Geologic Map of Baranof Island, southeastern Alaska

Susan M. Karl; Peter J. Haeussler; Glen R. Himmelberg; Cathy L. Zumsteg; Paul W. Layer; Richard M. Friedman; Sarah M. Roeske; Lawrence W. Snee

doi:10.3133/sim3335

USGS · sim3335

Geologic Map of Baranof Island, southeastern Alaska

Susan M. Karl·Peter J. Haeussler·Glen R. Himmelberg·Cathy L. Zumsteg·Paul W. Layer·Richard M. Friedman·Sarah M. Roeske·Lawrence W. Snee

View original source ↗Read source document ↗Export metadata ↓

Abstract

This map updates the geology of Baranof Island based on fieldwork, petrographic analyses, paleontologic ages, and isotopic ages. These new data provide constraints on depositional and metamorphic ages of lithostratigraphic rock units and the timing of structures that separate them. Kinematic analyses and thermobarometric calculations provide insights on the regional tectonic processes that affected the rocks on Baranof Island. The rocks on Baranof Island are components of a Paleozoic to Early Tertiary oceanic volcanic arc complex, including sedimentary and volcanic rocks that were deposited on and adjacent to the arc complex, deformed, and accreted. The arc complex consists of greenschist to amphibolite facies Paleozoic metavolcanic and metasedimentary rocks overlain by lower-grade Triassic metasedimentary and metavolcanic rocks and intruded by Jurassic calc-alkaline plutons. The Paleozoic rocks correlate well in age and lithology with rocks of the Sicker and Buttle Lake Groups of the Wrangellia terrane on Vancouver Island and differ from rocks of the Skolai Group that constitute basement to type-Wrangellia in the Wrangell Mountains. The Jurassic intrusive rocks are correlative with plutons that intrude the Wrangellia terrane on Vancouver Island but are lacking in the Wrangell Mountains. The rocks accreted beneath the arc complex are referred to as the Baranof Accretionary Complex in this report and are correlated with the Chugach Accretionary Complex of southern and southeastern Alaska and with the Pacific Rim Complex on Vancouver Island. Stratigraphic correlations between upper- and lower-plate rocks on Baranof Island and western Chichagof Island with rocks on Haida Gwaii and Vancouver Island, in addition to correlative ages of intrusive rocks and restorations of the Fairweather-Queen Charlotte, Chatham Strait, and Peril Strait Faults that define the Baranof-Chichagof block, suggest Baranof Island was near Vancouver Island at the time of initiation of arc magmatism in the Early Jurassic. Early Eocene plutons that intruded the accretionary complex outboard of the arc on Baranof Island are attributed to anatectic melting of trench sediments resulting from subduction of a spreading center. Oligocene intrusive rocks on Baranof Island correlate in age and composition with intrusive rocks in the Kano Plutonic Suite on Haida Gwaii, and similar magmatic sources are inferred.

Explore related subjects

Scientific Investigations Map Report

Source-reported bounding extent: 56.16696465022672° to 57.57477906967287° latitude; -135.889892578125° to -134.6209716796875° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Susan M. Karl, Peter J. Haeussler, Glen R. Himmelberg, Cathy L. Zumsteg, Paul W. Layer, Richard M. Friedman, Sarah M. Roeske, Lawrence W. Snee. 2015. Geologic Map of Baranof Island, southeastern Alaska. https://doi.org/10.3133/sim3335

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Altitude of the potentiometric surface and depth to water in the Mississippi River Valley alluvial aquifer, spring 2024

Potentiometric-surface and depth-to-water maps for spring 2024 were created for the Mississippi River Valley alluvial aquifer using groundwater-altitude data from 1,151 wells completed in the Mississippi River Valley alluvial aquifer and from the altitude of the top of the water surface in area rivers from 160 U.S. Geological Survey and U.S. Army Corps of Engineers streamgages. The potentiometric-surface and depth-to-water maps for 2024 were created to support investigations to characterize the Mississippi River Valley alluvial aquifer as part of the U.S. Geological Survey Water Availability and Use Science Program. Sufficient data were available to map the potentiometric surface and depth to water of the Mississippi River Valley alluvial aquifer for spring 2024 for about 83 percent of the aquifer area. The potentiometric contours ranged from 0 to 330 feet (ft) above the North American Vertical Datum of 1988. The regional direction of the groundwater gradient was generally to the south-southwest, except in areas of groundwater-altitude depressions, where the groundwater gradient direction was into the depression, and near rivers, where the groundwater gradient direction was either from the aquifer to the river or from the river into the aquifer. Groundwater depressions in the potentiometric-surface map are in the lower one-half of the Cache region and in most of the Grand Prairie and Delta regions. Depth to water by well in the Mississippi River Valley alluvial aquifer in spring 2024 ranged from 0.27 ft above land surface to 145.65 ft below land surface.

