Date of Award


Degree Type

Bachelors Thesis

Degree Name

Bachelor of Science in Geological Engineering



First Advisor

Dr. Eugene S. Perry


Unique feldspar porphyries, syenitic in appearance, and granitic in composition, form an unusually thick sill intrud­ing pre-Cambrian Belt graywacke about eight miles south of Whitehall in southwestern Montana. Commercial deposits of gold and silver ores occur nearby, and may possibly be genet­ically related to the porphyry, although direct association is not evident. The geologic age is believed to be late Cretaceous or early Tertiary, and the sill may be related to the Tobacco Root batholith.