TITLES AND ABSTRACTS OF PAPERS 87 



MIGRATION OF GE08YNGLINES 

 BY AMADEUS W. GRABAU 



(Abstract) 



The author, as opposed to Haug and others, distinguishes between geosyn- 

 clines, or belts of concurrent deposition and subsidence parallel to the old land, 

 and fore-deeps, or suboceanic areas of subsidence with a minimum of deposi- 

 tion. A consideration of a number of such geosynclines of various geological 

 ages, and in various parts of the world, brings out the fact that on the folding 

 of the strata of the geosyncline, and their elevation into a mountain chain, a 

 new geosyncline came into existence, parallel to the earlier one, but within the 

 region of the former old land, which supplied the material for the sediments 

 of the preceding geosyncline. Thus the geosyncline migrates toward the old 

 land. European examples are: The Molasse Channel, formed w^ith the first 

 folding of the Alps ; the new geosyncline along the outer border of the newly 

 formed Carpathians; and the similar late Tertiary geosyncline north of the 

 Caucasus. In North America the deposits of the Newark geosyncline rest, 

 in part at least, on the surface of the old land of late Paleozoic time, which 

 includes some of the older Paleozoic strata ; but the evidence in this case is not 

 so clear as in others, probably because of the absence of the older Triassic. In 

 western North America, however, we find a progressive westward migration of 

 the geosynclines in Tria-Jurassic, Comancho-Cretacic, and Tertiary times, so 

 that each series rests, in part at least, on the old land of the preceding geo- 

 syncline, though gradual overlap on the folded series, as this becomes peue- 

 planed, may also occur. It is, of course, recognized that in front (east ) of the 

 folded Paleozoics of the Cordilleran region (in the present Rocky Mountain 

 region) deposition continued throughout Mesozoic and later time, just as later 

 Tertiary deposits continued to form south of the Alps, inside of the Car- 

 pathian arch (Hungarian or Pannonian Basin), and south of the Caucasus. In 

 all of these regions there is essential concordance of strata, though discon- 

 formities exist, except where later overlaps bring the younger strata to rest 

 on the eroded parts of the folded series. 



So far as the available data permit judgment, a similar migration of geo- 

 synclinal belts occurred on the first elevation of the Atlas Mountains of North 

 Africa and the Andes of South America, and it appears that this is a principle 

 of wide applicability. 



Presented by the author extemporaneously. 

 Discussed by Prof. Bailey Willis. 



GEOTECTONIC ADAPTATION THROUGH RETARDATION OF THE EARTH'S 



ROTATION 



BY CHARLES R. KEYES 



(Abstract) 



From the results of recent curious experiments in geotectonics, it is inferred 

 that the larger relief features of our globe are not the complex dynamical 

 phenomena commonly fancied, but that all are merely somewhat different ex- 



