June 19, 1914] 



SCIENCE 



907 



Chehalis formation is characterized espe- 

 cially by Venericardia horni Gabb, Meretrix 

 californica Gabb and an austral flora, the 

 Olequa formation by Pecien (Chlamys) 

 landesi Arn., Venericardia horni Gabb, and a 

 tropical flora, and the Arago or lone forma- 

 tion by Turriteila merriami Dickerson, a 

 form of F. horni with obsolete ribs (variety 

 aragonia A. & H.) and a tropical flora. 



The Chehalis and Olequa horizons lie in 

 juxtaposition, and constitute the coal-bearing 

 Eocene of western Washington. The upper 

 or Olequa horizon has not been definitely 

 recognized in Califoria, but the lower or 

 Chehalis horizon is the apparent equivalent of 

 the Eocene of New Idria, Salt Creek, Coalinga, 

 Canada de las TJvas, Simi Valley, Topa Topa 

 Mountain, Santiago Canyon, and presumably 

 Rose Canyon near San Diego, as well as the 

 plant-bearing shales near Lake Elsinore. 



Looking at a map of the Pacific coast, it is 

 evident that these deposits were formed in two 

 embayments. The Puget Basin covered 

 western Washington from the south base of 

 the Olympic Mountains to the Columbia 

 Eiver, an arm reaching northward to Van- 

 couver, British Columbia, while the main 

 body extended inland to the foot of the here 

 more recently developed Cascade Range and 

 probably farther, for the Swauk formation of 

 central Washington apparently represents de- 

 posits formed near the east margin of the 

 same great stretch of marsh and estuary. 

 The Tejon basin covered the San Diego mesa, 

 the Los Angeles coastal plain, and crossed 

 the San Gabriel and Santa Tnez Ranges in 

 a long arm extending into the San Joaquin 

 Valley and northward through the Coast 

 Ranges as far as New Idria. As the deposits 

 are usually more or less marine in origin, it 

 is evident that this embayment was rather of 

 the type of an open roadstead than the partly 

 detached brackish estuary in which the Wash- 

 ington deposits were formed. 



The Arago or lone beds represent a horizon 

 younger than any Tejon recognized in the 

 Tejon or Puget basins. They do not occur 

 in juxtaposition, but are developed in differ- 

 ent districts, lying indiscriminately across 



older rocks. The Arago or lone beds have been 

 recognized in three basins, the Crescent basin, 

 a narrow arm extending inland along the 

 north base of the present Olympic Mountains 

 to the vicinity of Port Crescent, Washington; 

 the Arago basin, a broad open roadstead 

 covering the Coast Range, Williamette Valley, 

 and Umpqua basin of Oregon, the marine 

 deposits of the south and west being gradu- 

 ally replaced to the north and east by debris 

 from the Eocene volcanoes of the Cascade 

 Mountains ; and the lone basin which extended 

 inland between the north terminus of the 

 Mount Hamilton Range and the higher Coast 

 Mountains of northern Lake County, to lap 

 the base of the Sierra Nevada. This embay- 

 ment spread southward through the San 

 Joaquin Valley to Pacheco Pass and San 

 Joaquin Canyon, and north to OroviUe and 

 perhaps beyond. Most of the deposits were 

 laid down in a sea of considerable depth as 

 shown by the glauconitic sandstones and the 

 paucity of coal beds, but there is a tendency 

 for the marine beds of the eastern border at 

 Merced Palls, the Mokelumne River south of 

 lone, and South Oroville Table Mountain to 

 grade up into the rhyolitic tuffaeeous plant 

 beds between lone and Carbondale and at 

 Oroville Table Mountain, while in the dis- 

 trict about the Big Bend of Pit River only 

 deposits of the latter type are known. 



As already noted, the Tejon type section in 

 the Canada de las TJvas was taken in beds of 

 the Tejon embayment, and since the name 

 Tejon series has always been used in a loose 

 sense the writers have proposed to retain it in 

 such a way as to cover the Chehalis and Ole- 

 qua formations of the Puget embayment, as 

 well as the deposits of the Tejon embayment. 



The Arago or lone beds, occurring as they 

 do in basins distinct from those in which the 

 Tejon series is developed and being formed at 

 a different period, must be treated as a dis- 

 tinct division of the Eocene. The earlier 

 name is the lone formation,^ the Arago hav- 

 ing been given several years later. 



3 The gravels underlying the mud flows of 

 Marysville Buttes often mapped as lone are of 

 very much later age. 



