GIS-BASED SURFICIAL GEOLOGIC MAPPING IN MAINE

Since 1986 the Maine Geological Survey has conducted a program of detailed 1:24,000 surficial geologic quadrangle mapping. This work has been done through COGEOMAP and STATEMAP cooperatives with the U.S. Geological Survey. Over 60 quadrangles have been completed in the southwestern part of the state, including the entire Maine portions of the Portland and Kittery 1:100,000 map sheets. The products for each quadrangle consist of a geologic map, surficial materials data map, and report summarizing the Quaternary stratigraphy and history of the quadrangle. The materials maps combine data from surface exposures, well logs, test borings, and seismic lines. All maps are produced in color using the Survey's geographic information system. A standardized color scheme has been developed to depict groups of related map units such as glacial-lake deposits. Each map is accompanied by color photos that show stratigraphic sections and other Quaternary features. The majority of surficial map units in Maine represent Pleistocene deposits formed by late Wisconsinan glaciation. These include large quantities of sand and gravel, detailed mapping of which is essential for resource inventory and aquifer delineation. The quadrangle mapping program has also provided a better understanding of the style and pattern of deglaciation, facies relationships of glaciomarine deposits, isostatic crustal adjustments, and changes in sea level. In the coastal lowland, recessional ice-margin positions are reconstructed by correlation of moraines, submarine fans, and ice-contact glaciomarine deltas. Inland from the marine limit, sand and gravel deposits that were undifferentiated on earlier reconnaissance maps are resolved into sequences of glaciolacustrine deltas and other waterlaid sediments. As map coverage of the state becomes more extensive, the 1:24,000 surficial mapping will be combined by GIS to produce regional syntheses of the 1:100,000-scale quadrangle series.