INEQUALITIES OF SEDIMENTATION 363 



areas in the case of sandy bottoms is doubtless the tendency of 

 sands to move rapidly under current action and smother the marine 

 Hfe which attempts to hve on them. Dr. G. A. Huntsman, who 

 has been engaged in studying the conditions under which marine 

 animals live in the Gulf of St. Lawrence has directed attention 

 to another factor in producing lifeless zones. He states : 



By means of these traps we discovered that a barren zone existed off the 

 Cape Breton shore, comprising the part of the sloping bottom between the 

 depths of 10 and 20 fathoms. In this zone the temperature at the bottom 

 underwent violent fluctuations, often in the course of a day or so, at one time 

 being as high as 65° F., and at another as low as 39° F. This was caused by 

 the winds, for when the wind was blowing on-shore it drove the surface water 

 against the coast and heaped it up forcing the deeper colder water down; 

 then when it changed and blew off-shore the warm surface water was driven 

 away from the coast and the cold water welled up from below to take its place, 

 and so flooded the zone. The effect of this on the slow moving bottom animals 

 may be imagined. Few of them would be able to stand such changes, but the 

 active fishes are able to move up and down the slope and avoid these 

 changes.^ 



Seasonal variation. — Another factor in the variation in the rate 

 of sedimentation in the sea is the seasonal factor. The annual 

 seasonal changes in the sea result in marked differences in the 

 amount of organic materials deposited on the sea bottom during 

 different parts of the year. The registration of seasonal changes 

 by banding in the volume of clastic sediments in aqueoglacial 

 deposits has been exhaustively discussed by Sayles.^ Comparable 

 with the great contrasts in the volume of lacustrine sediments 

 deposited during different parts of the annual cycle are the different 

 amounts of organic materials which the plankton life of the sea 

 showers on the bottom in winter and in summer. It is possible 

 that we may yet be able to interpret some of the fine lamination 

 in sea-laid deposits in the precise terms of years. "In early spring 

 there is a great awakening in the oceans comparable with the grow- 

 ing of the grass and the budding of the trees on land." This 

 awakening corresponds to the time when the alkalinity of the sea 

 is at a maximum. 



^Canadian Fisherman, May, 1917. 

 = R. W. Sayles, op. cit. 



