1848.] 



SHARPE ON THE GEOLOGY OF OPORTO. 



1-45 



Gneiss. 



Micaceous schist. 



(B.) Lower Silurian Formation. 



The series of crystalline rocks 

 just described is overlaid on its 

 eastern flank by a band of rocks of 

 sedimentary origin, of which clay- 

 slate is the principal feature. This 

 band of slates commences northward 

 on the coast near Esposende, about 

 thirty miles north of Oporto, from 

 which place it runs to the S.S.E., 

 meeting the Douro at Jeremunde, 

 about twelve miles above Oporto ; 

 here it crosses the Douro and con- 

 tinues to the southward, where I 

 have not followed it. 



On the north of the Douro the 

 band in question varies from four 

 to eight miles wide, being bounded 

 eastward by granite and sienite, 

 which form the greater part of the 

 province of Entre Minho e Douro. 

 The most interesting part of its 

 course is to the south of Vallongo, 

 from which place to the Douro the 

 slates overlie a carbonaceous de- 

 posit containing several beds of 

 anthracite, which have long been 

 worked at the village of San Pedro 

 de Cova, about eight miles E.N.E. 

 of Oporto, and two miles S.S.W. of 

 Vallongo, and five miles north of 

 the Douro. 



Sea. 





o 



< 



•J 



< 



o 



o 

 P 



o 





Foz. 



(a.) Vallongo Section. 



The slate formation is developed 

 on a larger scale at this part than 

 it is farther to the north : the Ama- 

 rante road traverses the formation 

 from its eastern boundary near 

 Baltar, where it abuts against sie- 

 nite, and crosses the beds in a de- 

 scending order from E.N.E. to 

 W.S.W. : this is nearly the line of 

 this section, fig. 2. The series is as 

 follows in descending order : — 



1. Micaceous sandstone usually 

 of a yellowish colour, with some 

 beds near its base of grey carbona- 

 ceous sandstone ; usual dip E.N.E. 



o 



•Si 



o 



OX 



Micaceous schist. 



Gneiss. 



Micaceous schist. 



Chloritic schist. 



Coal. 

 Carbonaceous"] 



shales and > Ferns. 



sandstones. J 

 Orthis, Trilobites, &c. 



San Pedro 

 da Cova. 



y^!& Vallongo. 



Ponte 

 Ferreira, 



Carbonaceous 

 shales, &c. \A 



A 



Baltar. 



