Evaluating controls on ice dynamics in the north-east Atlantic using an event stratigraphy approach

Abstract

An event stratigraphy approach is used to examine controls on late Devensian-age glacial events in Ireland. The event stratigraphy, based on onshore geological evidence, is constructed from relative-age relationships of cross-cutting bedforms found behind ice margins, and radiometric dates from ice-marginal landforms. The event stratigraphy can be compared with the Greenland GRIP ice core δ 18O proxy climate record and high-resolution marine records in the north-east Atlantic. These records reflect different aspects of the coupled ice–ocean–atmosphere system on different scales. Prior to Heinrich event 1 at ∼14.5 14C kyr BP (cal. ∼17 kyr BP) the glacial event stratigraphy in Ireland more closely matches events recorded in North Atlantic marine cores. After Heinrich event 1 the Ireland glacial event stratigraphy better fits with the Greenland δ 18O record. This shift in phasing relations in the north-east Atlantic following Heinrich event 1 reflects a range of variables including onshore ice retreat, changes in sea-ice cover and strengthened thermohaline circulation. The GRIP event stratigraphy may therefore not always be the most appropriate ‘standard’ against which to compare all glacial/climate records in the north-east Atlantic region. Late Devensian glacial events in Ireland match better to shifts observed in the marine record, suggesting an ocean driver of glacial events in north-west Europe.