46 BUREAU OF AMEEICAN ETHNOLOGY [bull. 52 



exposed by the little Eio Saladillo where it issues from a smaU 

 reservoir. Thirty to forty meters from the reservoir and close to 

 the stream is a layer 30 cm. thick, composed of the brown earth 

 with many little pebbles the size of a pea, more or less. Most of 

 these consist of secondary limestone or tosca, but pebbles of burnt 

 earth are not uncommon. They are precisely like little water- 

 worn fragments of brick. On following this horizon down the 

 valley, other bits of burnt earth were found, including one 2 cm. to 

 3 cm. in diameter. All of these were imbedded in the Pampean 

 earth. They exhibited no impressions and contained no inclusions 

 which might give a clue to their origin. 



On the eastern coast, near Miramar, the sea cliff affords a section 

 of the Pampean terrane, in which Ameghino identifies two forma- 

 tions, the upper one of which he calls Ensenadean and the lower 

 one Chapalmalean. The latter is a brown ferruginous loess-loam 

 and forms the lower part of the bluffs. In it, at a height of 1 meter 

 above the beach, 8 kilometers north of Miramar, occurs a mass of 

 distinctly reddish, orange, and blackish earth, not bricklike, wliich 

 contrasts with the surrounding brown loess-loam. Its horizontal 

 length is about 1 meter; its thickness is 30 cm. The upper surface 

 is irregular and there are small isolated masses of the red surrounded 

 by the brown clay. The principal mass of red clay is 60 cm. long 

 and 10 cm. thick. It is banded in various shades of red. At the 

 bottom it is distinguished by a sharp contact, where it passes in 

 the distance of approximately a milhmeter from the red into a 

 larger, dark-brown and black mass that fades away below into the 

 brown loess. 



The red earth is a portion of the loess loam, wliich has been dehy- 

 drated. The darker brown color is also due, in all probability, to 

 a peculiar condition of the iron oxide. The black, which occurs 

 chiefly, if not exclusively, on joint planes in the clay, is caused by a 

 film of specular iron oxide. 



This coloring might have been occasioned by a fire burning on 

 the surface that is now red. Similar effects of dehydration occur, 

 however, not infrequently as a result of a slow process of chemical 

 change, without heat, producing more or less distinct ferruginous 

 nodules. Fine ferruginous clays in which capillary moisture circu- 

 lates are favorable to the reaction. This is undoubtedly the expla- 

 nation of the particular occurrence observed in the Chapalmalean 

 north of Miramar. 



In contrast to the preceding fogon, which the \vriter does not 

 class with the tierra cocida, there are certain specimens found 

 somewhat nearer Miramar, but also m Pampean terrane — whether 

 in that portion which Ameghino would class as Chapalmalean or as 

 Ensenadean, the writer is not sure. The specimens are small pieces of 



