PALEONTOLOGY ZORRITOS FORMATION II 



formation yields oil in places, but the source is undoubtedly 

 the Heath formation. 



Faulting rather than folding characterizes the structure of 

 the region, most of which. consists of a series of tilted fault- 

 blocks. There are several lines of major faulting, the 

 direction of which is a bit more northerly than thai of the 

 coast line, parallel to which the fault-blocks are usually tilted 

 inland. In addition there are countless transverse faults 

 which break the region up into a veritable mosaic. The 

 general result is, ordinarily, that the Heath formation is 

 exposed at the base of the major blocks, with either the 

 Upper Zorritos or the Lower Zorritos at the summit, the 

 series dipping inland until it is interrupted by the next 

 longitudinal fault, or crossed by a diagonally transverse 

 fault. About Boca Pan the whole series is broken up into 

 very small blocks, and the structure is unusually intricate. 



The sections exposed along the coast, where the cliffs 

 parallel, roughly, the lines of major faulting, give small hint 

 of the actual structural complexity of the region, and, with 

 the exception of points at which transverse faults break the 

 series, the beds appear to dip in continuous succession, undu- 

 lations bringing the various members to light and carrying 

 them under again. The impression obtained from Grzy- 

 bowski, who saw little more than the coastal exposures, is 

 rather that there is no great complexity. The recent study 

 has brought out the true nature of the structure as indicated 

 above. Grzybowski's idea that no great structural difficul- 

 ties existed was undoubtedly the reason for his failure to 

 recognize the separate entity of the Variegated beds. 



At a point not far north of Caleta Grail the Heath beds 

 are faulted against the Variegated on the line of one of the 

 transverse faults. The similarity in lithology of the two 

 beds might lead a hurried worker to miss the fault; how- 

 ever, on the ridge north of Caleta Grau the Lower Zorritos 

 formation is seen to overlie the Heath, and the contact be- 

 tween the two may be clearly traced to the point at which 



