INTERGRADATION OP THE KNOXVILLE AND HORSETOWN. 213 



From both stratigraphic and paleontologic points of view, therefore, 

 the evidence strongly supports the opinion that the Knoxville and Horse- 

 town beds in northern California and Oregon are a successive and con- 

 tinuous conformable series of sediments laid down without perceptible 

 interruption. 



Since the Knoxville beds pass upward without interruption into the 

 Horsetown beds and the latter in the same way grade into the Chico 

 beds, we arrive at the conclusion contained in the first proposition of the 

 thesis, namely : 



The Cretaceous strata of northern California and Oregon, embracing 

 the Chico, Horsetown and Knoxville beds, or, in other words, the Chico 

 and Shasta beds, are an essentially conformable and continuous series of 

 sediments formed without a distinct interruption. For this series Mr 

 Stanton and 1 have agreed to use the name Shasta-Chico series. 



Distribution and Composition of the Shasta-Chico Series. — The distribution 

 of the Knoxville beds in the Coast range south of the fortieth parallel 

 is described, so far as yet known, chiefly by Becker, Turner and Fair- 

 banks in a number of papers* They are well developed on Elder creek. 

 If we place the upper limit so far up as to include all the .l>"v//a-bearing 

 strata, they extend, according to Fairbanks, as far northward as Cold fork. 

 Tehama county, near the Shasta county line. At that point the present 

 writer has observed the Shasta group to rest unconformably upon the 

 metamorphic rocks, and the unconformity is conspicuous. 



The Horsetown beds have been definitely recognized only a few miles 

 south of the fortieth parallel, but in the opposite direction they have 

 been traced a long distance. From Elder creek, where they conformably 

 overlie the Knoxville beds, they extend northward far beyond the latter, 

 unconformably overlapping the older metamorphic rocks, to Horsetown 

 and Texas springs, nearly as tar north as Redding. 



This overlapping is well shown in the Horsetown beds themselves. 

 Ammonite* ramosus and A. batesii were found on the South fork of Elder 

 creek near Aucella and in conformable strata far beneath the latest strata, 

 containing Aucella. The writer has not found these ammonites to extend 

 above the middle portion of the Horsetown beds. In the vicinity of Ono, 

 on the North fork of Cottonwood, they are common near the uncon- 

 formable contact between the Cretaceous and metamorphic rocks, but 

 have not yet been discovered as far north so Horsetown, where only the 

 upper members of the Horsetown beds occur. Ammonites hoffmanni and 

 A. breweri, which occur at Horsetown and farther southward just above 



*G. F. Becker: Bulletin 19, U. S. Geol. Survey; U. S. Geol. Survey Monograph xiii: and Hull. 

 Geol. Soc. Am., vol. 2, pp. 201-208. 



W. II. Turner • Bull. Geol. Soe. Am., vol. 2, pp. 399-401. 



H.W.Fairbanks: American Geologist, vol. ix, p. 159, March, 1892 ; ib., vol. xi, p. 69, February, 1893. 



XXXII— Bum.. Geol. Soc. Am., Vol. 4, 1892. 



