43 8 



DONALD ('. BARTON 



degradation in the course of time, the deposits must be temporary in 

 character, and usually of recent geologic age. They may be wholly 

 or in pari lacustrine, fluviatile, alluvial (cone or fan), landslide, or 

 fluvioglacial. The stratification should be rather irregular, and 

 the constituent grains should be angular to subangular. 



To this type of deposit should be referred possibly some of the 

 deposits of the Upper Indus Valley, although from the descriptions 



of the deposits it is not 

 quite clear whether they 

 are really arkosic or not. 

 3. Deposits of cold 

 {high-latitude t subglacial) 

 climate. In the high lati- 

 tudes, the effects of dis- 

 integration are not pro- 

 nounced, or at least they 

 are not noted in the lit- 

 erature. " Disinl egra- 

 tion" is reported many 

 times, hut in most eases 



Fig. |. Photomicrograph of Pondville (.Mass.) 



it is clearly Mock disin- 



orkose, an arkose Eormed under moist temperate tegration that is meant, 

 conditions, showing tin- quartz ami feldspar grains a-nA m no case has the 



in a fine grained matrix of quartz ami argillaceous . , , . . 



, . . ' 1 , • .. . . writer been able to make 



material. Magnification, 15 diameters. 



it out clearly to be granu- 

 lar disintegration. That the effects oi the latter are not notice- 

 able may be due in large part to the relatively recent glacial 

 erosion of the products of the preglacial disintegration, or, in 

 regions oi considerable relief, it may be due in part to excessive 

 block disintegration and erosion. As the temperature range is 

 often great, and the lower part includes the critical point oi 

 freezing, and as, furthermore, hydration can take place at the 

 surface during tin- summer and, in regions not too far north, 

 at all times below the level oi freezing, there would seem to 

 be no theoretical reason Why granular disintegration should not 

 take place. Granitic and gneissic blocks exposed on the surface 

 of glaciers in many cases show noticeable disintegration, although 



