• 



THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Art. XXX. — The Formation and Distribution of Fluviatile 

 and Marine Gravels ; by Herbert E. Gregory. 



Outline. 



Introduction 

 Fluviatile Gravels 



Comparative rates of subaerial and marine erosion 

 Summary analysis of river work 

 Distribution and preservation of river gravel during a 



single physiographic cycle 

 Distribution and preservation of gravel during inter- 

 rupted cycles 

 Tectonic interruptions 

 Climatic fluctuations 

 Gravel at river mouths 

 Gravels of Marine Origin 

 Definitions 



Physiographic development of a coastal belt 

 Application to the formation and distribution of gravels 

 Distribution and preservation of marine gravel 

 during a single physiographic cycle 

 Initial over-flat profile 

 Initial over-steep profile 

 Evidence from maps 

 Distribution and preservation of marine gravel during 

 interrupted cycles 

 Effect of coastal downwarp 

 Effect of coastal upwarp 

 Conclusion 



Introduction. 



The absence of criteria for the interpretation of consolidated 

 and unconsolidated gravels is a particularly serious obstacle to 

 work in the Colorado Plateau Province, where a confusing 

 variety of structure and the extreme scarcity of fossils render 

 the usual means of differentiation of secondary value. During 

 an excursion across the Colorado Plateau in 1900, the import- 



Am. Jour. Sci.— Fourth Series, Vol. XXXIX, No. 233.— May, 1915. 

 32 



