The surface hydrology of Regions 2 and 3 is dominated by five rivers: 

 Kennebec, Sheepscot, Damariscotta, Medomak, and St. George Rivers. 



The Kennebec River drains 7,045 kin2 and has an average discharge of 

 126 cu m/sec at Bingham, Maine. Extreme flows may reach 1,670 cu m/sec. In 

 1977, the Kennebec River discharged an average of 196 tons of suspended sedi- 

 ment daily (U.S.G.S., 1978). 



The Sheepscot River, which is more typical of remaining rivers within the 

 region, drains 383 km2, has an average discharge of 6.9 cu m/sec and extreme 

 flows of about 200 cu m/sec. 



Region 4 (Port Clyde to Blue Hill Bay) 



Bedrock Geology: 



The bedrock geology of Region 4 marks the transition from one of domi- 

 nant structural control by folded and faulted metamorphic rocks to a terrain 

 dominanted by igneous plutonic intrusions - the transition occurs in the 

 vicinity of Penobscot Bay. 



The terrain west of the Bay, including that which underlies the Isleboro 

 Islands, is dominated by Ordovician and Silurian non-rusty schists, metamor- 

 phozed volcanic rocks and non-metamorphozed volcanic rocks dominated by tuffs 

 and rhyolites. These rocks, primarily of Devonian and Silurian Age form ring- 

 dike complexes where volcanic rocks surround the granitic intrusions in concen- 

 tric plan. 



Numerous quarrys were established on coastal areas and islands with 

 granite intrusion because of handy water transport access to the building 

 stone. Of note are building stone granite quarrys on Hurricane and Vinalhaven 

 Islands. 



Metal sulfide mining has also been active in this region. Although the 

 last remaining copper mine closed in 1977 (Blue Hill, Maine), activity in this 

 region has been moderate, apparently because of mineralization associated with 

 metamorphism of volcanic rocks adjacent to granitic intrusion bodies. 



Seismically, Region 4 has historically been less active than Region 1, 

 2 or 3 as far as magnitude of events. Approximately sixteen recorded 

 seismic events have occured in this area of magnitude I or greater since 

 1766. One event of magnitude V occured in Winterport in 1938. All other 

 events were of lower intensity. Rand and Gerver (1976) report a remobiliza- 

 tion of a fault plane in Sears Island due to glacial loading or unloading. 

 This event occured approximately 56,000 years ago and resulted in a traceable 

 movement of rocks at the surface of about 2 to 3 cm. Thompson (1979) has found 

 evidence for a similar remobilization along the Norumbega Fault Zone which runs 

 through the northern part of the region. 



(Continued) 

 2-D-5 



10-80 



