1879.1 **** [Derby. 



determination of the age of the formation, which can hardly be older than 

 the Cretaceous, and since these fossils are in disturbed beds, which are 

 overlaid by the horizontal deposits referred to the Tertiary, we cannot 

 well consider them as more modern than the Cretaceous. 



Fossil leaves, very similar in appearance to those of the Serra de Pai- 

 tuna, have been found at Tonantins on the Solimoes, at Uatapucara on the 

 Tapajos, and at Prainha on the Lower Amazonas, in beds that appear to be 

 Tertiary or recent. A critical examination is required to prove whether or 

 not these fossils from the different localities are identical, or belong to the 

 same horizon. For the present it seems to me most probable that they are 

 distinct, those of Paituna being the most ancient. It is worthy of note that 

 the fossil leaves at Prainha are in beds of clay and conglomerate that are 

 slightly inclined, and it is possible that, notwithstanding their modern ap- 

 pearance, they may prove to belong to the Cretaceous. 



These fossils being in the upper bed of sandstone, the age of the lower 

 beds and of the intermediate sandy shales, between the limits of Upper 

 Devonian and Cretaceous, is undetermined. They are, however, so similar 

 in lithological character, to the fossil leaf beds, that I refer them provis- 

 ionally to the Cretaceous. What is well proven is, that the elevation of 

 the anticlinal of Erere took place during, or after, the Cretaceous age. In 

 this connection I may add, that the beds of the numerous Cretaceous basins 

 along the eastern coast of Brazil are always more or less disturbed and 

 inclined. 



Near the mouth of the Trombetas we found inclined beds of sandstone, 

 containing pebbles of shale which appear to me to have come from the De- 

 vonian or Carboniferous beds, which occur farther up on the same river. In 

 the same region there is a high serra, called Curumu, composed of hard sand- 

 stone, the beds of which appear, as seen from a distance, to be inclined, 

 and I suspect that in that region will be found the equivalents of the 

 Erere Cretaceous beds. 



To the south of the mouth of the Amazonas, between Salinas and Bra- 

 ganca, Sfir. Penna has lately discovered fossiliferous limestone, similar to 

 that of the Cretaceous basins of Pernambuco and Sergipe. In the Solimoes 

 region there is also, according to Chandless and Coutinho, an extensive 

 Cretaceous area, on the river Purus, characterized by the remains of Mosa- 

 saums and turtles. 



The disturbances which all the formations thus far described have suf- 

 fered, were accompanied by eruptions of igneous rocks. In the metamor- 

 phic region, the syenite and perhaps a part of the granite may belong to 

 this category, a question that can only be solved by further study. In the 

 same region, and also throughout the Palaeozoic region, diorite is very 

 common, forming immense dykes, and sometimes apparently forming 

 sheets between the strata of sedimentary rocks. Another igneous rock of 

 doubtful character, which I have referred to as trap, forms numerous nar- 

 row dykes in the Erere and Alenguer region, traversing both the Palaeozoic 

 and the Cretaceous beds. The surface is always decomposed, presenting a 



