Northeast Indian Ocean Marine Sediment core 17I106 Data Set

Abstract

Carbon-14 and calibrated calendar ages of mixed planktonic foraminifera measured in core 17I106; the clay minerals percentage of smectite, illite, kaolinite and chlorite in core 17I106; the Sr-Nd isotopes of core 17I106.The clay minerals and Sr-Nd isotopes were used to trace sediment provenance and potential climate forces in the records, and even found that Intertropical Convergence Zone (ITCZ) controlled rainfall in Myanmar and further determined the supply of clay minerals on the millennium scale.The gravity core 17I106 was collected by the R/V Shiyan 1 vessel belonging to the South China Sea Institute of Oceanology (SCSIO), 278 Chinese Academy of Sciences (CAS), from the Ninetyeast Ridge, northeast of the Indian Ocean. This core has a total length of 162 cm and 279 consists of gray to green silty clays subsampled at 1-cm intervals. The age model of core 17I106 was reconstructed based on 10 accelerator mass spectrometry (AMS) 14C dates and Bayesian interpolations between these dates. AMS 14C dating was performed on mixed planktonic foraminifera at Beta Analytic Inc. More than 20 mg of intact mixed planktonic foraminifera shells were selected from 282 the >150 μm fractions of each sample (10 g dried sample). All radiocarbon ages were converted and reported as calendar years before present with the Calib8.2 software program and the Marine20 calibration dataset. Clay minerals (<2 μm) were separated from the sediment samples according to Stokes' settling velocity principle after organic materials and carbonates were removed with 15% hydrogen peroxide (H2O2) and 0.1 N chlorohydric acid (HCl), respectively. Following evaporation in ethylene glycol for 24 hours, the clay mineral slides were measured using routine X-ray diffraction (XRD) equipment (Bruker Inc, D8 ADVANCE). The clay mineral abundance was calculated by measuring the peak areas of smectite (15-17 Å), illite (10 Å) and kaolinite/chlorite (7 Å). The relative proportions of kaolinite and chlorite were calculated from the ratio of the 3.57 Å/3.54 Å peak areas. The relative percentages of the four main clay minerals were estimated by calculating the integrated peak areas of characteristic basal reflections using Topas5P software with the empirical factors reported by Biscaye (1965). The reproducibility error of this method is ± 5-10%. This work was carried out in the Key Laboratory of Ocean and Marginal Sea Geology, SCSIO, CAS. Twenty-two samples from core 17I106 were selected for isotope analyses. The strontium (Sr) and neodymium (Nd) isotopic compositions of the sediment samples were measured using a Thermo Scientific Multi-Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICP-MS Nu plasma) at the Key Lab of Marine Sedimentology and Environmental Geology, Ministry of Natural Resources, China. The organic materials and carbonates were removed from the samples using H2O2 and HCl, respectively. Approximately 200 mg of each powdered sample was placed in a stainless steek-lined polytetrafluoroethylene (PTFE) bomb, and 1 ml HF and 1 ml HNO3 were added. The sealed bombs were heated to 185 ℃ for approximately 36 hours, followed by heating on a hot plate to evaporate to dryness following cooling. Then, Sr and Nd were extracted and purified using 300 Rb-Sr and Sm-Nd columns. To make direct comparisons more convenient, the Nd isotopic ratio results were expressed as εNd (0)=[(143Nd/144 301 Nd)meas/0.512638-1]*10000, using the corresponding chondritic uniform reservoir (CHUR) value (Jacobsen and Wasserburg, 1980). The replicate NBS-987 analyses performed during the study gave a mean 87Sr/86 302 Sr of 0.710310 ± 0.000003 (2s), close to its certified value of 0.710245. Similarly, replicate JNDi-1 analyses gave a mean 143Nd/144 303 Nd of 0.512112 ± 0.000004 (2s); its certified value is 0.511860.