132 GEOLOGY OF THE DENVER BASIN. 



dip for these beds of between b> : and 15 to the southeast. The beds to the 

 south have been l>ut slightly, it' at all, disturbed. To this structure is plainly 

 due the character of the topographical depression in which lies the lower 

 coal branch of the Marshall district. The amount of the stratigraphic 

 throw at the center of the fault, the point of its greatest depression, is 

 about 260 feet. The southwestern end of the fault is nearly coincident 

 with that of the main fault, while the eastern end originates in the same 

 fold as that in which the middle break had its origin. As in the case of its 

 associate faults, the position of the present break is not precisely mapped, 

 the fracture itself being obscure. It is, however, distinctly traceable in the 

 field from the succession of the strata on either side and from the fragmen- 

 tary character of the rock lying in proximity to it. 



A.s alternatives of the foregoing structure it is possible, in the first 

 place, that the main fault and that described as its southern branch may 

 be coincident from their southwest end to a point a few hundred feet east 

 of the Marshall mine No. ,">. and that thence they may first begin their 

 divergence, the trend to this point being that of the southern branch, X. 

 62 1'... which is that of the fault plane in the No. ."> mine. Again, it may 

 be that instead of the south fault being actually a branch of the one 

 described as the •'main" or north fault, the main fault may originate 

 independently and to the north of this southern fracture, at approximately 

 its point of union with the fault described as the middle one. 



The above alternatives are suggested as possible, but in any event the 

 question is of slight economic importance, as the amount of ground involved 

 is small and highly fractured. 



The Muff fault, if actually existing, lies along the brow of the blurt" 

 on the south side of the Marshall Basin. It is shown as a dotted line on 

 the map. The existence of this fault is not clearly established, but there 

 is a certain amount of evidence pointing to it. consisting in (a) the occur- 

 rence upon the narrow table above, and to the south or rear of the bluff 

 which carries the upper bench of coal, of what appears to be the upper por- 

 tion of the basal sandstones of the Laramie: (h) the topographic depression 



which a part of the table itself has suffered and which resembles in kind 

 that of the interfaull block to the north: and (c) the report that in one of 



