Our field work and geochronologic studies in northern Hebei and western Liaoning areas indicate that the major Mesozoic contractional events in the Yanshan belt are of(1) pre-Middle Jurassic(Indosinian?),(2) Late Jurassic and(3) Early Cretaceous age. The first N-S shortening could be a consequence of the collision of the Mongolian arcs along the Solon suture against the North China plate. Siberian-North China plate colli-