Abstract:
The 45°N of North Atlantic is located at the central zone of the ice-rafted detritus (IRD) belt of the North Atlantic, where the marine sediments contain rich environmental and climatic information of high-resolution. The sedimentary records there are used for reconstruction of the pale-oceanic environment since the last glacial in this study. IRD contents, planktonic foraminiferal assemblages and their oxygen and carbon isotopes (δ
18O and δ
13C) from the core Hu71-377, are used as major tools. Combined with AMS
14C dating and oxygen isotope stratigraphy, five Heinrich layers are identified in the MIS3 and MIS2, in which the Heinrich layer 1, 2 and 4 have obvious IRD peaks, high relative abundance of
Neogloboquadrina pachyderma and light δ
18O values, but no obvious light δ
18O are observed in the Heinrich layer 3 and 5. The difference in δ
18O between the Heinrich layers 3 and 5 and the Heinrich layers 1, 2 and 4 may suggest the impacts of melt water on the upper water column. Further, the offsets between δ
13C
N.incompta and δ
13C
N.pachyderma may also reflect the changes in the mixed layer and thermocline during the Heinrich events. The δ
13C offsets were close to zero during Heinrich 1 and Heinrich 2, attributing to the vertical mixing of seawater driven by strong winds. And the δ
13C offsets became larger during Heinrich 4 and Heinrich 5, indicating that the seasonal thermocline became shallower, which supports the inference of the penetration of the North Atlantic Current. What’s more, the planktonic foraminiferal assemblages may reflect the properties of the water masses in the upper water column, especially the relative abundance of
N. pachyderma and
Neogloboquadrina incompta may indicate the sea surface temperature (SST) changes during MIS3.