William Henry Mathews
Published: 1963
Total Pages: 44
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Unconsolidated sediments in the Fort. St. John area include a twice repeated succession of gravel overlain by sand, silt, and clay, and each of these in t urn be till of eastern origin. Both succession are interpreted as: (1) gravel laid down by Peace River during or at the close of interglacial (and preglacial?) intervals, (2) fine sediments laid down in lakes ponded in Peace River valley by ice advancing from the east, and (3) till laid down after ice reached Fort St. John area. The younger till [early Wisconsin (?)] is covered by sediments, chiefly clay, from a series of proglacial lakes, and by local postglacial deposits. The topography of the uplands reflects the form of the stream-eroded Cretaceous bedrock, modified slightly by glacial erosion and by the deposition of a thin mantle of till. Landform at intermediate levels is determined largely by sediments which were deposited in proglacial lakes both preceding and following the last glaciation from the east. Since the draining of the last proglacial lake Peace River has cut a trench 700 feet deep below the lake floor and 150 to 250 feet below its interglacial channel. Lice from the Cordilleran area reached to within 15 miles of Fort St. John, overriding areas from which the early Wisconsin (?) eastern ice had already withdrawn. The Quaternary history here is important in localizing the few available aquifers for shallow farm wells, and may have significantly influenced migration of early man into central North America.
