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Sand, gravel, clay, and other unconsolidated materials that overlie bedrock are known as surficial deposits. They cover most of Maine's land surface and include sediments deposited by water, wind, and glacial ice. Glacial deposits are by far the most abundant surficial materials in Maine.
Surficial geologic maps are compiled from field work, well and test hole data, and aerial photograph interpretation. In the field, the geologist examines as many exposures of surficial materials as time and access allow, recording information on the type, thickness, texture, and structure of the sediments exposed. Reconnaissance-level surficial maps are prepared by examining gravel pits and other readily accessible exposures of surficial earth materials, and gathering information on remote areas through the interpretation of aerial photographs. Detailed-level mapping involves more comprehensive field work, together with compilation of data from wells, test borings, seismic surveys, and other sources. Well and test hole information is important in determining the thickness of surficial deposits and mapping the extent of older deposits covered by younger materials. The geologist prepares two maps for each quadrangle: the surficial geologic map, and a companion surficial materials map that shows the actual data points used in compiling the geologic map. These maps show as much information as the author could assemble, but they are not intended to replace highly detailed site-specific data that may be needed for some projects.
The Maine Geological Survey also collaborates with scientists from the University of Maine's Climate Change Institute in studies of the last glacial episode in Maine. This work is resulting in much new information on climate change and the Ice Age history of Maine, and the glacial deposits that cover much of our state.
Last updated on December 27, 2007
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