Geology of the upper Tick Canyon area, Los Angeles County, California
The upper Tick Canyon area, approximately seven square miles in extent, lies between Agua Dulce Canyon and Mint Canyon in the easternmost pelt of the Ventura Basin in southern California. This area was mapped in detail on a scale of 1000 feet to one inch and the stratigrephic and structura...
Summary: | The upper Tick Canyon area, approximately seven square
miles in extent, lies between Agua Dulce Canyon and Mint
Canyon in the easternmost pelt of the Ventura Basin in
southern California. This area was mapped in detail on a
scale of 1000 feet to one inch and the stratigrephic and
structural relationships of the exposed rocks were established.
The oldest rocks in the area are of highly metamorphosed
metasedimentary and metavolcanic types, which are intruded
by igneous bodies of presumed pre-Cretaceous age. This crystalline complex is in fault contact with the rocks of the Vasquez series, the oldest unit in a thick section of Tertiary sedimentary and volcanic rocks.
The Vasquez series is perhaps Oligocene in age and was
deposited under nonmarine conditions in an elongate trough of fault-block origin. The rocks are mainly fine-to coarse-
grained elastic sediments. Interlayered with them are
basaltic and andesitic flows and shallow intrusive masses,
that form with the sediments a total section of about 4500
feet. This section thickens rapidly east of the area mapped.
Overlying the Vasquez strata with a distinct angular unconformity is a series of conglomerates and siltstones of
the late Lower Miocene Tick Canyon formation. This unit is
approximately 900 feet thick, but thins rapidly to the west
within the area under consideration. The Upper Miocene Mint
Canyon formation, which also consists of nonmarine elastic
sedimentary rocks overlies the Tick Canyon formation throughout the area. These two formations probably are separated by an unconformity, along which there may be local angular discordance of a few degrees.
Almost flat-lying, Pleistocene stream deposits occur
throughout the area at an elevation of several hundred feet
above the present, newly alluviated valley bottoms.
Some strike-slip faulting with northeasterly trend took
place after Mint Canyon time, perhaps during the Pliocene
epoch. This may be related to the San Andreas fault, which
lies ten miles to the northeast.
All folds and faults that involve the sedimentary beds
probably can be related to adjustments taking place in the
underlying crystalline rocks. The forces causing these adjustments probably were active throughout much of Tertiary
and Quaternary time, and activities do not appear to have
ceased as yet.
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