Neogene history of the deep western boundary current at Rekohu
ODP Site 1124, located 600 km east of the North Island of New Zealand, records post-middle Oligocene variations in the Pacific Deep Western Boundary Current (DWBC) and New Zealand’s climatic and tectonic evolution. Sediment parameters, such as terrigenous grain size, flux, magnetic fabric, and non-d...
| Main Authors: | , , |
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| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
2004
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| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.547.2945 http://globalchange.umich.edu/Ben/Publications/joseph_mg_2004.pdf |
| Summary: | ODP Site 1124, located 600 km east of the North Island of New Zealand, records post-middle Oligocene variations in the Pacific Deep Western Boundary Current (DWBC) and New Zealand’s climatic and tectonic evolution. Sediment parameters, such as terrigenous grain size, flux, magnetic fabric, and non-depositional episodes, are used to interpret DWBC intensity and Antarctic climate. Interpretations of DWBC velocities indicate that the Antarctic Circumpolar Current reached modern intensities atV23 Ma, as the tectonic seaways expanded, completing the thermal isolation of Antarctica. Periods of more intense bottom water formation are suggested by the presence of hiatuses formed under the DWBC at 22.5^17.6, 16.5^15, and 14^11 Ma. The oldest interval of high current intensity occurs within a climatically warm period during which the intensity of thermohaline circulation around Antarctica increased as a result of recent opening of circum-Antarctic gateways. The younger hiatuses represent glacial periods on Antarctica and major fluctuations in the East Antarctic Ice Sheet, whereas intervals around the hiatuses represent times of relative warmth, but with continued current activity. The period between 11 to 9 Ma is characterized by conditions surrounding a high velocity DWBC around the time of the formation and stabilization of the West Antarctic Ice Sheet. The increased terrigenous input may result from either changing Antarctic conditions or more direct sediment transport from New Zealand. The Pacific DWBC did not exert a major influence on sedimentation at |
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