ABSTRACTS OF PAPERl^^ 91 



LATE TERTIARY AND PLEISTOCENE TERRACE PLAINS OF THE MIDDLE 



ATLANTIC COASTAL PLAIN 



BY CHESTER K. WENTWORTH ^ 



(Ahstract) 



The terraces and associated formations of the middle Atlantic Coastal Plain 

 and adjacent parts of the Piedmont Plateau are mainlj^ of fluviatile and sub- 

 ordinately of marine origin. In the basin of the Potomac River there are six 

 in number, which may practicably be mapped as follows : Tenley, Brandywine, 

 Sunderland, "C" (Wicomico of Shattuck), "B" (Talbot of Shattuck in part), 

 and "A"' (Talbot of Shattuck in part). The two earlier are wholly fluviatile 

 as far eastward as the present coast i the latter four are fluviatile in the west- 

 ern part of their area and marine in the area adjacent to the coast. The 

 present inclination of the terrace plains is to a large extent the original slope 

 of deposition and is due only subordinately to crustal deformation. Fluviatile 

 and marine portions of the terraces are separated by rather abrupt changes 

 in inclination, which are not duplicated in the attitudes of higher and older 

 terraces in the vicinity. 



The problems of correlation of plains are still far from solution for the 

 whole coastal area, but the distribution of the glacial boulders and of other 

 unique lithologic constituents of certain of the formations in the area studied 

 most in detail promises to be of great value, as broader areas to the north and 

 south are studied with closer attention to physical and lithologic characters 

 than these have received in the past. 



The clear identification of the early Pleistocene Sunderland terrace, as dis- 

 tinct from the present river grade to a point well into the Allegheny Plateau, 

 is of great value in separating Pleistocene from probable pre-Pleistocene ter- 

 race remnants, and by its comparison with later terraces this study joins with 

 studies in other regions in demonstrating the very great duration of earlier 

 Pleistocene epochs. 



Eead by title. 



GLACIAL DEPOSITS OF MISSOURI AND ADJACENT DISTRICTS 

 BY FRANK LEVERETT 



(Abstract) 



The Kansas drift forms a nearly continuous sheet, except where cut away 

 in valleys about to the Missouri River in Missouri and the Kansas River in 

 northeastern Kansas. 



South of these streams and also along the Mississippi below Hannibal, Mis- 

 souri, and between the Mississippi and Illinois rivers in Pike and Calhoun 

 counties, Illinois, there are scattered boulders and smaller erratics extending 

 from 10 to 30 miles or more beyond the definite till sheet. These may repre- 

 sent an earlier glaciation than the Kansan and be reduced on that account to 

 a scanty deposit. The topographic situation is such that no ponding of waters 



^ Introduced bv A. C. Trowbridge. 



