APPENDIX n 

 Geology of the Characterization Area by Region 



Although the basic geologic tramework of the Maine coast within the 

 characterization area originated from similar tectonic, glacial and post- 

 glacial processes from a broad, regional standpoint, significant variations 

 do occur from region to region. 



The regional differences are described below on a more detailed basis 

 than the general presentation describing the role of geology in the ecosystem 

 of the characterization area. The regional descriptions cover bedrock, surfi- 

 cial, marine and hydrologic geology, as well as soils. 



Region 1 (Cape Elizabeth to Cape Small) 



Bedrock Geology: 



The coastal lowland tracts of Region 1 is dominated by steeply dipping 

 (almost vertical) metamorphic schists and gneisses cut by high angle faults. 

 Local intrusion of granitic igneous rocks occur in Portland and Westbrook 

 (Hussey and Pankiwskyj , 1975) . 



The structural grain of the bedrock trends northeast - southwest, control- 

 ling the bedrock surface topograpny and the orientation and distribution of 

 islands and land mass peninsulas in Casco Bay. This structural trend is due 

 to the orientation of bedrock folding and regional faults. 



Six regional faults have been recognized by Hussey (1971). Five faults 

 are high angle faults paralleling the structural grain. A thrust fault, 

 running along the inner shore of Casco Bay, also trends northeast - southwest. 

 These faults are most likely on the order of 140 million years old. 



The rocks of this region have been defined by Hussey (1971) as belonging 

 to the Casco Bay and Merrimack Groups (cambro-Ordovician and Silurian Age, 

 respectively) . Significant rock types are the Spurwink Limestone (.Chebeague 

 Island and South Portland) and the rusty schists of the Gushing Formation which 

 imparts significant amounts of iron to the groundwater. 



The Merrimack Group lies inland from Casco Bay and is intruded by granitic 

 plutons. Granite is actively mined from one small plutonic body on the 

 Westbrook - Portland line (Blue Rock Industries) and these small granite 

 bodies are presently being studied as potential underground petroleum storage 

 facilities. 



Surficial Geology: 



Region 1 is dominated by an areal coverage of marine sands and silty clays 

 of the Presumpscot Foramtion. The marine sediment covers 70% of the area, 

 occurring as relatively thick (up to 100 feet) deposits at low elevations. 



(Continued) 

 2-D-l 



10-80 



