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Science 21 April 2006:
Vol. 312. no. 5772, pp. 428 - 430
DOI: 10.1126/science.1120044
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Reports

Timing and Climatic Consequences of the Opening of Drake Passage

Howie D. Scher* and Ellen E. Martin

Department of Geological Sciences, University of Florida, Gainesville, FL 32611, USA.


Figure 1 Fig. 1. Plate tectonic reconstructions illustrating locations of {epsilon}Nd records and the time-progressive evolution of worldwide seawater {epsilon}Nd values from the early middle Eocene, late middle Eocene, and late Eocene. Atlantic sector ODP Sites 1090 and 689 are designated by solid squares. (A) Locations of ODP Site 1090 and other relevant sediment cores and Fe-Mn crusts on a late Eocene plate tectonic reconstruction. Solid circles distinguish locations with middle to late Eocene Nd isotope records. Open circles correspond to locations of older and younger Nd isotope records that are discussed in the text. (B to D) Numbers represent the arithmetic mean of Nd isotope data from samples falling within the corresponding time interval. Numbers in italics represent a linear interpolation through the midpoint of the time interval using adjacent data points (table S3). Sources of the Nd isotope data used in this figure are contained in table S3. [View Larger Version of this Image (37K GIF file)]
 

Figure 2 Fig. 2. Nd isotope records, temperature and ice volume, and productivity proxy records from Atlantic and Indian sector sediment cores, and the global composite {delta}18O record for the middle Eocene to early Oligocene. (Top) Reactive phosphorus mass accumulation rate (Pr MAR) data for ODP Site 1090 from Anderson and Delaney (14), including early middle Eocene data from their auxiliary material that has been plotted according to the extended chronology for ODP Site 1090 described in table S1. (Middle) {epsilon}Nd records for Sites 1090 (solid circles) and 689 (open circles). The error bar represents 2{sigma} external reproducibility (10). The Eocene range of Pacific and Atlantic {epsilon}Nd values are noted on the left y axis. (Bottom) {delta}18O values for the global composite and ODP Sites 689 (Maud Rise) and 748 (Kerguelen Plateau). All Southern Ocean {delta}18O data are from Cibicidoides spp. reported relative to the Vienna Pee Dee belemnite standard ({per thousand} VPDB) and have been adjusted by + 0.64 {per thousand} to account for vital effects. Sources of {delta}18O data are as follows: ODP Site 689 (6); ODP Site 689, high resolution; and ODP Site 748 (31), global composite (1). Gray bars highlight inferred associations between changes in ocean circulation and sea surface productivity in the Atlantic sector. The vertical dashed gray line highlights the onset of radiogenic {epsilon}Nd values and the termination of the MECO (31). [View Larger Version of this Image (39K GIF file)]
 

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