Influence of sediment source and type on the magnetic susceptibility of fiord and shelf deposits, Baffin Island and Baffin Bay, N.W.T.

Abstract

Volume and mass magnetic susceptibility are measured on Recent and late Quaternary sediments from the fiords and shelf of eastern Baffin Island, Baffin Bay, and the northern Labrador Sea. Major changes in hinterland bedrock geology are associated with order of magnitude changes in magnetic susceptibility. The fiords that head into the Proterozoic Foxe Fold Belt have mass magnetic susceptibilities (MS) of ~ 2–4 × 10−7 m3/kg, compared with 25–60 × 10−7 m3/kg in sediments derived from Archean gneisses and granites. Another low-MS region is the middle reach of Frobisher Bay. MS studies in Cambridge, McBeth, and Itirbilung fiords included analyses of surface samples and samples from Lehigh (< 3 m) and piston (< 11 m) cores. Lehigh cores had higher MS values on average than the piston cores, suggesting a coarsening in texture or an increase in the flux of magnetic minerals during the last 0.3–3 ka. An analysis of the MS logs of 17 piston cores indicated that six broad patterns of MS can be recognized based on a combination of the MS trend with depth and the number of MS modes in the frequency distribution. Specific comparison of lithofacies logs and the MS signal indicates that variations in MS are frequently associated with changes in texture, but in some cases significant changes are independent of texture and represent major fluctuations in source materials.