Arkansas, Illinois, Kentucky, Louisiana, Mississip↗

USGS2026

Color-Shaded Relief Bathymetry of Lake Chelan, Washington

In 2023, the U.S. Geological Survey (USGS) completed a 3-week field operation in Lake Chelan, Washington, the third deepest lake in the conterminous United States, to acquire sediment cores, high-resolution bathymetry data, and chirp sub-bottom profiles. The high-resolution bathymetry displayed in this map publication was collected using a Norbit Winghead i67-curved array multibeam system; raw data were cleaned and gridded (3 by 3 meters [m]) in the Teledyne CARIS software. In some locations where the slopes of Lake Chelan are near-vertical, multibeam returns were sparse, resulting in artifacts resembling holes that appear as grey dots within the color-shaded bathymetric relief. Although the 2023 bathymetric mapping of Lake Chelan resulted in similar morphometric characteristics to previous hydrographic campaigns (table 1; Kendra and Singleton, 1987; Pelletier and others, 1989), these new data provide a much more detailed understanding of the two physiographic basins that comprise Lake Chelan: the deeper (as deep as 445.8 m [fig. 1]; previously reported as 453 m) and narrower (1–2 kilometers [km] wide) Lucerne Basin to the north, and the shallower (as deep as 127.8 m [fig. 1]), and wider (2–3 km wide) Wapato Basin to the south. With this detailed imaging of Lake Chelan, we find pervasive morphological evidence of slope failure and mass-transport deposits (MTDs) in at least 89 locations within the lake and 63 subaqueous deltas (fig. 2). The deeper Lucerne Basin is dominated by steep slopes and numerous subaqueous deltas fed by steep fluvial catchments, whereas the Wapato Basin contains numerous landslide scarps, scars, and debris aprons along the more gently sloping lake margins, and abundant relict kettle structures from the Pleistocene deglaciation. Lake Chelan’s geomorphic, geophysical, and sediment data contain important records of glacial retreat and advance, regional volcanic eruptions, and earthquakes that generate ground motions severe enough to induce landslides recorded in the sediment as MTDs. The epicenter of the 1872 Washington State Earthquake (M 6.5–7.2; Bakun and others, 2002; Brocher and others, 2017; Sherrod and others, 2021) is along the Spencer Canyon Fault, near the southern end of Lake Chelan. Shaking from this earthquake was strong enough to affect local aquifers, induce liquefaction of unconsolidated sediments, produce large seiches (Brocher and others, 2018), and likely cause landslides within Lake Chelan.

Washington↗

USGS2026

Spectral characteristics and mapping of lithium-rich playas in the Basin and Range Province, western United States

This report presents a comprehensive set of prospectivity maps for lithium in brines located within the playas of the Basin and Range Province of western United States. The prospectivity assessment is based on criteria established in the descriptive deposit model outlined in a previous U.S. Geological Survey report, with a focus on regional remote sensing methodologies. The playas within the study area have been systematically ranked according to several key factors, including size, the presence and abundance of source rocks, vegetation as an indicator of water availability, documented prospects, and data products derived from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor. Notably, the deposits in the playa of Clayton Valley make it stand out as the sole lithium brine-producing playa in the United States. The ASTER sensor provides optimal regional coverage, characterized by a 60-kilometer swath width and unique multispectral capabilities that are not available with other remote sensing instruments. This report and the accompanying maps are intended to serve as resources for further multidisciplinary assessments of lithium or other elements or commodities where prospectivity can be inferred from the presence of proxies such as alteration minerals.

Arizona, Baja California, California, Chihuahua, I↗