Late-Wisconsinan chronology and history of vegetation in the Ogilvie Mountains Yukon Territory

Abstract

Studies of Pleistocene geology and history in the western Ogilvie Mountains, bordering on the east of the unglaciated region in Yukon, were made by Hughes who has recognized three major glacial episodes characterized by successive advances and retreats of valley glaciers originating in cirques along the axis of the southern Ogilvie Ranges. Palynological studies and radiocarbon dating have been used to support and confirm the chronology of complex moraine sequence. The youngest of these glacial episodes is believed to have culminated prior to 10,000-12,900 years ago. The history of late 'Wisconsinan vegetation in this area, as inferred from palynological and paleobotanical studies, holds special interest because of the postulated survival of plants in the adjacent unglaciated area which provided a potential lateglacial dispersal centre in addition to migrations reaching the area later from the southeast and south. It seems that birch, alder, willow and spruce were among the early. pioneers from the western source. A mixing of the western and eastern floral elements after deglaciation is an interesting problem. The magnitude of the postglacial climatic changes appears to have been smaller than in the more southerly regions. At several sites studied, the onset of the permafrost regime has been an important factor in the development of vegetation, because of its influence on both the groundwater conditions and soil development.