GEOLOGY OF THE MAIN WINE PRODUCING AREA OF THE OKANAGAN VALLEY, BRITISH COLUMBIA

The Okanagan Valley of British Columbia extends north from the 49th parallel into the central southern interior of the province. The southern part of the valley has a moderate climate suitable for fruit crop production. During the past 15 years wine grape cultivation has been the fastest growing industry in this area.

The valley lies on the boundary between the Omenica and Intermontane belts of the Canadian Cordilla. Bedrock, ranges from high grade gneiss, possibly as old as Precambrian, to basalt deposited during the last 2 million years. It includes granitic plutonic rocks, a variety of metamorphic rocks, a variety of volcanic rocks, and sedimentary rocks. In most lower areas rock is covered by silt, sand, gravel, and diamicton consisting of glacial deposits formed between about 10,000 to 20,000 years ago and nonglacial materials formed during the last 10,000 years.

The area includes three main wine grape growing regions. Okanagan River Region, extending from Osyoos to Okanagan Falls, is primarily underlain by glacial fluvial sand and gravel and alluvial fan deposits. Southern Okanagan Lake Region, from Okanagan Falls to Peachland, is primarily underlain by glacial lake silt. Central Okanagan Lake Region is underlain by a mixture of sand and gravel, diamicton, and glacial lake silt. Climate tends to be measurably warmer and drier in the south than in the north. Aspect and geomorphology of vineyards vary throughout the valley.

The unconsolidated materials on which soils are developed are primarily fresh (unweathered). They consist of a heterogeneous mixture of the bedrock types found throughout the valley and as a consequence their chemical composition varies little from one part of the area to an other. What does vary is texture and thickness - characteristics which influence rooting depth and availability of water and nutrients to plants. This setting provides a great number of climatic, aspect, and soil drainage niches where viticulturalists can site vineyards which are able to produce many of the world's top varietal wine grapes.