302 



NA TURE 



[July 29, 1897 



Nathorst, Greenland bolanically belongs to Europe, and not to 

 America. Though this throws doubt on the permanence of the 

 separation of Greenland and North-west Europe, it does not 

 prove any change in the Arctic Ocean inconsistent with the 

 theory of the permanence of ocean basins. As we, therefore, 

 cannot prove that Ihe resemblances between ihe inhabitants of 

 the Arctic lands on opposite meridians have been established 

 by migration across the Arctic Ocean, instead of around it, we 

 cannot hope for much help from biological evidence in deter- 

 mining the age of the Arctic Basin. 



We are therefore compelled to rely on the facts of the strati- 

 graphical geology of the Arctic regions, of which a short outline 

 is accordingly advisable. This is illustrated by the accompany- 

 ing sketch map (Fig. i). The rocks of the Arctic regions belong 

 to the following systems : the Archean, Cambrian, Silurian, 

 Devonian, Carboniferous, Triassic, Jurassic, Cretaceous, Lower 

 or Middle Tertiary, and Pleistocene. 



The largest part of the Arctic land is occupied by rocks be- 

 longing to the Archean system. They form the whole founda- 

 tion of Greenland, and occur in Baffin's Land, 

 Labrador and the eastern part of British 

 North America ; westward they plunge below 

 the Devonian and Crelaceous rocks of the 

 Mackenzie River Basin, and reajipear in the 

 Yukon River and in Alaska. They occupy 

 an enormous extent of Siberia, reappearing 

 at intervals beneath Palaeozoic rocks and 

 Pleistocene tundras : they form the backbone 

 of the Ural mountains, and of their northern 

 continuation the islands of Nova Zemlya ; 

 west of the White Sea they cover nearly the 

 whole of Finland, the Kola Peninsula, and 

 Scandinavia, and a ridge of them extends up 

 Western Spitsbergen, and forms most of 

 North-East Land and its off-lying islands. 



The age of the next series is somewhat un- 

 certain. Its members overlie the Archean 

 rocks unconformably, while they are always 

 earlier than any fossiliferous beds with which 

 they may be associated. The series consists 

 of red sandstones and coarse conglomerates, 

 with quartzites and dolomites. The rocks are 

 regularly bedded, and are often horizontal; 

 but they may be violently contorted and 

 roughly cleaved. This series does not form 

 huge continental blocks like the Archean, but 

 occurs as a belt which may at one time have 

 been continuous around the Arctic Ocean. 

 Representatives now occur in northern 

 Norway and Spitsbergen ; in eastern, western 

 and .southern Greenland, in Labrador, the 

 basin of the Coppermine River, and at one 

 or two places on the Siberian coast. Fossil 

 remains occur occasionally, but none have yet 

 been described which settle the age of the 

 series. But from stratigraphical considera- 

 tions this series is probably of Lower Cam- 

 brian, or possibly Torridonian age. 



In the next system representative fossils 

 are abundant, and they show us that in 

 Silurian times a large part of the Arctic area was covered 

 by a sea, whose waters were warmer than those of the pre- 

 sent Arctic Ocean. The Silurian rocks occur in belts. One 

 belt runs down Smith's Sound, and then, bending westward, 

 crosses the islands of North Devon, North Somerset, and 

 Victoria Land. So that the Silurian Sea apparently covered 

 most of the American Archipelago, and extended up two gulfs, 

 of which one ran across Baffin's Land, and another up Hudson's 

 Bay. But most of Arctic North America was then above the 

 sea. The shore line of the Silurian Arctic Ocean skirted the 

 American coast as far west as Cape Parry ; thence it swept 

 northward, and it is not until we reach the Indigirka River and 

 the new Siberian Islands that we again find exposures of 

 Silurian rocks. In the basins of the Indigirka, Lena, and 

 Yenesei the Silurian limestones occupy a wide extent of country; 

 but approaching Europe the land again extended northward, 

 and it is even possible that there was no direct communication 

 between the Silurian Arctic Ocean and the seas that then 

 covered parts of England and occupied the basin of the Baltic, 



NO. 1448, VOL. 56] 



If any connection existed, it probably occurred as a strait frorr. 

 the Gulf of Finland to the White Sea. 



In the succeeding Devonian period the Arctic Sea was larger: 

 one arm of it ran up the basin of the Mackenzie River, and 

 covered a wide tract in British North America. In North- 

 eastern Europe a similar inroad of the sea had occurred; for 

 marine Devonian deposits are known from Nova Zemlya and 

 the flanks of the Ural Mountains, and they cover a large par: of 

 the district of Timan and the Petchora Basin. 



The accompanying sketch map (Fig. 2) illustrates the probable 

 limits of the Arctic Sea in the Silurian period, and the extent 

 of its transgression in the Devonian. 



In addition to the marine Devonian deposits, others are known 

 which were probablyjformcd on land or in inland seas; but more 

 satisfactory evidence of land conditions occurs in the Carbon- 

 iferous period, when the extent of the land was probably much 

 greater. In Arctic America the sea had withdrawn to the 

 north, and only covered the north-western part of the American 

 Archipelago, the central belt of Grinnell Land, and part of 



Prob.-xble limits of the Arctic Ocean in the Silurian (lined area) and of its transgression 

 in the Devonian (dotted area). 



Southern Alaska. All Europe north of the sixtieth parallel was a 

 land area, except for a gulf in the Timan region of North-eastern 

 Russia : Nova Zemlya was then an island chain, while most of 

 Spitzbergen was submerged. But the advance of the sea in this 

 area was more than counterbalanced by its recession from 

 Eastern Siberia. 



The Triassic Arctic Ocean was probably smaller than that of 

 the (^arboniferous period. The retreat of the sea from the 

 American Archipelago, which had been gradually taking place 

 throughout Palaeozoic times, was now complete, but marine 

 Triassic rocks in Arctic America are known from Alaska. 

 In the Old World the best-known Triassic deposits are the 

 barren red sandstones of various parts of north-western Europe; 

 but a sea, inhabited by a very rich and interesting fauna, then 

 occupied the Mediterranean area, covered most of Switzerland, 

 and stretched eastward across the Balkan Peninsula into Russia, 

 and possibly into India. At the same time a great Triassic sea lay 

 to the north of Europe and Asia ; it covered Spitsbergen and, 

 probably, also Franz Josef Land, and skirting the Eurasian coast- 



