Page 4 - macneill1947
P. 4
2.
AB$TRAQT
Six formations of Tertiary and Quaternary Age are
present south of the Santa Clara River in the Easternmost
Ventura .Basin.
The upper Miocene non-marine Mint Canyon formation is
suooessively overlain by the uppermost .Miocene marine ''Modelo"
formation, the lower Pliocene marine Pico formation, the
Pliooene-Pleistooene non-marine Saugus formation, and by
Pleistocene terrace deposits and Heoent alluvium. Angular
unoonformities characterize most of the boundaries between
these formations, but disconformable relationships appear to
exist locally.
As a result o1' two or more major periods of defor-
mation, the rocks are highly folded, with broken anticlines
and dips that vary from horizontal to ve,rtical. Overturning
ooours at least at one place. Compressive stresses from the
north appear to have been the most active agents of deformation;
but the block-type San Gabriel fault. which runs through the
Southern part of the Humphreys Station area, may have had some
tilting effect upon the beds throughout this whole region.
In general, the structural trend is northwest-
southeast. Broad folds in the Mint Canyon fonnation plunge
northwestward at low to moderate angles. Post-Modelo thrust-
ing from the north has developed minor folds on the limbs of
the mqor folds. Superimposed on the highly folded formations
are the later formations, themselves slightly folded.
As a result of ~uaternary erosion, the topography is