Geology of Northwestern Spitsbergen. 421 



slates with lamellibranchs, that are in turn overlain by the 

 uppermost known Devonian sediments, grey sandstones and 

 shales with Upper Devonian fishes, plant remains, and some 

 ostracods, among others a big Isochilina. The total thickness 

 of the two series is estimated to be at least 4000 m. The 

 younger of the two has its main distribution on the west side 

 of Wijde Bay, and may be named the Wijde Bay Series. Here 

 probably belong the Upper Devonian slates found by Nathorst 

 at Klaas Billen Bay in the Ice Fjord. 



This is not the place to go into the far-reaching discussion 

 as to the mode of deposition of this vast amount of Devonian 

 sediments, the total thickness of which is about 10,000 m. A 

 fact that is, however, to be noted is the occurrence of fossils 

 of marine types, such as the big ostracods and some of the 

 lamellibranchs, along with the fishes in each of the four thick 

 series. In this respect, the Old Red system of Spitzbergen 

 differs from that of Scotland, which it in general much 

 resembles. 



We have : 



In Spitzbergen In Scotland 



Wijde Bay Series Upper Old Red 



Grey Hoek Series Middle Old Red (Orcadian) 



Wood Bay Series Lower Old Red (Caledonian) 



Red Bay Series Downtonian 



Both the Grey Hoek Series and the Orcadian differ litholog- 

 ically from the usual type of Old Red in consisting chiefly of 

 grey and argillaceous material. 



We know from the Swedish investigations that the Devonian 

 has been locally deformed in pre-Carboniferous time, and we 

 therefore must assume that there is a break in sedimentation 

 between the two systems, although unfortunately the boundary 

 between the Wijde Bay Series and the Carboniferous has as 

 yet not been seen. This lack of knowledge is in part due to 

 the fact that the Upper Devonian and the Lower Carboniferous 

 are lithologically very similar and poor in fossils, rendering 

 stratigraphical distinctions difficult. 



The Carboniferous of northwestern Spitzbergen has been 

 studied in some detail, and two papers on that subject have 

 been published recently.* On this occasion, we need only 

 mention some few facts. The Lower Carboniferous plant- and 

 coal-bearing sandstone was found to be much greater in thick- 

 ness than was formerly supposed. At the mouth of the Ice 



*01af Holtedahl : "Zur Kenntnis der Karbonablagerungen des westlichen 

 Spitzbergens. T. Eine Fauna der Moskauer Strife," Videnskapsselsk. Skrif- 

 ter, I. Mat.-Naturv. Klasse, Christiania, 1911; "IT. Allgemeine strati- 

 graphische und tektoniscbe Beobaehtungen," loc. cit., 1912. 



