528 EEPOET UNITED STATES GEOLOGICAL SURVEY. 



slightly toward the west, the dip increasing somewhat near the range. 

 Soon after crossing the AYCstern rim of the Green Eiver Basin the two 

 l)ranches unite, and a few miles below are joined by a small branch com- 

 ing from the north, when a more southerly direction is assumed, and the 

 cireek Hows out into a broad valley, in which it is side by side with the 

 Green, and iiually, to use an anatomical term which exactly descril^es 

 it, joins the latter by anastomosis. There are at least five islands formed 

 by the two streams in the lower end of the broad valley. This '\-alley 

 forms one of the finest meadow areas on the Green, Avith a few groves 

 of cottonwoods. The Green enters the valley flowing south, and near 

 the southern end turns abruptly eastward, leaving it to flow southward 

 into a caiion-like valley that extends to the mouth of Piuey Creek. East 

 of Green Eiver are low bluffs of variegated Wahsatch beds, and farther 

 back high terraces or remuants of terraces appear capped by the white 

 beds of the Green Eiver Group. Horse Creek hugs the blufts on the 

 west side of the valley, and between the creek and Marsh Creek an 

 area of Green Eiver beds extends westward toward the hills. Nearer 

 Green Eiver, however, the surface is much eroded, and all that lemains 

 of the Green Eiver Group is to be seen as capi)iugs of a few isolated 

 buttes. The gray, greenish, and red marls and sands of the Wahsatch 

 cire the j^revaibng rocks. These are eroded into rounded hills covered 

 with loose drift in places composed of i)ebbles of quartzite, reddish sand- 

 stones, and occasionally fragments of limestones, all evidently derived 

 from the surrounding mountains, especially those to the west and north. 



Station 13 is located about 3 miles south of Horse Creek and a little 

 over 2 miles west of Green Eiver. The summit is composed of a thin 

 layer of hard white limestone, the upper surface of which is covered 

 with petrified cases of caddis-tiies which have been described by Prof. 

 S. H. Scudder.* Below the limestone is a gray and yellow micaceous 

 sandstone loosely aggregated. Still farther down are soft gray and 

 pink beds that weather into bad-lands. The outcrop is about 100 to 150 

 feet. The country between Horse Creek and Marsh Creek is a " bad-land " 

 country covered with sage-brush. Along the small creek that occupies 

 the depression between Horse Creek and Marsh Creek there are numer- 

 ous alkali flats. 



Marsh Creeh is one of the largest of the western branches of the Green, 

 and is formed by two stream^ of about equal importance. The northern, 

 to which the name Marsh Creek has been applied, collects its watei' fi-om 

 the Meridional Valley between the mountains and the line of uj^lift 

 that forms the western rim of the basin. The Southern Branch rises 

 among the Carboniferous limestones of the Wyoming Eange and cuts 

 across the Meridional YaUey, receiving a branch from the south, and 

 with an easterly course flows out into the basin through a caiaon cut in 

 an anticlinal of Jurassic? limestones. On these limestones the varie- 

 gated Wahsatch beds are seen dipping uuconformably to the eastward. 

 This creek has been named Lander Creek. It joins the main stream 

 about 12 miles from the rim formed by meridian fold, and from this 

 point to the Green, Marsh Creek is in a broad valley lined with willows. 

 All the streams in the basin are conspicuous for their want of timber. 

 Between Marsh Creek and the Bitterroot, "bad-lands" prevail. On the 

 eastern slope of the basin rim White Clay Greeli rises and flows parallel 

 to Marsh Creek, only a mile or two miles from it. Instead of cutting"^ 

 across to the Green as Marsh Creek does, it turns abruptly southward 

 through a depression to join the river near the mouth of Bitterroot 



* Bulletin U. S. Geol. Snrv., vol. iv, No. '2, p. 543. 



