This map is the result of field investigations by DGGS in 1997 and 1998. This geologic map and report supersede the previously released Public Data File 99-24C, Preliminary surficial-geologic map of the Healy A-6 Quadrangle, southcentral Alaska. The current map has been updated to include mapping of areas adjacent to the Healy A-6 Quadrangle. Field investigations were part of a two-year mapping program to provide geologic ground truth for airborne geophysical surveys flown by DGGS in the Chulitna region of southcentral Alaska during 1996.

This map is the result of field investigations by DGGS in 1997 and 1998. This geologic map and report supersede the previously released Public Data File 99-24B, Preliminary interpretive bedrock geologic map of the Healy A-6 Quadrangle, southcentral Alaska. The current map has been updated to include mapping of areas adjacent to the Healy A-6 Quadrangle, newly interpreted bedrock units based on newly acquired analytical, paleontologic, and Ar40/Ar39 data. Ages for the rock units were modified. Field investigations were part of a two-year mapping program to provide geologic ground truth for airborne geophysical surveys flown by DGGS in the Chulitna region of southcentral Alaska during 1996.

This map is the result of field investigations by DGGS in 1997 and 1998. This geologic map and report supersede the previously released Public Data File 99-24B, Preliminary interpretive bedrock geologic map of the Healy A-6 Quadrangle, southcentral Alaska. The current map has been updated to include mapping of areas adjacent to the Healy A-6 Quadrangle, newly interpreted bedrock units based on newly acquired analytical, paleontologic, and Ar40/Ar39 data. Ages for the rock units were modified. Field investigations were part of a two-year mapping program to provide geologic ground truth for airborne geophysical surveys flown by DGGS in the Chulitna region of southcentral Alaska during 1996.

This report provides detailed (1:63,360-scale) mapping of the Tanana A-1 and A-2 quadrangles (500 square miles; equivalent to eight 7.5-minute quadrangles). The area is part of the Manley Hot Springs-Tofty mining districts and adjacent to the Rampart mining district to the south of the Tanana B-1 Quadrangle. This report includes detailed geologic construction materials and geologic hazards data. The Tanana A-1 and A-2 Quadrangles and surrounding area comprise several isolated mountainous ridges in the western Yukon-Tanana Upland of interior Alaska.

Alaska Division of Geological & Geophysical Surveys (DGGS) has conducted 1:63,360-scale geologic mapping of the Sagavanirktok B-1 Quadrangle (640 square km�equivalent to four 7.5 minute quadrangles). This mapping project reinterprets micropaleontologic correlations for 17 Sagavanirktok Quadrangle wells, and reprocesses data from the one publicly-available seismic line. Surface geologic mapping, subsurface-to-surface stratigraphic age control, and seismic framework are required to reliably decipher the complex geology of this key area of the Brooks Range. Outcrops within the Sagavanirktok B-1 Quadrangle are the closest surface expressions of Prudhoe Bay source and reservoir rocks. This study yields critical petroleum-related information from these surface exposures, and how they relate to the area subsurface stratigraphy.

In support of the proposed Susitna-Watana Hydroelectric Project, the Alaska Division of Geological & Geophysical Surveys (DGGS) developed a Geographic Information System (GIS)-based geologic compilation of published and unpublished maps for twelve, inch-to-mile (1:63,360-scale) quadrangles encompassing the proposed hydroelectric project footprint, including the anticipated reservoir and surrounding area. DGGS geologists reviewed and analyzed existing geologic mapping for quality and completeness, and the maps were converted for use in GIS. The conversion process included scanning and georeferencing the original hard-copy map documents, creating a geodatabase, digitizing the geologic data, assigning attributes, and producing a digital data product for public release. The best available geologic mapping was synthesized into a single compilation data layer, and is packaged along with georeferenced scans and digitized vector files of the original geologic source maps. Bedrock geology was reviewed and revised by an independent contractor to ensure consistency with current geologic interpretations of the area. This geodatabase product will be a valuable reference resource for developers, planners, and scientists working on the hydroelectric project, as well as for any other projects in the area.

