Magnetic susceptibility patterns and provenance of ice-rafted material at Feni Drift, Rockall Trough: implications for the history of the British–Irish ice sheet

Abstract

Piston core ENAM 97-09 from Feni Drift, Atlantic margin west of Ireland provides a record of IRD input variability and provenance during the last ∼250,000 yrs. The IRD patterns can be related to Late Devensian (<30,000 yrs BP) ice advances and retreats at the southwestern sector of the British–Irish ice sheet (BIIS) known from terrestrial investigations. Inferences can be made about the BIIS evolution during earlier periods, which is poorly constrained from the land record. Detrital carbonate and (meta)sedimentary rock fragments represent two major IRD types, which were dominantly derived from Irish inland ice and the Irish Sea ice stream, respectively; additional evidence for the latter source is based on heavy mineral data. Input from other circum-North Atlantic ice sheets, notably the Laurentide ice sheet, is minor compared to British–Irish IRD, at least during periods of maximum expansion of the BIIS. This is consistent with the marginal location of the core site with reference to the main North Atlantic IRD belt. On the other hand, Laurentide IRD presumably accounts for minor IRD peaks at times of reduced ice volume in the British Isles. The main magnetic susceptibility peak during late isotope stage 2/Termination I can be related to IRD input from the Laurentide ice sheet, following early decay of the BIIS. A similar pattern is observed during oxygen isotope stage 6. These observations are consistent with recent provenance studies indicating that only Laurentide IRD carries a strong magnetic susceptibility signal.