92 WARREN DUPRE SMITH AND EARL L. PACKARD 



extended eastward to the Blue Mountains, where the sediments 

 now comprising the major portion of the Cretaceous outcrops were 

 deposited. 



The rocks of the Cretaceous system represent a presumably 

 conformable series, which everywhere lies unconformably upon a 

 complex of older beds. Tertiary strata generally are found to be 

 markedly discordant with the Cretaceous. A long erosion interval 

 appears to have followed the withdrawal of the Chico sea, during 

 which time folding and intrusions occurred, followed by erosion 

 which removed Cretaceous sediment of unknown extent. 



The igneous rocks of the Cretaceous include gabbro, basalt, 

 dacite-porphyry, and other rocks now altered to serpentine. These 

 cut the Myrtle group in the order mentioned. 



The Knoxville fauna is meager, including the boreal Aucella 

 piochii (Gabb) and A. crassicollis Keyserling characterizing the 

 lower and upper Knoxville respectively. The tropical Horsetown 

 fauna from Riddle comprises about fifteen species, several of which 

 are known from the California Chico. The Chico of Rogue River 

 valley, at Mitchell, and near Antone in eastern Oregon have yielded 

 a large fauna having local characteristics, yet being closely related 

 to the Upper Cretaceous of California and having strong affinities 

 with the Cretaceous of the Orient.' As yet no marine reptiles, so 

 well represented in the interior sea to the eastward, have been dis- 

 covered in the Pacific Coast province. 



Four Pacific Coast Mesozoic floras, known as the Oroville, the 

 Oregon, the Shasta, and the Chico, have been recognized by paleo- 

 botanists and have yielded evidence as to the age of certain beds 

 which is difficult to reconcile with that afforded by the marine 

 invertebrates. The oldest of these, the Oroville, is from California 

 and is thought to be Middle Jurassic or pre-Maraposa. The Oregon 

 flora is represented by the Thompson Creek, Douglas County, 

 locality, and consists of over one hundred species, which show close 

 affinities with the Oolite, Middle Jurassic, yet they appear to be 

 associated with Knoxville invertebrates which paleontologists 

 consider as belonging to Lower Cretaceous. The Shasta fauna 

 from Elk River, Jackson County, is certainly associated with a 



' F. M. Anderson, op. cit., p. 6.-2. 



