Spences Bridge volcanic-plutonic belt 

(mid-Cretaceous) 

(Southern British Columbia, Canadian Cordillera, units Kv)

Lower part consists chiefly of intermediate, locally felsic, calc-alkalic, continental-margin arc volcanic and 
lesser plutonic rocks of mid-Cretaceous age (105 Ma). Upper part consist of mafic andesites that are 
possibly rift related. For paleomagnetic determinations, data from 100 Ma sedimentary and volcanic rocks 
yield grade A southerly displacements of 13o+5o with respect to North America. The volcanic rocks of the 
belt overlie both Cache Creek and Quesnellia terranes and are associated with hypabyssal and deeper 
granitic plutons along strike. The Spences Bridge volcanic-plutonic belt is correlated with the Gravina-
Nutzotin-Gambier volcanic-plutonic-sedimentary belt (Monger and others, 1994), and may also be the 
youngest part of the Middle Jurassic and younger Tahtsa-Twin Sisters-Francois Lake magmatic 
assemblage. REFERENCE: Thorkelson and Smith, 1993; Monger and others, 1994.