Geology of the Barkerville-Cariboo River area, central British Columbia
LccQE 187 S85 1980 Fiche
LcshGeology - British Columbia - Barkerville area
Geology - British Columbia - Cariboo River area
Sedimentation and deposition
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AbstractAn area lying along a northwest-southeast orogeric trend in the Barkerville-Cariboo River area was mapped at scales of 1:20,000 and 1:50,000. The study was undertaken to determine the internal stratigraphic relationships and to establish possible correlations with the stratigraphy of other areas in the Canadian Cordillera. The hypothesis of a Devona-Mississippian Cariboo Orogeny was tested in the light of stratigraphic and structural data. The Cambro-Hadrynian stratigraphy of Barkerville-Cariboo River is equivalent to that determined by Campbell et al. (1973) for the Cariboo Mountains to the east. This Cambro-Hadrynian shelf sequence and the unconformably overlying Upper Ordovician to Permian rocks are part of the North American Craton. The Ordovician unconformity becomes more pronounced westward, bevelling through Cambrian and into Hadrynian strata. The Ordovician event responsible for this unconformity is here named the Little Diastrophism. Deposition from the Upper Ordovician to the Permian or Triassic is interrupted by a possible Silurian erosional event and several younger hiati. The Ordovician to Permian strata represent primarily, a black shale basin with intermittent shallow-water carbonate developement, a Devonian volcanic and volcaniclastic event and elastic debris flows. An Upper Devonian debris flow, the Guyet conglomerate is deposited into a moderately deep, black shale basin. The conglomerate's composition, internal features and relationship to surrounding rocks do not suggest a local pre-depositional orogeny. The Devona-Mississippian Cariboo Orogeny does not exist as defined by Johnston and Uglow (1926), Sutherland Brown (1957, 1963) and White (1959). The Guyet conglomerate is a "elastic wedge" which may signify distant tectonism. It is suggested that the term Cariboo Diastrophism be applied to such a possible Upper Devonian tectonic event. This Cariboo Diastrophism has no structural manifestation in the Barkerville-Cariboo River area. The Snowshoe Formation is considered to consist of unconformably juxtaposed Kaza Group, Ordovician to Permian strata and rocks younger than the sub-Triassic unconformity. The Antler Formation is in part of Lower Pennsylvanian age and is thrust from the west in at least a portion of the area. The thrusting must be post-Lower Perrnian and is probably post-Upper Triassic. The Antler has suffered the affects of the Columbian Orogeny and was in place prior to the climax of that orogeny. There are four phases of folding, the first three of which are associated with cleavage developement. Only the second phase is pervasive, forming the mesoscopic and macroscopic folds. There are at least four phases of faulting; northeast to southwest thrust; steep reverse and normal; steep, south side down transverse; and northnortheast trending right-lateral strike-slip. The fold and fault phases belong to the Jurassic to Cretaceous Columbian Orogeny. The metamorphism occurred during and just after the major structures. It, too, must then be Columbian. Elliott's (1970) strain measurement technique was computerized and used to analyze the strain of the Guyet conglomerate. A method was devised and partially computerized for determining the strain ellipsoid from strain ellipses measured on three perpendicular planes not parallel to the principal strains.
Bibliography: p. 325-335.