358 Pampean Formation paet n. 



Pampean formation. But as, at the very commencement 

 of the Pampean period, if not at a still earlier period, 

 the Sierra Yentana formed a boundary to the south, — 

 the Cordillera or the plains in front of them to the 

 west, — the whole province of Corrientes probably to 

 the north, for, according to M. d'Orbigny, it is not 

 covered by the Pampean deposit, — and Brazil, as known 

 by the remains in the caves, to the north-east ; and as 

 again, during the older tertiary period, land already 

 existed in Western Banda Oriental and near St. Fe 

 Bajada, as may be inferred from the vegetable debris, 

 from the quantities of silicified wood, and from the 

 remains of a Toxodon found, according to M. d'Orbigny, 

 in still lower strata, we may conclude that at this an- 

 cient period a great expanse of water was surrounded 

 by the same rocky framework which now bounds the 

 plains of Pampean formation. This having been the 

 case, the circumstance of sediment of the same nature 

 having been deposited in the same area during an im- 

 mense lapse of time, though highly remarkable, does 

 not appear incredible. 



The elevation of the Pampas, at least of the southern 

 parts, has been slow and interrupted by several periods 

 of rest, as may be inferred from the plains, cliffs, and 

 lines of sand-dunes (with shells and pumice-pebbles) 

 standing at different heights. I believe, also, that the 

 Pampean mud continued to be deposited, after parts of 

 this formation had already, been elevated, in the same 

 manner as mud would continue to be deposited in the 

 estuary of the Plata, if the mud-banks on its shores 

 were now uplifted and changed into plains : I believe 

 in this from the improbability of so many skeletons 

 and bones having been accumulated at one spot, where 

 M. Hermoso now stands, at a depth of between 800 and 

 1,000 feet, and at a vast distance from any land except 





