A multi-proxy reconstruction of oceanographic conditions around the Younger Dryas–Holocene transition in Placentia Bay, Newfoundland

Abstract

Abstract A marine sediment core from Placentia Bay off the south coast of Newfoundland was studied to reconstruct past oceanographic conditions based on a multiproxy approach, including diatoms, benthic foraminifera, grain size analysis, IP25, X-Ray fluorescence, calcium carbonate and total organic carbon content. Based on 6 radiocarbon dates, the 513.5 cm long core spans the age interval from ca. 13 to 10 cal kyrs BP and thus captures the transition from the Younger Dryas stadial into the Holocene at sub-decadal resolution. The Younger Dryas was characterized by cold Arctic water taxa of diatoms and benthic foraminifera and a stratified water column with high sea ice cover and low productivity due to strong influence of the Labrador Current. During the second half of the Younger Dryas, after ca. 12.2 cal kyrs BP, the influence of the Labrador Current gradually decreased and sea ice conditions became more variable. The transition towards the Holocene is characterized by a sequence of events starting with turnovers in the biogenic proxies followed by an abrupt retreat of sea ice and a rise in productivity. These events are believed to be related to a northward migration of the Gulf Stream–Labrador Current oceanic front. The Younger Dryas termination is directly followed by a detrital carbonate layer associated with the final phase of the Heinrich 0 event, linked to Laurentide Ice Sheet dynamics. During the early Holocene productivity remained high, with minimal sea ice cover, reduced stratification and stronger influence of warmer, Gulf Stream-derived waters.