55 8 Valley of Copiapo. paeth. 



thrown from it ; hence this fourth axis is mainly 

 uniclinal towards the SE., and just like our third axis, 

 only locally anticlinal. 



The above strata of porphyritic conglomerate [G] 

 with their south-eastward dip, come abruptly up against 

 beds of the gypseous formation [H], which are gently, 

 but irregularly, inclined westward : so that there is 

 here a synclinal axis and great fault. Farther up the 

 valley, here running nearly north and south, the gypse- 

 ous formation is prolonged for some distance ; but the 

 stratification is unintelligible, the whole being" broken 

 up by faults, dikes, and metalliferous veins. The strata 

 consist chiefly of red calcareous sandstones, with nume- 

 rous veins, in the place of layers, of gypsum ; the sand- 

 stone is associated with some black calcareous slate-rock, 

 and with green pseudo-honestones, passing into porce- 

 lain-jasper. Still farther up the valley, near Las Amo- 

 lanas [I], the gypseous strata become more regular, 

 dipping at an angle of between 30° and 40° to WSW., 

 and conformably overlying, near the mouth of the ravine 

 of Jolquera. strata [K] of porphyritic conglomerate. The 

 whole series has been tilted by a partially concealed 

 axis [L], of granite, andesite, and a granitic mixture 

 of white feldspar, quartz, and oxide of iron. 



Fifth Axis of Elevation (Valley of Copiapo, near 

 Las Amolanas). — I will describe in some detail the 

 beds [I] seen here, which, as just stated, dip to WSW., 

 at an angle of from 80° to 40°. I had not time to 

 examine the underlying porphyritic conglomerate, of 

 which the lowest beds, as seen at the mouth of the 

 Jolquera, are highly compact, with crystals of red oxide 

 of iron ; and I am not prepared to say whether they 

 are chiefly of volcanic or metamorphic origin. On 

 these beds there rests a coarse purplish conglomerate, 

 very little metamorphosed, composed of pebbles of 



