.'. NOTES ON Till-: ROCKY FORK COAL FIELD OF MONTANA. 

 Location and general Features. 



The Rocky Fork coal field lies at the foot of the Beartooth mountains 

 and south of Yellowstone river, Montana. The quality of coal, the thick- 

 ness and great number of the seams, with the unproved extent of the 

 field, make it of great importance notwithstanding the distance to the 

 larger centers of consumption. A branch line leaves the Northern Pacific 

 railway at Laurel, 13 miles west of Billings, and runs up Clarices fork of 

 the Yellowstone and its tributary, Rocky fork, to the mines and themin- 

 ,ing town of Red Lodge. 



The topography of the field is of a type common along the eastern base 

 of the mountains. Very gently sloping plains abutting sharply against 

 the steep rocky slopes of the mountains stretch out for many miles north- 

 ward. These plains are trenched by longitudinal drainages, the larger 

 streams from the mountains flowing in rather broad gravel-filled valleys. 

 the smaller streams beading in the plateau cutting down the benchland 

 slowly and exposing the tilted and eroded rocks which form the mesa. 

 Toward the south the mountains rise abruptly in rocky, buttressed slopes 

 to the crest of Ike Beartooth range, an unexplored glacier-crowned moun- 

 tain mass having the highest peaks in Montana. Toward the north the 

 table-land fades into the benchland and rolling hills of the Crow reser- 

 vation, a well watered country with broad alluvial bottom lands and well 

 grassed uplands, greedily coveted by the settlers of the surrounding coun- 

 try. The mountain slopes and valleys are wooded with a heavy growth 

 of pine timber, but the table-lands of the coal field are bare of trees and 

 shrubs, save along the water-courses, though well grassed and bright with 

 the colors of innumerable flowers. 



The general features of the geology of the region are simple ; a section 

 shows a series of sandstones resting on the marine cretaceous in the val- 

 ley of the Yellowstone, dipping gently from 3° to 5° toward the moun- 

 tains but disturbed by gentle warping of the beds. These sandstones, 

 which near the mountains dip more steeply (averaging 15°) and carry 

 the coal seams, are faulted against the Paleozoic limestones which form 

 the mountain flanks : the latter weather in great combs and ledges, dip- 

 ping away from the mountains at high angles. 



The benchlands which form so conspicuous a feature of the coal held 

 are covered by a thick mantling of more or less rounded drift, sometimes 

 to a depth of 160 feet. This gravel effectually conceals the truncate! 



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