The Disturbance of Arctic Lake Sediments by "Bottom Ice": A Hazard for Palynology

Résumé

A small unnamed lake, 100 m long and 3 m deep, about 15 km north of Pelly Lake, Keewatin District was largely frozen on Jun 15, 1966. Surface ice had melted by Jul 1, but water temp remained near freezing due to ice on the lake bottom. Blocks of bottom ice, which subsequently floated to the surface, were filled with sand and mud; these sediments were released as ice blocks floated and melted. It is suggested that the origin of "mud-center" lakes may be explained by such a process. Massive mixing of bottom sediments in shallow arctic and subarctic lakes, in Recent time and even under Pleistocene and late-glacial conditions is probable. Stratigraphic disturbance of lacustrine deposits, which will render them useless for palynologic research, would occur.