The middle Eocene White Lake and Skaha Formations in the White Lake Basin, British Columbia, record the sedimentary and volcanic infilling of a supradetachment basin that developed during the latter stages of Okanagan metamorphic core complex uplift. The 1.1 km thick White Lake Formation is characterized by volcanogenic fluvial, sheetflood, and sediment gravity flow deposits interbedded with trachyandesite lava beds. Facies relations and paleocurrent indicators suggest White Lake strata accumulated on a west-sloping alluvial plain. Sedimentary clasts in the White Lake Formation were derived from Paleozoic to Cenozoic sources exposed in hanging wall blocks of the Okanagan Valley Fault. The 0.3 km thick Skaha Formation overlies White Lake Strata and records an apparent increase in brittle tectonism. Megaclast-and boulder-rich debris flow deposits as well as pervasively shattered rock avalanche and colluvial deposits, indicate that Skaha beds accumulated on coalesced alluvial fans, shed from both hanging wall and footwall sources exposed along the OVF. The coarse-grained and shattered nature of avalanche deposits implies that they were emplaced following catastrophic slope failure, triggered by earthquakes, volcanism, or moist, slope-destabilizing climatic events. The limited spatial extent and overall lithologic character of the White Lake and Skaha strata are similar to the apparently coeval Klondike Mountain Formation in northernmost Washington. White Lake Basin strata, however, are more complexly interstratified, more severely disrupted by post-depositional faulting and folding, and contain a more complete record of core complex unroofing. Such differences underline the difficulties of developing a general sedimentary-tectonic-volcanic model for this region.