0. HoltedaliJ — A Tillite-like Conglomerate. 167 



making the deciphering of the geologic history a rather 

 complicated matter. 



The oldest members of the Sparagmite division are 

 known from the more northern district only. Here, as for 

 instance between the Gudbrandsdal and Oesterdal, abont 

 75 km. north of Mjosen, the oldest sparagmite is a some- 

 what metamorphosed rock, having a conglomerate at the 

 very base, and is seen to rest on the somewhat nndnlating 

 surface of pre-Cambrian gneiss. In the southern part of 

 the area the oldest zone, the gray or older sparagmite, 

 several hundred meters in thickness, is a dark gray, gen- 

 erally coarse sandstone rich in grains of feldspar, with 

 some layers of dark arenaceous shale. Then follows a 

 relatively thin zone with red and greenish shale and thin 

 beds of limestone. The earlier time of strong denudation 

 and rapid sedimentation of the detritals derived from 

 granites and gneisses, of which the thick sparagmite zone 

 tells, changed later into one with only slow deposition in a 

 playa-like basin of water. 



Denudation again became active, indeed to a quite 

 remarkable extent, for above the last-mentioned zone 

 there is a very coarse conglomerate, in places 100-200 

 meters thick, the Biri conglomerate, consisting of bowl- 

 ders very often of large size, up to 1 meter in length. 

 The bowlders, made up of granite, gneiss, quartzite, dia- 

 base, and limestone, are well rounded and distinctly 

 water-worn. A river transport of such coarse material 

 certainly presupposes a relatively steep grade of the land. 



Through an intermediate zone of gray sparagmite and 

 shale, the sequence passes into the Biri limestone, the 

 thickness of which in places is as much as 100-150 meters. 

 This zone in part consists of a compact gray (generally 

 more or less magnesian), often arenaceous limestone, the 

 main constituent being, however, a black argillaceous 

 limestone. In the compact variety there are at Lake 

 Mjosen intraformational conglomerates, with angular 

 pieces of limestone lying at very different angles, thus 

 indicating very shallow waters. There are also oolitic 

 and at one locality stromatolitic limestones, which appear 

 to have been chemically precipitated. In spite of much 

 seeking for fossils, none were found. 



Over the limestones then follows an accumulation of 

 huge masses of coarse elastics, the younger, or red, spar- 



