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.

The engineering-geologic map, on two sheets, is derived electronically from the surficial-geologic map of the initial segment of the proposed natural gas pipeline corridor through the upper Tanana valley (Reger and others, PIR 2008-3a) using Geographic Information System (GIS) software. Surficial-geologic units were initially identified by interpretation of false-color ~1:63,000-scale infrared aerial photographs taken in July 1978, August 1980, and August 1981 and locally verified by field checking in 2006 and 2007. The map shows the distribution of surficial-geologic and bedrock units grouped genetically with common properties that are typically significant for engineering applications.

During 2009, the Alaska Division of Geological & Geophysical Surveys continued a program, begun in 2006, of reconnaissance mapping of surficial geology in the proposed natural-gas pipeline corridor through the upper Tanana River valley. The study area is a 12-mi-wide (19.3-km-wide) area that straddles the Alaska Highway from the western boundaries of the Tanacross B-3 and A-3 quadrangles near Tetlin Junction eastward to the eastern boundaries of the Nabesna D-1 and C-1 quadrangles along the Canada border. Mapping during 2008-2009 in the Tanacross and Nabesna quadrangles linked with the mapping completed in the Tanacross, Big Delta and Mt. Hayes quadrangles in 2006-2008. Surficial geology was initially mapped in this third corridor segment by interpreting ~1:65,000-scale, false-color, infrared aerial photographs taken in July 1978 and August 1981 and plotting unit boundaries on acetate overlays. Verification of photo mapping was accomplished during the 2008 and 2009 summer field seasons, when map units were described, soil pits were hand dug, and samples were collected for analyses. The engineering-geologic map is derived electronically from the surficial-geologic map and shows the distribution of surficial-geologic and bedrock units grouped genetically with common properties that are typically significant for engineering applications.

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.

This map shows the distribution of unconsolidated deposits and undifferentiated bedrock exposed at the surface in the Sagavanirktok A-3, A-4, B-3, B-4, and portions of the Sagavanirktok A-5 and B-5 quadrangles. Units were mapped by interpretation of stereo pairs of approximately 1:65,000-scale false-color infrared aerial photographs taken in June and August 1978, as well as 2.5 m and 10 m resolution SPOT imagery collected in 2009 and 2010. Fieldwork was completed in 2008.

During 2009, the Alaska Division of Geological & Geophysical Surveys continued a program, begun in 2006, of reconnaissance mapping of surficial geology in the proposed natural-gas pipeline corridor through the upper Tanana River valley. The study area is a 12-mi-wide (19.3-km-wide) area that straddles the Alaska Highway from the western boundaries of the Tanacross B-3 and A-3 quadrangles near Tetlin Junction eastward to the eastern boundaries of the Nabesna D-1 and C-1 quadrangles along the Canada border. Mapping during 2008-2009 in the Tanacross and Nabesna quadrangles linked with the mapping completed in the Tanacross, Big Delta and Mt. Hayes quadrangles in 2006-2008. Surficial geology was initially mapped in this third corridor segment by interpreting ~1:65,000-scale, false-color, infrared aerial photographs taken in July 1978 and August 1981 and plotting unit boundaries on acetate overlays. Verification of photo mapping was accomplished during the 2008 and 2009 summer field seasons, when map units were described, soil pits were hand dug, and samples were collected for analyses.