5o8 PRINCIPLES OF STRATIGRAPHY 



village it is about twelve feet. "In the delta of the Yukon a depth 

 of over fifteen feet was seen at one locality. A depth of 150 to 300 

 feet has been assigned by several observers to the tundra, where it 

 is exposed in a sea clifif on Eschscholtz Bay, at the head of Kotzebue 

 Sound." Here the surface layer of humus is rich in mammalian 

 remains. It is evident that the conditions here differ from those 

 found in North Europe, where the rising ground ice eventually puts 

 a stop to further peat formation. Russell thinks that in Alaska 

 "there is apparently no reason why this process [of growth above, 

 decay below, and conservation of the partly decayed vegetation by 

 freezing] might not continue indefinitely, so as to store up vegetable 

 matter in a way that is only paralleled in the most extensive coal 

 fields." (sg:i2/.) 



"On the flood plains of the larger rivers, and generally through- 

 out all the lowlands of Alaska, peaty deposits are forming in the 

 same manner as on the tundra, modified, however, by the growth of 

 arborescent vegetation and by the intrusion of sand and clay in 

 places that are flooded during the high-water stage of the rivers. 



"At many localities along the Yukon, sections of peaty deposits 

 are exposed often eight or ten feet thick and several long. The 

 bluffs . . . are from fifteen to twenty feet high . . . and nearly 

 always frozen solid. . . . Some of the vegetable layers are in- 

 terstratified with sand and clay ; others at the surface are still in- 

 creasing in thickness and have a dense forest growing on them. 

 Not infrequently there is a stratum of clear ice interbedded with 

 the layers of peat, sand and clay." (Russell-39.) 



The moist, cool climate prevailing over eastern Canada has also 

 been conducive to the extensive growth of peat bogs, which cover 

 all the area around the St. Lawrence and the Ottawa, as well as 

 on Newfoundland and on the smaller islands off the coast. On 

 Anticosti Island in the Gulf of St. Lawrence there are peat beds 

 covering in some cases areas from one hundred to more than a 

 thousand acres in extent, with a thickness of ten feet or over. 

 (Twenhofel-48 : (5(5.) The peat rests on sands and gravels, some- 

 times with il/va arcnaria, and at other times it rests directly upon 

 the eroded limestone surface of early Palaeozoic age. The lower 

 peat deposits often contain tests of sea urchins { Strongylocentrotus 

 drdbachiensis), fragments of lobsters and crabs, gastropods, etc., 

 wdiich are brought there by birds, chiefly crows, or which have been 

 washed up by unusually high waves and tides. These marine or- 

 ganic remains are often very abundant. In the wooded areas, 

 where trees have only a slight foothold owing to the -shallowness of 



