476 J. BARKELL ORIGIN OF THE MAUCH CHUNK SHALE 



accumulated as a foreland plain. The Miocene sediments constituting 

 the Siwalik forma,tion alone reach a thickness in northwest India of 

 14,000 feet and suggest the competence of the sedimentation to exclude 

 the sea. A like consideration of the evidence furnished by the Upper 

 Devonian and Carboniferous sediments of Pennsylvania vs^ould seem to 

 show that the generation of the older Appalachians then existing was 

 equally competent to continuously exclude the sea from the eastern side 

 of the geosyncline; that it certainly did so during the Mauch Chunk 

 epoch it has been sought to demonstrate in the present paper. 



There is abundant evidence, however, that the sea has at times occupied 

 portions of the lower plains of the Indus during the later Tertiary, cor- 

 responding again to the evidence of a marine invasion of southern Penn- 

 sylvania during Lower Mauch Chunk times. The present broadly ex- 

 tended character of the Indus delta may then be compared with that 

 broad development of land which seems to have occurred at the close of 

 the Mauch Chunk. 



These comparisons, while not intended to convey the idea that the 

 Appalachians were ever of Himalayan magnitude, are suggestive of a 

 more massive range of mountains and a wider land area to the eastward 

 of the Pennsylvanian geosyncline than is customarily thought of as exist- 

 ing in Upper Devonian and Carboniferous times. Such a larger view is 

 believed, however, by the writer to be in the direction of the truth. 



