406 



J. E. Hyde — Desiccation Conglomerates. 



thickness persistently. It is composed almost entirely of peb- 

 bles of limestone varying in size from that of very coarse sand 

 grains to four and one half-inches in diameter, the largest seen. 

 The bulk of the layer is made up of fragments from one-fourth 

 inch to one inch in diameter, with considerable amounts of 

 much finer material scattered between. Each pebble is so 

 cemented to the upper surface of the limestone layer that about 

 half of it stands out in relief, the lower half being buried in a 

 matrix consisting principally of small limestone fragments 

 which might be termed very coarse sand. During deposition 

 the dark shale overlying filled not only all the interstices between 

 the projecting pebbles but settled down into the smaller spaces 



between sand grains. When the blocks are removed and 

 exposed to the weather this shale is quickly washed out, all 

 trace of it being removed in time, and the conglomeritic sur- 

 face is left exposed exactly as it was when first covered up. 

 It has every appearance of a land surface strewn with a thin 

 layer of limestone pebbles and coarse sand, such as one might 

 see to-day under suitable conditions, and so fresh is it that it is 

 difficult to believe that one is looking at a land surface which 

 was covered during Paleozoic time. 



Although the great majority are less than one inch, pebbles 

 up to two inches or more in diameter are not uncommon. 

 Those more than one inch in diameter are all flat and usually 

 about three-eighths of an inch thick, although at one point the 

 thickness of a number reaches an inch. The outlines of the 

 large pebbles are quite irregular but in general are definitely 

 polygonal with numerous concave sides as shown in the outline 

 figures. These pebbles all lie flat in the stratum. The edges, 

 although sometimes noticeably angular, are usually more or 



