Abstract:

 We have measured the boron isotopic compositions in marine planktonic foraminifers Globigerinoides sacculifer (500600 μm and 300355 μm) and Globigerinoides ruber (300355 μm and 250300 μm) from three tropical ODP sites (Pacific Site 806, Atlantic Site 664 and Carribean Sea Site 999) during the last glacial maximum and the Holocene. Due to the limits of available sample amounts and unexpected boron loss during sample preparation, boron isotopic compositions of small size foraminifers are susceptible and large size foraminifers are better to be used for boron isotopic analysis, especially on glacialinterglacial timescales. Because of the possible enhanced dissolution effects during the last glacial maximum, δ11B in G.sacculifer from both Site 806 and Site 999 are much lower than the expected values. Whereas δ11B in G.ruber are free of the dissolution effects, and can record the changes of seawater pH. The δ11B in G.ruber from the three sites during the last glacial maximum is averagely (1.3±1.2)‰ (2 s.e.) higher than the Holocene values and comparable to the theoretical values (1.6 ‰).

Key words:

Key words: boron isotope; foraminifer; last glacial maximum; seawater pH; Globigerinoides sacculifer