PAN GONG: A GLACIAL LAKE 609 



question can be answered, but it is significant because it adds another 

 to the examples where a pecuHar type of basin is associated with 

 glaciation among lofty mountains. The essential features of the 

 Pangong basin agree with those of the fiords of Norway and the 

 valley lakes of Switzerland and other places. The finding of so 

 perfect an example of the type on the edge of the Tibetan plateau, 

 where the theory of glacial erosion would lead us to expect it, lends 

 probabihty to the theory. The rarity of such lakes among the 

 Himalayas seems to be due to the fact that most of the valleys slope 

 steeply and uniformly and have no portions of gentle grade where 

 the glaciers would be checked and caused to deepen their beds. 



Pangong during later glacial epochs. — The history of Pangong 

 after the completion of the rock basin is recorded chiefly in lacustrine 

 deposits and shore-hnes, which, together with numerous old moraines, 

 indicate two extremes of moisture, or at least of lake and glacier 

 expansion intervening between extremes of aridity or of lake and 

 glacier contraction. At the mouth of the little tributary whose fan 

 has been wrongly supposed to be the cause of the accumulation of 

 the waters of Pangong, there are some narrow terraces, remnants of 

 an older, larger fan. The latter must have been formed after the 

 retreat of the last great basin-scouring glacier, and at a time so arid 

 that the main stream was not large enough to carry away the debris 

 brought in by the tributary. If the fan were to be reconstructed 

 from its fragments, it would fill the outlet valley to a depth of 200 

 feet, more or less ; that is, to approximately the level of the highest 

 of the strands presently to be described. As the deposits associated 

 with these strands are sahne, it appears that at the time of the 

 accumulation of the fan the lake had no outk-t, and hence that the 

 epoch was arid, perhaps as arid as the present. 



On the approach of the next glacial epoch the glaciers on the 

 sides of the Pangong basin descended several thousand feet, as is 

 evident from the moraines which they deposited a few hundred or a 

 thousand feet above the lake. The latter must have expanded 

 and finally overflowed, for it cut away the fan across the Hp, as 

 may be inferred from the terraced remnants. Before overflowing 

 however, it must, while still saline, have stood at a level of 

 nearly 200 feet long enough to deposit a thin layer of calcareous 



