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University of California Publications. [Geology 



the most part well stratified and have a thickness which is esti- 

 mated at about 250 feet. Where the base is exposed, the forma- 

 tion rests in some places upon the Tank Andesite, as on the 

 west side of Tehachapi Creek below Cable, in some places on a 

 coarse agglomerate made up of andesitic fragments, and in other 

 exposures directly upon the rocks of the Bed-rock Complex. In 

 every case where it is exposed it is overlain by the alluvium of 

 the Tehachapi formation. The limestones are cherty and contain 

 fresh-water molluscan remains such as species of Planorbis and 

 Pkysa in a good state of preservation. The clays are more or 

 • less admixed with fine volcanic ash and in such beds there are 

 often remains of roots and stems which have been thoroughly 

 silicified. Not only are the limestones cherty but they pass along 

 the strike into beds which are composed almost wholly of evenly 

 stratified light colored to white cherts. These cherts outcrop 

 rather boldly and as they occur near the base of the series they 

 facilitate the delimitation of the area of the formation. The 

 pebble beds are not more than a few feet thick and are composed 

 of smoothly rounded pebbles of small size. These beds of course 

 indicate shallow water conditions and proximity to the shore 

 line of the lake. The occurrence of volcanic ashes in the clays 

 and as distinct beds may indicate a survival into the lacustral 

 period of the volcanic activity, which gave rise to the pre-lacus- 

 tral and underlying Tank Volcanics ; but it may also be explained 

 as due to the erosion of these earlier volcanic deposits. To the 

 east of Tehachapi Creek these fresh-water beds strike southeast 

 from Cable and dip southwest beneath the overlying Tehachapi 

 alluvium at angles varying from 12° to 20°, for a distance of 

 nearly 3 miles, beyond which the outcrop can no longer be fol- 

 lowed with certainty. The strike at the point where the outcrop 

 ends probably swings around to south and follows the lower east 

 flank of the ridge extending toward Tehachapi station. To the 

 west of the creek below Cable they dip southerly and thence 

 going south the strike swings around to north and south with 

 an easterly dip and at a point about a mile north of Cable sta- 

 tion the dip of the beds is vertical. About three-quarters of a 

 mile southwest of Tehachapi station near the cemetery there is 

 an outcrop of calcareous clays from beneath the Tehachapi 



