1890.] GEOLOGISKE IAGTTAGELSER FRA TRONDHJEMS STIFT. 



56 



of some importance for the determination of the middle zone 

 of our section that Prof. Vogt has found probably primordial 

 dictyograptus in a black schist interstratified in mica-schist south 

 of our section and probably in strike with its middle zone. 



The supposed Silurian in the eastern part of our section 

 consists mainly of argillaceous mica-schist and clay-stone. This 

 has been the designation for various greenish, greyish, finely 

 grained or microscopically dense rock, which have an earthy 

 fracture and show no schistosity or indistinctly such. A micro- 

 scopical examination shows that they have nothing like clay in 

 their structure but are throughout crystalline; the most important 

 constituents ascertained are plagioclase, quartz, actinolite, chlorite, 

 muscovite, calcspar; biotite occurs partly in comparatively large 

 porphyric individuals which may be seen even with the naked 

 eye. An apparently more sandstonelike variety of claystone has 

 generally been called clay-sandstone. 



In the part of the section in question I have at some places 

 found indistinct fossils viz. in limestone favosites. In north of 

 the line of section Mr. Alfred Getz has found argillaceous mica- 

 schist with tetragraptus (monograptus convolatus) monograptits 

 Halli (?) and a rastrites. 



Fig. p. 13 is from a railway cutting; it shows a dislocation 

 a. a. The rock is an unschistose clay-stone interstratified with 

 greenish argillaceous mica-schist. The part at X is pictured in 

 one third of natural size under the main figure. Here also the 

 schistosity of the argillaceous mica-schist is indicated. It differs 

 from the stratification and dips away from the observer. The 

 80 cm. broad part at A is part of the claystone layer 1. which 

 has been dragged along the fault. 



The western part of the section towards Trondhjem reseni- 

 bles very much the eastern part. Some diagrams show details 

 of the mutual relations of stratification and schistosity. Fig. on 

 page 16 shows a section in one half natural size. The rock is 

 finely grained sandstone dipping almost perpendicularly. The 

 rock is penetrated by almost horizontal thin plates or veins ot 

 quartz folio wing this schistosity. The uppermost fig. p. 19 shows 



