HIGH-RESOLUTION ROCK MAGNETIC STUDY OF A LATE PLEISTOCENE CORE FROM THE LABRADOR SEA

A high-resolution rock magnetic study of a Late Pleistocene core from the Labrador Sea, north of the Eirik Ridge on the Greenland rise, reve als three main features in the downcore variation of the rock magnetic parameters. Two are at the glacial - interglacial transitions (i. e., isotope stages 6 - 5e and 2 - 1), showing magnetic grain-size coarsen ing and increased magnetic concentration and accumulation. The magneti c grain-size coarsening and increased magnetic concentration associate d with 6 - 5e transit ion and continuing into substage 5e are related to climatic influences. The magnetic grain-size coarsening and increas ed magnetic concentration and accumulation at the 2 - 1 transition app ear to be climate related, although increased tephra concentrations ma y perturbate the record during this interval. Previous, studies in thi s region have connected the coarsening of magnetic grain size during t ransitions to current winnowing of the finer fraction during interglac ial conditions. The interpretation of the present study is that the co arsening is primarily due to increased detrital deposition related to ice retreat and the associated melt-water flux from southern Greenland . The third magnetic feature corresponds to the initial part of stage 2 where there is a distinct interval of higher coercivity. This high c oercivity interval has no obvious correlation to climate change, but a ppears to be related to the increased preservation of ultrafine single domain ferrimagnetic material due to a lack of reduction diagenesis w ithin this interval. The preservation of oxic conditions within this i nterval is indicated by a color change within the sediments.