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Cache Creek group and contiguous rocks, near Cache Creek, B.C.

University of British Columbia

The Cache Creek Group in the type area is characterized by oceanic rocks such as radiolarian chert, fusulinid limestone and pillow basalt. Three divisions have been made in the Cache Creek Group in this study: 1) structurally lowest is the melange unit (which has been identified as a subduction complex); 2) an overlying greenstone unit; and 3) the Marble Canyon Formation. Emplacement of the Marble Canyon Formation and greenstone unit on the underlying melange unit is believed to have occurred in the Early to Mid-Jurassic along a shallow dipping thrust fault. This emplacement may have caused soft sediment deformation features in the Early to Mid-Jurassic Ashcroft Formation. Felsic volcanic rocks and associated tuffs and volcaniclastic sediments are found mainly along the east side of the Cache Creek Group. These felsic rocks have been called the Nicola(?) Group and based on lithological correlation are of probable Late Triassic age. The Nicola(?) Group is correlated both with the western belt of the Nicola Group as described by Preto (1977) and the Pavilion beds as described by Trettin (1961). Blocks of Nicola(?) Group tuffs have been found in the Cache Creek Group melange unit. This indicates that in Late Triassic time the Cache Creek Group and Nicola(?) Group were adjacent to one another. Paleoenvironmental and geochemical evidence indicate an ocean island or platform depositional environment for the Cache Creek Group. Tropical shallow seas covered most of these islands. Lack of continental sediments indicates that the Cache Creek Group was distant from any major land masses.

Text

2010-03-31

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http://hdl.handle.net/2429/23230

Geological Sciences

University of British Columbia

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