A sediment sequence from Loon Lake, Geographical Society Ø, East Greenland, was geophysically, sedimentologically, biogeochemically, and biologically investigated in order to reconstruct the entire history of the lake. The chronology of the 10.25 m long sequence is based on three AMS 14C dating performed on marine fossils. In the basal part of the sedimentary record a diamicton represents the deposition during the Last Glacial Maximum. Subsequent to deglaciation at c. 10,250 cal. yr BP Loon Lake area was inundated by the sea and marine sediments were deposited. A turbidite interspersed into the marine sediments at around 8300 cal. yr BP could be a result of the Storegga Tsunami or of increased meltwater supply after the 8.2 kyr BP cooling event. Marine sedimentation continued at least until c. 7500 cal. yr BP, when the isostatic rebound terminated this state. Full limnic conditions became established at c. 6000 cal. yr BP. Compared with other studies in this area such a late isolation is presumably a result of the delayed retreat of the fjord-filling outlet glacier in the Kejser Franz Josephs Fjord. The climate history documented in the Loon Lake sediments is widely masked by the sea-level history.