LATE-GLACIAL AND POSTGLACIAL DEPOSITIONAL-ENVIRONMENTS IN THE NORWEGIAN TRENCH, NORTHERN NORTH-SEA

The late Weichselian sequence in the northern part of the Norwegian Tr ench is composed of eight units. The two lowermost units are massive, firm to stiff diamictons, interpreted to have been deposited beneath i ce-streams that in ail likelihood reached the shelf edge. They are ove rlain by glaciomarine and normal-marine sediments deposited after 15 0 00 BP. The first phase of glacial retreat from the Norwegian Trench (1 5 000-14 800 BP) was very rapid and left a thin layer of proximal sedi ments on top of the tills. This was followed by a period with lower ac cumulation rates (14 800-13 600 BP), probably as a result of rapid sou rce retreat and cold meltwater inhibiting dropstone fall-out. The end of this interv al marks the change from ice-stream calving in cold wat er to melting on land. According to lithologic and isotopic data, the maximum rate of Fennoscandian ice-sheet disintegration took place arou nd 12 500 BP. The water temperatures declined significantly and rates of sedimentation and ice-rafting fell in association with the Younger Dryas period. The final retreat of the ice began as early as 10 500 BP , and the transition to normal-marine sedimentation is reflected by pr ecipitation of iron oxide followed by pyrite, reduced sedimentation ra tes, and a change from terrigenous to biogenic sedimentation.