TRANSLATIONS AND NOTICES 



OF 



GEOLOGICAL MEMOIRS, 



On the Borders of the Fossiliferous and so-called Primitive 

 Formation; and On the so-called Primitive Formation of 

 the South Coast o/Norwiy*. By David Forbes, F.G.S. 



[" Geologiske Undersogelser ved Groendsen af det Forsteenings forende og den 



saakaldte Information." 

 " Om den saakaldte Information ved Norges Sydkyst." ' Christiania Naturforskere 



Modets Forhandlinger/ 1857.] 



The trap-dykes are, in this notice, first described as being the most 

 modern rocks in the district, and particularly frequent in the Silurian 

 strata, cutting through the beds and sending numerous branches 

 along the lines of stratification to considerable distances, and fre- 

 quently extremely thin— sometimes less than one inch in thickness. 



The zircon-syenite, next in age, covers a vast extent of territory as 

 a cap ; and under this, in parts, a similar cover of augitic porphyry is 

 visible. 



In contact with these igneous rocks are thin beds of a hardened 

 white or grey sandstone, so altered, that any fossils, if ever present, 

 have been obliterated. These rest conformably on the Upper Silu- 

 rian beds, and, from their position, are regarded by the author as 

 of Devonian age. The Silurian series with its fossils are next 

 noticed ; and, as the lowest beds of this series contain in abundance, 

 in the more northern parts of the basin, Fenestella socialis, Agnostus 

 pisiformis, and a Lingula, they are considered as the equivalent of 

 the British Lingula-flags. The whole of these beds have a dip to 

 the east, which is due to a series of north and south faults, which 

 make the apparent thickness much greater than in reality is the 

 case. 



Below these the rocks have been described and mapped by Keil- 

 hau as belonging to his primitive or gneiss formation. The exami- 

 nation by Mr. Forbes showed, however, that gneiss was but rarely 

 present, and that the coast-line was formed by a series of basin- 

 shaped beds of metamorphic schists and quartzites. Below, and 

 conformable to the lowest Silurian bed above-mentioned, is found a 



* The latter of these Memoirs being but a continuation of the former, they 

 are both here noticed together. 



VOL. XIV. PART II. D 



