1921] Prick: Faunas of Bautista Creek and San^ Timoteo Caiion 291 



earthquake of Christmas morning, 1900, when a great bend in the 

 hills a mile and a half across gave way and filled the air of the whole 

 countryside with dust clouds. The vertical displacement of some 

 seventy feet is clearly marked in the surrounding walls. Over the 

 tumbled area the old vegetation grows unharmed. A forester's trail 

 wliich formerly crossed this area is now forced to a wide detour to 

 the east. 



The materials of the Bautista deposit are markedly different from 

 those of the San Timoteo to the northwest, in the evenness of the 

 bedding and in the total absence of cobble-bearing strata. Moreover, 

 the minutely classified strata of fine lacustrine sands and lustrous clays 

 which are present in the main central and higher portions of the type 

 locality are quite unknown in either of the San Timoteo horizons. It 

 is in these clays and fine sands that the best of the Bautista fossil 

 material has been secured. Another difference between the western 

 and eastern areas is the frequent occurrence in the Bautista of con- 

 centric sections of calcareous pipes, which range in size from the 

 diameter of a twig to that of a large oak, and point to the former 

 prevalence of hot springs. Mica and gypsum are also more common 

 in the Bautista than in the San Timoteo or the Eden. The surface 

 of the ground itself shows a further dift'erence, the coarse hard litter of 

 quartz gravel and granite cobbles of the San Timoteo being replaced 

 by the disintegrating remains of interstratified calcareous layers. 



Conditions suggest that : (1) these great southwestern deposits were 

 derived from erosion of a neighboring highland, in part through a 

 process of weathering such as that now going on in the interesting 

 granitic faces at the head of Rouse's Canon, wliich are indistinguish- 

 able at short distances from the whiter sand bluffs of the sedimentary 

 areas; (2) the materials of erosion were accunuilated on an old land 

 surface crossing the basement complex, and were later raised and 

 faulted down, as indicated by the general plane of contact between 

 the north and south boundaries of the sediments and the granites, a? 

 well as by such visible points of deeper meeting as that at the mouth 

 of South Fork. 



Occurrence 



The present day surface of the Baiitista deposits offers a con- 

 siderably richer field for the collection of fossils than either the San 

 Timoteo or the Eden. Mr. Blackburn found the original equine 

 mandible within a recently burnt-over area at the mid-southern 

 extremity of the typical exposure, where careful examination of the 



