Postglacial water-level changes of a small lake in southern Quebec, Canada

Sediment stratigraphy and palaeobotanical data from five cores were used to reconstruct the postglacial water-level changes of a small lake in souther n Quebec. The cores were taken along two transects from the centre of the l ake to the margins. Lake level was relatively high before 11 000 cal. BP, w hen sedimentation was characterized by the deposition of silty gyttja (13 0 00 cal. BP) and marl (13 000-11 000 cal. BP). From 11 000 to 7000 cal. BP, a sediment hiatus was indicated by the lack of two regional pollen zones be tween the marl and the overlying gyttja, suggesting either nondeposition or erosion of the previously deposited sediments due to a low lake level. The lake level was approximately 2 m lower than present on the basis of macrof ossil assemblages. A rise in the water level of about 1 m occurred around 7 000 cal. BP, which was interrupted by a second lowering between 6100 and 44 00 cal. BP, as indicated by a hiatus in the pollen stratigraphy. During thi s low period, the water level was at least 2 m lower than present. The last 4400 years are characterized by a continuous rise. The lake-level fluctuat ions are broadly synchronous with other palaeohydrological records in north eastern United States, Ontario, and Subarctic Quebec, implying broad-scale climatic control.