depths. This event, known as the Holocene transgression, had an important 

 effect on existing shelf and marginal marine sediment deposits. Although 

 these effects may have been modified by ongoing geological processes , the 

 imprint of the transgression is clearly evident in many places. 



18. An important application of historical analysis of potential borrow 

 sites is to determine if they are essentially relict (formed by processes no 

 longer prevalent), or recent (the result of ongoing processes). Relict status 

 is usually evidenced by the fact that the sediment size distribution, composi- 

 tion, organic constituents, or sedimentary structures reflect an environment 

 of deposition that is not consistent with the existing environmental 

 conditions . 



Geomorphologv 



19. Geomorphology is the study of landforms (whether terrestrial or 

 subaqueous), their origin, development, and the processes that create and 

 modify them. Because of established or probable relationships between geo- 

 morphic features and other geological factors such as lithology, geological 

 history, and sedimentary processes, a study of geomorphic features in an 

 exploration area can be a valuable element in planning an exploration program 

 and analysis of results. 



20. The geomorphic features occurring in marginal marine, continental 

 shelf, and lacustrine areas are in some cases entirely the result of existing 

 geological processes (recent) and in other cases, the product of past environ- 

 mental conditions (relict). In most cases, relict features have, to some 

 extent, been modified by existing processes. In marine areas, many relict 

 geomorphic features were formed under subaerial conditions during the low sea 

 level stand of the last major glaciation, or under marginal marine conditions 

 during the Holocene transgression. Recent geomorphic features are largely 

 found in the marginal marine zone, but some features, found farther offshore, 

 may be recent or drastically modified relict forms. 



21. Studies of marginal marine and continental shelf geomorphic fea- 

 tures have shown that some types of constructional features are usually com- 

 posed of sand or sand and gravel mixtures, and are potentially usable for 

 beach fill borrow sources. Most of these features are of recent age or were 

 formed during the Holocene transgression. Because of their geomorphic 



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