Overview
The purpose of this report is to show graphically how the Klamath Mountains grew
from a relatively small nucleus in Early Devonian time to its present size while
rotating clockwise approximately 110°. This growth occurred by the addition of large
tectonic slices of oceanic lithosphere, volcanic arcs, and melange during a sequence
of accretionary episodes. The Klamath Mountains province consists of eight
lithotectonoic units called terranes, some of which are divided into subterranes. The
Eastern Klamath terrane, which was the early Paleozoic nucleus of the province, is
divided into the Yreka, Trinity, and Redding subterranes. Through tectonic plate
motion, usually involving subduction, the other terranes joined the early Paleozoic
nucleus during seven accretionary episodes ranging in age from Early Devonian to
Late Jurassic. The active terrane suture is shown for each episode by a bold black
line. Much of the western boundary of the Klamath Mountains is marked by the
South Fork and correlative faults along which the Klamath terranes overrode the
Coast Range rocks during an eighth accretionary episode, forming the South Fork
Mountain Schist in Early Cretaceous time.
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First posted March 3, 1998
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