Coquitlam Drift: a pre-Vashon Fraser glacial formation in the Fraser Lowland, British Columbia

Abstract

Coquitlam Drift is formally defined and stratotypes established for it in the Coquitlam – Port Moody area, B.C. It is a Pleistocene formation consisting of till, glaciofluvial, ice-contact, and glaciomarine sediments deposited between 21 700 and 18 700 years BP, during the Fraser Glaciation (late Wisconsin) and prior to the main Vashon glacial maximum at about 14 500 years BP. The drift was deposited in short pulses by valley and piedmont glaciers fluctuating into the Fraser Lowland from the Coast Mountains to the north and Cascade Mountains to the east.

The Cordilleran Ice Sheet and the Glacial Geomorphology of Southern and Central British Colombia

“…Along the coast, fiord glaciers terminated in coalescent piedmont lobes that covered the coastal lowlands and parts of the continental shelf, and extended, in places, to the shelf edge where they calved into deep water (Fig. 2) Alley, 1979;Clague, 1975bClague, ,1988Clague etal., 1982aClague etal., , 1990Fulton, 1968Fulton, ,1975Fulton and Smith, 1978;Fyles, 1963;Hicock andArmstrong, 1981,1983;Howes, 1981Howes, ,1983Ryder, 1976Ryder, , 1981 Alley, 1979;Clague, 1975bClague, , 1988Clague etal., 1982aClague etal., , 1990Fulton, 1968Fulton, ,1975Fulton et Smith, 1978;Fyles, 1963;Hicock et Armstrong, 1981Howes, 1981Howes, , 1983Ryder, 1976Ryder, , 1981.…”

“…Although ice may have been fairly extensive in the northern Strait of Georgia and Hecate Strait by 25 000 to 23 000 years BP, most areas east of the Coast Mountains remained ice free until after 21 000 years BP, and some areas were not overridden until after 17 000 years BP (Clague et al, 1980). A localized and short-lived expansion of valley glaciers into Fraser Lowland, the Coquitlam Stade, occurred about 21 500 years BP (Hicock and Armstrong, 1981). Most of the Lowland was not overridden until after 18 000 years BP 1 however, and adjacent Chilliwack River valley may still have been ice free 2000 years later (Clague et al, 1988a).…”

36Cl dating of the classic Pleistocene glacial record in the Northeastern cascade range, Washington

“…During the last (Fraser) glaciation, mountain glaciers coalesced and entered the Fraser Lowland of British Columbia about 21,000 14 C years (25,000 cal years) ago (Coquitlam advance; Hicock and Armstrong, 1981;Booth and others, 2004). The Puget Lobe subsequently reached its maximum extent about 14,000 14 C years ago (16,900 cal yr ago) (Vashon advance; Armstrong and others, 1965;Porter and Swanson, 1998) (fig.…”

Climatic Conditions in the Western and Northern Cordillera During the Last Glaciation: Paleoecological Evidence

“…(Fig. 1, area 1) The transition from the Olympia non-glacial interval to early Fraser (Wisconsin) Glaciation was apparently gradual on the coast, beginning about 29 ka and continuing until the Coquitlam (Evans Creek) Stade of alpine glaciation between 21.5 and 18.5 ka (Hicock and Armstrong, 1981). Lowland vegetation near Vancouver appears to have been open coniferous parkland with abundant subalpine indicator herbs such as Bistorta, Polemonium, and Valeriana sitchensis recovered from Quadra Sand dated at 24.5 ka (Mathewes, 1979).…”

“…Based on pollen records and radiocarbon dated wood between 21.7 and 18 ka (Clague et al, 1980;Hicock and Armstrong, 1981), trees were always present in the proximity of lowland glaciers. As expected, the common genera were true fir {Abies) and spruce [Picea) but usually without species identifications, except when needles or cones are also recovered, which generally confirm subalpine species.…”