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Groeneveld, Jeroen (2008): (Table 1) Comparison between bulk ICP-OES measurements and LA-ICP-MS analyses for Mg/Ca and Sr/Ca ratios of Globigerinoides sacculifer from ODP Hole 165-1000A [dataset]. PANGAEA,, Supplement to: Groeneveld, Jeroen; Nürnberg, Dirk; Tiedemann, Ralf; Reichart, Gert-Jan; Steph, Silke; Reuning, Lars; Crudeli, Daniela; Mason, P (2008): Foraminiferal Mg/Ca increase in the Caribbean during the Pliocene: Western Atlantic Warm Pool formation, salinity influence, or diagenetic overprint? Geochemistry, Geophysics, Geosystems, 9, Q01P23,

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We constructed a high-resolution Mg/Ca record on the planktonic foraminifer Globigerinoides sacculifer in order to explore the change in sea surface temperature (SST) due to the shoaling of the Isthmus of Panama as well as the impact of secondary factors like diagenesis and large salinity fluctuations. The study covers the latest Miocene and the early Pliocene (5.6-3.9 Ma) and was combined with d18O to isolate changes in sea surface salinity (SSS). Before 4.5 Ma, SSTMg/Ca and SSS show moderate fluctuations, indicating a free exchange of surface ocean water masses between the Pacific and the Atlantic. The increase in d18O after 4.5 Ma represents increasing salinities in the Caribbean due to the progressive closure of the Panamanian Gateway. The increase in Mg/Ca toward values of maximum 7 mmol/mol suggests that secondary influences have played a significant role. Evidence of crystalline overgrowths on the foraminiferal tests in correlation with aragonite, Sr/Ca, and productivity cyclicities indicates a diagenetic overprint on the foraminiferal tests. Laser ablation inductively coupled plasma-mass spectrometry analyses, however, do not show significantly increased Mg/Ca ratios in the crystalline overgrowths, and neither do calculations based on pore water data conclusively result in significantly elevated Mg/Ca ratios in the crystalline overgrowths. Alternatively, the elevated Mg/Ca ratios might have been caused by salinity as the d18O record of Site 1000 has been interpreted to represent large fluctuations in SSS, and cultivating experiments have shown an increase in Mg/Ca with increasing salinity. We conclude that the Mg/Ca record <4.5 Ma can only reliably be considered for paleoceanographical purposes when the minimum values, not showing any evidence of secondary influences, are used, resulting in a warming of central Caribbean surface water masses after 4.5 Ma of ~2°C.
Related to:
Groeneveld, Jeroen; Tiedemann, Ralf (2005): Magnesium/Calcium ratio and Sea surface temperatures of Site 165-1000. PANGAEA,
Groeneveld, Jeroen; Tiedemann, Ralf (2005): Uncorrected Mg/Ca and sea surface temperature data for Site 165-1000. PANGAEA,
German Research Foundation (DFG), grant/award no. 5472008: Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas
Latitude: 16.553700 * Longitude: -79.867400
Date/Time Start: 1996-02-01T04:00:00 * Date/Time End: 1996-02-02T22:30:00
Minimum DEPTH, sediment/rock: 122.75 m * Maximum DEPTH, sediment/rock: 123.25 m
165-1000A * Latitude: 16.553700 * Longitude: -79.867400 * Date/Time Start: 1996-02-01T04:00:00 * Date/Time End: 1996-02-02T22:30:00 * Elevation: -915.9 m * Penetration: 553.2 m * Recovery: 538.28 m * Location: Caribbean Sea * Campaign: Leg165 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 59 cores; 553.2 m cored; 0 m drilled; 97.3 % recovery
Average results are shown from multiple ablation profiles through cleaned G. sacculifer tests from two contaminated, with crystalline overgrowths, samples (14-5-115 and 14-5-125) and two uncontaminated, without crystalline overgrowths, samples (14-5-95 and 14-5-145). The calculated Mg/Ca ratios derived from the LA-ICP-MS measurements agree, within the method standard deviation of 5-10%, to the whole-test ICP-OES measurements performed on the same samples.
32 data points

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