50 GEOLOGICAL SURVEY OF THE TERRITORIES. 



nessee Pass to the cauon, a distance of eighty miles. Our camp was 

 on the north base of the jieak, above timber-line, at the very sources of 

 some of the little branches of the Platte. The granite rocks cropped 

 out all around us, although the greater portion of the surface was 

 covered with grass, and the moist valleys were peculiarly fresh and 

 green. The lower portion of the Upper Arkansas Valley is indeed a 

 j)ark, and far more beautiful, though not so large as the South Park 5 

 but its origin is very different. The South Park is an area of depression, 

 that is, it is a basin surrounded by lofty ranges of mountains, underlaid 

 with rocks of the sedimentary group, which shows that it has never 

 been elevated equally with the surrounding mountain-j?auges. The Ar- 

 kansas Park is an area of upheaval and erosion, and nowhere in it are 

 any sedimentary rocks exposed older than the modern lake-deposits. 

 A few small streams flow into the Arkansas Eiver from the east side, 

 but the main drainage is from the west side. Descending into the val- 

 ley on the west side of the Park range, from the base of the Buffalo 

 Peaks, we found the traveling very difficult; the sides of the mountains 

 covered with debris and very precipitous. The fallen timber adds also 

 much to the labor of traveling. The autumnal fires sweep over the 

 sides of the mountains, killing the pines, and the winter and spring 

 winds lay them down in every direction, forming a i^erfect net-work 

 Beaching the valley nearly opposite Mount Harvard, we camped for 

 two days on the bottom to make a study of this interesting region. By 

 following our route of travel in our narrative, we are enabled to note 

 down the local details of the geology from point to point, on which any 

 general remarks we may make are founded. The maps, which will soon 

 be published, will enable the geological reader to follow these routes 

 with ease ; and, in connection with the sketches and sections, we hope 

 to make our observations clear. 



The point from which we will start now on our march up the Arkan- 

 sas Eiver is at the head of the Arkansas Park, a little below the mouth 

 of Pine Creek. The valley here begins to expand out somewhat, and is 

 about half a mile in width. There are several abandoned farms on the 

 bottom. Lower down in the main park, or valley, are some excellent 

 farms and prosperous settlements. The decline of the mining interest 

 has caused the upper portion of the valley to be almost entirely deserted. 

 A few years ago there were many thousands of miners in the valley, and 

 every gulch was filled with placer-diggings. Granite bid fair to become a 

 city and spread itself over a considerable area on both sides of the mines. 

 ]S"ow the buildings are all fast going to decay. A few miners still linger 

 among the old " placers," but the mining period has passed away. 



I have spoken of the finer sediments which were deposited in the 

 ancient lake, in the lower portion of the valley to the southward. The 

 waters that rushed down from the north lost the greater part of their 

 force in the broader, deeper waters of the southern portion. Here the 

 fine material which was ground from the granite rojcks by water and ice 

 to the northward was carried, and the greater stillness of the waters 

 then allowed it to settle on the bottom more quietly, forming a group 

 of marly strata at least 1,200 feet in thickness, which have weathered 

 into the peculiar architectural forms which characterize the modern lake- 

 deposits farther north in which the remains of so many extinct verte- 

 brate animals have been found. As we ascend the valley from the 

 lower end, these lake-deposits become coarser and show evidences t)f 

 deposition in more turbulent waters, until at the upper end the huge 

 rounded bowlders predominate. Near the bridge about five miles below 

 Granite are long, lone ridges of the coarse drift or detrital matter on 



