GEOLOGY OF OKANAGAN VALLEY WINE REGION OF BRITISH COLUMBIA

The Okanagan is a 200 km long trough which extends north from the 49 th parallel into central southern interior of British Columbia. The southern part of the Okanagan has a moderate climate suitable for fruit crop production. During the past 10 years wine grape cultivation has been the fastest growing industry in this area.

Bedrock, ranges from high grade gneisses, possibly as old as Precambrian, to basalt deposited during the last million years, and includes granitic gneiss, granitic plutonic rocks, phyllite, argillite, greenstone, andesite, dacite, rhyolite, clastic volcanic rocks, sandstone, conglomerate, and shale. Most of the valley floor and lower slopes are underlain by silt, sand, gravel, and diamicton. Glacial deposits include glacial lake, glacial fluvial, and direct glacial deposits that were laid down during the last glaciation (about 10,000 to 20,000 years ago). The other unconsolidated materials are stream, slope, and lake deposits, that formed during the last 10,000 years. These were largely derived from glacial deposits.

Present-day topography developed during the several glaciations that have occurred during the past 2 my. Erosion during these episodes has carved deep, fiord-like troughs along pre-existing valleys which followed fault lines. During glacial advances valleys were clogged with large volumes of sand and gravel. Glacial processes locally eroded bedrock but mainly redistributed the existing unconsolidated materials. As a consequence, the materials that line the valley are a heterogeneous mixture derived from many different bedrock sources.

Vineyards have been established primarily on glaciofluvial and fluvial benches, fans, glacial lake deposits, and slope deposit complexes derived mainly from glacial deposits. Soil parent material is mainly unweathered and of mixed prevenance. This means that the parent material composition is roughly similar throughout the Valley. What does vary is texture and thickness - characteristics which influence rooting depth and availability of water and nutrients to roots.