The tonal patterns, directly tied to sensed temperatures, broadly coincide with different topographic expressions that, in turn, are controlled by structure. The Coast Plutonic complex, which comprises the Coast Ranges, consists principally of Cretaceous and Tertiary granitic rock with some eugeosynclinal sedimentary and volcanic rocks of Late Paleozoic to Tertiary age, probably intermingled with some Early Paleozoic and Precambrian units.
Granitic intrusions are comagmatic with the volcanic rocks.
The belt was deformed at various times from Early Mesozoic to the Neogene. This belt is separated from the Omineca Crystalline Belt to the east by the Fraser and Pinchi faults that mark change in crustal structures. The belt is overlain by metamorphosed Paleozoic and Lower Mesozoic volcanogenic and pelitic rocks and Tertiary volcanic rocks. The eastern border of the Omineca Crystalline Belt largely coincides with the Rocky Mountain trench. Its east margin is bounded by the Back Range fault, the first of a series of west-dipping thrusts that characterize the Rocky Mountain Belt.