168 GEOLOGT2 OF THE DENVER BASIN. 



grained bed which may <>r may qoI be «;isil \ separated from the stratum 

 nex1 succeeding. In the section there is merely a marked line between 

 the conglomerate (7) and a sandy or gravelly bed of practically the same 

 composition but of liner grain. This is followed upward by sands and 

 then by sandy clays, and these by darker, purer clays, to which succeeds 

 again a coarse gravel layer (9), followed once more by transition l>e<|s. 

 The bed at 9 is more probably the equivalent of the darker conglomerate 

 usually found at about this horizon than is the better-defined conglomerate 

 below (7). 



'The detailed description of the foregoing section is intended to show 

 the peculiar composition normal for the strata of the Denver series in those 

 horizons and also to bring out clearly the conditions which must have 

 attended the deposition of such fine-grained sediments. It is (dear that 

 the small pebbles so universally found have been greatly reduced in size 



through continued abrasion; that the transition from the coarse layers al 

 the base of a certain series upward through the finer and finer sediments 

 to clays, which are as a rule succeeded by a sudden change to coarse 

 materials, must indicate the periods of comparative rest or disturbance of 



the waters of these seas. Furthermore, the presence of considerable tree 

 stumps in erect position with roots in mud layers and broken trunks in 

 sand 01' gravel, shows that the water was shallow or even that low -laud 

 masses alternated with shallow seas. Probably the latter was the case. 

 The accumulation of these strata was slow and they represent a long 

 epoch of sedimentation. 



Outcrops at the southeastern point of South Table Mountain. Opposite tile middle ol the 



foot-like extremity of South Table Mountain is a knoll connected with the 

 slope of the mountain by a ridge, and on the south side of this knoll is a 

 little basin. From the basalt contact down to the bottom of this basin 

 and on the ridge and knoll are good outcrops of horizontal strata which 

 again illustrate the occurrence of the beds found in the preceding section 



within 101) feet of the basalt. Here the section is not quite continuous, 



and the tin" grain of mosl of the gravelly layers makes a direct comparison 

 difficult, but it is still plain that the sections are equivalent so far as they go. 



At nit tret below the basalt appears a light-Colored layer, with pebbles of 



