Age determinations on sediment cores from the North Atlantic

Here we present evidence that the most recent six of the 'Heinrich layers', deposited between 14,000 and 70,000 years ago, record marked decreases in sea surface temperature and salinity, decreases in the flux of planktonic forminifera to the sediments, and short-lived, massive discharges of icebergs originating in eastern Canada.

The path of the icebergs, clearly marked by the presence of ice-rafted detrital carbonate, can be traced for more than 3,000 km - a remarkable distance, attesting to extreme cooling of surface waters and enormous amounts of drifiting ice. The cause of these extreme events is puzzling. They may reflect repated rapid advances of the Laurentide ice sheet, perhaps associated with reductions in air temperatures, yet temperature records from Greenland ice cores appear to exhibit only a weak corresponding signal.