

- ORETACEOUS AND TERTIARY—SOUTH FORK OF BELLY RIVER. 135 
Five miles east of the entrance of the pass, and north of the Mount Wilson 
Range, exposures of thin-bedded clays and argillaceous sandstones, with 
occasional beds of hard flaggy sandstone, were seen. The whole are of 
various shades of light grey, and though curiously folded and faulted, not 
much altered. Some surfaces of the sandstone are strewn with small 
carbonaceous fragments, but no recognizable fossils were found. (Plate 
IX., Fig. 1.) , 
334. The South Fork of the Belly River—which rises between the 
Mount Wilson and Chief Mountain ranges, and flows northward out upon 
the plain—where its valley is contracted among the mountains, in some 
places lies between high banks, which though in most cases composed 
of drift, in one locality, about four miles north of the Line, showed a 
section of beds probably Tertiary. The beds are thin sandstones and clays, 
like the last, and dip northward at an angle of about 15°. These beds 
here actually lie in a retired valley among the older rocks of the moun- 
tains. Further down the same stream, large fragments of lignite, 
exactly resembling that of the eastern Tertiary rocks, were found. As 
drift at this elevation is altogether derived from the mountains, and not 
so far travelled as that of the lower levels, it is almost certain that in this 
valley there exist some beds of Tertiary lignite. 

