Igneous Rocks
Updated 14 February 2014
Igneous rocks are those formed from cooling and crystallization of magma. When this occurs at the surface, the rocks are termed volcanic and typically have a fine texture (small crystals) due to the rapid rate of cooling. When the magma cools slowly deep within the Earth, the rocks are termed plutonic or intrusive and typically have a coarse texture (large crystals) due to the slow cooling rate. In the south Okanagan we have both volcanic and plutonic igneous rocks.
Volcanic rocks are associated with the Marama Formation. These rocks are typically felsic (high in silica and feldspar) and are classified as dacite. Volcanic activity in the south Okanagan occured during the Eocene period (~55-34 mya) building a number of current mountains, including Giant's Head, Mount Boucherie and Knox Mtn. As well, Munson Mtn is a chunk of Marama Formation volcanic rock that was stranded on the east side of the Okanagan Valley Fault. The locations of volcanic rock can be seen on the map below (polygons labelled "V") or for more detail on the map of Okulitch (2013).
Plutonic rocks are found on both sides of the valley. Typically the rocks are felsic granite or granodiorite and may be partially metamorphosed in some areas as they are associated with the Okanagan Valley Fault. Examples can be seen at Skaha Bluffs, Trout Creek canyon and along Fairview-White Lake Road near Oliver. Above the highway just north of Oliver is an outcropping that hosts an extremely large vein of quartz that has been quarried by Pacific Silica. The locations of plutonic rock can be seen on the map below (polygons labelled "P") or for more detail on the map of Okulitch (2013).
References
Cannings, R. 2009. Roadside Nature Tours Through the Okanagan: A Guide to British Columbia's Wine Country. Greystone Books. 182p.
Mathews, W and Monger, J. 2010. Roadside Geology of Southern British Columbia. Heritage House Publishing. 404p.
Okulitch, AV. 2013. Geology, Okanagan Watershed, British Columbia (3 sheets). Geological Survey of Canada, Open File 6389. http://geoscan.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/fulle.web&search1=R=292220
Roed, MA and Fulton, RJ (eds.) 2011. Okanagan Geology South. Okanagan Geology Committee. 238p.
Igneous rocks are those formed from cooling and crystallization of magma. When this occurs at the surface, the rocks are termed volcanic and typically have a fine texture (small crystals) due to the rapid rate of cooling. When the magma cools slowly deep within the Earth, the rocks are termed plutonic or intrusive and typically have a coarse texture (large crystals) due to the slow cooling rate. In the south Okanagan we have both volcanic and plutonic igneous rocks.
Volcanic rocks are associated with the Marama Formation. These rocks are typically felsic (high in silica and feldspar) and are classified as dacite. Volcanic activity in the south Okanagan occured during the Eocene period (~55-34 mya) building a number of current mountains, including Giant's Head, Mount Boucherie and Knox Mtn. As well, Munson Mtn is a chunk of Marama Formation volcanic rock that was stranded on the east side of the Okanagan Valley Fault. The locations of volcanic rock can be seen on the map below (polygons labelled "V") or for more detail on the map of Okulitch (2013).
Plutonic rocks are found on both sides of the valley. Typically the rocks are felsic granite or granodiorite and may be partially metamorphosed in some areas as they are associated with the Okanagan Valley Fault. Examples can be seen at Skaha Bluffs, Trout Creek canyon and along Fairview-White Lake Road near Oliver. Above the highway just north of Oliver is an outcropping that hosts an extremely large vein of quartz that has been quarried by Pacific Silica. The locations of plutonic rock can be seen on the map below (polygons labelled "P") or for more detail on the map of Okulitch (2013).
References
Cannings, R. 2009. Roadside Nature Tours Through the Okanagan: A Guide to British Columbia's Wine Country. Greystone Books. 182p.
Mathews, W and Monger, J. 2010. Roadside Geology of Southern British Columbia. Heritage House Publishing. 404p.
Okulitch, AV. 2013. Geology, Okanagan Watershed, British Columbia (3 sheets). Geological Survey of Canada, Open File 6389. http://geoscan.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/fulle.web&search1=R=292220
Roed, MA and Fulton, RJ (eds.) 2011. Okanagan Geology South. Okanagan Geology Committee. 238p.