|
|||||
|
|
Late Quaternary distal tephra-fall deposits in lacustrine sediments, Kenai Peninsula, Alaska |
|
| Authors: | Christian S de Fontaine R Scott Anderson Christopher F Waythomas |
| Institution: | a Department of Geology, Northern Arizona University, Flagstaff, AZ 86011-4099, USA b Department of Geology/Center for Environmental Sciences and Education, Northern Arizona University, Flagstaff, AZ 86011-4099, USA c Center for Environmental Sciences and Education/Quaternary Sciences Program, Northern Arizona University, Flagstaff, AZ 86011-5694, USA d Department of Earth and Environment, Mount Holyoke College, South Hadley, MA 01075, USA e U.S. Geological Survey and Alaska Volcano Observatory, 4230 University Drive, Suite 201, Anchorage, AK 99508, USA f Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, L-397, 7000 East Avenue, Livermore, CA 94551, USA |
| Abstract: | Tephra-fall deposits from Cook Inlet volcanoes were detected in sediment cores from Tustumena and Paradox Lakes, Kenai Peninsula, Alaska, using magnetic susceptibility and petrography. The ages of tephra layers were estimated using 21 14C ages on macrofossils. Tephras layers are typically fine, gray ash, 1-5 mm thick, and composed of varying proportions of glass shards, pumice, and glass-coated phenocrysts. Of the two lakes, Paradox Lake contained a higher frequency of tephra (0.8 tephra/100 yr; 109 over the 13,200-yr record). The unusually large number of tephra in this lake relative to others previously studied in the area is attributed to the lake's physiography, sedimentology, and limnology. The frequency of ash fall was not constant through the Holocene. In Paradox Lake, tephra layers are absent between ca. 800-2200, 3800-4800, and 9000-10,300 cal yr BP, despite continuously layered lacustrine sediment. In contrast, between 5000 and 9000 cal yr BP, an average of 1.7 tephra layers are present per 100 yr. The peak period of tephra fall (7000-9000 cal yr BP; 2.6 tephra/100 yr) in Paradox Lake is consistent with the increase in volcanism between 7000 and 9000 yr ago recorded in the Greenland ice cores. |
| Keywords: | Tephra Lacustrine sediment Volcanic ash Ash fall Tephrochronology Late Quaternary Cook Inlet Alaska |
| 本文献已被 ScienceDirect 等数据库收录！ | |