woodworth: geological expedition to brazil axd chile. 125 



concerning the change of level accompanying the earthquake of 1835. 

 As Darwin noted, little or no evidence of the elevation claimed by him 

 and Fitzroy could be seen by a subsequent visitor. The Old Fort 

 at Penco (Old Concepcion) is shown in Plate 4. The alleged evidence 

 of elevation prior to this famous incident pertains largely to marine 

 shells found on the hills about the Bay of Concepcion. Another 

 feature which undoubtedly is the result of relative uplift of the land 

 is the alluvial plain upon which the modern city of Concepcion stands. 



Ulloa (1772, 2, p. 252-254) who visited Concepcion Bay as early 

 as 1744 describes the occurrence of shell deposits from six to twelve 

 feet and more in thickness within four of five leagues from the shore 

 and also on the tops of hills fifty toises (320 feet) high. He mentions 

 seeing one deposit at a height of twenty toises. 



Darwin (1887, p. 310) speaks of "the vast number of sea-shells 

 scattered over the land, up to a height of certainly 600, and I believe," 

 he states, "of 1000 feet." He appears to have entertained no doubt 

 that these shells were evidence of an elevation of a former sea-bottom 

 to these heights as explaining the occurrence of the shells. 



The shell deposits described by Ulloa in the plain about Concepcion, 

 though I did not see them, presumably are in their natural site as 

 the}' form a part of the tilted plain of the "Formation of sand and 

 shells " described by Pissis. This plain at Concepcion I estimated by 

 aneroid to be forty-five feet above sea-level. Westward towards 

 Talcahuano there are successive lower levels, that at the golf links 

 I made seventeen feet, and the next lower level adjacent to the bay of 

 Concepcion about ten feet. The surface has been more or less modified 

 by the blowing of sands by the winds. I saw several boulders in the 

 upper dark stratified sands of the plain between Concepcion and 

 Talcahuano along the railway cuts. One of these blocks was eighteen 

 inches in diameter. These boulders were in an embedded position 

 and would seem to demand floating ice for their transportation. It 

 is to be presumed that the water-laid portions of the deposits are 

 therefore of Pleistocene date. 



Back of Concepcion the plain of sand abuts against the base of 

 the Coastal Cordillera at the hill called Cerro Caracol. I searched in 

 vain for any definite beach along the upper limit of the plain, but 

 stream-action would long since have obscured such local deposits at 

 this juncture. Above this level to the top of Cerro Caracol the 

 granitic rock displayed only evidences of long continued atmospheric 

 weathering and the \-ertical lines of dissection worked out by running 

 water. Nowhere did I observe signs of the Pleistocene stand of the 



