1853.] RIBEIRO AND SHARPE BUSSACO. 139 



At Luzo and Pego de Seixo, on the west flank of the Serra de 

 Bussaco, the sandstone is coarse and incoherent, of a deep red colour ; 

 at Luzo it passes downwards into a very coarse conglomerate which 

 rests on crystalline schists : at Pego de Seixo the beds covering the 

 carbonaceous deposits are a fine purple micaceous sandstone. Finally, 

 at Campo da Ceira it is at the top a hard conglomerate passing down 

 into a green or yellow sandstone, and then into an incoherent con- 

 glomerate resting on mica schist : at this spot the total thickness of 

 the two divisions is above 100 metres. The usual dip of the beds 

 is to some point between W. and S. at about 10°, and occasionally as 

 high as 18° ; the strike varies from N. to N. 30° W. Where these 

 sandstones rest on the Carboniferous series there is the strongest con- 

 trast between the mineral characters of the two rocks and a want of 

 conformability between them, the red sandstone dipping W. only 10°, 

 and the carboniferous beds dipping 20° in the same direction. This 

 want of conformity of the red sandstone with the beds below it, and 

 its separation in respect to organic remains from the Lias above it 

 {ante, p. 137), its variegated colours, and its analogy in mineral cha- 

 racters, have led to classifying it with the Gres Bigarre of France. 



Carboniferous Formation. — An extensive series of beds of 

 conglomerate, sandstone, clay, and psammite, in all about 400 metres 

 in thickness, and containing an abundance of vegetable remains, extends 

 about two kagues northward and two leagues southward from the 

 north end of the Serra de Bussaco. The prevailing rock is a pudding- 

 stone consisting in general of quartz pebbles in a cement of white, 

 yellow or red siliceous sandstones ; these pass in places into a coarse, 

 yellow micaceous or carbonaceous sandstone : occasionally, instead of 

 the puddingstone, there is in the lower part of the deposits a breccia 

 of angular fragments of the older argillaceous and micaceous schists 

 of the neighbourhood set in sandstone or in ferruginous clay : this 

 breccia passes into a coarse sandstone with vegetable impressions : 

 the puddingstone also contains petrified stems and sometimes small 

 patches of coal. 



The sandstones which alternate with the puddingstones vary in 

 colour and character, and contain small fragments of coal and various 

 vegetable remains ; some of the beds resemble those of the basin of 

 anthracite of San Pedro de Cova* ; there are also alternating beds of 

 hardened clay or marl. In the middle and lower parts of the for- 

 mation occur argillaceous beds of various colours and characters, 

 containing geodes of red oxide of iron and well-preserved vegetable 

 impressions in abundance. These are well seen at Fonte do Salgueiro, 

 near the grounds of the Convent of Bussaco. 



Between the beds of conglomerate are schistose sandstones inter- 

 stratified with carbonaceous shale like that which overlies the coal in 

 the coal-fields of England and France, and between these are thin 

 beds of coal varying from ^ inch to 3 inches thick, Avhich burns to a 

 good coke. Both the sandstones and shales contain vegetable im- 

 pressions f ; but the Asterophyllites and Sphenopteris occur together 



* See Journal of the Geol. Soc. vol. v. p. 147. 



t Mr. Bunbury's report in the Appendix contains a list of all the Plants sent 

 over by Senhor Ribeiro which were in a condition to be determined. 

 VOL. IX. PART I. L 



