Glaciation events in the Pliocene--Pleistocene volcanic succession of Iceland

Abstract

The primarily volcanic succession of rocks in Iceland was accumulated during the Miocene to Holocene Epochs at the divergent plate boundary between North America and Eurasia. The present paper re- views the evidence for distinct changes in sedimentary and volcanic facies during the Middle and Late Pliocene and the Pleistocene related to recurrent expansions ofglaciers. The preservation ofan exceptionally long and well preserved record ofNorthern Hemisphere terrestrial glaciations in Iceland is related to the climatically sensitive geographical location and to frequently extruded lava flows which hamper the erosion ofunderlying sediments. Explosive volcanism contributes to high sedimentation rates and produces extensive time markers. Recent advances in the interpretation ofdiamictites and volcaniclastic deposits intercalated between primary volcanic products and between a variety ofsediments have contributed to the establishment ofa coherent re- gional overview ofthe glaciation history ofIceland. Palaeomagnetic studies ofthe volcanic sequence enable correlation between sections at reversal levels, and absolute radiometric dating efforts during the last few decades have added to the reliability of the chronology. The oldest regional glaciation of Iceland occurred at close to 2.5 Ma, but the glaciers began to expand periodically from local mountainous massifs at 3.8 Ma. Miocene glaciation as early as 7 Ma was apparently confined to high mountains in the southeastern part of Iceland. Instances ofearly Pleistocene and Pliocene interglacial sediments on Tjörnes and Snaefellsnes, both marine and terrestrial, give insight into the climatic significance ofthe glaciation events in Iceland.