122 Prof. A, E. Nordenskibld — Geology of Spitzbergen. 



stone is many times intersected by thin coal-seams, and at a by one 

 of considerable thickness. The succession of strata here is : 

 White sandstone (uppermost) ... ... ... 2-0 metres 



Soft black sandstone mixed with coal 0*5 ,, 



Good coal 0-1 ,, 



Shale 0-1 „ 



Sandy shale with coal-seams ... 0-6 „ 



Pure coal 0-6 ,, 



Shale 0-1 „ 



Good coal 0*3 ,, 



The fossils, which exclusively consist of vegetable impressions, 

 were found chiefly west of a, in a sandstone containing some iron, 

 partly in the shales lying next the coal. 



I do not know with certainty any other place where coal-seams 

 and strata with vegetable impressions belonging to this division occur 

 on Spitzbergen. It is, however, possible that the seam of coal 

 referred to at greater length farther on, and a hard, fossiliferous 

 sandstone, which are exposed on the steep slopes of the mountain 

 ridge between Advent Bay and Coal Bay, belong to this period. 



YII. Diabase} — The eruptive rocks which overlie the marine 

 Jurassic strata on Agardh's Moimtain form the most recent of the 

 plutonic formations which have been formed on Spitzbergen, and it 

 cannot therefore be out of place here to describe with some minute- 

 ness this important member of the geological structure of the country. 

 This rock was first discovered by the geologists who took part in 

 the French Expedition in the frigate La BechercJie, and who, after 

 their return home, described it under the name of "selagite ou sienite 

 Jiypersthemque.'' A more complete account of its occurrence is given 

 by me in my work on the geology of Spitzbergen, in which I have 

 employed the word hyperite as synonymous with selagite for denoting 

 this rock. Through Descloiseauz's remarkable examination of hy- 

 persthene, and the new methods of obtaining a knowledge of the 

 compouent parts of rocks by microscopic examination of thin plates, 

 it has appeared that a great many of the rocks which were thought 

 to contain hypersthene contain instead some other variety of augite, 

 and in this way many rocks which were formerly called hypersthe- 

 nite do not contain the mineral from which they obtained their 

 name. Among the number of these is the Spitzbergen hypersthenite, 

 according to examinations made by Zirkel (Neues Jahrb. fiir Min. 

 1870, p. 808), Tornebohm (private communication), and others. The 

 name by which the rock was formerly denoted must therefore be 

 exchanged for another, and I shall in this case, following Zirkel's 

 determination, employ the name diabase, although dolerite perhaps 

 were a more correct designation for the eruptive rocks from these 

 localities on Spitzbergen. 



The Spitzbergen diabase consists of an equal-grained mixture of 

 labradorite, a species of augite and titaniferous iron. It has, when 

 freshly broken, a greyish-black or greenish-black colour, which often 



^ In my sketch of the geology of Spitzbergen I have noticed the plutonic rocks 

 plentifully occurring in these regions under the name of hyperite. According to 

 later microscopical examinations of the rock, this name ought to be exchanged for 

 diabase. 



