(Table 1) Strontium isotope ratios of ODP Hole 121-758A ...

• Main Authors: Clemens, Steven C, Farrell, John W, Gromet, L Peter
• Format: Dataset
• Language: English
• Published: PANGAEA 1993
• Subjects: Sample code/label; DEPTH, sediment/rock; AGE; Strontium-87/Strontium-86 ratio; Strontium-87/Strontium-86 ratio, error; Replicates; Drilling/drill rig; Mass spectrometer Finnigan MAT 261; Leg121; Joides Resolution; Ocean Drilling Program ODP; Planktonic foraminifera
• Online Access: https://dx.doi.org/10.1594/pangaea.769903; https://doi.pangaea.de/10.1594/PANGAEA.769903

The 87Sr/86Sr ratio of sea water has increased gradually over the past 40 Myr, suggesting a concomitant increase in global chemical weathering rates (Raymo et al., 1988, doi:10.1130/0091-7613(1988)016<0649:IOLCMB>2.3.CO;2; Capo and DePaolo, 1990, doi:10.1126/science.249.4964.51; Hodell et al., 1990, doi:10.1016/0168-9622(90)90011-Z; Raymo and Ruddiman, 1992, doi:10.1038/359117a0; Caldeira, 1992, doi:10.1038/357578a0; Palmer and Edmons, 1992, doi:10.1016/0016-7037(92)90332-D). Recently, Dia et al. (1992, doi:10.1038/356786a0) analysed a 250-kyr 87Sr/86Sr record, and found superimposed on this gradual increase higher-frequency 87Sr/86Sr variations which appeared to follow a 100-kyr cycle; this periodicity corresponds to one of the prominent cycles in the Earth's orbital parameters, which are known to modulate the patterns of solar insolation and hence climate (Berger, 1978, doi:10.1016/0033-5894(78)90064-9; 1989, doi:10.1016/1040-6182(89)90016-5; Imbrie et al., 1992, doi:10.1029/92PA02253). The ... : Strontium isotopes were measured on the acetic acid-soluble portions of five or ten hand-picked and ultrasonically cleaned tests of the planktonic foraminifera Globorotalia menardii (>425 µm). Samples were analysed for 87Sr/86Sr by thermal ionization mass spectrometry with a Finnigan-MAT 261 mass spectrometer using static multiple collection with simultaneous collection of mass 85 to monitor for the presence of Rb. The filament current was raised over a period of 45 min to yield a stable 88Sr signal of ~4 * 10**11 A. We did not detect a statistically resolvable signal at mass 85, and any possible corrections are of the order of 2-3 * 1**-6. Results were normalized for mass fractionation to a 86Sr/87Sr ratio of 0.1194 according to an exponential fractionation law. The site 758 87Sr/86Sr ratio measurements were made between May and October 1992 during which time one or more aliquots of the standard NBS-987 were analysed with each spectrometer run (6-12 samples). The external error associated with NBS-987 ...