Page 13 - lopezrobert1974

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!distinctly different from the rest of the Piru Creek
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Frainage Basin. The general flow of the streams in the

iupper portion of the basin is to the east while in the
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:lower portion of the basin the streams tend to flow to-
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~ards the south; also the topography of the upper portion
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:is mountainous with very few valley flats while the lower
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;portion is characterized by topography of g~ntle rolling
'hills with frequent wide valley flats adjacent to the

iCr~ek's channel. These factors can in part be explained

lby the geological history of the area which shows that

I".G• the Piru Creek Drainage Basin is included in that

portion of the Transverse Ranges which make up a part of

:the eastern end of the Ventura stratigraphic basin~ The

Transverse Ranges are of a complex structural and strati-

graphic province, they were formed by marine deposition

throughout most of the Tertiary Period," (Hershey 1902:6)
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:and since th$t period have been altered as a result of
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;the extreme tectonic activity. The portion of the lower

:Piru Creek Drainage Area between the Pyramid Rock damsite

:and the San Felicia Dam appears to be formed in "e~~ thick.
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!sedimentary sequences composed of moderately well consol-
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idated sandstone and conglomerates with interbedded shale

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. .
t
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- e
w.1cn are c1arac er1st1C o f th 'I' . t. ,.., . d Basement
h
er 1ary ~er1o Q
.rock for ~che sedimentary series is an assemblage of pre-
•Cretaceous igneous and metamorphic rocks which underlies
much of the high country in the uppar portion of the
i, -~ •.