Planar coordinates are encoded using coordinate pair Abscissae (x-coordinates) are specified to the nearest 0.000064 Ordinates (y-coordinates) are specified to the nearest 0.000064 Planar coordinates are specified in meters The horizontal datum used is North American Datum of 1927. The ellipsoid used is Clarke 1866. The semi-major axis of the ellipsoid used is 6,378,206.4. The flattening of the ellipsoid used is 1/294.98. Geologic data used in the compilation was derived from the field maps and notes generated by this project as well as data from other sources as noted in the 'Source_Information' section. Location data for geologic point coverages was acquired from hand held GPS units and compiled on paper field maps, air photos, and notebooks. A paper compilation map composed of all of the geologic information elements was scanned and digitized using a digitizing tablet. Spatial data attributes were attached to data objects using ArcInfo. Attributes were verified for consistency and completeness during the creation of the metadata. Location data and estimated position errors were manually entered into a spreadsheet. Sample numbers and locations with selected data were spatially registered and analyzed in ArcGIS software. Location data was determined visually using topographic maps at a scale of 1:63,360 and 1:50,000 (nominal) scale, color-infrared aerial photographs. See 'Source_Information' section for horizontal positional accuracy of locations not measured by DGGS. This data set includes coverages that contain information about geologic units, their ages, and field sample locations at 1:63,360 scale. Current publication is available on paper. To purchase this or other printed reports and maps, contact DGGS by phone (907-451-5020), e-mail (email@example.com), or fax (907-451-5050). Payment accepted: Cash, check, money order, VISA, or MasterCard. Printed publication can be purchased for $15.00 (contact information below) plus shipping if mailed. Digital files on CD-ROM are available for $10.00 (contact information below). No fees charged for downloaded files. Source.