15S C. Schnchert — Russian Carboniferous and Permian. 



limestone (certainly the upper member or Chideru formation) is 

 not younger than any part of the Permian of the Urals or 

 Timan. The Schwagerina brachiopod fauna of the Urals 

 seemingly arrives later in India, and during this interval has 

 greatly changed. It is this altered character that dominates the 

 faunas of the Middle and Upper Prodnctus-limestone. This 

 alteration is seen in the progressive development and specializa- 

 tion, not only of the Lyttoniidse, but as well of the Kichtho- 

 fenidse and the terebratuloids. 



9. In regard to the contention of the Indian geologists and 

 Noetling that the Indian Prodnctus-limestone passes without 

 stratigraphic break into the Triassic, some weight should be 

 given to Tschernyschew's faunal argument. In Kentucky, 

 the Devonian overlaps the Ordovician, and in Alabama, the 

 Carboniferous the Ordovician, without visible stratigraphic 

 break ; if it were not for the fossils entombed, the maps of 

 these regions would have shown but one formation. From 

 the fact that not a single species is known to pass from the 

 Productus-limestone into the higher Ceratites-bearing beds of 

 India, one would naturally look here for a late Permian or early 

 Triassic land interval, followed by an overlap of Triassic age. 

 However, the fact that no unconformity nor break in sedi- 

 mentation has been discovered either in the Salt Range or in 

 the central Himalayas, and further that in the latter area there 

 is a great unconformity between the Permian and the Lower 

 Carboniferous (which has a thickness of 5,000 feet), are evidence 

 rather against the supposition that the Triassic overlaps the 

 Permian. The absence of any Permian species in these lower 

 Ceratites beds and the rapid lithologic change between the 

 Permian and Triassic may here be necessary conditions result- 

 ing from the great u revolution " taking place in both hemi- 

 spheres between the Paleozoic and Mesozoic. It is not only 

 the colder glacial land waters poured into the oceans of Per- 

 mian time at many widely separated areas that have changed 

 the long previous equable habitat of marine faunas, but exter- 

 mination came as well through the greatly reduced continental 

 shelves, due to the higher altitudes of the continents in the 

 Northern Hemisphere during late Permian time. (This 

 is especially true for North America.) In other words, the 

 stable conditions of the Productus-limestone were interrupted 

 by the Permian revolution going on elsewhere, killing the 

 entire fauna of this immediate region. That this revolution 

 did aifect the Salt Range seas is seen by the change in 

 sedimentation, and with it came extermination of its life fol- 

 lowed very shortly by an immigration of a new but not greatly 

 changed ammonite fauna. 



