Quaternary stratigraphy and glacial history of the Peace River valley, northeast British Columbia 1 Gregory M.D. Hartman and John J. Clague Abstract: Two Cordilleran and three Laurentide glacial advances are recorded in Quaternary sediments and landforms in the Peace River valley, northeast British Columbia. The advances are inferred from fluvial gravels, glaciolacustrine sedi- ments, and tills within nested paleovalleys excavated during three interglaciations and from the distribution of granitoid clasts derived from the Canadian Shield. Till of the last (Late Wisconsinan) Laurentide glaciation occurs at the surface, ex- cept where it is overlain by postglacial sediments. The advance that deposited this till was the most extensive in the study area, and the only advance definitively recognized in western Alberta south of the study area. Late Wisconsinan Cordil- leran till has not been found in the study area, but Cordilleran and Laurentide ice may have coalesced briefly during the last glaciation. Support for this supposition is provided by the inferred deflection of Laurentide flutings to the southeast by Cordilleran ice. The earliest Laurentide advance may have been the least extensive of the three Laurentide events recog- nized in the study area. Erratics attributed to this advance occur only east of the Halfway River – Beatton River drainage divide. Re ´sume ´: Deux avance ´es glaciaires de la Cordille `re et trois de l’Inlandsis laurentidien sont e ´videntes dans les se ´diments et la topographie du Quaternaire de la valle ´e de la rivie `re de la Paix, dans le nord-est de la Colombie-Britannique. Les avance ´es sont de ´duites a ` partir des graviers fluviatiles, des se ´diments glacio-lacustres et des tills dans des pale ´ovalle ´es emboı ˆte ´es excave ´es durant trois pe ´riodes interglaciaires et a ` partir de la distribution des clastes granitoı ¨des provenant du Bouclier canadien. Un till de la dernie `re glaciation laurentidienne (Wisconsinien tardif) se retrouve a ` la surface, sauf la ` ou ` il est recouvert de se ´diments post-glaciaires. L’avance ´e qui a de ´pose ´ ce till a e ´te ´ la plus extensive dans le secteur a ` l’e ´tude et c’est la seule avance ´e de ´finitivement reconnue dans l’ouest de l’Alberta, au sud du secteur a ` l’e ´tude. Aucun till de la Cordille `re datant du Wisconsinien n’a e ´te ´ trouve ´ dans le secteur a ` l’e ´tude. Cependant, la glace de la Cordille `re et celle de l’Inlandsis laurentidien pourraient s’e ˆtre unis durant une bre `ve pe ´riode au cours de la dernie `re glaciation. Cette hypothe `se est soutenue par la de ´flexion infe ´re ´e de rainures glaciaires laurentidiennes vers le sud-est par la glace de la Cordille `re. L’avance ´e glaciaire laurentidienne la plus pre ´coce pourrait e ˆtre la moins e ´tendue des trois e ´ve ´nements laurenti- diens reconnus dans le secteur a ` l’e ´tude. Les blocs erratiques attribue ´s a ` cette avance ´e ne se retrouvent qu’a ` l’est de la ligne de partage des eaux entre les rivie `res Halfway et Beatton. [Traduit par la Re ´daction] Introduction The Quaternary stratigraphy of Peace Valley was docu- mented 30 years ago by Mathews (1978) but, since then, some researchers working in northeast British Columbia and northwest Alberta have come to conclusions incompatible with Mathews’ interpretation of the history of Cordilleran and Laurentide glaciations of the area. Moreover, the Quater- nary history along the entire Canadian Rocky Mountain front has, in recent years, been revised. Early researchers inferred up to four Laurentide glaciations of the Alberta Plateau, but recent work has reduced this number, and some workers have suggested that only one advance reached Edmonton, Simonette, and Watino (Fig. 1). The number of Cordilleran advances has also been reduced from that proposed by early workers. These revisions have been driven, in part, by improve- ments in describing and interpreting sediments, especially diamictons (Eyles et al. 1983). Equally important, Mac- Donald et al. (1987) demonstrated that radiocarbon ages on gyttja and some freshwater aquatic plants suffer an ‘‘old carbon effect.’’ These and other developments led to the re- evaluation of interpretations based on incorrectly described deposits or spurious radiocarbon ages. The work of early re- searchers however, cannot be completely discounted. Henderson (1959), Tokarsky (1967), St-Onge (1972), and Mathews (1978) present evidence for multiple glaciations that is not dependent on lithofacies interpretations and radio- carbon ages. Even recent researchers, however, do not agree on the ex- tent and times of Cordilleran advances and whether or not Received 30 March 2007. Accepted 30 October 2007. Published on the NRC Research Press Web site at cjes.nrc.ca on 25 June 2008. Paper handled by Associate Editor R. Gilbert. G.M. Hartman. 2 Department of Earth Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada; Present address: AMEC Earth and Environmental, 5681 70th Street, Edmonton, AB T6B 3P6, Canada. J.J. Clague. Department of Earth Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada. 1 This article is one of a selection of papers published in this Special Issue on the theme Geology of northeastern British Columbia and northwestern Alberta: diamonds, shallow gas, gravel, and glaciers. 2 Corresponding author (e-mail: greg.hartman@gmail.com). 549 Can. J. Earth Sci. 45: 549–564 (2008) doi:10.1139/E07-069 # 2008 NRC Canada