Geology of the Delphine Creek area, southeastern British Columbia: implications for the proterozoic and paleozoic development of the cordilleran divergent margin
Strati graphic and structural relationships within, and adjacent to, the Delphine Creek area of southeastern British Columbia are consistent with the hypothesis that the Cordilleran divergent margin formed at the western edge of North America following rifting during the Late Proterozoic and continental separation at the approximate start of the Paleozoic (e.g. Stewart, 1972, 1976; Bond and Kominz, 1983). Within the study area, there is evidence for extensional faulting during deposition of the Middle Proterozoic Dutch Creek Formation <Purcell Supergroup), the Upper(?) Proterozoic Mount Nelson Formation, the Upper Proterozoic Toby Formation and Horsethief Creek Group (Windermere Supergroup), the Middle Devonian Mount Forster Formation, and . the Middle and Upper(?) Devonian Starbird(?) Formation. Extensional faulting during the Early Paleozoic is inferred from regional stratigraphic relationships. Syndepositional faulting has had a significant influence on lateral variations in the thicknesses of, and facies distributions within, Proterozoic and Paleozoic stratigraphic sequences. Angular unconformities below the Mount Forster Formation and Starbird(?) Formation record folding events. The Middle Proterozoic Purcell Supergroup is interpreted to have been deposited in a failed rift. The Mount Nelson Formation, which was in previous studies considere d to be part of the Purcell Supergroup, is probably close ly r el ated in age to the ri f t stage deposits of the Upper P roterozoic Windermere Supergroup, and is interpreted as the pre-rift stage deposit o f the margin. Extension, and possible contraction and/or strike-slip tectonism, during the Middle (and Late? ) Devonian may have occurred within a back-arc setting. Uplifted arches present during the Proterozoic and Paleozoic are suggested to have been analogous to the uplifted basin margins that flank modern rifts. Texturally and mineralogically immature sediments of the Upper Proterozoic Horsethief Creek Group were derived from Lower Proterozoic basement rocks and pre-Windermere Supergroup strata that were exposed in uplifts that flanked the Horesethief Creek rift basin on the east, and at least locally, the west side. The northwest-trending Windermere High is considered to have been an arch that was related to lithospheric extension at the outer part of the margin during the Early Paleozoic. The West Alberta . Arch may have been an uplift that was related to mid-Devonian extension. Mesozoic structures in the study area comprise phase one thrust faults, phase two folds (and related faults) that deform the phase one thrusts, and phase three thrusts that cut phase one and phase two structures and may have a component of transcurrent displacement.
Bibliography: p. 423-446.
Root, K. G. (1987). Geology of the Delphine Creek area, southeastern British Columbia: implications for the proterozoic and paleozoic development of the cordilleran divergent margin (Unpublished doctoral thesis). University of Calgary, Calgary, AB. doi:10.11575/PRISM/19492