DENVEE OF GEEEN MOUNTAIN. 177 



About some pebbles in this heavily iron-bearing stratum then- is a shell 

 of limonite nearly an inch in thickness, in which an imperfect radiate 

 structure can be seen. A.rchean strongly predominates over eruptive 

 material in all the strata from this horizon upward. Dakota conglomerate 

 bowlders were noticed at and near the iron-bearing horizon. One of them 

 was 2 feet in diameter. 



The sandy matrix of the crumbling conglomerates is chiefly composed 

 of quartz and red feldspar. Besides the stratum especially mentioned 

 there is a slight appearance of iron oxide in the cemenl a1 many places, 

 the result being a firmer nick in all instances. Large bowldei's, with an 

 average diameter of from 1 to "_' feet, are thickly piled in together in some 

 layers, with smaller ones in the interstices. 



While conglomerate nicks strongly predominate in all of Section I>, 

 fine-grained beds appear in places, though perhaps with but limited lateral 

 development, much .-is the conglomerates appear in the fine-grained beds of 

 the lower portion of the formation. Thus, a few feet below the point A on 

 the profile, there appears a dark, arenaceous clay stratum, containing much 

 vegetable matter. Seen on the lineof profile it appears to be a well-defined 

 horizon occurring as a break in the conglomerate series, but this stratum 

 can not be identified as such at a distance of but a few yards to the north 

 (in a ridge where there are good croppings. Probably the conglomerate 

 succeeding it was deposited in turbulent water-, which locally or perhaps 

 generally destroyed the fine deposil of a period of quiet. The study of 

 the conglomerate series made it evident that fine-grained beds of 1< ><-;i 1 

 development might occur at almost any horizon, probably representing in 

 all cases remnants of a layer of former continuity. In subdivision h no 

 continuous lied of tine grain was found, hut one noticeable local stratum 

 was observed a few yards north of the line of section on the northern 

 ridge. Here is a dark clay stratum. L8 feet thick, with coarse sandstone 

 above it. The clay is dull-purplish in color and has a few gravel stones 

 mixed in with it. One foot more or less below the Sandstone is a local 

 layer of lignitic material, a part of which is changed into true jet of great 

 brilliancy. In part of this layer the woody fiber and toughness are still 

 preserved. Tracing these- lieds southward the) wedge out rapidly, and on 

 MON XXVIt 12 



