- Lithology is the science of the mineral composition and classification of rocks, and their mode of occurrence in nature. This polygon data layer shows the dominant lithology and geochemical, termed lithogeochemical, character of near-surface bedrock in Massachusetts. The bedrock units in the map are generalized into groups based on their lithological composition and, for granites, geochemistry. Obtained from the U.S. Geologocal Survey (USGS), the data set provides digital geologic information that may be applied to the analysis of water-quality characteristics of surface water and shallow ground water, and soil and stream sediment characteristics based on bedrock lithogeochemistry. The geologic characterization provided in this classification is intended to portray significant bedrock geologic features that influence stream sediment and soil chemistry and water quality. The source geologic map scales range from 1:100,000 to 1:500,000. The spatial accuracy of the layer is estimated as 1.5 km. For more details, please see the complete FGDC-style metadata produced by the USGS. The layer is stored in ArcSDE and distributed as BEDROCKLITHOLOGY_POLY.
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