SONOYTA — SIERBAS PINACATE — TULE. 



75 



This group, like all the adjoining mountains, consists of crystalline feldspathic rock. The 

 present structure of the Salada hills indicates a general geognostical disturbance of the relative 

 position they must have once sustained. They vary in relative height, and the rocky parts 

 are often covered with debris. The relative position as well as the direction of the sierras 

 between this place and Sonoyta show a deviation from the parallelism so characteristic of north- 

 western Sonora. 



The water of the Kio Sonoyta appears above ground for the last time near Quitobaquita. On 

 the southeast side of the Cerros de la Salado fresh palatable water can be got in its bed by 

 digging to a depth of about three feet. Just below, it becomes so salt that even famishing 

 mules will not touch it. This salt water has given its name to the adjoining mountains. From 

 this point southward the country is open, presenting to the view a bold and isolated mountain 

 group at some distance, known as Sierra Pinacate. Its name, signifying beetle, does not seem 

 to have reference to any peculiarity in appearance or formation. In consequence of the entire 

 absence of water, the Sierra Pinacate is almost inaccessible ; it is, however, celebrated throughout 

 Sonora for wonderful and inexhaustible layers of rock-salt, which is said to be stored up in 

 immense masses, arranged in diversified strata and of a variety of colors. This Pinacate, in 

 all probability, bears a close geological relationship to the Cerros de la Salada. 



West of the Salada hills a wide, waterless desert stretches out, studded with numberless 

 isolated little peaks and a variety of mounds, composed of the crystalline feldspathic rock or 

 igneous masses — the latter is either trapitic, amygdaloid, or porphyritic. Southward, this 

 desert is bounded by low ridges or, rather, gradual risings of the diluvial main ; north and west 

 by bold volcanic sierras. A rugged cordillera, known as the Sierra Tule, limits this desert on 

 the west, and breaks oif what would be otherwise an uninterrupted continuation of the great 

 Colorado waste. 



There are playas near the centre of this desert plain, and sometimes just after a rain charcos 

 of drinkable water. Towards the Sierra del Tule, there is an ascent over an immense bed of 

 dark versicular trap, from which rise small black and white hills or mounds. These gradually 

 increase in size and number in the vicinity of the mountains, and assume an elongated shape, 

 with the usual bearing S.E. and N.W. Finally they unite with the latter, and form spurs of 

 the main mountain mass. — (See outline sketch No. 58, of azimuth line.) 



The black and white rocks which constitute this mountain appear in one place closely packed 

 or pressed together ; in another they shoot up as separate oranches. The dip and strike with 

 the stratification and cleavage are contorted, and in most places entirely obscured ; at another 



PLnTO-TOLCANIO PEAKS 8TCDDIN0 THE MAL-PAIS EAST Of THE BIEERA TCLB. 



place again they are traceable even at a distance of a mile. This is a mountain block — the 

 upheaved corner of a bed of feldspathic syenite or granite changed into granitic lava or regular 



