Variations In Sediment Discharge And Icebergs Supply And Their Impact On The Sea-surface Characteristics On The Newfoundland Basin Of The Northwest Atlantic

Ice rafting movement is an important component of paleo marine environment change research.One of the largest ice sheets in the late Pleistocene period,the Laurentide Ice Sheet（LIS）,covered most past of northern North America,periodically sheds icebergs and supplied meltwater to the Labrador Sea,which is then transported to the south via the Labrador Current（LC）and extended to the southwest.These iceberg rafting events are most commonly known as the Heinrich massive iceberg rafting events,which profoundly impacted the North Atlantic and its surrounding regions.The Newfoundland Basin of northwestern Atlantic are adjacent to the LC on both sides of the north and west,which is the starting and ending area of the subpolar gyre（SPG）.The Newfoundland Basin is far away from the northern Laurentide ice-streams and glacial ice and is considered one of the key areas to reconstruct the historical dynamics of the LIS and its numerous ice-streams discharge.In recent years,many scholars have successively studied the sedimentology,paleoclimatology,and micropaleontology to reconstruct the past instability of the LIS from the Labrador Sea and the North Atlantic,however,there are relatively few studies on the Newfoundland Basin area.In this study,sediment core Hu9007-08 collected from the Milne Seamount of the Newfoundland Basin is used to reconstruct the past sediment discharge and meltwater supply from the LIS.This research counted the ice-rafted debris（IRD）,the abundance of various planktonic foraminifera and their assemblages and relative abundances which were combined with the oxygen and carbon isotopes that were determined in the planktonic foraminifer as well.In addition,the sediment physical properties were determined by measuring the magnetic susceptibility,digital spectrophotometric reflectance,portable X-ray fluorescence（p XRF）derived element data on the bulk sediments,and core photography.These properties were used to identify and analyze various sediment facies to assess sediment sources from different locations of the eastern Canadian land and continental margin.Oxygen and carbon isotopes in the planktonic foraminifer Neogloboquadrina pachyderma were used to construct the isotope stratigraphy of core Hu9007-08 in which the younger period of the record was bracketed by AMS-¹⁴C dates to constrain the age model.In conjunction with the AMS-¹⁴C dates and tie points from the oxygen isotope curve,the age model of core Hu9007-08 was established through using the latest"Ra Ca2020"MATLAB code which suggests that the core covers the sediment discharge and climate events as far back as 243 ka.The results of the study showed that a large amount of IRD deposited in the Newfoundland Basin came from the northern Hudson Bay.Five Heinrich events（HEs）（H11,H5,H4,H2,and H1）and sea surface cooling and cold events（C21 and C24）are identified in core Hu9007-08.Although other small IRD events are identified in core Hu9007-08 during the MIS7,MIS6 and MIS4 which might not necessarily related to the HEs.During HEs,theδ¹⁸O value was significantly reduced,the abundance of N.pachyderma was higher,and the abundance of Neogloboquadrina incompta was reduced,this indicates that a large amount of terrigenous sediments were discharged into the Newfoundland Basin of the Northwest Atlantic during the HEs,accompanied by the production of glacial meltwater,and the intrusion of polar water which caused the decrease of sea surface temperature（SST）and sea surface salinity（SSS）in the study area.Other smaller IRD events did not correspond to a significantly lowerδ¹⁸O value,which is likely to be affected by the North Atlantic Current（NAC）and insolation.The higher abundance of N.pachyderma indicates that smaller IRD events are also accompanied by the intrusion of polar water,which affects the SST and SSS in the Newfoundland Basin.The application of planktonic foraminifera assemblages and their corresponding isotopes to assess the characteristics of the ocean surface in the Newfoundland Basin may be expected to provide more theoretical foundations for the reconstruction of the paleo-ocean environment of the Northwest Atlantic.