8 . JOHAN Kii.k, M.-X. Kl. 



many years ago, discovered distinct trail marks of a crustacean on a 

 slab from the lower part of the series in the section at Kroksund in 

 Ringerike. This specimen is to be seen in the Pal.eontological collection 

 of the University of Kristiania. One of these trails corresponds quite 

 closely with those ver\' commc)iily [(juiul in the section of Rudstangen 

 in Ringerike. On the same slab we notice another trail of quite a 

 different kind which has not been found again. 



7'he sandstone in Brumunddalen as is well known, occupies a peculiar 

 position. According to investigations made by BjØRLYKKE and by the 

 present writer, it must be assumed tliat the formation of this sandstone 

 had commenced as early as the Wenlock period. No fossils were dis- 

 covered in this district either. 



The Occurrence and Development of the Sandstone Series 



in Ringerike. 



My investigations of the Sandstone Series were begun in the Ringe- 

 rike district, where the whole series can probably be most easily studied. 

 The following will be a short, preliminary account of the development 

 of the series in Ringerike. It is based on studies of the nearest environs 

 of Kroksund, Sundvolden, and Krokkleven, and probably may be modified 

 to some extent b}- continued investigations. 



The Sandstone Series here forms the beautiful and imposing precipice 

 on the eastern side of Stensfjord and Tyrifjord, southward to Næs. The 

 formation almost everywhere has a slight dip towards the south-east, and 

 it is overlaid by the massive beds of porphyry that form the uppermost 

 steep cliff of the entire ridge. 



The well known section of Kroksund and Krokkleven, which in its 

 broad features was drawn by MURCHISON ^ as early as 1844, shows 

 the tectonic of this area. The section was subsequently exhibited by 

 Th. KjERUl.F- in 1857, and later by the present author in 1908 ^. All 

 these sections were drawn quite schematically. 



As already indicated by Keile^au, it seems natural to divide this 

 huge series of sandstone into a loirer jx^it'f rich in shales, and an upper 

 part poor in shales. 



The lower part of the whole series is exposed on the Western side 

 of Kroksund, where in the familiar section at the main road it is seen 



^ A lecture at a Naturalists' Meeting in Kristiania 1844. 

 - Lieber die Geologie d. südl. Norwegens, 1857. Pi. III. 

 ■"* Das Obersilur im Kristianiagebiete 1908. Profil pl. I. 



