Age determination of North Atlantic sediment cores

Coupled measurements of delta18O and accelerator mass spectrometry (AMS) 14C in a particular species of planktonic foraminifera may be used to calculate sea-level estimates for the last deglaciation. Of critical importance for this type of study is a knowledge of the seasonality of foraminiferal growth, which can be provided by delta18O measurements of modern shells (core tops, plankton tows). Isotopic (delta18O, AMS-14C dating) and faunal records (transfer function sea surface temperature) were obtained from two cores in the North Atlantic at about 37°N. The locations were chosen to obtain high sedimentation rate records removed from the major ice-melt discharge areas of the last deglaciation. Based upon Globigerina bulloides data, four delta18O-based sea-level estimates were calculated: -67 +/- 7 m at 12,200 yr B.P. and -24 +/- 8 m at about 8200 yr B.P. for core SU81-18; -83 +/- 10 m at 12,200 yr B.P. and -13 +/- 11 m at about 8500 yr B.P. for core SU81-14. Using a second working hypothesis concerning the seasonability of G. bulloides growth, it is suggested that the sea-level rose by about 40 m during the millennium which followed 14,500 yr B.P.