Éléments d'une climatostratigraphie du Pléistocène moyen et tardif dans l'est du Canada par l'analyse palynologique et isotopique du forage 84-030-003, mer du Labrador

• Published in: Canadian Journal of Earth Sciences
• Main Authors: Vernal, A. de, Hillaire-Marcel, C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1987
• Subjects: Labrador Sea; Neogloboquadrina pachyderma; North Atlantic; Subarctic
• Online Access: http://dx.doi.org/10.1139/e87-178; http://www.nrcresearchpress.com/doi/pdf/10.1139/e87-178

The piston and gravity cores 84-030-003, collected in the southern Labrador Sea, have been sampled for detailed palynological and isotopic analyses. The δ 18 O record on foraminifera (Neogloboquadrina pachyderma, left-coiling) indicates a stratigraphy spanning isotopic stages 8 to 1, i.e., over ca. 300 000 years. The isotopic record allows the calculation of a mean sedimentation rate of approximately 5 cm/ka.The pollen and spore contents of the sediments are low. The low pollen influxes (generally less than 1 grain/cm 2 per year) and the dominance of Pinus suggest aeolian transport over long distances with southwest–northeast to south-southwest–north-northeast trends. Dinoflagellate cyst concentrations are relatively low, indicating a low regional phytoplanktonic productivity. The assemblages are, however, diversified. They reflect influences from the North Atlantic Drift and from the Labrador Current. The occurrence of warm-temperate to tropical Impagidinium species in deposits suggests an almost permanent penetration of North Atlantic water masses into the Labrador Sea during the middle and Late Pleistocene. This divergence was apparently interrupted during the last glacial maximum of isotopic stage 2. Increases in the concentration of dinocysts such as Operculodinium centrocarpum, Nematosphaeropsis labyrinthea, and Bitectatodinium tepikiense were recorded during interglacial maxima of stages 7, 5, and 1. These dinocyst peaks indicate a high primary productivity and cool-temperate to subarctic conditions in surficial water masses offshore eastern Canada. In addition, they are probably related to a strong hydrodynamic regime of the Labrador Current. Fluctuations in the dinocyst concentrations are in most cases synchronous with the δ 18 O changes of foraminifera, indicating a strong relationship between the paleo-oceanography of the Labrador Sea and the Quaternary glaciations.