The identification and characterisation of the North Atlantic Heinrich Events using environmental magnetic techniques

Abstract

Heinrich Events (HEs) define intervals of major ice rafting from the Laurentide Ice Sheet (LIS) into the North Atlantic during that last glacial period. The discovery of potential European-sourced precursors to HEs suggest that the smaller, but climactically sensitive, European ice sheets (EIS) may have played a role in the triggering of HEs and their impact on global climates. Environmental magnetism has proved itself to be a useful, rapid and non-destructive tool in the identification and quantification of provenance in sediments from various depositional environments. In this work, environmental magnetic analyses are applied to marine sediment records from the European margin of the NE Atlantic and known to contain ice-rafted debris (IRD) from both LIS and EIS sources. The primary aim in the work of this thesis is to evaluate the methodology as a means of distinguishing IRD provenance. From the data obtained here it is possible to identify several magnetic events that correspond to the HEs and other layers of detrital material and which correlate well to previous standard petrological analyses performed on the same core materials. Magnetic signatures differ within the HEs, suggesting a changing balance of input from multiple sources as opposed to a single LIS source. The data suggest a phasing of these compositional differences through individual HEs. The potential of using environmental magnetic techniques in the identification of IRD provenance within marine sediments is discussed, as is the significance of the observed provenance variations within the cores studied.