling Program; Ocean circulation; Pacific Ocean; Paleo-oceanography; Paleoclimatology; Paleogene; Rare earths; Sea water; Shatsky Rise; Stable isotopes; Tertiary; Thermohaline circulation; West Pacific
Coordinates: N260200 N260200 W1475600 W1475600
N165200 N165200 W1380600 W1380600
N074800 N074800 W1420100 W1420100
N120200 N120200 W1434200 W1434200
Record ID: 2008122361
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