100 University of California Publications in Geology [Vol. 8 



crowded up against the granite and of having been sharply folded against it. 

 The result has been to throw the strata into anticlines and synclines, some of 

 which have reversed dips. The stratification in this basal formation is more 

 distinct and even than anywhere else in the fragmental portions of the series. 

 As we follow the contact of the series against the granite slopes of Montara 

 Mountain from San Pedro Point southeastward, it becomes apparent that these 

 basal beds have been dropped out of sight by a fault parallel to the axis of 

 the ridge, so that higher and higher horizons of the series come against the 

 granite. If the basal formations of San Pedro Point were all coarse-grained, 

 it might be supposed that we had to deal simply with a case of transgression 

 of sediment from northwest to southeast. But a portion of the basal formation 

 is a fine, bluish-black clay-shale. While, therefore, it is possible that a 

 portion of the contact of the granite against higher and higher portions of 

 the series may be due to transgression, it seems more probable tliat the greater 

 part of it is due to faulting. It is also possible that the rocks classed here 

 as the basal detrital formation of San Pedro Point may be an older series 

 separated from the Franciscan series by an unconformity. This suggestion 

 has little to support it at present beyond the fact that the relations of these 

 rocks to the San Francisco sandstone are not clear, and that the latter very 

 commonly contains fragments of black shale similar to that of San Pedro Point. 

 But whether transgression or unconformity, or both, occur, the fault is present. 



Mr. G. D. Gerson again investigated these beds in the spring of 

 1907 and found the fossil locality from which the main collection came. 



The section along the sea cliff from Devil's Slide to Tobin Station, 

 a quarter of a mile north of San Pedro Point, gives the following 

 sequence of beds : 



(4) Soft tan-colored sandstone and thin-bedded shale, 200-300 feet. 



(3) Coarse sandstone and conglomerate, 200-300 feet. 



(2) Thin-bedded, fine-grained, gray sandstone and black shale with 



black limestone, 300-400 feet. 

 (1) Basal conglomerate and sandstone resting on Montara granite at 



Devil's slide, 300-400 feet. 

 Total, 1200-1400 feet. 



The basal conglomerate (1) appears only at Devil's Slide and (4), 

 the upper sandstone and shale, only in the center of the section. 

 There are at least two or three folds with some faulting in the cliff 

 section. The fossils occur in (3), the coarse sandstone and conglom- 

 erate, at the head of a small canon south of Tobin Station, and east 

 of San Pedro Point at an elevation of 350 feet. This coarse sand- 

 stone bears a peculiar relation to the underlying shales and sandstones. 

 An unconformity is suggested, but the strata are faulted only a short 

 distance away — one or two hundred feet south — and the relation of 

 the two may be due to this movement. Large boulders of granite in 

 coarse sandstone and conglomerate occur in an exposure along the 

 road from San Pedro to Half Moon Bay. Possibly they are blocks 



