332 Pampean Formation. part it. 



both in tint and compactness.' 1 The plain northward of 

 this point is very level, but with some depressions and 

 lakes ; I estimated its height at from forty to sixty feet 

 above the Parana. At the A. Medio the bright red 

 Pampean mud contains scarcely any tosca-rock ; whilst 

 at a short distance the stream of the Pabon forms a 

 cascade, about twentv feet in height, over a cavernous 

 mass of two varieties of tosca-rock ; of which one is 

 very compact and semi-crystalline, with seams of crys- 

 tallised carbonate of lime : similar compact varieties 

 are met with on the Salidillo and Seco. The absolute 

 identity (I speak after a comparison of my specimens) 

 between some of these varieties, and those from Tapal- 

 guen, and from the ridge south of Bahia Blanca, a dis- 

 tance of 400 miles of latitude, is verv striking. 



At Eosario there is but little tosca-rock : near this 

 place I first noticed at the edge of the river traces of 

 an underlying formation, which, twenty-five miles 

 higher up in the estancia of Gorodona, consists of a 

 pale yellowish clay, abounding wuh concretionary 

 cylinders of a ferruginous sandstone. This bed, which 

 is probably the equivalent of the older tertiary marine 

 strata, immediately to be described in Entre Eios, only 

 just rises above the level of the Parana when low. The 

 rest of the cliff at Gorodona, is formed of red Pampean 

 mud, with, in the lower part, many concretions of 

 tosca, some stalactiformed, and with only a few in the 

 upper part : at the height of six feet above the river, 

 two gigantic skeletons of the Mastodon Andium were 

 here embedded; their bones were scattered a few feet 

 apart, but many of them still held their proper relative 

 positions : they were much decayed and as soft as cheese, 



1 I quote these words from my note-book, as written down on 

 the spot, on account of the general absence of stratification in the 

 Pampean formation having been insisted on by M. d'Orbigny as a 

 proof of the diluvial origin of this great deposit. 



