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Title: Holocene lahars and their byproducts along the historical path of the White River between Mount Rainier and Seattle: Geological Society of America Field Trip

Abstract

Clay-poor lahars of late Holocene age from Mount Rainier change down the White River drainage into lahar-derived fluvial and deltaic deposits that filled an arm of Puget Sound between the sites of Auburn and Seattle, 110-150 km downvalley from the volcano's summit. Lahars in the debris-flow phase left cobbly and bouldery deposits on the walls of valleys within 70 km of the summit. At distances of 80-110 km, transitional (hyperconcentrated) flows deposited pebbles and sand that coat terraces in a gorge incised into glacial drift and the mid-Holocene Osceola Mudflow. On the broad, level floor of the Kent valley at 110-130 km, lahars in the runout or streamflow phase deposited mostly sand-size particles that locally include the trunks of trees probably entrained by the flows. Beyond 130 km, in the Duwamish valley of Tukwila and Seattle, laminated andesitic sand derived from Mount Rainier built a delta northward across the Seattle fault. This distal facies, warped during an earthquake in A.D. 900-930, rests on estuarine mud at depths as great as 20 m. The deltaic filling occurred in episodes that appear to overlap in time with the lahars. As judged from radiocarbon ages of twigs and logs, at least three episodesmore » of distal deposition postdate the Osceola Mudflow. One of these episodes occurred about 2200-2800 cal yr B.P., and two others occurred 1700-1000 cal yr B.P. The most recent episode ended by about the time of the earthquake of A.D. 900-930. The delta's northward march to Seattle averaged between 6 and 14 m/yr in the late Holocene.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
15013757
Report Number(s):
UCRL-JRNL-200324
TRN: US200803%%752
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Journal Article
Journal Name:
Published in: Geological Society of America Field Guide 4, doi: 10.1130/0-8137-0004-3(2003)4<209:HLATBP>2.0.CO;2, doi: 10.1130/0-8137-0004-3(2003)4<209:HLATBP>2.0.CO;2, June 6, 2003, pp. 209-223
Additional Journal Information:
Journal Name: Published in: Geological Society of America Field Guide 4, doi: 10.1130/0-8137-0004-3(2003)4<209:HLATBP>2.0.CO;2, doi: 10.1130/0-8137-0004-3(2003)4<209:HLATBP>2.0.CO;2, June 6, 2003, pp. 209-223
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; DEPOSITION; DRAINAGE; EARTHQUAKES; FLOORS; PUGET SOUND; SAND; TREES; VALLEYS; WHITE RIVER

Citation Formats

Brown, T A, Zehfuss, P H, Atwater, B F, Vallance, J W, and Brenniman, H. Holocene lahars and their byproducts along the historical path of the White River between Mount Rainier and Seattle: Geological Society of America Field Trip. United States: N. p., 2003. Web.
Brown, T A, Zehfuss, P H, Atwater, B F, Vallance, J W, & Brenniman, H. Holocene lahars and their byproducts along the historical path of the White River between Mount Rainier and Seattle: Geological Society of America Field Trip. United States.
Brown, T A, Zehfuss, P H, Atwater, B F, Vallance, J W, and Brenniman, H. Thu . "Holocene lahars and their byproducts along the historical path of the White River between Mount Rainier and Seattle: Geological Society of America Field Trip". United States. https://www.osti.gov/servlets/purl/15013757.
@article{osti_15013757,
title = {Holocene lahars and their byproducts along the historical path of the White River between Mount Rainier and Seattle: Geological Society of America Field Trip},
author = {Brown, T A and Zehfuss, P H and Atwater, B F and Vallance, J W and Brenniman, H},
abstractNote = {Clay-poor lahars of late Holocene age from Mount Rainier change down the White River drainage into lahar-derived fluvial and deltaic deposits that filled an arm of Puget Sound between the sites of Auburn and Seattle, 110-150 km downvalley from the volcano's summit. Lahars in the debris-flow phase left cobbly and bouldery deposits on the walls of valleys within 70 km of the summit. At distances of 80-110 km, transitional (hyperconcentrated) flows deposited pebbles and sand that coat terraces in a gorge incised into glacial drift and the mid-Holocene Osceola Mudflow. On the broad, level floor of the Kent valley at 110-130 km, lahars in the runout or streamflow phase deposited mostly sand-size particles that locally include the trunks of trees probably entrained by the flows. Beyond 130 km, in the Duwamish valley of Tukwila and Seattle, laminated andesitic sand derived from Mount Rainier built a delta northward across the Seattle fault. This distal facies, warped during an earthquake in A.D. 900-930, rests on estuarine mud at depths as great as 20 m. The deltaic filling occurred in episodes that appear to overlap in time with the lahars. As judged from radiocarbon ages of twigs and logs, at least three episodes of distal deposition postdate the Osceola Mudflow. One of these episodes occurred about 2200-2800 cal yr B.P., and two others occurred 1700-1000 cal yr B.P. The most recent episode ended by about the time of the earthquake of A.D. 900-930. The delta's northward march to Seattle averaged between 6 and 14 m/yr in the late Holocene.},
doi = {},
journal = {Published in: Geological Society of America Field Guide 4, doi: 10.1130/0-8137-0004-3(2003)4<209:HLATBP>2.0.CO;2, doi: 10.1130/0-8137-0004-3(2003)4<209:HLATBP>2.0.CO;2, June 6, 2003, pp. 209-223},
number = ,
volume = ,
place = {United States},
year = {2003},
month = {10}
}