Three temporally distinct Lower Jurassic volcanic successions are exposed in the Spatsizi River area of the Stikine Terrane (Stikinia), northern British Columbia. U-Pb zircon dating reveals that (1) the age of the oldest succession, the Griffith Creek volcanics, is ca. 206 Ma; and (2) the middle unit, the Cold Fish Volcanics, is ca. 194 Ma, consistent with its Early Pliensbachian biostratigraphic (ammonite) age. The age of the youngest unit, the Mount Brock volcanics, is Early to Middle Toarcian, also on the basis of ammonites. The Griffith Creek volcanics were folded along with older strata prior to deposition of the Cold Fish succession.

An inherited component of zircon in some of the analyzed zircon fractions indicates that Precambrian basement or Lower Paleozoic strata of Precambrian provenance was present in the Stikinian subsurface. An evolved basement is also suggested by fluorine-rich compositions of high-silica Cold Fish rhyolites.

The three volcanic successions were deposited in the Early Jurassic along the northeastern margin of the Hazelton Trough, a long-lived marine basin which lay between mainly subaerial volcanic arcs on the eastern and western sides of Stikinia. In Early Pliensbachian to Middle Toarcian time, strata in the Spatsizi River area recorded at least 2.6 km of subsidence, consistent with protracted regional subsidence in and around the trough. Extensional tectonism, and to a lesser degree thermal subsidence and local volcanic foundering, are considered the main causes of subsidence.