Marine Geology: 



Region 6 has a valuable distribution of marine systems. The coastal 

 portion from Cherryfield to Cutler are characterized by small fine-grained 

 estuaries which empty into wave- or tide-dominated neutral embayments. 

 The neutral embayments open onto a narrow wave-shoal platform which 

 terminates abruptly at the 70 meter isobath where the Fundican Fault 

 separates Paleozoic from Mesozoic rocks (Uchupi 1968), 



From Cutler to Lubec, the bathymetry and shoreline topography are very 

 steep, only a wave shoal platform extends from cliff shorelines for a few 

 kilometers until the 70 meters isobath. 



The segment from Lubec to Calais is characterized by fine-grained 

 estuaries (St. Croix and Dennys River), wave-shoal embayments and fan 

 deltas where streams draining the volcanic bedrock debouch onto extensive 

 tidal falts. 



Sedimentation within these systems is little understood - little 

 data exists as to sedimentation rates. Fink (1975) found suspended sediment 

 concentrations in the St. Croix river to vary between 4 and 22 milligrams 

 per liter. 



Investigations by EG&G (1973) and the U.S. Army Corps of Engineers 

 (International Joint Commission 1959) indicate about 13 meters of estuarine 

 sands, silts and clays infill the Cobscook Bay embayment, indicating about 

 1 mm of deposition annually in the channels, a slow rate of deposition 

 compared to the southwestern regions of the characterization area. 



Much of the sediment source for the intertidal deposits is derived 

 from wave erosion of shoreline banks. Shoreline retreat of up to 1 meter 

 annually has beai noted by Timson and Kale (1977) along the Machias and 

 Cutler shorelines. 



Hydrology: 



Several rivers drain or run through region 6. The major river is the 

 St. Croix River. Discharge of the St. Croix is a mean annual rate of 76.2 

 cu m/sec with peak flows averaging above 600 cu m/sec. The river delivers 

 approximately 67 tons of suspended sediment daily to the estuary in con- 

 centration averaging about 8.8 mg/1 (U.S.G.S. 1978). 



The Machias River is the next largest river draining Region 6. The 

 Machias drains 1184 km with average discharges of 26 cu m/sec and extremes 

 exceeding 420 cu m/sec. 



The Dennys River is representative of small rivers draining the region. 

 The Dennys drains only 239 km^ with an average discharge of 5.4 cu m/sec 

 and extremes only reaching 111 cu m/sec. 



(Continued) 



2-D-lO 



