231: 



been invaded l)y the ice sheet, and at the same time tlie drainagx' was held 

 up by the interference of the ice slieet at the mouth of Bean Blossom. 



The evidence of the arrest of drainage at the time of ice invasion is 

 found in the occurrence of a series of benches, inaptly termed terraces by 

 some writers, rimming the eastern and northern slope of the valley at 

 various points within the limit of Monroe County and are reported to occua' 

 with increased frequency in Brown. 



In all the sections and cuts found in the benches, only clay and sandy 

 materials appeared. No limestone and sandstone exposures, such as miake 

 up the valley slopes, were found in the benches; their contents are un- 

 doubtedly made up of the wash and soil-creep brought into the valley from 

 the uplands, the clay portion l)eing derived from the decomposed lime- 

 stone and the sand constituency from the underlying knob stone. 



The benches vary much both in form, areal extent and elevation above 

 the valley lloor. They are invariably attached to the slope, and exhibit in 

 most instances a remarkably flat or sometimes gently sloping surface 

 towards the outer edge. The outer rim is usually lobate in form, with 

 narrow, young valleys extending towards the rock slopes, and sometimes, 

 so far, as to traverse the entire width of the bench. The slope of the outer 

 edge is usually steep and well detined. In some cases the tops of the 

 benches are slightly undulating or rolling. Those, however, seldom attain 

 the elevation of the flat-topped ones. In Marion and Washington Town- 

 ships they may be traced continuously for three or more miles, and attain 

 a width of something over half a mile. They also vary much in elevation 

 above the valley floor, attaining a maximum height in Marion Township, 

 sections 19 and 20, of seventy or more feet, and decreasing gradually down 

 stream, luitil in section 32, Washington, they are found to be some' twenty- 

 five to thirty feet above the A'alley floor. 



That these benches must have lieen deposited in water is attested to 

 l)y various criteria. The fiat tops, steep angle on the front, and stratifica- 

 tion show that they aie delta-like accumulations brought in during the 

 arrest of the drainage and not terraces in technical sense, although they 

 appear very much like the latter so far as form is concerned. 



The various elevations attained in different parts of the valley may be 

 due to different levels at which the hiked valley stood during the hiking 

 period, or it may be accounted for in part, at least, to the larger contribu- 

 tion of residual materials from uplands to the upper part of the valley by 

 the northern tributaries, than hy similar streams emptying into Bean 



