A 237-year coral record of Sr/Ca ratios and oxygen isotopes collected from Bicol, the Philippines: raw data

A 2.5-m-long core (SWGM03–01) was collected from a Porites sp. colony at 6 m below mean sea level on 16 March 2002. The core was drilled vertically from the top of the colony and then cut into 7-mm-thick slabs in the laboratory. The δ18Ocoral values of samples covering the period from 1890 to 2002 was analyzed using an online system comprising an IsoPrime Isotope-ratio mass spectrometer (GV Instruments Ltd.) coupled to a Multicarb automatic sample treatment system at the Geological Survey of Japan (GSJ), whereas the δ18Ocoral values of samples predating 1890 were determined by the Center for Advanced Marine Core Research at Kochi University (KCC) using a same system used at GSJ. All δ18Ocoral data were normalized to Vienna Pee Dee Belemnite (V-PDB) using the NBS-19 standard (δ18O = +2.2‰) from the U.S. National Institute of Standards and Technology. The International Atomic Energy Agency standard IAEA-603 (δ18O = –2.37 ± 0.04‰) was also used for some measurements conducted at KCC. The standard deviations of replicate δ18O measurements of the standards during the mass spectrometer runs were 0.04‰ (1s) and < 0.10‰ (1s) at GSJ and KCC, respectively. Concentrations of Ca and Sr were measured by inductively coupled plasma optical emission spectrometry (ICP-OES) using an IRIS Advantage system (Thermo Electron Co., Ltd) at GSJ and an Agilent 720 system (Agilent Technologies) at Okayama University. Each sample was first weighed (100 ± 10 µg) and then dissolved in 2% HNO3. Sr/Ca analyses of samples covering the period after 1883 were conducted at GSJ, and samples predating 1890 were analyzed at Okayama University, respectively, with a 6-year overlap to confirm measurement consistency. The analytical precision (RSD) of the Sr/Ca measurements was < 0.37% (1s) made at both facilities. Measurements of Sr/Ca were mostly performed on microsamples, every 0.8 mm and 1.6 mm for the first 46 years and the remainder of the record, respectively. Given that mean growth rate is approximately 8.0 mm/yr, temporal resolution of the Sr/Ca analyses for the most recent 46 years of the record was approximately monthly, whereas for the rest of about 190 years, the resolution was mostly bimonthly. The temporal resolution of the d18O analyses was bimonthly throughout most of the core. An age model for the period before 1982 was constructed using the Sr/Ca ratios with Sr/Ca maxima (indicating relatively cool SSTs) corresponding to growth mainly in winter (January or February). Other Sr/Ca ratios in this time interval were then converted to the time domain by simple linear interpolation. For the period 1982–2002 in which Sr/Ca analyses were conducted with higher time resolution, the precise timing of the coolest SSTs was determined using IGOSS weekly SSTs then converted to the time domain. This age model for the entire core was confirmed and fine-tuned by counting annual density bands on the X-radiographs of the coral core and applied to d18O record as well.