Environmental Magnetism

 

Environmental magnetism aims to characterize the variability inherent in the environment. We use magnetic methods to aid in the interpretation of the environment, operating both at the present day and in the past. With careful targeting these techniques can potentially yield higher discriminatory power and resolution than can be afforded by more traditional characterization methods. The scope of environmental magnetic applications is very broad and rapidly spreading. Initial studies were concerned with lake sediment sequences but common applications now include core correlation, sediment tracing, geological delineation and mapping, environmental change and reconstruction and studies of paleoclimatic, paleoseismic, paleoenvironmental and diagenetic variability. Almost every project currently underway in the P-mag lab includes an environmental magnetic component. For example, we are fingerprinting suspended sediments draining the Greenland Ice Sheet into the North Atlantic Ocean. Additionally, we are using a series of deep-sea sediment cores from the North Atlantic to trace the relative effects of ice sheets and changes in bottom water circulation during the Holocene and into the last deglacial period.

Figure 1: Day plot (after Day et al., 1977) of terrestrially derived silt (3-63 µm) from Greenland (green data) and Iceland (black data) to visualize the variation in magnetic grains size with source. Note that Icelandic silts possess relatively similar fine PSD magnetic grain sizes. In contrast Greenland silts fall further along the SD/MD mixing line (e.g. Dunlop 2002) possessing higher concentrations of coarser PSD and MD grains highlighting the discrimination of source afforded by this fraction. All data from Hatfield et al., (2013).