SURFICAL GEOLOGIC MAPS DELINEATE AQUIFER DISTRIBUTION IN MAINE
A complex of sand and gravel deposits in the village of Gray, Maine (Figure 1), constitutes a major aquifer. The complex is composed of a series of glacial marine deltas, formed when the margin of the last great ice sheet was retreating. The land surface was depressed by the weight of the ice, and t...
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| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.398.5075 http://www.agiweb.org/environment/publications/mapping/graphics/maine.pdf |
| Summary: | A complex of sand and gravel deposits in the village of Gray, Maine (Figure 1), constitutes a major aquifer. The complex is composed of a series of glacial marine deltas, formed when the margin of the last great ice sheet was retreating. The land surface was depressed by the weight of the ice, and the sea flooding the area and was in contact with the ice front. At the ice margin, glacial meltwater charged with sand and gravel emanated from drainage tunnels into the sea, and provide the sediment to construct the ice-marginal deltas. After the ice sheet melted away, the land began to emerge from the sea. By the time the land was fully emerged, the deltas were recharged by precipitation, with fresh water replacing the saline ocean water in the interstitial voids of the sand and gravel deposit, thereby producing an excellent groundwater resource. Because sand and gravel deposits are used for many activities, careful delineation of the aquifer is a necessity to protecting the resource. Figure 1: Location of Gray, Maine. Geologic Map: A part of the surficial geologic map of Gray is shown in Figure 2 (Weddle, 1997). The map shows the distribution of materials of glacial origin that mantle the bedrock of the area. The village center of Gray is at the crossroads, left center of the map. Till (Pt) was deposited directly from the glacier as it melted and is an unsorted mix of cobbles, sand, silt and clay. The symbol Ptd indicates areas where this material is less than 10 feet thick. Marine mud (Pp) was deposited by the ocean when it was briefly higher over this area. Glacial marine deltas are shown by the unit abbreviations beginning with Pmd. These are the primary sand and gravel |
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