Geology Reference
In-Depth Information
with pillow lavas are found in the same terrane. The
region further to the south. In actuality, the tectonic
Sixes terrane has been compared to the Central Mel-
activity in the Sierras took place millions of years later
ange terrane of northern California and, like the Gold
in the middle Cretaceous. However, the phrase, late
Beach terrane, may have been displaced northward into
Jurassic and early Cretaceous Nevadan Orogeny, was so
southern Oregon by faulting in late Cretaceous or
firmly entrenched in West Coast tectonic geology that
lower Tertiary time.
it is still
a
useful milepost to understanding the history
of the region.
Except for the coastal terranes, the Klamath
Mesozoic Plutons
Mountain province has been intruded by igneous
During an interval near the end of the Jurassic
plutonic bodies which cooled to coarsely crystalline
period intensive folding and faulting in the Klamath
rocks at depths beneath the earth. The plutons vary in
Mountains was accompanied by the intrusion of
size from exposures covering less than one square mile
plutons. This mountain building episode was historical-
ly called the Nevadan Orogeny because it was thought
to be synchronous with intrusions of the Sierra Nevada
Tertiary uplift and the Condrey Mountain dome in the
Oregon Klamath Mountains (after Kays and Ferns,
1980; Donato, Coleman, and Kays, 1980)
