Surficial geology and soils . The substrate of terrestrial habitats is 

 either bare bedrock or unconsolidated surficial deposits derived from glacial 

 drift. Exposed bedrock is predominant in the coastal zone in ridge tops, 

 coastal mountains, and islands. Bedrock surfaces constitute a substantial 

 portion of the terrestrial habitat in Lincoln, Sagadahoc, Knox, Hancock, and 

 Washington Counties. Exposed bedrock is obviously inhospitable to plant 

 growth and to most types of human activity. 



The unconsolidated surface deposits, however, present a variety of substrate 

 surfaces by virtue of the variable characteristics of the glacial, glacial- 

 related, and postglacial deposits from which surface soil textures are 

 derived. Because deglaciation along the Maine coast was accompanied by marine 

 submergence and local glacial readvances (Stuiver and Borns 1975; and Bloom 

 1963) the distribution and stratigraphy of the coastal surficial deposits are 

 complex and varied. A generalized stratigraphy for the coast can be 

 recognized, however, and related to terrestrial topography. 



Lower elevations on the upland are characterized by glacial till above 

 bedrock, covered by marine silts and clays of the Presumpscot Formation. 

 Unsorted and stratified tills in the form of moraines sometimes lie on and 

 within the fine-grained marine deposits (figures 2-22 and 2-23). 



Elevations above 290 feet (88 m) and below higher ridge and mountain 

 elevations are characterized by basal till deposits overlain by stratified 

 glacial-stream deposits. At elevations from 240 to 350 feet (73 to 107 m) , 

 late glacial beach, spit, and delta sands and gravels mark the highest 

 elevations of marine incursion (figure 2-24) . 



Ridge flanks, coastal mountain tops, and most of the coastal islands are 

 characterized by bare ledge or thin glacial tills, both basal and ablation 

 (Thompson 1977) . 



At all elevations, topographic depressions are filled and are filling with 

 wetland organic deposits (figure 2-25). 



Coastal zone surface soils are derived from the bedrock or glacial-derived 

 inorganic deposits. Organic soils are classified according to parent 

 material, relief, and drainage (Bushnell 1942). Rourke and coworkers (1977) 

 recognize three major and four minor soil types present in the coastal zone. 

 The three major types and their characteristics are: 



1. Peru-Marlow-Lyman. This soil association represents Spodosols: 

 mineral soils in which iron, aluminum, and organic matter have been 

 leached from surface soil horizons and accumulated in lower horizons. 

 The soils have formed in loamy glacial till and are distributed 

 throughout Cumberland and Washington Counties. Peru and Marlow soils 

 are deep, with restrictive, slowly permeable layers, and they occur on 

 ridge slopes. Lyman soils are thin (25 to 50 cm thick; 10 to 20 

 inches), lie over bedrock, and occur on ridge tops and steep slopes. 



2. Hermon-Lyman-Peru. These soils are Spodosols developed on glacial 

 till. This association occurs in Washington and Hancock Counties. 

 Hermon soils are deep, well drained, and often bouldery and occur on 

 ridge tops and hillsides. 



2-45 



10-80 



