July 10, 1914] 



SCIENCE 



69 



All the localities described by Turner have 

 been visited. At the last-mentioned locality, 

 "the red sandstone quarry three miles south- 

 east of Buena Vista," the writer obtained 

 Venericardia planicosta new variety. Mere- 

 irix hornii Gabb, Psammohia cf. hornii 

 (Gabb), O-lycimeris ep., Crassaiellites sp., 

 Turritella merriami Dickerson, Natica sp. and 

 Clavella sp. The Venericardia planicosta 

 found here is the yariety with the obsolete 

 ribs. All of these forms were collected from 

 the sandstone five to ten feet beneath the 

 Neocene shore gravels. While the fauna is 

 limited in species, it is typical of the upper- 

 most, the Siphonalia sutterensis, zone of the 

 Tejon. The sandstone member in this vicin- 

 ity, with a dip of only one degree toward the 

 west, attains a thickness of 250 feet. It rests 

 upon the clay, an altered rhyolitic tuff which 

 is only fifty to one hundred feet in thickness. 

 This in turn rests upon the steeply tilted 

 eastern dipping Mariposa slates of the bed 

 rock series. The same sandstone occurs on 

 the hill east of Buena Vista Peak, and with 

 about the same thickness. A half mile east 

 of this hill the lower clay member becomes 

 appreciably thinner and is only 25 to 50 feet 

 thick. On Waters Peak one half mile further 

 east, the clay member and a good part of the 

 sandstone member are missing and only the 

 massive upper fifty feet of the sandstone mem- 

 ber is found resting upon the eroded surface 

 of the Mariposa elates. 



The third member, the clay rock recognized 

 by Turner, appears to the writer to be merely 

 a decomposition product of a rhyolitic tuff. 

 A rhyolitic tuff rests directly upon the sand- 

 stone member in the vicinity of Buena Vista 

 Peak. The writer's opinion is confirmed by 

 an examination of the strata as exposed in 

 Jones' Butte. A clay rock was found resting 

 upon the sandstone member. In certain places 

 this rock was found to be an unaltered rhyo- 

 litic tuff. 



From the above description it is seen that 

 this formation appears to have been deposited 

 by a sea which transgressed from the west. 

 Two or more of the three members of the lone 



are very persistent over the Jackson Quad- 

 rangle, the Lodi Quadrangle, the Sacramento 

 Quadrangle, the Sonora Quadrangle, and they 

 can be recognized readily by their lithologic 

 characters, low westerly dip, and stratigraphic 

 position beneath the andesitic tuffs and upon 

 the Mariposa slates or other members of the 

 bed rock series. 



TTntiL these three members were studied 

 at the type locality, the relationship of 

 the small area south of Merced Falls, 

 which was mapped by Eansome and Turner 

 as Tejon, to the adjoining lone tuffs and clays 

 was obscure. The clays, sand and tuffs exposed 

 one mile west of Merced are lithologically 

 identical with those of the lowermost mem- 

 ber, and the red sandstone mapped as Tejon, 

 found here, is identical with that of the second 

 or sandstone member of the lone of the type 

 locality. The same condition evidently pre- 

 vailed here as in the area between Waters Peak 

 and Buena Vista Peak, that is, a deposition 

 along the shore line of a rapidly transgressing 

 western sea. In this sandstone, casts of 

 Cardita planicosta, var. hornii, with obsolete 

 ribs were found near the top. The authors of 

 the Sonora Folio, Messrs. Turner and Ean- 

 some^ describe this as follows: 



"Tejon formation. — The only rooks referable 

 to this period are a few isolated patches of light- 

 colored sandstone which occur capping some low hills 

 in the southwest corner of the quadrangle. South 

 and southeast of Merced Falls are two level- 

 topped buttes capped by this sandstone, which rests 

 almost horizontally upon the nearly vertical edges of 

 the Mariposa slates. The basal bed is crowded with 

 angular fragments of the slate and with abundant 

 pebbles of white vein quartz, while the upper beds 

 are composed of a light-colored quartzose sandstone 

 with frequent bands of small quartz pebbles. 

 Marine fossils (Venericardia planicosta) are fairly 

 abundant in the upper bed at the west end of the 

 butte that lies one mile south of Merced Falls. 

 These sandstones are overlain to the west by the 

 light-colored sandstones of the lone formation. 

 The two series are probably not absolutely con- 

 formable, as the lone beds transgress onto the 

 rocks of the Bed-rock series farther north." 



3 Turner, H. W. and Eansome, F. L., Sonora 

 Folio, U. S. Geological Surrey, p. 2, 1897. 



