70 WILLIAM T. M. FORBES 



porphyry. 1 The tuff which covers large areas east of the city, 

 and makes the hill west of it, is made of the same volcanic rock. 

 North of Ortakoi there is a long outcrop of the same type of rock, 

 apparently here a lava flow, interbedded between two layers of 

 late conglomerates, which in their turn have been made up of 

 the schists, etc., of the region, and also of a fine-grained sandstone 

 evidently not very old. Over the upper bed is a layer of white 

 tuff, which one would naturally associate with the trachytes at 

 Angora, and over this again a flow of very dark trap of indefinite 

 extent. This trap would seem to make all the mountains to the 

 north, at least for some distance. There are also dykes of it cutting 

 all the earlier beds, and necks of it north and northeast of Ortakoi. 

 There is a small neck of the Angora trachyte also penetrating the 

 limestone three miles south of Ortakoi. 



To sum up, there seem to have been the following periods of 

 deposit: '(i) the system of limestones and schists which were 

 probably metamorphosed and eroded before the next period; 

 (2) the sandstone which formed an element of the conglomerates, 

 and so must have had time to become consolidated before the 

 date of the eruptions ; (3) the eruptions of Angora trachyte, form- 

 ing also the white, and porphyry tuffs (during lulls in this the con- 

 glomerates north of Ortakoi were deposited by the precursor of 

 the Enguri Su); (4) the period of the dark traps. Since the last 

 there has been time for the whole lansdcape to be eroded down to 

 its roots, leaving even the latest volcanic rocks as necks, and flows 

 which have been tilted to decided angles. 



Almost a continuation of the Angora complex is the district 

 about Kylyjlar. Just north of Assi Yuzgad there is a volcanic 

 mass, apparently a sheet extending northward. Soon after reach- 

 ing the hilltop the marbles about Assi Yuzgad, which have domi- 

 nated since the last watershed west of the town, are in their turn 

 replaced by an area of dense dark volcanic rock, mostly altered 

 into serpentine, which extends, with various admixtures, almost 



1 Bukowski has studied the igneous rocks of this district at some length. He 

 finds the dominant rocks to be a variety of andesite, with quite a number of other 

 igneous types, however. So probably the so-called trachyte and trap of the older 

 geologists of Asia Minor should often be interpreted rather as andesite. He traces 

 the extent of this igneous area to the north. See the Bibliography. 



