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This map illustrates extents and types of unconsolidated deposits and bedrock in the Big Delta A-4 Quadrangle, Alaska. This map is based on field observations begun by P�w� in 1949 and by Reger in 1976. Unit characteristics and extents were determined during field visits and by interpreting 1:40,000-scale black-and-white aerial photographs taken in August 1949 and 1:63,360-scale, false-color infrared aerial photographs taken in July 1978, August 1980, and August 1981.
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Note: No formal accuracy tests were conducted and these data are disseminated to allow discussion related to methods. Sample Analyses: Samples were processed at both the USGS in Menlo Park, CA, and at UC Berkeley following established methodology for separating organic material from sinter (Howald et al., 2014; Lowenstern et al., 2016; Slagter et al., 2019). First, the exterior surface of each sample was removed using a rock saw, and then any further material was removed if there was any visible algal material in the interior of the sample. Second, samples underwent a series of chemical baths. Samples were crushed and soaked in 30% hydrogen peroxide for 48 hours to remove any remaining modern algae. Once cleaned,...
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Between 27 and 11 kyr ago, during the last major (Naptowne) glaciation, the northwestern and western Kenai Peninsula and the Cook Inlet trough were covered by ice except for local nunataks and small refugia, like the Caribou Hills. Landforms related to four glacial stades are recognized and paleogeographic maps document ice limits, drainage systems, glacial-impounded lakes, and glaciomarine terraces. Numerous multidisciplinary studies of glacial, vegetation, and insect histories document Holocene climatic changes.
This data release contains data for two papers, published 16 years apart, that focus on the earthquake and tsunami history of Bradley Lake, a coastal lake in southern Oregon: Paper 1 - Kelsey, H.M., Nelson, A.R., Hemphill-Haley, E.M., and Witter, R.C., 2005, Tsunami history of an Oregon coastal lake reveals a 4600 yr record of great earthquakes on the Cascadia subduction zone: Geological Society of America Bulletin, v. 117, p. 1009–1032, doi: 10.1130/B25452.1. Paper 2 - Nelson, A.R., DuRoss, C.B., Witter, R.C., Kelsey, H.M., Engelhart, S.E., Mahan, S.A., Gray, H.J., Hawkes, A.D., Horton, B.P., and Padgett, J.S., 2021, A maximum rupture model for the central and southern Cascadia subduction zone—reassessing ages...


map background search result map search result map Core photographs, descriptions, 14C ages, and other supplemental data for Kelsey et al. (2005) and Nelson et al. (2021) about Bradley Lake tsunami history and megathrust earthquake recurrence in the central and southern Cascadia subduction zone A Guide to the Late Quaternary History of Northern and Western Kenai Peninsula, Alaska Surficial geology of the Dalton Highway (Itkillik-Sagavanirktok rivers) area, southern Arctic foothills, Alaska Geologic map of the Big Delta A-4 Quadrangle, Alaska a. Carbon Isotope Data a. Carbon Isotope Data Geologic map of the Big Delta A-4 Quadrangle, Alaska Surficial geology of the Dalton Highway (Itkillik-Sagavanirktok rivers) area, southern Arctic foothills, Alaska A Guide to the Late Quaternary History of Northern and Western Kenai Peninsula, Alaska Core photographs, descriptions, 14C ages, and other supplemental data for Kelsey et al. (2005) and Nelson et al. (2021) about Bradley Lake tsunami history and megathrust earthquake recurrence in the central and southern Cascadia subduction zone