DOI: 10.1594/pangaea.945744
title: Benthic foraminiferal assemblages from sediment core MSM45/19_2

description: The presented data originates from the 1306cm long gravity core MSM45-19-2 (58°45.68 N, 61°56.25 W, 202m water depth) taken during R/V Maria S. Merian cruise MSM45 in August 2015 at 202 m water depth on the northern Labrador Shelf, northeast Canada, northwest Atlantic. In order to fully understand the dynamics that contributed to the establishment of modern Labrador Sea circulation, detailed reconstructions of the major paleoceanographic changes through the Holocene are critical. Therefore, this study aims to provide new information on bottom (i.e. subsurface) water mass composition as well as on changes in primary productivity and sea-ice conditions in the LC during the Holocene. Reconstructions are based on benthic foraminiferal assemblages.Foraminiferal assemblages were counted in 15–20 and 50-cm intervals between 0–200 and 200–1300 cm core depth, respectively. Sample resolution in the upper core section was increased because of lower sedimentation rates. Each sample contained about 20 mL of wet sediment that was extracted using two syringes of 1.5 cm diameter. Samples were wet sieved through mesh sizes of 1000, 100, and 63 μm and dried. When necessary because of large sample size, the dried samples were subsequently split using a splitter. Foraminifera of the 100–1000 μm fraction were analyzed on a picking tray (following Seidenkrantz et al., 2007). At least 300 specimens were counted in each sample to obtain statistically sound numbers. Species abundances are expressed as percentages of the entire fauna. Foraminiferal concentrations, which is the number of specimens found in 1 mL of wet sediment, were calculated for all samples except for eight samples in the upper core section that were added later to increase the sample resolution. Since the wet volume of the additional samples could not be sufficiently quantified, we could not calculate foraminiferal concentrations for these samples.Only benthic foraminifera are present throughout the core. A total of 33 species were identified comprising 13 agglutinated and 20 calcareous taxa (Figure 3; Appendix 1). The main taxa are E. clavatum, I. helenae, C. reniforme, B. frigida, and N. labradorica, and the most common accessory species are E. albiumbilicatum, E. takayanagii, S. feylingi, and C. lobatulus.We differentiated four distinct climatic periods in the western Labrador Sea. From 8.9 to 8.6 ka BP, the Labrador Shelf was dominated by polar water outflow from Baffin Bay and covered by perennial sea ice. Between 8.6 and 7.4 ka BP, a strong subsurface inflow of warmer Atlantic water masses is ascribed to an intensification and redirection of the West Greenland Current. At 7.4 ka BP, the decreased influence of Atlantic water masses on the Labrador Shelf marks the establishment of winter convection leading to the formation of Labrador Sea Water in the central basin. Concurrently, an intensified polar water outflow through the Canadian Gateways strengthened the inner Labrador Current, and higher primary productivity suggests longer spring blooms because of a shorter sea-ice season during the Holocene Thermal Maximum. In the late Holocene after 3 ka BP, periodic fluctuations of primary productivity may tentatively be correlated with stronger and weaker northwesterly winds