The sediments of Lake Logurinn - A unique proxy record of Holocene glacial meltwater variability in eastern Iceland

The full Holocene development of the large (8100 km(2)) Vatnajokull ice cap in Iceland with its many outlet glaciers is poorly known. The idea of an early deglaciation, leading to a glacier-free period in mid-Holocene, followed by the Neoglaciation is still the main concept for the glacial history in the North Atlantic region, including Iceland. We have examined a continuous sediment record from the glacier-fed Lake Logurinn in eastern Iceland to infer Holocene meltwater variability of Eyjabakkajokull, which is a surge-type outlet glacier of the Vatnajokull ice cap. We focus on the early and mid-Holocene, and our data show that Eyjabakkajokull receded rapidly during the final phase of the last deglaciation, and did not deliver glacial meltwater to Lake Logurinn by 9000 years BP, suggesting that Eyjabakkajokull was significantly smaller than today at that time. The return of glacial meltwater transport to Lake Logurinn, and thus a return of Eyjabakkajokull is dated to ca 4400 years BP, suggesting an almost 5000 years long glacier-free period during early and mid-Holocene. During this time period, we infer that the 8.2 ka cold event did not cause a significant expansion of Eyjabakkajokull, however, we note a marked decrease in the aquatic productivity in Lake Logurinn, which is suggested to be the result of shorter ice-free seasons of Lake Logurinn. The Holocene Thermal Maximum is inferred by a period of maximum Holocene aquatic productivity, and dated to ca 7900-7000 years BP. Following the re-formation of Eyjabakkajokull ca 4400 years BP, we suggest that the glacier reached stable conditions ca 1700 years BP, and remained fairly stable until the later part of the Little Ice Age, when Eyjabakkajokull reached its maximum Holocene extent. (C) 2012 Elsevier Ltd. All rights reserved. (Less)