Early tertiary stratified rocks, Greenwood map-area, (82e1/2), British Columbia

Early Tertiary continental sedimentary rocks and volcanic rocks and their intrusive equivalents underlie much of Greenwood map-area (82 E / 2), British Columbia. Lying with marked unconformity on Cretaceous and older rocks, the Eocene Kettle River Formation consists of feldspathic and lithic volcanic sandstone and shale, with subordinate conglomerate, pyroclastic rocks and dacite, derived largely from acidic and intermediate volcanic rocks and basement rocks. Thickness of this unit ranges from a few hundred to at least 4, OOO feet. Volcanic rocks, mainly flows, comprise the overlying Eocene Marron Formation, which is conformable with, and a partial facies equivalent of, the Kettle River Formation. This formation ranges from 300 to 6, OOO feet in thickness, and consists of a lower division of sodic trachyte and minor phonolite, an intermediate division of andesite, and an upper division of andesite tending dacite. This stratigraphy is remarkably similar to that in the type -area of the Marron Formation, 30 miles east northeast of Greenwood map-area. Intrusive equivalents of these flows form numerous small bodies. In one place the Marron Formation is overlain by a possible slide breccia of Oligocene (?)·age; everywhere else the upper contact is a Pleistocene or Recent erosion surface. These rocks are preserved in structurally low fault blocks cut by and bounded by numerous normal faults. Displacement on the faults ranges from a few inches to at least 6, OOO feet, and although some faulting probably occurred during deposition of the early Tertiary rocks, most appears to be later, and is possibly Oligocene in age. The only other Tertiary structures are large anticlines formed by arching of Tertiary stratified rocks over intrusions consisting of rocks equivalent to extrusive rocks forming the lower part of the Marron Formation.