Cascade plutonic complex
Cascade plutonic complex
Early Cretaceous to Late Jurassic, ~143(?) and ~152-156 Ma
Irregularly zoned from hornblende-biotite quartz diorite, tonalite, monzotonalite, diorite, and granodiorite east-northeast of Lake Oroville. Most zircon U-Pb dates from this pluton are ~152-156 Ma (Rousseau, 2016; Langenheim and others, 2021), but one is ~143 Ma (Day and Bickford, 2004), suggesting a possible second phase for this pluton, perhaps equivalent to the roughly coeval early phase of emplacement for the adjacent Bald Rock plutonic complex (unit Gbr). This unit has also yielded a hornblende Ar-Ar date of ~150 Ma (Fagan and others, 2001). Al-in-hornblende geobarometry indicates emplacement at about 4 kbar for this pluton (McLeod, 1990).