A 200 ka geomagnetic chronostratigraphy for the Labrador Sea: Indirect correlation of the sediment record to SPECMAP

A chronostratigraphic framework for the last 200 ka, based on relative variations of geomagnetic paleointensity, has been derived for the Labrador Sea where δ18O stratigraphies are compromised by lack of benthic foraminifera and environmental perturbations of the planktic record. Relative paleointensity records derived from three Labrador Sea piston cores are correlated to a recently developed 200 ka paleointensity composite (Sint-200) [Y. Guyodo, J.-P. Valet, Earth Planet. Sci. Lett. 143 (1996) 23–36]. The chronology for Sint-200 was derived by correlating oxygen isotope stratigraphies from individual paleointensity records to the SPECMAP chronostratigraphy. The correlation of Sint-200 to Labrador Sea paleointensity records allows the SPECMAP chronology to be imported into the Labrador Sea. Although comparisons of the chronostratigraphy based on paleointensity correlations with those derived from AMS 14C dates and δ18O data indicate significant discrepancies, support for the new chronostratigraphic framework is provided by: (1) consistent correlation of Labrador Sea detrital layers to North Atlantic Heinrich layers; (2) general consistency between planktic δ18O values and the SPECMAP reference curve; and (3) feasible prediction for the age of ash layer 2. As the new chronostratigraphy is tied to SPECMAP, Labrador Sea sediment cores can now be directly compared with any SPECMAP dated record.