BLOCK AND ALHAMBRA FORMATIONS 287 



glacial origin. Von Drasche, while explaining away the moraines of 

 Schimper, describes a great block scratched and polished which was 

 found near the Camino de los Xeveros.* 



Description of the Guadix Formation 



the block formation 



For a study of the Block formation one has only to go from the Al- 

 hambra of Granada, past the Cemiterio, into the valley of the Genii. 

 Immediately after passing the cemetery on the crest of the divide be- 

 tween the Eio Darro and the Eio Genii the change in the deposits is 

 apparent. From a loosely consolidated deposit of gravel containing 

 large and small, well rounded pebbles, mainly of a single type, with 

 maximum size a few inches in their longest dimension, one here encoun- 

 ters a deposit the pebbles of which are dark colored diorites and gabbros, 

 together with garnetiferous schists, fissile mica-schists, and many other 

 crystalline types of rock foreign to the immediate neighborhood. The 

 size of the pebbles also varies from a fraction of an inch to boulders 

 whose dimensions must be measured in feet. There is, further, to be 

 observed a noteworthy frequency of faceted boulders which in shape are 

 not to be distinguished from those found in a bank of glacial till. Many 

 blocks are polished, but the writer was unable to discover any on which 

 glacial scratches could be made out. On the dump from a mining shaft 

 sharply faceted blocks were found in abundance which are with little 

 doubt derived from the lower layers of the formation, and these are pol- 

 ished in a noteworthy manner. The surface of these blocks gives, how- 

 ever, the impression of slickensides rather than of glacial polish, and, in 

 view of the description by von Drasche of such forms in the Sierra 

 Xevada, any other explanation would seem to be superfluous, f The 

 source of the blocks is clearly the slopes of the Sierra Xevada on which 

 the Genii has its source. 



THE ALHAMBRA FORMATION 



The Alhambra formation occupies the valley of the Darro, which has 

 its rise not in the crystalline rocks of the Sierra Xevada, but in the 

 Triassic dolomite of the Sierra Harana. The uniformity in petrographic 

 type of its pebbles and their smoother contours, find in this their explana- 

 tion. The thickness of the Alhambra formation can be little short of 



* Loc. cit, p. 121. 



t "Diese Schiefer sind ungemein murbe : ein Hammerschlag auf einer grossen Block 

 laspt denselben in ein Haufwerk von KrummtiiichriKen Flatschen zerfallen, die auf der 

 gewolbten Flache stets eine Art Seidenglanz zeigen. Es scheint als ob die ganze 



Seltiefermasse in sich selbst verrutscht ware." 



