DIASTROPHISM AND THE FORMATIVE PROCESSES. VI 

 FORESET BEDS AND SLOPE DEPOSITS 



T. C. CHAMBERLIN 



University of Chicago 



Nearly all marine sediments are carried to their resting-places 

 in one or another of three general ways: (i) by rolling or sliding 

 down relatively steep slopes, where gravity is the chief factor and 

 the agitation of the water only an auxiliary agency; (2) by being 

 forced along low slopes where agitation and currents are essential 

 factors; and (3) by flotation, where the relative levity or fineness 

 of the material is an essential factor. These are conveniently 

 called (i) foreset beds, (2) topset beds, and (3) flotation beds. If 

 we may use these terms in a rather free and broad sense, based on 

 the dominant feature, with neglect of intergradations and alter- 

 nations, it will be convenient to speak of the shelf-sea deposits as 

 topset beds, of the deposits of the abysmal slope as foreset beds, 

 and of the deep-sea deposits as flotation or bottom-set beds, 

 though flotation contributions enter in notable measure into the 

 composition of both the other classes. 



The abysmal deposits were the subject of our last discussion, 

 and in earlier articles the shelf -sea deposits were under study. It 

 remains to see, so far as w€ may, what bearings on diastrophic 

 problems the foreset beds have, taking as our leading type those 

 that lie on the abysmal faces of the continental terraces. 



These foreset beds are formed of a coarser and a finer element. 

 The coarser embraces material that has been rolled or pushed by 

 stages over the upper face of the continental shelves until the 

 oceanward edges of these were reached, beyond which the material 

 has descended the steeper slopes under degrees of agitation of 

 milder sorts than those required to move them over the upper face 

 of the shelves. These materials may be said to be the overflow of 

 the topset or shelf-sea beds. As these slope deposits are gradually 



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