Open AccessTectonic rotations and translations in western Canada; new evidence from Jurassic rocks of Vancouver Island *
Author(s) -
Irving E.,
Yole R. W.
Publication year - 1987
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1987.tb01678.x
Subject(s) - geology , clockwise , paleomagnetism , apparent polar wander , paleontology , terrane , mesozoic , cretaceous , magnetostratigraphy , igneous rock , southern hemisphere , tectonics , polar wander , seismology , structural basin , fold (higher order function) , mechanical engineering , climatology , engineering
The Lower Jurassic Bonanza Group (Sinemurian and Pliensbachian lavas and tuffs about 205 to 195 Ma) on northwestern Vancouver Island possesses a stable remanent magnetization with a mean direction ( D, I ) of 276°, 42° (13 sites distributed through 1800 m of section, 128 specimens, k B = 50, α 95 = 6°) palaeopole 22° N, 154° E ( dm, dp = 9°, 6°). Reversals are present, but one polarity is dominant and most directions are westerly. The palaeolatitude is 24 ± 6°, with the usual ambiguity as to whether it is north or south of the palaeoequator. To determine the relative motions between ancestral North America and Vancouver Island, these data are compared with determinations from peri‐Atlantic igneous rocks dated radiometrically in the same time interval. The use of model apparent polar wander paths for this purpose is criticized. A net, post‐Jurassic northerly motion of 9 ± 7° or 57 ± 7° is indicated, depending on the chosen hemisphere of origin. The net post‐Jurassic rotations, relative to cratonic North America, are 66 ± 7° anticlockwise or 114 ± 7° clockwise for the northern and southern hemispheres, respectively. Such large rotations are, apparently, a common feature of early Mesozoic rocks of the Canadian Cordillera. It is suggested that these large and variable rotations characterize the deformation occurring during the pre‐mid‐Cretaceous amalgamation of the various terranes of British Columbia.