GRAVELS AND BOULDER-CLAYS. 39 



miles eastward), and there found reason to believe that the Saskatchewan 

 gravels of the plains represent and gradually pass into a " western boulder- 

 clay " in approaching the mountains. This observation has remained un- 

 published, but now appears to bcwell established, and it follows from it, 

 taken in connection with the facts already summarized, that there are no 

 less than three distinct boulder-clays in the region here treated of, the old- 

 est or " western " boulder-clay being followed in time by that previously 

 named the " lower " boulder-clay, which is in turn distinctly separated 

 from the " upper " boulder-clay over a considerable part of the district, at 

 least, by interglacial deposits. The western boulder-clay, as its name im- 

 plies, contains no Laurentian or Huronian material, while such material, 

 as well as limestone derived from the Winnipeg basin, is present in both 

 the others. This general statement will serve as a clue to many of the 

 observations subsequently detailed. 



In further presenting the results of recent observations attention will 

 first be given to the sections found on the Belly and Oldman rivers, to 

 the surface of the plains in their vicinity, and to the wide low area which 

 is occupied by the tributaries of the Oldman in the neighborhood of the 

 mountains. 



Sections in the Valleys of Oldman and Belly Rivers. 



Although in the report of 1882-'84: the occurrence of two boulder-clays 

 with an interglacial deposit was noted at Coal Banks (now Lethbridge) 

 and a photograph was reproduced showing these deposits there running 

 for miles along the bluffs of the river valley, no detailed section was re- 

 corded for this place. A careful examination was made of this section 

 in 1894, at a place about four miles north of Lethbridge, with the follow- 

 ing result : The valley of the river at this place is cut down about 300 

 feet into the prairie. From 50 to 80 feet above the water level is occu- 

 pied by dark shales of the Pierre formation of the Cretaceous, resting 

 upon which, along a perfectly even line, are the Saskatchewan gravels or 

 " quartzite drift," with a thickness from 10 to 15 feet. The upper part of 

 the shales, to a depth of two feet, is weathered and brownish in color. 

 The gravels are coarse, often containing stones up to six inches in diam- 

 eter, all well smoothed and water-worn, but often not j^erfectly rounded. 

 They are generally arranged in a rather tumultuous manner; that is, 

 not in regular layers graded according to size, and with the pebbles some- 

 times standing on end. The interspaces are filled with a coarse gray 

 sand, and a similar material forms occasional discontinuous layers a few 

 inches or feet in thickness on the upper surface of the gravels. The 

 stones are chiefl}^ characteristic Rocky Mountain quartzites, but a con- 

 siderable number of pebbles of limestone from the same source are in- 

 cluded, as well as a few examples of the peculiar Rocky Mountain 



VI— Bull. Geol. Soc. Am., Vol. 7, 1895, 



