The proposed research will examine the possibility that Bear Creek Foredeep evolved on thermally young continental lithosphere as a result of collapse of an immature passive continental margin. Research will involve an integrated approach, combining geological and geochronological field investigations of selected areas with geophysical modelling of related gravity anomalies the Thelon Tectonic Zone (infered suture) and two-dimensional modelling of the basin - Thelon Zone system. Models will be used to make first-order predictions concerning basin geometry and stratigraphic architecture of basins formed on cold vs. warm lithosphere. The models will then be compared to the observed characteristics of Bear Creek Foredeep as a method of evaluating the thermal condition of the lithosphere during basin development. Evaluating the thermal age of the lithosphere during subsidence of Bear Creek Foredeep constitutes a critical test of the hypothesis that passive continental margins may have been, on the average, more short-lived than in younger times (cf. Hoffman and Bowring, 1984).