(Table 1) Strontium isotope data for marine barnacles, ODP Hole 178-1103A

Strontium isotope ratios from multiple plates of two barnacle fragments from Site 1103 (Ocean Drilling Program Leg 178) provide maximum age estimates for the oldest glacial sedimentary package drilled. Three moderately preserved barnacle fragments from 262.63 meters below seafloor (mbsf) yielded a mean best-fit age of 7.4 Ma. A single, well-preserved fragment from the same horizon yielded a best-fit age of 12.2 Ma. Two moderately preserved fragments from 262.98 mbsf yielded a mean best-fit age of 7.8 Ma. The calculated mean strontium ages of 7.8 and 7.4 Ma agree well with the diatom estimates of 8.68 to 5.89 Ma for the underlying sediments.

Strontium isotope ratios of planktonic foraminifera from ODP Site 119-744 on the Kerguelen Plateau, Indian Ocean (Table 1)

87Sr/86Sr ratios of well-preserved early Miocene-Oligocene planktonic foraminifers from Site 744 in the southern Indian Ocean provide the highest southern latitude Sr isotope record of this age. The isotopic data have been calibrated with the site magnetostratigraphy. 87Sr/86Sr ages were also determined using the Sr isotope-age equations of Miller et al. (1988, doi:10.1029/PA003i002p00223) and Hess et al. (1989, doi:10.1029/PA004i006p00655). There is good agreement between the calculated ages from 87Sr/86Sr measurements using these equations and those derived from magnetobiostratigraphy. In addition, these equations were useful for inference of sediment ages in intervals where the paleomagnetic record is not well resolved and the biostratigraphy is inconclusive. The Site 744 87Sr/86Sr record can be used for correlation of Antarctic and low-latitude sequences and biostratigraphical zonation of foraminifers, radiolarians, diatoms, and calcareous nannofossils. This record will assist in the development of the high southern latitude biochronology.

Pleistocene-Pliocene strontium-isotope ratios of ODP Site 107-653 (Table 1)

Strontium isotopic determinations were made on samples from the Pliocene-Pleistocene sequence recovered at ODP Hole 653A, the proposed "deep-sea type section" for the Mediterranean region. Biostratigraphic correlations can be combined with the patterns of variations in the 87Sr/86Sr values to delineate the following: (1) the earliest Pliocene (MP11 to basal MP12 zones) is distinguished by fluctuations in the ratio, probably related to the unstable paleoceanographic conditions following the Zanclean flooding and initial in-filling of the Mediterranean after the Messinian desiccation, (2) during most of the Pliocene between approximately 4.5 and 2.4 Ma (MP12 to MP15 zones) the 87Sr/86Sr values remain relatively constant, producing a plateau in the strontium isotope-depth curve for this period, and (3) beginning at approximately 2.4 Ma (across the MP15/MP16 boundary) and continuing into the latest Pleistocene, the 7Sr/86Sr values increase significantly but show fluctuations that have both positive and negative slopes. The presence of a plateau in the curve generated for the Mediterranean type section duplicates in greater detail the late Neogene results reported by DePaolo (1986, doi:10.1130/0091-7613(1986)14<103:DROTNS>2.0.CO;2). The virtual lack of change in the ratio between 4.5 and 2.4 Ma essentially eliminates strontium isotopes as a high-resolution correlation method for this period. The fluctuations in the ratio beginning at 2.4 Ma may be a reflection of major climatic changes occurring in the latest Pliocene-Pleistocene. The relationship between glacial-interglacial cycles and seawater 87Sr/86Sr values suggested by DePaolo (1986) and Capo and DePaolo (1987) is uncertain but should be tested as significant increases and decreases in 87Sr/86Sr of seawater have apparently occurred since 2.4 Ma.

Strontium isotope analysis of seawater and at a mixture of planktic foraminifera during the Paleocene and Early Eocene from different holes of ODP Leg 2008

We refined the strontium isotope seawater curve for the Paleocene and early Eocene by analysis of samples recovered from the Walvis Ridge during Ocean Drilling Project (ODP) Leg 208. The highest 87Sr/86Sr values occurred in the earliest Paleocene at 65 Ma and generally decreased throughout the Paleocene, reaching minimum values between 53 and 51 Ma in the early Eocene before beginning to increase again at 50 Ma. A plausible explanation for the 87Sr/86Sr decrease between 65 and 51 Ma is increased rates of hydrothermal activity and/or the eruption and weathering of large igneous provinces (e.g., Deccan Traps and North Atlantic). Strontium isotope variations closely parallel sea level and benthic d18O changes during the late Paleocene and early Eocene, supporting previous studies linking tectonic reorganization and increased volcanism to high sea level, high CO2, and warm global temperatures.

Strontium isotope and rare earth element geochemistry of basalts from DSDP Leg 37

87Sr/S6Sr ratios have been determined on eleven whole rock basalt samples from DSDP Leg 37. The 87Sr/S6Sr ratios range from 0.70305 +/- 4 to 0.70451 +/- 4 due to alteration and contamination with seawater Sr. Leaching with 5% HF has only a small effect on the 87Sr/86Sr of the samples. However, treatment with 6M HCl in acid digestion bombs at 130°C removes the contaminant more effectively. Altered plagioclase and olivine are dissolved during this process. The mean 87Sr/86Sr of four HCl-treated samples from hole 332A is 0.70299 and that for five samples from hole 332B is 0.70297. The 87Sr/86Sr ratios of treated samples from holes 333A and 335 are 0.70304 +/- 4 and 0.70316 +/- 4, respectively. These 87Sr/86Sr ratios are within the range observed for other basalts elsewhere along the Mid-Atlantic Ridge in the North Atlantic. REE distribution patterns have been determined for four samples, three from hole 332B and one from hole 335. CeN/YbN ratios range from 0.58 to 1.30 and do not correlate with 87Sr/86Sr ratios. The source regions of these basalts appear to have been variable in REE abundances.

Precision and long-term stability of clumped-isotope analysis of CO2 using a small-sector isotope ratio mass spectrometer

RATIONALE The ratio of the measured abundance of 13C18O bonding CO2 to its stochastic abundance, prescribed by the delta 13C and delta 18O values from a carbonate mineral, is sensitive to its growth temperature. Recently, clumped-isotope thermometry, which uses this ratio, has been adopted as a new tool to elucidate paleotemperatures quantitatively. METHODS Clumped isotopes in CO2 were measured with a small-sector isotope ratio mass spectrometer. CO2 samples digested from several kinds of calcium carbonates by phosphoric acid at 25 degrees C were purified using both cryogenic and gas-chromatographic separations, and their isotopic composition (delta 13C, delta 18O, Delta 47, Delta 48 and Delta 49 values) were then determined using a dual-inlet Delta XP mass spectrometer. RESULTS The internal precisions of the single gas Delta 47 measurements were 0.005 and 0.02 parts per thousand (1 SE) for the optimum and the routine analytical conditions, respectively, which are comparable with those obtained using a MAT 253 mass spectrometer. The long-term variations in the Delta 47 values for the in-house working standard and the heated CO2 gases since 2007 were close to the routine, single gas uncertainty while showing seasonal-like periodicities with a decreasing trend. Unlike the MAT 253, the Delta XP did not show any significant relationship between the Delta 47 and delta 47 values. CONCLUSIONS The Delta XP gave results that were approximately as precise as those of the MAT 253 for clumped-isotope analysis. The temporal stability of the Delta XP seemed to be lower, although an advantage of the Delta XP was that no dependency of delta 47 on Delta 47 was found. Copyright (c) 2012 John Wiley & Sons, Ltd.