262 OLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



form sheets extending horizontally for a mile or more. "Split Rock" is a 

 detached mass of such a conglomerate lying in the river on the Kentucky 

 side. The conglomerate from which it is broken extends up to a height 

 of nearly 100 feet above the river and for a distance of one-eighth mile 

 or more along the bank. It extends for more than a mile along the valley, 

 lying mainly below the mouth of Wolper Creek. Back of this, at a height 

 of about 300 feet above the river, is another conglomerate mass, known 

 as the "Middle Creek conglomerate," which was discussed some years since 

 by Sutton.^ From the wide difference of level at which these conglomer- 

 ates occur Sutton drew the inference that they are widely different in age, it 

 being assumed that they are terrace remnants. In the writer's opinion, as 

 just indicated, the conglomerates are to be classed as exceptionally^ stony 

 till rather than the deposit of a stream, and the wide difference in altitude 

 may signify nothing as to time relations. Indeed, the writer was unable to 

 discover any evidence that the two conglomerates differ greatly in age. 

 An imcemented stony deposit above the level of the upper conglomerate is 

 discussed below. 



A sheet of silt or white clay covers the Illinoian drift in this region as 

 well as in the region to the west occupied by the Illinois glacial lobe, which 

 appears to be a continuation or extension of the loess of the central part of 

 the Mississippi Basin. The white clay is but 3 to 6 feet thick on the flat 

 parts of this region, and is usually largely removed from valley slopes. 

 The drift knolls above noted are covered by it unless their slopes are very 

 abrupt. It conceals the till and bowlders to a great degree on the uplands, 

 leaving only the eroded valley slopes to afford natural exposures. The 

 amount of white clay is not sufficient to produce a notable valley filling. 

 It thus differs from the till which, as stated above, has filled valleys to a 

 perceptible degree all along the drift border. The distribution, structure, 

 and relationships of the white clay are taken up in some detail farther on. 

 The structure of the drift border may generally be easily determined from 

 natural exposures, and such exposures have furnished data for the statements 

 just made; but in valleys, and also on Chestnut Ridge, wells have been 

 of service in revealing the drift structure. A few records are accordingly 

 given. 



^Glacial or ice deposits in Boone County, Ky., of tw3 distinct and widely distant periods, by 

 George Sutton: Proc. Am. Assoc. Adv. Sci., Vol. XXV, 1876, pp. 225-231; also Tenth Ann. Kept. 

 Geol. Survey Indiana, 1878, pp. 108-113. 



