146 GEOLOGY OF THE DENVER BASIN. 



line west-southwest through Scranton is a bed of lignite, probably of much 

 higher horizon than that of the coals in the western half of the held. 

 Northward the lignite disappears, and in the deeper borings, 800 to 900 

 feet, only shales, ironstones, and occasional streaks of coal arc met with. 

 Neither the base of the Laramie nor, indeed, any of the lower sandstones 

 are reached within this eastern area. Water-bearing, sandy layers occa- 

 sionally occur, notably in the Gilbert well, 800 feet deep, midway between 

 First and Second creeks and the meridians of 104° 4;V and 104° 50', but 

 these are probably local developments in the upper series of the formation. 



The line of the Arapahoe bordering the Laramie area on the north is 

 only approximately determined, on account of overlying deposits of gravel, 

 sand, and loess, but it is shown on the map probably within 1 mile of its 

 proper location. The most important outcrops of the Arapahoe occur on 

 Third Creek, near the eastern edge of the held. The sandstones are here 

 characteristically, and, for the prairie region, rather exceptionally developed, 

 the looseness of texture, the bright yellow to white appearance, the coarse- 

 ness, the siliceous composition, and the flinty character of the pebbles, all 

 being present. The thickness of the sandstones is here between 15 and 

 30 feet. 



The line between the Denver and Laramie formations is distinct, 

 following for several miles the southern bluffs of Coal or Sand ('reek and 

 crossing thence to the north on the lower part of the stream. The con- 

 glomerates and clays of the Denver form an almost continuous outcrop 

 from the eastern limit of the field to the creek crossing of the narrow- 

 gauge railroad leading to the Scranton coal mines, displaying local dips 

 in one direction or another, but in general approximately horizontal. 

 Exposures are also frequent in the ditches to the south of Coal Creek, 

 particularly in the large High-Line < 'anal and in the gulches below it. 



The line between the Monument Creek and older formations is very 

 irregular, being influenced both by contours and by the uneven surface of 

 the beds upon which it rests. The formation lies in a horizontal position, 

 so far as can be determined, and weathers into bold mesas with sharp 

 bluffs. 



The detailed relations of the Laramie, Arapahoe, and Denver, at the 

 western end of the Laramie area, can not be determined, owing to the 



