Timing of the last deglaciation in Lithuania

Boulders from the Gruda Moraine, which is associated with the maximum extent of the Scandinavian Ice Sheet (SIS) during the last glaciation, and the Baltija (also referred to as the South Lithuanian), the Middle and North Lithuanian moraines, which are associated with recessional stages of the SIS, were sampled for surface exposure dating using Be-10. By combining these data with existing radiocarbon ages, we developed a chronology for the retreat of the SIS margin in Lithuania. Our new Be-10 ages suggest that the SIS margin began to retreat from its maximum extent at 18.3 +/- 0.8 Be-10 kyr. Based on a probable correlation of the Baltija Moraine with the Pomeranian Moraine in Poland, we infer that the Baltija Moraine was formed following a re-advance of the SIS margin. The ice margin retreated from the Baltija position at 14.0 +/- 0.4 Be-10 kyr. The SIS-margin retreat paused at least two more times to form the Middle Lithuanian Moraine at 13.5 +/- 0.6 Be-10 kyr and the North Lithuanian Moraine (tentatively correlated to the Pajuris Moraine) at 13.3 +/- 0.7 Be-10 kyr. Subsequent ice-margin retreat from the North Lithuanian Moraine represented the final deglaciation of Lithuania. Direct dating of these moraines better constrains the relation of ice-margin positions in Lithuania to those in adjacent countries as well as the SIS response to climate change.