stratigraphic data listed in Firth et al. (1996).2. ALKENONE UNSATURATION ESTIMATES OF SEA-SURFACE TEMPER
(Prahl et al., 1988) to the growth temperature. In most cases, field and laboratory culture studies have assumed that E. huxleyi is the dominant alkenone-producing species in the modern ocean. We report here on the results of Uk ′37 time series applied to sedi-ments that significantly predate the ev...
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.550.7459 http://www-odp.tamu.edu/publications/159T_SR/CHAPTERS/CHAP_02.PDF |
| Summary: | (Prahl et al., 1988) to the growth temperature. In most cases, field and laboratory culture studies have assumed that E. huxleyi is the dominant alkenone-producing species in the modern ocean. We report here on the results of Uk ′37 time series applied to sedi-ments that significantly predate the evolutionary appearance of E. huxleyi at about 0.26 Ma. Pliocene through late Miocene-age samples were obtained from ODP Hole 958A at a rate of two per section from Cores 159-958A-5H through 14H. Age assignment of the samples was derived from a smoothed-spline fit of biostratigraphic age esti-mates (Firth et al., 1996) as a function of depth (Fig. 1). The sampling resolution is ~60 k.y. for the time interval 2.2−4 Ma, and ~25 k.y. for the interval from 4 to 6.5 Ma. It is important to note that this sampling is below the resolution required to detect obliquity- (41-k.y. period) and precessional- (23- and 19-k.y. periods) related climatic cycles and at about the limit for resolving 100-k.y. cycles related to eccen-tricity. Orbital-scale variance is evident in core photographs of Site 958 sediments, which show alternating lithologies on decimeter scales (see Firth et al., 1996). Orbital-climatic sensitivity in Pliocene and late Miocene time periods has already been demonstrated by analyses of oxygen isotopes (Raymo et al., 1992; Shackleton et al., 1995) and lithologic time series (Bloemendal and deMenocal, 1989; deMenocal, 1995). We thus consider our results to provide an indica-tion of the variance of sea-surface temperature (SST) from 2.2 to 6.5 Ma in the subtropical North Atlantic that will need development through high-resolution sampling. METHODS Samples (~6 g dry weight) were freeze-dried and extracted in a 3:1 (v/v) methanol:hexane solution using an automated pressurized |
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