Surficial-Geologic Map of the Eagle A-2 Quadrangle, Fortymile mining district, Alaska
Dates
Publication Date
2001-05
Start Date
1999
End Date
2001
File Modification Date
2014-05-22 11:36:00
Citation
Pinney, D.S., 200105, Surficial-Geologic Map of the Eagle A-2 Quadrangle, Fortymile mining district, Alaska: State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (DGGS), http://dx.doi.org/10.14509/2671.
Summary
The Alaska Division of Geological & Geophysical Surveys (DGGS) has conducted 1:63,360-scale geologic mapping of the Eagle A-2 Quadrangle (270 square miles; equivalent to four 7.5-minute quadrangles). The area is part of the 100-year old Fortymile mining district and is located in eastern Alaska near the Alaska-Yukon border. This map illustrates the distribution of a variety of unconsolidated deposits and undifferentiated bedrock in the Eagle A-2 Quadrangle, Fortymile mining district. It was prepared by the interpretation of 1:63,360-scale, false-color, infrared aerial photographs taken from July 1978 through August 1981 and is locally verified by ground observations during field visits. The results should be considered reconnaissance [...]
Summary
The Alaska Division of Geological & Geophysical Surveys (DGGS) has conducted 1:63,360-scale geologic mapping of the Eagle A-2 Quadrangle (270 square miles; equivalent to four 7.5-minute quadrangles). The area is part of the 100-year old Fortymile mining district and is located in eastern Alaska near the Alaska-Yukon border. This map illustrates the distribution of a variety of unconsolidated deposits and undifferentiated bedrock in the Eagle A-2 Quadrangle, Fortymile mining district. It was prepared by the interpretation of 1:63,360-scale, false-color, infrared aerial photographs taken from July 1978 through August 1981 and is locally verified by ground observations during field visits. The results should be considered reconnaissance in nature. The dominant unconsolidated deposit is colluvium, which mantles most surfaces other than the tops of ridges and those areas immediately adjacent to streams. Three levels of stream terrace can be traced along major drainages at elevations of roughly 200, 100, and 30 meters above modern streams. A fourth low terrace is limited to the southwest part of the map area. Pleistocene mammalian remains have been recovered from ice-rich organic silt and muck overlying placer gravels in many valleys.
This project, resulting map, geospatial data are intended to provide a geologic map and a geologic interpretation of the Fortymile mining district at 1:63,360 scale. Previous published 1:63,360 scale geologic maps of this area have been reconnaissance-level maps or only covered portions of the quadrangle. Mapping at 1:63,360 scale (or more detailed) is needed to identify critical geologic features that may relate to more regional structures or geologic units. These detailed observations are also critical to test or use in tectonic models. This map also provides a geologic base in which to interpret geochemical results from the concurrent DGGS rock sampling program.
