LITTORAL DEPOSITS 647 



trict is, however, best applied to all that part of the sea above the 

 deep-sea portion, i. c, approximately above the hundred-fathom line. 

 This is in conformity with usage of the term in bionomics (Ort- 

 mann-63 '.3), where the littoral fauna and flora are those occupying 

 the sea bottom within the illuminated region. It is in this sense 

 that the term littoral will be used throughout this book, while the 

 littoral zone or the zone between high and low water will be re- 

 ferred to as the shore. 



Littoral deposits are fovmd between the edge of the continental 

 shelf and the high-water edge of the shore. In the shore zone they 

 grade imperceptibly into continental deposits, through the zone of 

 the strand, while at the outermost margin of the littoral district they 

 grade into abyssal deposits. Around the margins of oceanic islands 

 the littoral belt is of greater or less width, according to the slope of 

 the submerged portion of the island. 



It is within the littoral district as here defined that by far the 

 largest proportion of clastic material is deposited. It is here also 

 that the bulk of the hydrogenic and the biogenic deposits of the sea 

 is formed. 



The Shore Zone {Inter Co-tidal Zone; Littoral Zone 

 in Restricted Sense). 



The separation of the shore zone, or that portion between high 

 and low-water mark, from the portion of the littoral district never 

 uncovered, is of very little significance from the lithogenetic point 

 of view, however much its import biologically. For, although this 

 zone is the focus of the destructive activity of the waves, their work 

 is not limited to this portion. It is known that wave work is very 

 effective at a depth of thirty feet, while at sixty it has still an in- 

 fluence upon the bottom deposits. In fact on a gently sloping coast, 

 the destructive work of the waves is found in the deeper water 

 away from tl>e shore, rather than in the shore zone. Neither has 

 the shore a distinctive type of sediment ; not even the pebbly sedi- 

 ment is confined to it, but occurs also at a distance from shore ; nor 

 are sands, muds or even organic deposits excluded from the shore, 

 the sands and muds being often more characteristic than the peb- 

 bles. As for organisms, only stationary or attached types dis- 

 criminate between the shore and the permanently submerged zone, 

 and among these certain ones do not make an absolute distinction. 

 The shore zone is, however, of significance in this respect, that 

 characters typical of continental deposits, such as mud cracks, rain- 



