coast southwest of Penobscot Bay (regions 1,2, and 3) are elongated in a 

 south-southwesterly direction (Damariscotta and St. George lakes for example). 



Lakes elongated in a south-southeasterly direction, parallel to apparent 

 glacial ice-flow, are common to the east of Penobscot Bay (regions 5 and 6). 

 Scouring developed apparently along lines of high ice-flow, along preglacial 

 drainage lines, and along structural weaknesses (joint planes) within igneous 

 bodies (Gardner, Beddington, and Green lakes for example; Davis et al. 1978a). 

 Smaller lakes occupy depressions within glacial sediments that were created 

 during ice-stagnation. Ice blocks surrounded or covered by glacial sediment 

 subsequently melted, forming depressions called kettles. Kettle lakes (the 

 third lake type) are abundant in Washington County (region 6), where 

 glaciodeltaic sedimentation was prominent. 



Lake substrates . Lake basins within the coastal zone are underlain by 

 bedrock, glacial till, or glaciomarine clay-silt substrates. Deglaciation was 

 sufficiently rapid along the Maine coast that the sea lavel rose faster than 

 rebound could occur (Stuiver and Borns 1975). Inundation of low-lying areas 

 (up to elevations of about 150 m; 495 ft) by marine waters left extensive 

 deposits of marine silt and clay (Presumpscot Formation) . The spillways of 

 many lake basins were below sea level for a short period of time, allowing the 

 silt and clay to be deposited on lake basin floors and margins (Davis et al. 

 1978a). 



Lacustrine sedimentation . Lake sedimentation can be differentiated 

 between limnetic (pelagial-profundal ; figure 7-3) sedimentation and littoral 

 sedimentation. Generally, sediments that are deposited in profundal 

 environments are derived from littoral sediments or have passed through the 

 littoral zone. Lacustrine sediments are mostly derived from lake watersheds 

 and delivered to the basin by overland flow, or from erosion of shore deposits 

 by waves. The amount of sediment delivered annually to a lake depends upon 

 several factors: precipitation, runoff volume, watershed soil distribution 

 and type, watershed vegetation, watershed agricultural activity, and local 

 wind and lake wave action. High levels of precipitation and runoff, 

 agricultural activity, extensive use of motor boats, construction in the 

 watershed, and stronger winds all increase sedimentation within the lake 

 basin. 



Sediments delivered to the deeper lake portions are limited to silts and 

 clays, which remain in suspension for up to tens of days. The sediment in 

 deep sections of lakes also contains varying amounts of fine organic debris 

 derived from the surrounding watershed, and the littoral and pelagial zones. 

 Essentially, these sediments are a fine-grained mud. Only rarely is this 

 sediment layered or graded; such structure is destroyed by mixing of sediment 

 brought about by resuspension during overturn (and more frequently in lakes 

 too shallow to stratify), and by the activities of animals burrowing within 

 the upper few centimeters of sediment. 



Geologic formations in the littoral environments can be broken down into 

 different morphological units. These units are rocky shores, beaches and 

 spits, littoral flats and deltas. Rocky littoral areas are common on the 

 margins of lakes that are carved into bedrock or situated in glacial boulder 

 tills. Little sediment can accumulate on these shores, because of a lack of 



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