To Heinrich and other scientists, the most conspicuous component of Heinrich event sediments was the ice rafted detritus. Comprised of sand grains, pebbles and even stones that were carried out
onto the shelf margin and beyond by icebergs, their true significance to climate events was not understood until the unusual composition of these lithic fractions was identified. Bond et al (1992) documented the presence of high concentrations of light
colored detrital carbonate within the ice rafted detritus. High IRD counts and abundances of detrital carbonate within the IRD reinforce the theory that Heinrich events are truly ice rafting events and not merely indications of reduced numbers of
Just as the light and dark shades of x-radiographs help scientists pinpoint the beginning and end of Heinrich events in the core record, the different coloration of detrital carbonate within a split core can also help scientists
determine Heinrich events. The patterns of Heinrich event detrital carbonate coloration within cores far away from the former ice margin is detectable only upon careful
examination. In contrast, the patterns of Heinrich event coloration at sites close to the margin, especially sites near the Hudson Strait, is much more easy to observe.
Bedford Institute of Oceanography
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