1914] 



Dickerson : Martinez of Rock Creek 



297 



reconnai&sance made to the northwest corner of the Rock Creek 

 Quadrangle, Mr. Butterworth and the writer found remnants of this 

 once extensive lava flow resting directly upon the rocks of the Base- 

 ment Complex. One area covered a square mile. Two or three smaller 

 areas were also located. At a locality nine miles N 20° W of Shoe- 

 maker the successive lava flows showed a dip of 15° N, demonstrating 

 that this formation took part in great movements which did not 

 affect the Pleistocene. 



PLEISTOCENE ( ?) FANGLOMEKATE 



Resting indifferently upon granites and limestones. Martinez sand- 

 stone, and the supposed Miocene formation, is a series of conglomerates 

 and fanglomerates varying in thickness from fifty to two hundred 

 and fifty feet. This formation is hest exposed in this area on the 

 Pallett Ranch. The conglomerate of this formation contains houlders 

 from all the underlying formations, granites, schists, sandstones of 

 Martinez age, fragments of the Miocene (?) sandstone, and hits of 

 very fresh andesitic rock which are evidently portions of the lava flow 

 whose remnants are found in the northwest corner of the quadrangle. 

 The formation is presumed to be of Pleistocene age and represents 

 deposits formed by coalescent alluvial cones. A few indeterminate 

 bone fragments were found in the clays along Pallett Creek. This 

 formation is quite extensive and in most places is separable from the 

 Recent alluvium. It is essentially a bolson deposit, and was laid down 

 under climatic conditions similar to those at present obtaining in this 

 vicinity, or possibly under even more arid conditions. Since its 

 deposition, movements have occurred along all the major fault lines 

 of the San Andreas rift. The Punch-bowl fault shows marked scarps 

 of Recent origin about fifteen to twenty-five feet in height. Along the 

 San Andreas fault line these sediments have been much deformed 

 and local dips as high as thirty degrees are common a mile south of 

 the confluence of Pallett and Rock creeks. Small outliers of the 

 Pleistocene ( ?) rest upon the limestone block which was uplifted 

 between the Rock Creek and Antelope Valley faults. 



