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Cook Inlet has been recognized as the second-largest petroleum province in Alaska, second only to the North Slope. The south-central Tyonek Quadrangle is an area of significant geologic interest because it is the only location in Cook Inlet where the entire producing stratigraphy of the basin is exposed on the surface. Additionally, this area encompasses the structural boundary between the forearc basin and its sediment source rocks. To better understand the petroleum system and the geologic relationships between the exhumed arc intrusive rocks and adjacent Cenozoic stratigraphy of the Cook Inlet forearc basin, during the summer of 2010 the Alaska Division of Geological & Geophysical Surveys conducted a federally-funded...
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Twenty-two igneous and metamorphic rock samples were collected in a 20-km-long swath centered on the Alaska Highway between Tetlin Junction, Alaska, and the Canada border. Igneous and metamorphic rock samples were submitted to the Apatite to Zircon, Inc. laboratory (A2Z), where zircon U-Pb age analysis, using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), was performed by Paul O'Sullivan. The 15 felsic plutonic rock samples and one gabbro sample yield Cretaceous zircon U-Pb weighted-mean ages ranging from 95.7 Ma to 106.2 Ma. Zircons from a metadiorite yield a Triassic weighted-mean age of about 241.9 Ma. Metamorphic zircons from two samples with felsic igneous protoliths yield Mississippian...
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Mineral Resources Section personnel from the Alaska Division of Geological & Geophysical Surveys (DGGS) carried out a geologic field survey, including mapping and sampling, in the eastern part of the Bonnifield mining district in the Fairbanks A-1 and A-2 and the Healy D-1 and D-2 quadrangles, Alaska, from June 16 through July 18, 2008. The fieldwork provides basic information critical to building an understanding of Alaska's geology and is part of an integrated program of airborne geophysical surveys followed by geologic mapping. Specifically, this work provides geologic context for geophysical surveys conducted in 2006. Interpretation and synthesis of this data has been presented in professional and trade meetings....
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View north toward basalt dike (photograph EI10) in Hakatai Shale, Unkar Group, on north side of river mile 77.2, at beginning of Hance Rapids. Shinumo Sandstone forms cliff at upper edge of photograph.
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Aerial view northwest toward basalt dikes (photograph EI06) on west side of Unkar Creek canyon in Solomon Temple Member of Dox Formation, Unkar Group, about 2 miles west of river mile 72.5.
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Aerial view north toward south side of Quaternary basalt neck and pyroclastic deposits of Yumtheska Vent West sample site, K-Ar age 0.780±0.15 thousand years (ka) (Wenrich and others, 1995).
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View northwest and downriver toward basalt cascades over Esplanade Sandstone at north rim, Redwall Limestone (large gray cliff), undifferentiated Devonian and Cambrian strata below Redwall Limestone cliff to river, from river mile 184.3.
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Aerial view north toward 18-million-year (Ma) Peach Spring Tuff (brown) that overlies white Tertiary West Water Formation in upper Milkweed Canyon.
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Aerial view north toward 900-foot-thick Cardenas Basalt of Unkar Group (black), that overlies Ochoa Point Member of Dox Formation, Unkar Group (red slope), overlain by Nankoweap Formation (purple strata), west side of Ochoa Point, 1 mile northwest of river mile 71.0.
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Aerial view north towards Vulcans Throne volcano in distance on north side of river mile 179.3. View in foreground is north along Toroweap Fault in lower Prospect Canyon at faulted unnamed Pleistocene cinder cone and alluvium on east side of Prospect Canyon. Mount Trumbull (Pliocene basalt) on skyline, left side of photograph.
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The Preliminary Interpretive Report 2004-3B, "Bedrock geologic map of the Livengood SW C-3 and SE C-4 quadrangles, Tolovana mining district, Alaska," is the bedrock geologic map of an approximately 123-square-mile area in the central Livengood Quadrangle, Alaska.
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View west toward sample site of basalt neck on south side of Grand Pipe, Pakoon Limestone, Sanup Plateau, 1.7 miles northeast of river mile 273.5. K-Ar age is 17.4±0.3 million years (Ma).
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View northwest toward basalt cascades over Esplanade Sandstone, Redwall Limestone (large gray cliff), Temple Butte Formation (lower left of photograph), north rim, north of river mile 184.3.
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View west from Toroweap campground area above river mile 178.2 toward Toroweap leap (at person), Lava Falls Rapids (lower left), and basalt lava cascades from Esplanade Sandstone.


map background search result map search result map Bedrock geologic map of the Livengood SW C-3 and SE C-4 quadrangles, Tolovana mining district, Alaska Preliminary bedrock geologic map data for the eastern Bonnifield mining district, Fairbanks and Healy quadrangles, Alaska Zircon U-Pb age data, Alaska Highway Corridor, Tanacross and Nabesna quadrangles, Alaska Major-oxide and trace-element geochemical data from rocks collected in 2010 in the Tyonek Quadrangle, Alaska CI07. Aerial view north toward south side of Quaternary basalt neck and pyroclastic deposits of Yumtheska Vent West sample site CI13. Hundred and Fiftynine Mile Dike at top of Redwall Limestone CI33. View west from Toroweap campground area toward Toroweap leap, Lava Falls Rapids, and basalt lava cascades CI39. Aerial view north towards Vulcans Throne volcano along Toroweap Fault CI54. View of the west-facing wall inside 1,000-year-old Little Spring volcano CI58. View north toward basalt cascade down north wall of river CI62. View northwest and downriver toward basalt cascades CI63. View northwest toward basalt cascades EI03. Aerial view north toward 900-foot-thick Cardenas Basalt of Unkar Group EI07. Aerial view northwest toward basalt dikes on west side of Unkar Creek canyon in Solomon Temple Member of Dox Formation EI09. View north toward basalt dike in Hakatai Shale WI29. Aerial view north toward 18-million-year Peach Spring Tuff WI42. View west toward sample site of basalt neck on south side of Grand Pipe WI51. Views northwest toward Miocene tuff beds in the Gyp Hills Bedrock geologic map of the Livengood SW C-3 and SE C-4 quadrangles, Tolovana mining district, Alaska Preliminary bedrock geologic map data for the eastern Bonnifield mining district, Fairbanks and Healy quadrangles, Alaska Major-oxide and trace-element geochemical data from rocks collected in 2010 in the Tyonek Quadrangle, Alaska Zircon U-Pb age data, Alaska Highway Corridor, Tanacross and Nabesna quadrangles, Alaska