Response of nannoplankton to major changes in sea-surface temperature and movements of hydrological fronts over Site DSDP 594 (South Chatham Rise, southeastern New Zealand), during the last 130 kyr

Author(s): Wells, Patricia; Okada, Hisatake
Author Affiliation(s): Primary:
48 Blackman Crescent, Canberra, Australia
Other:
Hokkaido University, Japan
Volume Title: Marine Micropaleontology
Source: Marine Micropaleontology, 32(3-4), p.341-363. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0377-8398 CODEN: MAMIDH
Note: In English. 48 refs.; illus., incl. 5 tables, sketch map
Summary: A high-resolution history of paleoceanographic changes in the subpolar waters of the southern margin of the Subtropical Convergence Zone during the last 130 kyr, is present in foraminiferal assemblages of DSDP Site 594. The foraminifera indicate that sea-surface temperatures during the Last Interglacial Climax were warmer than today, and that between substage 5d through to the end of isotope stage 2, temperatures were mostly cooler than Holocene temperatures. The paleotemperatures suggest that (1) the Subtropical Convergence was located over the site during substage 5e, later moving further north, then moving southwards to near the site during the Holocene, and (2) the Polar Front was positioned over the Site during glacial stages 6, 4, 2 and possibly parts of stage 3. Several major events are indicated by the nannofloral assemblages during these large changes in sea-surface temperature and associated reorganization of ocean circulation. First, the time-progressive trends between E. huxleyi and medium to large Gephyrocapsa are unique to this site, with E. huxleyi dominating over medium Gephyrocapsa during stages 5c-a, middle part of stage 4 and after the middle point of stage 3. This unusual trend may (at least partly) be caused by the shift of the Polar Front across the site. Second, upwelling flora (E. huxleyi and small placoliths) increase in abundance during stages 1, 3 and 5, suggesting that upwelling or disturbance of water stratification took place during the interglacials. Thirdly, there are no significant differences between the distribution patterns of the various morphotypes of medium to large Gephyrocapsa, and the combined value of all medium Gephyrocapsa increases in abundance during glacials (stages 2 and 4 and the end of stage 6), similar to the abundance trends in benthic foraminifera. Finally, subordinate nannofossil taxa also show distinctive climatic trends during the last glacial cycle: (1) Syracosphaera spp. are present in increased abundance during warmer extremes in climate (substages 5e, 5a, and stage 1); (2) Coccolithus pelagicus and Calcidiscus leptoporus dominate the subordinate nannofossil taxa, and their relative proportions seem to provide a useful paleoceanographic index, with C. pelagicus dominating when the Polar Front Zone is over the site (stages 6, 4 and 2), whilst C. leptoporus is relatively more abundant when the STC is positioned over the site (stages 1 and 5e). Increased abundance of C. pelagicus also can indicate intensified coastal upwelling. Abstract Copyright (1997) Elsevier, B.V.
Year of Publication: 1997
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 08 Paleontology, General; Absolute age; Algae; Benthic taxa; Biostratigraphy; C-14; Carbon; Cenozoic; Chatham Rise; Cores; DSDP Site 594; Dates; Deep Sea Drilling Project; Effects; Foraminifera; IPOD; Invertebrata; Isotopes; Leg 90; Marine sediments; Modern analogs; Nannofossils; Nannoplankton; Ocean circulation; Pacific Ocean; Paleohydrology; Paleotemperature; Plankton; Plantae; Pleistocene; Protista; Quaternary; Radioactive isotopes; Sea-surface temperature; Sediments; South Pacific; Statistical analysis; Upwelling
Coordinates: S453129 S453128 E1745653 E1745652
Record ID: 1998010710
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands