738 * ABSTRACTS OF PAPERS 



here different from those south of Watertown. Regarding the marine beach 

 of Gilbert Gulf, there are no marine shells, the calculated plain is too high 

 for sealevel, and the distinct deposits of marine shells are not of identical 

 epochs. Therefore there is no ground for the author's pronouncement of 

 their marine origin. 



East of Ogdensburg are beds of fine stratified clay with surface smoothed, 

 polished, and striated. It is covered with sand. Lying on the clay are a 

 very few small erratics, while no stones occur in the sand. This suggests 

 that a glacial advance occurred after the clay beds had been deposited, but 

 before the changed conditions arose which permitted the later accumulation 

 of sand. 



IXTERMINGLIXG OF PLEISTOCENE FORMATIOXS 

 BY B. SHIMEK 



Published as pages 709-712 of this Yolmne. 



LOESS A LITHOLOGICAL TERM 

 BY B. SHIMEK 



{Abstract) 



The term "loess" has commonly been understood as implying a more or less 

 distinct division of time. The facts are that there are several loesses de- 

 posited at different periods, and that loess does not designate a distinct period 

 of time, but indicates rather a condition of deposition, as do such terms as 

 "sandstone," "limestone," and "drift." 



Discussion 



Mr. F. V. Emerson : Loess is forming along the Missouri in central Mis- 

 souri. During the dry, late summer frciinent dust storms carry a yellow dust 

 to the bluffs, where it gathers and is easily observed on exposed surfaces. This 

 dust in all essentials resembles the material forming the thick loess beds. 



Prof. G. Frederick Wright: In judging of the date of the various deposits 

 of loess, it is important to keep in mind that throughout the entire period 

 through which the ice was advancing there were each sunmier pouring forth 

 from it powerful currents of silt-laden water, so that whenever there was 

 recession of the ice-front, great or small, there might be an accumulation of 

 loess which would be subsequently covered by the till of a later ice advance. 

 It is well, therefore, to name such deposits after the various stages of ad- 

 vance of the ice. 



But there was imr cxccUcncc a period coinciding closely with the departure 

 of the Iowa ice when silt-laden waters were so superabundant as to lead to 

 the building up of the loess deposits along the Missouri and other rivers 

 which have been especially under consideration. Here, as in China, there 

 was a special period when the accumulation of loess exceeded its ablation. 

 Both here and in China the erosive agents are now in the ascendant, so that 



