RELATIONS OF KNOXVILLE BEDS TO SHASTA GROUP. 395 



It is possible that some of the beds laid down as Knoxville on the geo- 

 logical map represent the Horsetown group, but no positive testimony on 

 this point has been gathered. This is rendered likely, however, by the find- 

 ing of Aucella and some other fossils associated with fossils of the Horse- 

 town group at Riddles, Oregon ;'^ so that the genus Aucella is not restricted 

 to the Knoxville beds. It would, perhaps, be safer to use the old name, 

 " Shasta group," for the lower Cretaceous beds at Mount Diablo. 



The Chico Beds. — These deposits are mostly rust-colored sandstones, espe- 

 cially in the upper part of the series. Underlying the sandstones there are 

 usually dark-colored shales with arenaceous and calcareous layers, indistin- 

 guishable lithologically from the strata of the Knoxville series; so that these 

 dark-colored shales are characteristic rather of the Cretaceous as a whole 

 than of any particular portion. 



Chico fossils occur northeast, east, southeast and south of the mountain ; 

 but, except toward the south of Curry creek, they are not particularly 

 abundant. Here, in the ravines that drain into the creek from the south 

 (heading west of Cave point), there are to be found very finely preserved 

 shells. The Chico beds contain, Irigonia evmisana, Meek ; Area hreweriana, 

 Gabb ; Anchura ealifornica, Gabb ; and numerous other characteristic fossils. 

 Inoceramus is common in limestone nodules on the high ridge south of the 

 main mountain. Ammonites^ Baculites, fragments of crustaceans, tubes of 

 Serpula, spines and teeth of elasmobranchs, foraminifera, and bits of fossil 

 w^ood were found also. 



Among the Ammonites was collected a large individual resembling stolizck- 

 anus, Gabb, of the Horsetown beds, but which Dr. White considers distinct 

 and has named Ammonites turneri.f 



Another new species described by Dr. White in the same bulletin, Scobi- 

 nella dilleri, occurs also in the Chico beds south of Curry creek. A consid- 

 erable amount of conglomerate is ^exposed in the ravines south of Curry 

 creek. It contains numerous pebbles of metamorphic rocks and of quartz 

 porphyrite. These last pebbles are probably derived from the Sierra Ne* 

 vada. Quartz porphyrite occurs abundantly in the foot hills of Calaveras 

 county. There are very few pebbles, however, of the red silicified shale of 

 the Mount Diablo metamorphic area, which is so abundant. This would 

 seem to indicate that the metamorphic rocks of the mountain were little 

 exposed to erosion during the Chico epoch. 



The Tejon Beds. — These beds are chiefly light-colored sandstones, some- 

 times nearly white, with some thinly bedded light-colored shales. To the 

 west of Cave point there are fine exposures of Tejon sandstone with curi- 

 ously formed cavities, apparently the effect largely of wind erosion. Char- 

 acteristic fossils (e. g., Turritella uvasana, Gabb, and Meretrix uvasana, Gabb) 



*This vol., pp. 201-208: G. F. Becker, " On the Early Cretaceous of California and Oregon." 

 t Bulletin U. S. Geol. Sur., no. 51, 1889, p. 26. 



