198 REPORTS ON INVESTIGATIONS AND PROJECTS. 



reached an agreement of views. Whatever mountains resulted from 

 the folding, the first Karpathians, were eroded to a hilly lowland, 

 though probably not to a well- developed peneplain. The lowland 

 was warped, giving rise to a second Karpathian range, whose rela- 

 tions to the first are not determined, but they appear to be coincident 

 in position. The Dunajec and similar streams, having developed on 

 the lowland, maintained their courses across the later upwarp, and 

 had worked out large valleys at the time of the Miocene submergence. 

 These valleys then became estuaries, and above the level of the 

 Miocene sea the tributary valleys widened, producing a well-defined 

 terrace. During a later epoch, probably the Pliocene, the range 

 was warped higher, and the estuarine deposits were eroded and the 

 valleys deepened. 



In this instance events are closely crowded in the Oligocene and 

 Miocene. Subsidence and deposition were followed by folding ; 

 there was an episode of general and deep denudation ; warping suc- 

 ceeded, occasioning renewed erosion, and then subsidence, producing 

 estuarine conditions — all this before the late Miocene, and since then 

 relatively slight warping. 



The Danube and the Balkan Mountains. — Professor Cvijic and I 

 followed the Danube from Belgrade to Turnu-Severin through the 

 canyon of the Iron Gate, passed through the Iskar Canyon to the 

 intermontane plain about Sophia, and thence proceeded by train to 

 Constantinople. 



The Iron Gate of the Danube has been an object of much study by 

 European geologists, but not as a physiographic problem. Our con- 

 tribution to the subject is therefore one of new facts and new views. 

 In brief, we observed a pre- Miocene topographic surface, which was 

 once a flattish hilly lowland, but which is now strongly warped and 

 eroded. The resulting mountains and valleys are the Balkans and 

 Transylvanian Alps. As in the Karpathians, this warping and ero- 

 sion occurred in an early Miocene time, and later Miocene strata are 

 deposited in the lower valleys. The Danube Canyon is that of the 

 antecedent river, which, being a master stream, maintained its course 

 across the upwarp. 



This is the interpretation at least as far as Milanovac, the point 

 whence the river turns sharply northeast and flows past Veliki Strbac, 

 the striking peak of limestone that hangs over the narrowest and 

 deepest part of the canyon. There is a marked difference in the fea- 

 tures below Milanovac and those above. The former are related to a 

 normal fault of Pliocene age, of which Veliki Strbac is theupthrown 

 side, and we conceive the corresponding course of the Danube to be 



