OLAF HOLTEDAHL. M.-N. Kl. 



Remarks on the Stratigraphy of the Kristiania Region. 



The geographic-geologic term »Kristiania region« embraces a strip of 

 land some 200 kilometers in length, and 40 to 60 km. in width, with its 

 longer axis NNE — SSW, situated in the south-eastern part of Norway. 

 The city of Kristiania lies near the middle of the eastern border-line. 

 Since geological investigations began in Norway, — early in the iQth 

 century, — this district has been recognised as of special interest, its 

 fossiliferous, stratified rocks, and varying types of igneous masses differing 

 greatly geologically from those of the districts to the west and east, where 

 Archean gneiss is the predominant variety. Brøgger's studies have shown 

 that the whole region represents a sunken piece of land, bounded by a 

 series of faults from the Archean that is found on both sides. Towards 

 the north the boundaries of the region are not so well defined, for it there 

 merges more gradually into the south eastern part of the mountain regions 

 of Central Southern Norway, with its highly metamorphic rocks. 



The stratified rocks of the Kristiania region, which are now known 

 to range from partly Lower, partly Middle Cambric to Highest Siluric, — 

 the Sandstone series at the top, which were previously believed to be 

 Devonic, having been proved to be of Siluric age by Professor Kiær's 

 discovery of the remains of fossil fishes and crustaceans, — have been 

 stratigraphically classified by a series of geologists, particularly Professors 

 Kjerulf, Brøgger, and Kiær. Kjerulf divided the whole succession into 

 a number of stages (i — 10), some of these into minor zones, and his work 

 was continued in greater detail by Brøgger as regards the Cambric, Lower 

 and Middle Ordovicic, and by Kiær in the Highest Ordovicic and Siluric. 



On looking at the geological map of the region (p. 7), we see that 

 only a comparatively small portion of it consists of sedimentary beds, the 

 greater part being composed of igneous rocks. The latter are party large, 

 laccolitic intrusions in the stratified rocks, partly wide-spread lavas that 

 have flowed out on the top of the youngest sedimentary member, — the 

 Downtonian sandstone. The igneous fields of the area divide the paleozoic 

 sediments naturally into various minor districts, some of which are totally 

 isolated, whilst others have connection with each other by narrow strips 

 of land with stratified rocks. 



The geographical division of the sedimentary part of the area, as will 

 be mentioned below, may at first sight appear somewhat remarkable when 

 judging from the map only, as e. g. a district that would seem to be well 

 defined geographically, as a single division, is divided into two, whereas 

 on the contrary several others are united or are not even considered at 



