Lear, Caroline H; Mawbey, Elaine M; Rosenthal, Yair (2010): (Table S3) Benthic foraminiferal Mg/Ca, Li/Ca and stable isotope ratios of ODP Site 122-761 [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.831022, Supplement to: Lear, CH et al. (2010): Cenozoic benthic foraminiferal Mg/Ca and Li/Ca records: Toward unlocking temperatures and saturation states. Paleoceanography, 25(4), PA4215, https://doi.org/10.1029/2009PA001880
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Abstract:
The sensitivities of benthic foraminiferal Mg/Ca and Li/Ca to bottom water temperature and carbonate saturation state have recently been assessed. Here we present a new approach that uses paired Mg/Ca and Li/Ca records to calculate simultaneous changes in temperature and saturation state. Using previously published records, we first use this approach to document a cooling of deep ocean waters associated with the establishment of the Antarctic ice sheet at the Eocene-Oligocene climate transition. We then apply this approach to new records of the Middle Miocene Climate Transition from ODP Site 761 to estimate variations in bottom water temperature and the oxygen isotopic composition of seawater. We estimate that the oxygen isotopic composition of seawater varied by ~1 per mil between the deglacial extreme of the Miocene Climatic Optimum and the glacial maximum following the Middle Miocene Climate Transition, indicating large amplitude variations in ice volume. However, the longer-term change between 15.3 and 12.5 Ma is marked by a ~1°C cooling of deep waters, and an increase in the oxygen isotopic composition of seawater of ~0.6 per mil. We find that bottom water saturation state increased in the lead up to the Middle Miocene Climate Transition and decreased shortly after. This supports decreasing pCO2 as a driver for global cooling and ice sheet expansion, in agreement with existing boron isotope and leaf stomatal index CO2 records but in contrast to the published alkenone CO2 records.
Further details:
Bryan, Sean P; Marchitto, Thomas M (2010): Mg/Ca-temperature proxy in benthic foraminifera from the Florida Strait. PANGAEA, https://doi.org/10.1594/PANGAEA.831060
Lear, Caroline H; Rosenthal, Yair; Slowey, Niall C (2002): Benthic foraminiferal Mg/Ca ratios. PANGAEA, https://doi.org/10.1594/PANGAEA.831131
Project(s):
Ocean Drilling Program (ODP)
Coverage:
Latitude: -16.737333 * Longitude: 115.535000
Date/Time Start: 1988-07-19T00:00:00 * Date/Time End: 1988-07-25T00:00:00
Minimum Elevation: -2179.0 m * Maximum Elevation: -2179.0 m
Event(s):
122-761 * Latitude: -16.737333 * Longitude: 115.535000 * Date/Time Start: 1988-07-19T00:00:00 * Date/Time End: 1988-07-25T00:00:00 * Elevation: -2179.0 m * Penetration: 732.9 m * Recovery: 281.2 m * Location: South Indian Ridge, South Indian Ocean * Campaign: Leg122 * Basis: Joides Resolution * Method/Device: Composite Core (COMPCORE) * Comment: 67 cores; 732.9 m cored; 0 m drilled; 38.4% recovery
Parameter(s):
| # | Name | Short Name | Unit | Principal Investigator | Method/Device | Comment |
|---|---|---|---|---|---|---|
| 1 | AGE | Age | ka BP | Geocode | ||
| 2 | Oridorsalis umbonatus, Lithium/Calcium ratio | O. umbonatus Li/Ca | µmol/mol | Lear, Caroline H | Inductively coupled plasma - mass spectrometry (ICP-MS) | size fraction 250-355 µm |
| 3 | Oridorsalis umbonatus, Magnesium/Calcium ratio | O. umbonatus Mg/Ca | mmol/mol | Lear, Caroline H | Inductively coupled plasma - mass spectrometry (ICP-MS) | size fraction 250-355 µm |
| 4 | Oridorsalis umbonatus, Lithium/Calcium ratio | O. umbonatus Li/Ca | µmol/mol | Lear, Caroline H | Calculated moving averages | 5 point |
| 5 | Oridorsalis umbonatus, Magnesium/Calcium ratio | O. umbonatus Mg/Ca | mmol/mol | Lear, Caroline H | Calculated moving averages | 5 point |
| 6 | Size fraction > 0.063 mm, sand | >63 µm | % | Lear, Caroline H | Grain size, sieving | |
| 7 | Size fraction > 0.063 mm, sand | >63 µm | % | Lear, Caroline H | Calculated moving averages | 5 point |
| 8 | Δ carbonate ion content | Δ[CO3]2- | µmol/kg | Lear, Caroline H | Calculated | assuming D[CO3]2- at 16.975 Ma = 0 µmol/kg using 'corrected' BWT |
| 9 | Δ carbonate ion content | Δ[CO3]2- | µmol/kg | Lear, Caroline H | Calculated | assuming D[CO3]2- at 16.975 Ma = 0 µmol/kg using 'uncorrected' BWT |
| 10 | Bottom water temperature | BWT | °C | Lear, Caroline H | Calculated | assuming BWT at 16.975 Ma = 10.25 |
| 11 | Bottom water temperature | BWT | °C | Lear, Caroline H | Calculated | assuming no saturation correction necessary (above threshold) |
| 12 | Cibicidoides mundulus, δ18O | C. mundulus δ18O | ‰ PDB | Lear, Caroline H | Mass spectrometer Finnigan MAT 252 | unadjusted, size fraction 250-355 µm |
| 13 | Cibicidoides mundulus, δ18O | C. mundulus δ18O | ‰ PDB | Lear, Caroline H | Calculated moving averages | 5 point, undajusted |
| 14 | Cibicidoides mundulus, δ13C | C. mundulus δ13C | ‰ PDB | Lear, Caroline H | Mass spectrometer Finnigan MAT 252 | unadjusted, size fraction 250-355 µm |
| 15 | Cibicidoides mundulus, δ13C | C. mundulus δ13C | ‰ PDB | Lear, Caroline H | Calculated moving averages | 5 point, undajusted |
| 16 | δ18O | δ18O | ‰ | Lear, Caroline H | with respect to PDB, seawater, using corrected BWT | |
| 17 | δ18O | δ18O | ‰ | Lear, Caroline H | with respect to PDB, seawater, using uncorrected BWT |
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
2998 data points
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