A succession of conglomerates, sandstones, siltstones, and tills, herein named the Dog Creek Formation, is sandwiched between flat-lying basalts along Dog Creek (lat. 51°36′N, long. 122°02′–122°12′W) for about 15 km east of Fraser River. The sedimentary succession rests disconformably on underlying basaltic lavas (herein referred to as the Harpers Creek Formation), which have yielded K–Ar dates of 1.3–2.9 Ma, and in one place, on a glaciated surface carved in metavolcanic rocks of Permian(?) age. The sedimentary succession is capped by basalt flows yielding K–Ar whole-rock ages of 1.1 Ma. The occurrence of proglacial beds and a glaciated surface in south-central British Columbia, 70 km away from any high mountains capable of supporting glaciers today, testifies to a major glacial stage in Early Pleistocene time. The record of sedimentation and volcanism sheds light on early incision of the nearby valley of Fraser River.