Structural geology of the eastern Bella Coola map area, southwest British Columbia

Rocks of the eastern Bella Coola (NTS 93 D) map area record several distinct deformational events representing episodic extension, contraction, and transpression in the region. Extension may have been coeval with the generation of volcanic sequences of the Jurassic Hazelton Group and Lower Cretaceous Monarch sequence. Lower Cretaceous Monarch sequence rocks exhibit tight, northeast-vergent folds and minor thrust faults. This contractional belt is cut by ductile protomylonitic to mylonitic transpressional shear zones (10-1000 m wide) that affect most rocks in the western portion of the mapped area, and are themselves cut by various granite and tonalite bodies. Brittle faults cut all rocks of the area and form prominent, north-south-trending topographic linear features.