Special Report 010

Special Report 010

SPE 010

Quaternary Stratigraphy and Surficial Geology Peace River, Final Report

Author(s) Leslie, L.E. Fenton, M.M. Date 2001-01-01

The surficial geology and glacial stratigraphy of the Peace River study area indicates the region was affected by at least two major ice advances. The surface morainal deposits, together with the flutes, and morainal ridges are evidence that the last glacial advance in the area consisted of an unobstructed southerly flowing Lauren tide Ice Sheet. Deglaciation is marked in the uplands by deposition from stagnant ice and erosion by meltwater channels flowing predominantly down slope; and by the formation of glacial lakes within the plateaus surrounding the towns of Manning and Peace River. Two glacial lake elevations are defined at 610 metres in the vicinity of the Peace River townsite, and at 520 metres surrounding Manning. Slumping initiated along the major rivers after drainage of the glacial lakes. Up to six terrace levels were formed as downcutting continued to the present level. Two processes active at present include slumping of surficial and bedrock material as the rivers cut laterally and the accumulation of organic sediments in bogs, swamps and other areas of poor drainage.

Six stratigraphic units have been defined. Unit A consists of a preglacial sand and gravel unit of Cordilleran provenance. An earlier ice advance is represented by a limited exposure of Sub-unit B1 consisting of a fluvial, subangular to surrounded, boulder to cobble size gravel of Canadian Shield provenance. The gravel bed is overlain by Sub-unit B2, a glacial advance deposit, which can be greater than 100 metres thick, consisting predominantly of sand, with interbeds of gravel, clay, and diamict. Unit C is the only glacial till deposit of the area. These units' compositional and textural characteristics are quite variable, both laterally and vertically due to deposition that took place from basal, englacial, and supraglacial environments. Unit D consists of glaciolacustrine sediments, which locally can exceed 30 metres in thickness. Recent deposits, consisting predominantly of alluvial, colluvial, and organic sediment make up Unit E.

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Leslie, L.E. and Fenton, M.M. (2001): Quaternary stratigraphy and surficial geology, Peace River - final report; Alberta Energy and Utilities Board, EUB/AGS Special Report 10, 156 p.