30 THE SERI INDIANS [eth. an.n. 17 



refer to one or more saline barrancas about the western base of the 

 same semirauge, probably in Arroyo Mariana. 



Ill brief, Arroyo Carrizal, Tinaja Anita, and Pozo Bscalante are the 

 only permanent waters, and Pozo Hardy, Barranca Salina, and Tinaja 

 Trinchera the only subpermanent waters actually known to Cau- 

 casians in all Serilaud, though it seems probable that permanent 

 water may exist at Aguaje Parilla and in Arroyo Mariana, and imper- 

 manent supplies near Bahia Esjience. There may be one or two 

 additional places of practically iiermaneut water in smaller quantity, 

 and a few other places in whicli saline water might be found either at 

 the surface or by slight excavation, and which niay be approximately 

 located by inspection of the map under guidance of the principles set 

 forth in the preceding paragrajihs; but this would seem to be the limit 

 of trustworthy water supply. During the humid seasons the waters 

 are naturally multiplied, yet it is ini|irobable that any of the arroyos 

 except Carrizal and Agua Dulce and a few minor gulches along the 

 more precipitous shores shed water into the gulf save at times of 

 extraordinary local flood.' 



The geologic structure of the Sonoran province is conijilex and not 

 well nnderstood. So far as the meager observations indicate, the basal 

 rocks are granites, frequently massive and sometimes schistose, some- 

 times intersected by veins of quartz, etc. The granitic mass is upthrust 

 to form the nuclei of Sierra Madre and other considerable ranges; it 

 also approaches the surface over large areas of plains. Resting uncou- 

 formably on the granites lie heavy deposits of shales and limestones, 

 commonly more or less metamorphosed; these rocks outcrop on tlie 

 slopes of most of the main ranges and form the entire visible mass 

 of some of the lower sierras and buttes, while they, too, sometimes 

 approach the surface of the sheetflood-carved plain. The rot-ks, both 

 calcareous and argillaceous, combine the characters of the vast Mesozoic 

 limestone deposits of eastern Mexico and the immense shale accumula- 

 tions of corresponding age in California, and hence probably represent 

 the later half of the Mesozoic. This is the only sedimentary series 

 recognized in the province. Both the granites and the sedimentary 

 beds are occasionally overlain by volcanic deposits, chiefly in the form 

 of niiicheroded lava-sheets and associated tuff-beds, which sometimes 

 form considerable ranges and buttes (notably Sierra Kunkaak, of 

 Isla Tiburon); these remnantal volcanic deposits are probably late 

 Mesozoic or early Tertiary. Newer volcanics occur locally, forming 

 mesas, as about Agua Nueva (40 miles northwest of Hermosillo), or 

 even coulees apparently tilling barrancas of modern aspect, as in the 

 vicinity of Bacuachito,^ or rising into cinder cones surrounded by 



'The i)hysiograpluc features of the Sonoran province in general are treatfd in greater detail in a 

 paper on Sheetflood Erosion, Bull. Geol. Soo. Am., vol. viii, 1897, pp. 87-1)2, and in a pa|icr on Papa- 

 f;ueria„Nat, (leog. Mag., vol. ix, 1898, pp. :i45-371 ; whilo certain local features are described m a paper 

 on Serilaud, prcpaied .jointly with Willard D. .Johnson, Nat. (Jeog. Mag., vol. vii. 1S96, pp. 125-1.'!3. The 

 aggregate available fresh water of Seriland is estimated on p. 181. 



» Noted by Willard D. Johnson. 



