GEOSYNCLINES 



901 



filling by sediment as a secondary consequence. Among subsequent 

 autbors, Haug (14, 15) has greatly extended this idea, and has in- 

 cluded under this title all great submarine depressions parallel to 

 land areas, such as the great depressions of the Pacific coast. (See 

 Chapter III and Figures 16 and 17, pages loi and 105.) These "fore 

 deeps" {Vorticfcn) are undoubtedly the direct result of deforma- 

 tion under strain, but they are not areas of excessive deposition. 

 Indeed, sedimentation here goes on with extreme slowness, and is 

 confined to materials normal to the deep sea. Haug has identified 

 among many of the deposits bathyal sediments (see Chapter XV), 

 which he regards as accumulations in geosynclines, and he holds 

 that the great thickness of these deposits indicates a progressive 

 deformation of the region of deposition. He finds that many 

 bathyal sediments pass laterally into neritic or shallow-water de- 

 posits, though other deposits in the geosynclines are throughout of 



Fig. 2_|9. Diagrammatic section of a geosyncline according to Haug. The 

 numbers i-io indicate the successive strata, which arc complete 

 in the center of the geosyncline but incomplete on its margins, 

 where thinning away of beds and overlap of others is characteris- 

 tic. (After Haug.) 



neritic origin. Haug does not, apparently, recognize the presence 

 of continental sediments in the geosynclines. though he finds these 

 on the margins. This type of sediment is, however, eminently 

 characteristic of the Appalachian region throughout, and is included 

 in the main mass of the sediment itself. 



The bathyal origin of many of the sediments in the geosyn- 

 clines of the Alpine region and elsewhere is by no means wholly 

 established, and it may be questioned whether, on the whole, sedi- 

 ments of that class are abundant or widespread. The frequent 

 marginal disconformities in the sediments of most geosynclines 

 lead one to the supi)osition that, after all, many of the so-called 

 bathyal deposits may be of littoral (neritic) origin, and that, fur- 

 thermore, repeated laying bare of the margins of the geosyncline 

 permitted erosion of the already deposited sediments. 



Haug recognizes the shading away of the sediments by overlap 

 and by thinning toward both sides of the geosyncline (Fig. 249) 



