Geologic investigation of the Haines-Takshanuk Mountains-Chilkat Peninsula area, Southeast Alaska

Geologic investigation of the Haines-Takshanuk Mountains-Chilkat Peninsula area, Southeast Alaska, Preliminary Interpretive Report 2025-4, provides the results of geologic mapping in the Haines-Takshanuk Mountains-Chilkat Peninsula area of Southeast Alaska. The study covers approximately 777 square kilometers across portions of the Skagway A-1, A-2, B-1, B-2, and B-3 quadrangles and culminates in a 1:50,000-scale surficial and bedrock geologic map. Field investigations were conducted at more than 550 stations by helicopter- and boat-supported teams from the Alaska Division of Geological & Geophysical Surveys (DGGS) and the University of Alaska Fairbanks (UAF). Observations included documentation of landform morphology, soil test pit sampling, structural measurements, Schmidt Hammer tests, and collection of rock samples for thin section, geochemical, and petrologic analyses. Organic samples were also obtained for radiocarbon dating. The project was initiated in response to the deadly December 2, 2020, landslide in Haines. The mapping enhances characterization of surficial deposits and bedrock units, provides critical information for landslide hazard assessment and emergency planning, and establishes a foundation for future studies of magmatic and mineralization history in Southeast Alaska. It also builds upon earlier work by Redman and others (1984) and Gilbert (1987, 1988), offering updated insights into the Chatham Strait fault system, Coast shear zone, and Coast Plutonic Complex, thereby strengthening both applied and scientific understanding of the region's geology. The dataset contains geologic, structural, stratigraphic, and geochronologic data organized according to the GeMS and AK GeMS mapping schemas. The complete report, geodatabase, and ESRI fonts and style files are available from the Alaska Division of Geological & Geophysical Surveys website: http://doi.org/10.14509/31417.

Tags: actinolite, alaska, alluvial, alluvial deposits, alluvial fan, alluvium, amphibolite, aplite, argillite, basalt, battery point, beach deposits, bedrock, bedrock geology, breccia, chert, chilkat river, chilkoot river, chlorite, colluvium, conglomerate, cretaceous, dalasuga island, delta deposits, deshu isthmus, devils punch bowl, dggs, diabase, diopside, diorite, dok point, epidote, false battery point, feldspar, felsic, ferebee river, ferebee valley, floodplain deposits, fossils, gabbro, garnet, gems db l3 compliant, gems db v2, geology, glacial deposits, glacial outwash, glacial outwash fan, glacial till, glaciers, glaciofluvial deposits, gneiss, granite, granodiorite, gravina-nutzotin belt, halutu ridge, haska creek, hazards, hornblendite, hydrology and surficial geology, igneous rocks, iron mountain, johnson creek, jualin mine, juneau mining district, kalhagu cove, kasidaya creek, kelgaya bay, kelgaya point, kicking horse river, kootznahoo formation, landslide, lehunua point, letnikof cove, lily lake, limestone, low point, ludaseska creek, marble, mesozoic, metabasalt, metamorphic minerals, metamorphic rocks, metamorphism, metasedimentary rocks, metavolcanic rocks, metavolcanics, migmatite, mink creek, monzodiorite, monzogranite, monzonite, mount harding, mount villard, mud bay, mudstone, nukdik point, paleozoic, paludal deposits, paradise cove, phyllite, plutonic complex, plutonic rocks, pyroxenite, quartzite, quaternary, regional metamorphism, rock glaciers, rustabach lake, sandstone, schist, sedimentary rocks, seduction point, shakuseyi creek, shale, sherman creek, siltstone, silurian, slate, statemap project, surface, surficial, surficial deposits, surficial geologic map, surficial geology, takhin river, takshanuk mountains, talus, tanani point, tanani village, tertiary, tonalite, triassic, tukgahgo mountain, ultramafic, ultramafic rocks, unconsolidated deposits, vanderbilt point, volcaniclastic rocks, yindastuki, zimovia point
Organization: State of Alaska