;66 



Pampean Formation : 



PAKT n. 



g. Green sands . 



h. Tertiary clay and sandstone (for details see fig. 32) . 

 A\. Hard sandstone at the bottom of the Barracas well . 

 k 2 . Very calcareous red clay, becoming more marly 

 beneath ; bored through to a depth of . 



Thickness- Thickness 



at Barracas at Buenos 



Feet Ayres. Feet 



66 62 



34 33 



44 



225 



This formation rests on various marine beds of in- 

 durated green clay, sand with corals, sandstone, and 

 limestone, altogether 107 feet in thickness. These 



No. 32. 



Detailed section of the Artesian "Well at Barracas. 



a. Sand 



b. Very arenaceous clay 



f Fine clay . 



" t Blue plastic clay ...... 



d. Tosca, with calcareous nodules .... 



e. Yellow sand, very fine and fluid, with quartz 



pebbles and fiuviatile sheUs .... 

 /. Green clay, more or less plastic and calcareous, 

 with iron pyrites, marine shells, and nodules 

 of lithographic stone 

 Green sand with shells and quartz pebbles 

 Shelly limestone - 

 Calcareous clay 

 Shelly sandstone . 

 Green arenaceous clay . 

 n. Shelly sandstone . 

 n. Speckled sand 

 o. Very compact arenaceous clay 

 p. Coarse sandstone . 

 q. Green sand, very fine and fluid, with quartz 

 pebbles and shells 



Thickness 

 in metres 

 . 4-33 

 . 8-02 

 . 1-05 

 . 2-90 

 . 2-30 



28-60 



20-30 

 •80 

 •45 



2-00 

 •25 



2-00 

 •30 

 •70 



2-25 



1-40 



2-35 



beds contain fragments of the great Ostrea Patagonica, 

 O. Alvarezii (?), Pecten Paranensw, and other shells, 

 apparently the same (but they have not been rigorously 

 compared) with those enumerated by M. A. d'Orbigny 

 and by myself as found at St. Fe Bajada, as well as at 

 various points on the coast of Patagonia. The already 

 enormous continuous extension of the Patagonian ter- 

 tiary formation is thus largely increased. Beneath 



