45. PLIOCENE PALEOCLIMATIC AND PALEOCEANOGRAPHIC HISTORY OF THE SOUTH ATLANTIC OCEAN: STABLE ISOTOPIC RECORDS FROM LEG 72 DEEP SEA DRILLING PROJECT HOLES 516A AND 5171
Stable isotopic analyses (18O/16O, 13C/12C) of both benthic and planktonic foraminifers from DSDP Holes 516A and 517 appear to reflect changing paleoclimatic and paleoceanographic conditions in the South Atlantic Ocean during the Pliocene. The δ 1 8 θ records of Cibicides wuellerstorfi and Globigeri...
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Text |
| Language: | English |
| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.561.2014 http://www.deepseadrilling.org/72/volume/dsdp72_45.pdf |
| Summary: | Stable isotopic analyses (18O/16O, 13C/12C) of both benthic and planktonic foraminifers from DSDP Holes 516A and 517 appear to reflect changing paleoclimatic and paleoceanographic conditions in the South Atlantic Ocean during the Pliocene. The δ 1 8 θ records of Cibicides wuellerstorfi and Globigerinoides sacculifer do not vary in phase with one another, indicating that the δ 1 8θ of C. wuellerstorfi is reflecting changing glacial ice volumes, but the δ 1 8 θ of G. sac-culifer is being influenced more by other factors, such as variable sea-surface temperatures and salinities. A net depletion in 1 8O and a series of very low-amplitude fluctuations characterize the late Pliocene planktonic δ 1 8 θ record. The stability of this section may be related to increasing surface-water temperatures in middle southern latitudes during northern hemisphere glacial ice buildup caused by differences in the phasing of the orbital precessional cycle be-tween the northern and southern hemispheres. Hole 516A is presently located in an area of strong δ13C gradients in the water column, and a similar situation prob-ably prevailed during the Pliocene. A record of the difference between the δ13C of C. wuellerstorfi and G. sacculifer (Δ13C) reflects times of increased or decreased similarity in δ13C between Circumpolar Water and subtropical surface waters throughout the Pliocene. Periods of increased or decreased Δ13C may reflect: 1) changes in water mass bound-aries because of expansion or contraction of a particular water mass, or 2) changes in the partitioning of 13C within the various components of the global carbon reservoir. These changes may be associated with glacial/interglacial climatic changes, such as the initiation of northern hemisphere glaciation. |
|---|