Geology of the Sleetmute C-7, C-8, D-7, and D-8 quadrangles, Horn Mountains, southwestern Alaska

Metadata Updated: October 4, 2025

Geology of the Sleetmute C-7, C-8, D-7, and D-8 quadrangles, Horn Mountains, southwestern Alaska, Report of Investigation 98-12, presents a geologic map of the Horn Mountains area in southwestern Alaska. Between the 1990, 1991, and 1992 field seasons, DGGS geologists mapped four 1:63,360-scale quadrangles in the lower Kuskokwim River basin in southwest Alaska. The mapped formations span from the Late Cretaceous to the Holocene. Central to the stratigraphy is the Kuskokwim Group, a ~2,300-meter-thick sequence of marine turbidites and fluvial deposits formed in a post-accretionary basin, containing Turonian to Santonian fossil assemblages. This group is intruded and overlain by meta-aluminous to peraluminous igneous rocks, including the Iditarod Volcanics, the Horn Mountains volcanic-plutonic complex, and granite porphyry dikes and sills--features likely associated with a north-verging subduction zone and related extensional tectonics. Unconsolidated deposits from the Late Tertiary to Holocene cover approximately 65% of the area, with four Pleistocene glaciations producing a radial pattern of outwash deposits surrounding the glacially sculpted Horn Mountains. Thermoluminescence and radiocarbon dating indicate glaciations during the Illinoian (~140,000 years BP) and Late Wisconsin (~13,600 years BP) periods. Bedrock units exhibit multiple folding and faulting events, which may have facilitated hydrothermal mineralization. The region hosts notable mineral resources, including mesothermal, boron-enriched base and precious metals in hornfels and cupolas; mercury-antimony-gold lodes in granite porphyry and altered mafic dikes; and heavy mineral gold placers. The complete report, geodatabase, and ESRI fonts and style files are available from the Alaska Division of Geological & Geophysical Surveys website: http://doi.org/10.14509/2588.

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Non-Federal: This dataset is covered by different Terms of Use than Data.gov. License: No license information was provided.

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Dates

Metadata Date	October 2, 2025
Metadata Created Date	October 4, 2025
Metadata Updated Date	October 4, 2025
Reference Date(s)	January 1, 1999 (publication)
Frequency Of Update	notPlanned

Metadata Source

ISO-19139 ISO-19139 Metadata
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FGDC Original FGDC Metadata
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Harvested from Alaska Division of Geological and Geophysical Surveys

Additional Metadata

Resource Type	Dataset
Metadata Date	October 2, 2025
Metadata Created Date	October 4, 2025
Metadata Updated Date	October 4, 2025
Reference Date(s)	January 1, 1999 (publication)
Responsible Party	Alaska Division of Geological & Geophysical Surveys (Point of Contact)
Contact Email	dggspubs@alaska.gov
Guid	edf1f84d-cd19-43af-a74d-8b8c6d4397a1_source
Access Constraints	Use Constraints: Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. The user specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product., Access Constraints: This report, map, and/or dataset is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below).
Bbox East Long	-158.238211
Bbox North Lat	62.001957
Bbox South Lat	61.498153
Bbox West Long	-159.000608
Coupled Resource
Frequency Of Update	notPlanned
Harvest Object Id	edf1f84d-cd19-43af-a74d-8b8c6d4397a1
Harvest Source Id	8f77b6d5-f630-4995-bdf3-0aee7158a7f3
Harvest Source Title	Alaska Division of Geological and Geophysical Surveys
Licence	The State of Alaska makes no expressed or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.
Lineage	This lineage was generated by the FGDC CSDGM to 19139 transformation
Metadata Language	eng; USA
Metadata Type	geospatial
Old Spatial	{"type": "Polygon", "coordinates": [[[-159.000608, 61.498153], [-158.238211, 61.498153], [-158.238211, 62.001957], [-159.000608, 62.001957], [-159.000608, 61.498153]]]}
Progress	completed
Spatial Data Service Type
Spatial Reference System
Spatial Harvester	True
Temporal Extent Begin	1990-01-01
Temporal Extent End	2026-01-01

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