Modern Pacific Coccolith Assemblages: Derivation and Application to Late Pleistocene Paleotemperature Analysis

Abstract

Factor analyses of relative abundance counts of coccoliths from selected Pacific Ocean core tops yield six assemblages that coincide with the following surface water masses and regions: (1) the Kuroshio system and Pacific Equatorial Water Mass; (2) the southern and northern central Pacific regions (both occupied by two assemblages), (3) the Western South Pacific Central Water Mass, and (4) Downloaded from 424 GEITZENAUER AND OTHERS the Subarctic Pacific and Intermediate Water Masses. The sixth assemblage represents a flora that is transitional between the subpolar and central Pacific regions in both hemispheres and that occurs as well within the Peru Current system.Transfer functions relating the assemblages to sea-surface temperatures were applied to coccolith populations that existed over the past 200,000 yr and that were taken from cores in the western equatorial Pacific (cores V28-238 and V28-239) and the eastern Pacific (core V19-55). The values produced are floral indices calibrated on seabed samples to be unbiased estimates of summer sea-surface temperatures (T s ), winter sea-surface temperatures (T w ), and seasonality (T s -TJ. T s in the western equatorial Pacific varies within relatively narrow limits, with a maximum range of 5.7° and 3.9°C. T w shows relatively greater fluctuation, with a maximum range of 8.9° and 6.3°C. T s and T w in the eastern Pacific show much less variation, with a maximum range of 1.9° and 3.3°C, respectively. There appears to be no correlation between T s and glacial events. A seasonality (T s -T w ) maximum occurs in midcycle just before glaciation in "glacial cycles" (Kukla, 1961) B, D, and E. The seasonality change is greater in the western equatorial cores.The foregoing adds evidence to support the theory that sea-surface temperature over the past 200,000 yr has not globally varied sinusoidally but is subject to complex regional dynamics.

Time-Progressive Morphometric Changes of the Genus Gephyrocapsa in the Quaternary Sequence of the Tropical Indian Ocean, Site 709

“…First, small forms of Gephyrocapsa (excluding G. protohuxleyi) are more abundant throughout the Quaternary sequence in Hole 709C than in the Pacific core. In addition, several reports have been given that imply environmental controls over the morphology of Gephyrocapsa species (i.e., Bukry, 1973;Geitzenauer et al, 1976Geitzenauer et al, , 1977Roth and Coulbourn, 1982). In these reports, specimens with high-angled bridges were found abundantly in low latitudes, whereas specimens with low-angled bridges were more common in high latitudes.…”

Calcareous nannofossils in the basal Zanclean of the Eastern Mediterranean Sea: remarks on paleoceanography and sapropel formation

“…In fact, in the DCM model, the increased primary production is confined to the lower part of the photic zone, whereas the upper layers may be characterized by relatively low primary production and may be also by higher temperatures (at least in summer). The latter would be responsible for the observed decreased abundances of C. pelagicus, this species being a well-known cold-water indicator (e.g., McIntyre and Bé, 1967;McIntyre et al, 1970;Geitzenauer et al, 1976).…”

Development and testing of transfer functions for generating quantitative climatic estimates from Australian pollen data

“…This approach of transferring values from taxa and trends in modern spatial datasets to fossil assemblages was then taken up by other branches of the biological sciences, e.g. Radiolaria (Sachs, 1973), diatoms (Maynard, 1976), coccoliths (Geitzenauer et al, 1976) and chironomids (Walker et al, 1991;Lotter et al, 1997Lotter et al, , 1999Battarbee, 2000). The application has been steadily growing as a method of palaeoclimatic reconstruction from pollen data in North America (Bartlein and Witlock, 1993) and Europe (Wick et al, 2003;Seppä et al, 2004;Kumke et al, 2004) (Sachs et al, 1977;Lowe and Walker, 1984).…”