14 



University of California Publications in Geology t VoL 11 



J. P. Smith 31 has come to the conclusion that the lower Knoxville 

 is the equivalent of the Mariposa. He states that the fauna of the 

 lower Knoxville is closely related to that of the Mariposa, containing 

 Jurassic types of Aucella, with the same poverty of other forms. He 

 believes that the line between the upper and lower Knoxville marks 

 the boundary between the Jurassic and the Cretaceous, since the fauna 

 of the upper Knoxville is certainly Cretaceous. 



The same conclusion has been reached by Knowlton, 32 who has 

 studied the flora of the Knoxville of Oregon. He states that the 

 flora of the Jurassic period is an exceedingly satisfactory means of 

 recognizing Jurassic beds, for the reason that it is of world-wide 

 occurrence and is made up of well marked types, which are everywhere 

 about the same and are easily identified. Its horizon has been checked 

 in many places by the stratigraphic relations and by its association 

 with a characteristic Jurassic fauna. On the basis of the presence 

 of this flora in the lower Knoxville, and its absence in the upper 

 Knoxville, he draws the line between the Jurassic and the Cretaceous 

 at the line dividing the upper and lower Knoxville, instead of at the 

 base of the Knoxville. 



Two other paleontologists, Pavlow 33 in Russia and Haug 33 in 

 Prance, also agree with the determinations made by Knowlton. If 

 they are right, the Franciscan must be older than the Mariposa. 



Opposed to this division of the Knoxville between two periods, 

 are Diller and Stanton. Diller, apparently on stratigraphic grounds, 

 puts the time-break between the Jurassic and the Cretaceous at the 

 great unconformity at the base of the Knoxville. Stanton 3 * points 

 out that the upper Knoxville is unquestionably Cretaceous, contain- 

 ing forms which are everywhere characteristic of that period. He 

 points to the absence of any distinct structural break between the 

 upper and lower Knoxville. He also claims that there is no faunal 

 break between the two divisions. There is a change, he admits, but no 

 sudden break which would justify the separation into different 

 periods. 



On account of the fact that the end of the Jurassic on the West 

 Coast was a period of great activity with enormous batholithic intru- 

 sions, and wide spread mountain-making movements, one might be 



31 Smith, J. P., Science, n.s., vol. 30, p. 346, 1909. 



32 Knowlton, The Jurassic Age of the "Jurassic Flora of Oregon," Am. 

 Jour. Sci., vol. 30, p. 33, 1910. 



33 Cited by Knowlton, ibid., p. 57. 



34 IT. S. Geol. Surv., Bull. 133, p. 30, 1895. 



