698 W. C. A'LDEN PRE-WISCONSIN GLACIAL DRIFT IN MONTANA 



ments of the Siyeh limestone are deeply etched. Beneath this is (B) a 

 10 to 15 foot band, where the till is oxidized to an orange or yellowish 

 tint. In this is more of the yellow oxidized limestone, some of the frag- 

 ments of which are thoroughly rotted. Underlying this zone and form- 

 ing the greater part of the section is (C) reddish till cemented by cal- 

 cium carbonate to a hard conglomerate which projects from the slope as 

 ledges. Most of the pebbles and boulders in this have fresh glaciated 

 surfaces, but some of the diorites are disintegrating; many of the buff 

 limestones are etched by solution and some have been removed, leaving 

 only a yellowish powder in the cavities. The reddish tint is due to the 

 large amount of red argillite. The calcium carbonate cement was prob- 

 ably derived by percolating waters from the solution of limestone frag- 

 ments in the upper part of the section. It is the projecting ledges of 

 conglomerate which give to the deposit, as seen from the valley below, 

 the appearance of stratification. Close examination reveals no assort- 

 ment of the material or bedding. Xo fragments of rock were noted 

 other than such as are derived from the mountains. About 250 feet of 

 drift was seen, but the base was not exposed. About half a mile farther 

 south a second similar exposure of this was examined. Here the yellow 

 band (B) was not so noticeable, but other evidences of weathering and 

 cementation are the same. Four miles north of this later scarp a third 

 exposure was examined by Mr. Thomas. He reports 250 feet of drift of 

 much the same composition as noted above. jSTo limestone was noted at 

 the top, though blocks of Siyeh limestone were seen in the conglomerate, 

 which extends to within 5 or 10 feet of the grassed top. 



From the material exposed at these several points it is apparent that 

 the capping of Saint Mary Eidge is a deposit of old drift identical in 

 character with the old drift on Two Medicine Eidge excepting for the 

 presence here of fragments of Siyeh limestone. Owing to the thick 

 woods and the large amount of landsliding on the southern half of the 

 steep slope, the upper limit reached by the Saint Mary glacier of the Wis- 

 consin stage could not be determined there. Farther north, about a mile 

 south of the point where the ridge is crossed by the Babb-Browning road, 

 a small but definite morainal ridge begins to be developed somewhat 

 below the crest of the smoothly curved top of the big ridge. This small 

 drift ridge, Avhich is evidently the lateral moraine of Saint Mary glacier, 

 was traversed about 3 miles and found to be strengthening toward the 

 north. South of Duck Lake this curves eastward with the crest of the 

 big ridge. This moraine carries plentiful blocks of limestone, but on 

 the smooth broad top to the east little else than quartzite pebbles were 

 noted. As determined from the sections described, these "quartzite 



