Rock magnetic proxies to infer terrigenous provenance variation on Björn Drift IODP Site U1554, preliminary results.

Reconstructing the North Atlantic Deep Water (NADW) formation and strength over time is fundamental to understanding North Atlantic and global ocean circulation and climate evolution. A multi-proxy approach on sedimentary core records can provide the temporal resolution needed to investigate NADW history for the last 12 Ma (from Upper Miocene to Pleistocene).

Here, we focus on the Björn Drift, located in the eastern flank of the Reykjanes Ridge, where the accumulation rate and provenance of sediment in the Iceland-Scotland Overflow Water (ISOW) path are sensitive to variations in the strength of NADW production as well as sediment production processes. IODP expeditions 384, 395C, and 395 drilled site U1554 (holes A-H) on the Björn Drift (60°7.5'N, 26°42.1'W, 1870 mbsl). A preliminary biostratigraphic and magnetostratigraphic age model defines the age of the basement-sediment interface at approx. 12 Ma and a maximum ≥10 cm/kyr accumulation rate. Preliminary rock magnetic analyses on selected discrete samples consist of bulk magnetic susceptibility, Anysteretic remanent Magnetization (ARM), and Isothermal Remanent Magnetization (IRM). These are compared with Nd-Sr isotopes (measured on the same samples) and used as proxies to examine sediment provenance in the Björn Drift. The aim is to determine changes to the endmember components before and after drift development. Correlations of these components with previous studies targeting IODP and ODP cores from the North Atlantic suggest that terrigenous sediment has a dominance of Icelandic source contribution in interglacial intervals and a dominance of European continental source contribution during glacial intervals.