448 H. R. Soworth — Elevation of American Cordillera. 



The Pampas deposit, he tells us, covers an area of 23,750 square 

 leagues, and rises gradually from the sea-level to a hundred metres 

 or more. It also fills small elevated valleys as at Tarija, at Cocha- 

 bamba, 2575 metres above the sea, and all the Bolivian plateau at 

 the mean height of 4000 metres ; so that it occurs at all heights 

 from the sea to the summit of the Cordilleras. It consists of a 

 homogeneous reddish unstratified loam. It is the same at Chiquitos 

 and Moxos, while on the Eio Piray it is somewhat mixed with clay, 

 and is the same on the high plateaux as it is on the Pampas, and 

 only contains Mammals' bones. It covers, in fact, the surface of 

 nearly all South America, and is the result of one general cause 

 (D'Orbigny, vol. iii. pt. 3, pp. 250, 251). It covers deposits of all 

 ages — Silurian, Devonian, Carboniferous, Triassic and Trachytic 

 (id. p. 253). If, as Darwin argued, this deposit was of fluvatile or 

 estuarine origin, how, says D'Orbigny, can we explain its presence 

 both on the plains and the high plateaux ? This makes it clear that 

 its cause was not a local but a general one {id. p. 255). 



Another fact which points the same moral is the absence of 

 stratification in these loamy beds. In certain places it is harder 

 or more or less sandy ; but these parts, far from being separated 

 from the rest by horizontal lines, which always show themselves in 

 beds deposited slowly from water, form one mass with indistinct 

 zones which are very transient. In one word, it may be said that 

 the Pampas mud was deposited in a very short time and was the 

 result of a great terrestrial commotion (d'Orbigny, vol. iii. pt. 3, 



Elsewhere he explains what, in his view, was the nature of this 

 commotion. He tells us how great dislocations took place in the 

 bed of the ocean to the west of the American continent. This dis- 

 location was coincident with the sudden or rapid upheaval of the 

 Andes over a length of 50 degrees or 1250 leagues. This upheaval 

 caused the sudden movement of the sea, which invaded all at once 

 the continent, carried off and overwhelmed the Mastodons which 

 inhabited the eastern flanks of the Bolivian Cordillera, the 

 Megatheriums, Megalonyxes, and the multitude of animals daily 

 being discovered in the caverns and the fissures of the mountains 

 of Brazil — all the species, in fact, which are extinct. It was then, 

 perhaps, that, mixed with the earth, the animals were tumultuously 

 deposited in the lower parts of the Tertiary basin of the Pampas, 

 and thus formed the immense deposit of Pampas mud (op. cit. vol. iii. 

 pt. 3, p. 82). 



Again he says : " My final conclusion from the geological facts 

 I observed in America is, that there was a perfect coincidence 

 between the upheaval of the Cordilleras, the destruction of the 

 great race of animals, and the great deposit of Pampas mud. Thus 

 these three questions of immense importance for American geology 

 and for the chronological history of faun^, may be explained by one 

 cause, namely, the upheaval of the Cordilleras, to which we may, 

 perhaps, attribute the analogous phenomena of which Europe has 

 been the theatre " {id. vol. iii. pt. 3, pp. 85, 86). 



