Stable isotopc record of ODP Site 114-704
We report a near-continuous, stable isotopic record for the Pliocene-Pleistocene (4.8 to 0.8 Ma) from Ocean Drilling Program Site 704 in the sub-Antarctic South Atlantic (47°S, 7°E). During the early to middle Pliocene (4.8 to 3.2 Ma), variation in delta18O was less than ~0.5 per mil, and absolute v...
| Main Authors: | , |
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| Format: | Other/Unknown Material |
| Language: | English |
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PANGAEA
1992
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| Subjects: | |
| Online Access: | https://doi.pangaea.de/10.1594/PANGAEA.735192 https://doi.org/10.1594/PANGAEA.735192 |
| Summary: | We report a near-continuous, stable isotopic record for the Pliocene-Pleistocene (4.8 to 0.8 Ma) from Ocean Drilling Program Site 704 in the sub-Antarctic South Atlantic (47°S, 7°E). During the early to middle Pliocene (4.8 to 3.2 Ma), variation in delta18O was less than ~0.5 per mil, and absolute values were generally less than those of the Holocene. These results indicate some warming and minor deglaciation of Antarctica during intervals of the Pliocene but are inconsistent with scenarios calling for major warming and deglaciation of the Antarctic ice sheet. The climate System operated within relatively narrow limits prior to ~3.2 Ma, and the Antarctic cryosphere probably did not fluctuate on a large scale until the late Pliocene. Benthic oxygen isotopic values exceeded 3 per mil for the first time at 3.16 Ma. The amplitude and mean of the delta18O signal increased at 2.7 Ma, suggesting a shift in climate mode during the latest Gauss. The greatest delta18O values of the Gaus anti Gilbert chrons occurred at ~2.6 Ma, just below a hiatus that removed the interval from ~2.6 to 2.3 Ma in Site 704. These results agree with those from Subantarctic Site 514, which suggest that the latest Gauss (2.68 to 2.47 Ma) was the time of greatest change in Neogene climate in the northern Antarctic and Subanthtic regions. During this period, surface water cooled as the Polar Front Zone (PFZ) migrated north and perennial sea ice Cover expanded into the Subantarctic region. Antarctic ice volume increased and the ventilation rate of Southern Ocean deep water decreased during glacial events after 2.7 Ma. We suggest that these changes in the Southern Ocean were related to a gradual lowering of sea level and a reduction in the flux of North Atlantic Deep Water (NADW) with the Initiation of ice growth in the northern hemisphere. The early Matuyama Chron (~ 2.3 to 1.7 Ma) was marked by relatively warm climates in the Southern Ocean except for strong glacial events associated with isotopic stages 82 (2.027 Ma), 78 (1.941 Ma), and 70 ... |
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