The Geologic Map Index of Alaska (Map Index) is a GIS web feature service paired with an interactive web map application that provides access to an actively growing geographic index of geology-related maps of Alaska and adjacent areas. This online research tool provides the locations and outlines of most DGGS and U.S. Geological Survey (USGS) geologic maps of Alaska in a single, interactive web application. It allows searches of the map database by geographic area of interest, keywords, publishing agency, dates, and other criteria. The search results link DGGS's comprehensive, multi-agency publications database, where users can view and download publications for free. Map Index provides access to traditional geologic maps and sample location, geologic hazards, and geologic resources maps. In addition, DGGS plans to add outlines and data to the application for new and remaining geologic maps published by DGGS, USGS, U.S. Bureau of Mines, and U.S. Bureau of Land Management. Reports without maps can be accessed through DGGS's comprehensive publications database, .

A rich legacy of geochemical data produced since the early 1960s covers the great expanse of Alaska; careful treatment of such data may provide significant and revealing geochemical maps that may be used for landscape geochemistry, mineral resource exploration, and geoenvironmental investigations over large areas. To maximize the spatial density and extent of data coverage for statewide mapping of element distributions, we compiled and integrated analyses of more than 175,000 sediment and soil samples from three major, separate sources: the U.S. Geological Survey, the National Uranium Resource Evaluation program, and the Alaska Division of Geological & Geophysical Surveys geochemical databases. Various types of heterogeneity and deficiencies in these data presented major challenges to our development of coherently integrated datasets for modeling and mapping of element distributions. Researchers from many different organizations and disparate scientific studies collected samples that were analyzed using highly variable methods throughout a time period of more than 50 years, during which many changes in analytical techniques were developed and applied. Despite these challenges, the U.S. Geological Survey has produced a new systematically integrated compilation of sediment and soil geochemical data with an average sample site density of approximately 1 locality per 10 square kilometers (km2) for the entire State of Alaska, although density varies considerably among different areas. From that compilation, we have modeled and mapped the distributions of 68 elements, thus creating an updated geochemical atlas for the State.

A rich legacy of geochemical data produced since the early 1960s covers the great expanse of Alaska; careful treatment of such data may provide significant and revealing geochemical maps that may be used for landscape geochemistry, mineral resource exploration, and geoenvironmental investigations over large areas. To maximize the spatial density and extent of data coverage for statewide mapping of element distributions, we compiled and integrated analyses of more than 175,000 sediment and soil samples from three major, separate sources: the U.S. Geological Survey, the National Uranium Resource Evaluation program, and the Alaska Division of Geological & Geophysical Surveys geochemical databases. Various types of heterogeneity and deficiencies in these data presented major challenges to our development of coherently integrated datasets for modeling and mapping of element distributions. Researchers from many different organizations and disparate scientific studies collected samples that were analyzed using highly variable methods throughout a time period of more than 50 years, during which many changes in analytical techniques were developed and applied. Despite these challenges, the U.S. Geological Survey has produced a new systematically integrated compilation of sediment and soil geochemical data with an average sample site density of approximately 1 locality per 10 square kilometers (km2) for the entire State of Alaska, although density varies considerably among different areas. From that compilation, we have modeled and mapped the distributions of 68 elements, thus creating an updated geochemical atlas for the State.

The engineering-geologic map is derived electronically, using Geographic Information System (GIS) software, from the surficial-geologic map of the second segment of the proposed natural gas pipeline corridor through the upper Tanana valley, a 12-mi-wide (19.3-km-wide) area that straddles the Alaska Highway through the upper Tanana River valley from the Robertson River eastward to near Tetlin Junction in the Tanacross Quadrangle (Reger and Hubbard, PIR 2009-6A). Surficial-geologic units were initially identified by interpretation of false-color ~1:65,000-scale infrared aerial photographs taken in July 1978, August 1980, and August 1981 and locally verified by field checking in 2007 and 2008. The map shows the distribution of surficial-geologic and bedrock units grouped genetically with common properties that are typically significant for engineering applications.