52 GEOLOGICAL SURVEY OF THE TERRITOEIES. 



fiued terraces, wbich on the east side rise 600 feet above the river. 

 The coarser materials were evidently deposited in water, and are 

 arranged in strata and appear not to have been disturbed to any great 

 extent by changes of level. On the west side the terraces slope down 

 more gradually, and are cut from west to east by deep gorges, by 

 streams from the main range. The valley itself extending to an eleva- 

 tion of 400 to GOO feet on either side, is filled up with more or less coarse 

 drift-deposits. These vary much at different points, sometimes made 

 up of huge bowlders, inclosed in loose gravel, sand, or clay, and again 

 a rather fine deposit of sand, gravel, or clay, to all appearances having 

 been deposited in comparatively quiet waters. At any rate there were 

 at all times portions of the lake that were not subject to great currents 

 • or any violent agitation. On the whole, however, the drift-materials 

 are very loose, showing that the movements of the water and ice were 

 from north to the southward. All over the surface are scattered in 

 vast quantities immense bowlders of granite, varying from a few feet to 

 50 feet in diameter. Below Granite, for four or five miles, the masses 

 of granite are remarkable for their number and size, which appear to 

 have been moved down Clear and Pine Creeks. Along the sides of 

 Clear and Pine Creeks are high ridges, or lateral moraines, which may 

 properly be compared to huge railway embankments, rising to a height 

 of 400 to 800 feet above the valleys of the streams. Below the mouth of 

 Pine Creek the valley soon expands, and the surface is covered with loose 

 bowlders, while the ridges and depressions are quite remarkable, and 

 give it almost an artificial appearance. These basin-like depressions 

 inclosed by the moraines are not unfrequently filled with water, form- 

 ing small lakes, often with no visible outlet. These little basins of water 

 occupy different elevations, from the bottom terrace near the river to 

 the point of junction of the drift on the mountain-sides, 800 to 1,200 

 feet above the river-bed. As we descend the river the bowlders dimin- 

 ish in size, are more rounded, and the deposits of fine materials increase 

 in thickness. Below the mouth of Chalk Creek the valley is covered 

 with a series of yellow- white marly beds, which are cut up into a 

 variety of singular forms, resembling the "Bad Lands" and reaching 

 an aggregate thickness of 800 to 1,200 feet. ' These were observed by 

 me in 1869 and named the "Arkansas marls." Overlying these marls 

 there is considerable thickness of coarse drift which forms to a great 

 extent the terraces which are very marked for a distance of 30 miles. 

 We can see, therefore, that the greater part of the finer sediments were 

 transported to the lower or south end of the river-lake, and deposited 

 in comparatively quiet waters. While we ascend the Arkansas Valley 

 toward the Tennessee Pass, the proofs of great force from the combined 

 action of water and ice are shown on a grand scale. It seems, too, that 

 while there is a variety of deposits in this valley resting upon the granites, 

 their history is consecutive and attributable to one general cause, local 

 glacial action, so far as I have yet observed. I repeat the same statement 

 which I made years ago, that I have observed no proof of any wide ex- 

 tended drift-action like that of the ISTew England States, but in the Eocky 

 Mountains the superficial deposits are all of local origin ; and the source 

 is usually limited to the drainage of the streams in which it is found. 

 For example, although, as I have stated, I believe that all the marls and 

 coarser deposits in the valley of the Upper Arkansas have the same 

 origin, however different in composition, the forces that produced them 

 are limited geographically to the drainage of the Upper Arkansas. I 

 could find no indications that any fragment of rock had been transported 

 even from so short a distance as beyond the drainage west of the Sa- 



