Page 4 - muehlberger1954
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          It is overlain by the  Vasquez  series which crops out over  a  wide  area,

          and  comprises interlayered fanglomerates  and  volcanic  rocks.  Where

          the  Martinez formation has been removed by erosion prior to  the

          deposition of the  Vasquez beds,  the  Vasquez  series  rests on the pre-

          Tertiary crystalline  rocks.  This unit is of doubtful Oligocene age,

          and has  a  maximum known thickness  of nearly  16, 000  feet:  The  Vasquez

          beds were  deposited in three  basins  separated by  ridges.  Late  in

          Vasquez time,  these  ridges were  buried by thick alluvial  fans  built

          northward from the San Gabriel Mountains,  and the  basins thus

          coalesced into  a  single broad alluvial  apron.

                       The upper Lower  Miocene  Tick Canyon formation and the

          Upper  Miocene  Mint Canyon formation,  which lie above  the  Vasquez

          series,  also  represent nonmarine  deposition of dominantly coarse-

          grained  sedimentary material.  These units  are widespread in the

          western part of the Soledad basin.          Sandstone and  siltstone of the

          ''Modelo"  formation  rest unconformably on the  Mint Canyon beds,  and

          reflect an  eastward encroachment of marine waters over  a  part of the

          basin in late  Miocene  time.  West of the  map area,  the  marine Plio-

          cene  Pico  formation and the  nonmarine  Plio-Pleistocene Saugus  forma-

          tion,  which grades westward into  a  marine facies,  overlie the  older

          rocks.     Terrace  deposits  of late  Pleistocene age  are common over

          much of the  area.  Recent alluvium is present in all of  the  major

          valley bottoms  and locally in  some  of the  minor  valleys.
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