Quaternary CaCO3 input and preservation with Antarctic Intermediate Water: mineralogic and isotopic results from holes 818B and 817A, Townsville Trough (northeastern Australia Margin)

Abstract

The Quaternary history of metastable CaCO3 input and preservation within Antarctic Intermediate Water (AAIW) was examined by studying sediments from ODP Holes 818B (745 mbsl) and 817A (1015 mbsl) drilled in the Townsville Trough on the southern slope of the Queensland Plateau. These sites lie within the core of modern AAIW, and near the aragonite saturation depth (~1000 m). Thus, they are well positioned to monitor chemical changes that may have occurred within this watermass during the past 1.6 m.y. The percent of fine aragonite content, percent of fine magnesian calcite content, and percent of whole pteropods (>355 μm) were used to separate the fine aragonite input signal from the CaCO3 preservation signal. Stable δ18O and δ13C isotopic ratios were determined for the planktonic foraminifer Globigerinoides sacculifer and, in Hole 818B, for the benthic foraminifer Cibicidoides spp. to establish the oxygen isotope stratigraphy and to study the relationship between intermediate and shallow water δ13C of ΣCO2 and the relationship between benthic foraminiferal δ13C and CaCO3 preservation within intermediate waters fo the Townsville Trough. Data were converted from depth to age using oxygen isotope stratigraphy, nannostratigraphy, and foraminiferal biostratigraphy. -from Authors