Vol. IV] ANDERSON AND MARTIN— NEOCENE RECORD 39 



hundred feet in thickness. With it are associated several small 

 areas of diabase which occur as intrusions into the sedimentary 

 rocks. Overlying the coarse granitic sandstone are several 

 hundred feet of rather brownish fine sandstone and clay shales. 

 Numerous well preserved fossils have been obtained from this 

 upper member of the Temblor. 



The average thickness of the Temblor group in the western 

 part of the area is between 1000 and 1500 feet. In the section 

 just described between the west border of the Carrizo plain 

 and the San Juan River it probably exceeds 2000 feet. 



Farther to the southeast the Temblor group attains a still 

 greater thickness, probably exceeding 2500 feet, where it in- 

 cludes one or more beds of white or rusty siliceous shale. This 

 is part of the thick series of Miocene rocks referred to in a 

 former paper by the senior author in which the estimated thick- 

 ness was greatly exaggerated on account of folding and re- 

 duplication.^ 



The section of the Temblor group east of the San Juan 

 River recalls the type section of the Temblor which is less than 

 20 miles to the northeast, on the eastern slope of the Temblor 

 Range near the Cameras Springs. As stated in the original 

 description, the middle member of the Temblor beds consists 

 of about 600 feet of "siliceous and clay shales with interstrati- 

 fied sandstone". 



These Temblor beds are mapped on the geological sheet of 

 the McKittrick-Sunset district as two narrow parallel zones 

 of "Vaqueros" strata separated by a thick bed of "Monterey 

 Shale.'" Similar occurrences of the Temblor group have been 

 noted in other districts, and in fact are not rare. The associa- 

 tion of diabase with the Temblor as intrusions near the top 

 of the group will be referred to again. These rocks are shown 

 on the extreme western border of the McKittrick-Sunset map, 

 though in not very accurate detail. 



The small area of strata indicated doubtfully as Oligocene 

 on the same map is probably the shale member of the Temblor 

 and lies stratigraphically between two well developed zones of 

 the same, in both of which are many undoubted species of 

 Temblor fossils. From the uppermost member of the Temblor 

 group at this point were obtained the following species : — 



1 Bu]l. Geol. Soc. Am., Vol. 15, pp. 581-582. 



2 Bull. No. 406, U. S. Geol. Surv., pp. 47-50. 



