Geology of the Harz Mountains. 249 



were being poured out over the surface as subaerial sheets, 

 and, like the intrusive bosses and sheets of diabase piercing 

 the Lower Carboniferous rocks round Edinburgh, they may 

 fairly be considered to belong to the same period of volcanic 

 activity as the interbedded masses above.^ 



3. FiEST Upheaval of the Harz. 



The rocks forming the core of the mountains were, as we 

 have seen, deposited without upheavals or other interruption, 

 from the basement of the Devonian to the top of the Culm 

 measures. The area in which the Culm was deposited 

 gradually approached the old coast-line and the water became 

 shallow, but deposition was at last arrested by a vast disturb- 

 ance which affected the w^hole region, and threw the newly 

 formed rocks into a series of sharply folded troughs and 

 arches. 



The same disturbance appears to have folded the older 

 rocks of the Ehenish provinces which strike in a similar 

 direction, i.e., N.E. or KE. by E. This is the general strike 

 of the rocks of the Upper Harz, which are most intensely 

 folded to the east of Clausthal, but towards the west the 

 undulations flatten out until between Seesen and Langel- 

 sheim the beds become nearly horizontal. 



The strike of the Hercynian rocks of the Lower Harz is 

 less uniform. These form, as shown on the map, an anticline 

 which trends normally from Herzberg through the granite of 

 the Brocken to Wernigerode. A second anticline extends 

 from Lauterberg north-eastwards to Andreasberg, then swings 

 round and runs eastwards past Hasselfelde to the neighbour- 

 hood of Harzgerode, where it bends northwards, and passes 

 out of the palaeozoic area at Gernrode. 



4. Irruption of the Granite. 

 The great changes just described were followed by the 



^ I should not have gone into such detail over this point had there not been 

 reason to suppose that some of the really intrusive diabases are regarded 

 as being interbedded by several writers on the Harz, Kayser, e.g., in his 

 valuable and interesting paper on the system of faults around Andreasberg, 

 asserts that the diabases of that district " are not dyke or stock-like masses 

 but — like all Harz diabases — interbedded sheets [eruptive Lager]. " 



