Spencer Wood | Boise State University (original) (raw)

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Papers by Spencer Wood

Research paper thumbnail of Author's personal copy Floodplain deposits, channel changes and riverbank stratigraphy of the Mekong River area at the 14th-Century city of Chiang Saen, Northern Thailand A B

Riverbank stratigraphy and paleochannel patterns of the Mekong River at Chiang Saen provide a geo... more Riverbank stratigraphy and paleochannel patterns of the Mekong River at Chiang Saen provide a geoarchaeological framework to explore for evidence of Neolithic, Bronze-age, AD 5th Century Yonok and AD 14-16th Century Lan Na Cultures. Typical bank stratigraphy charted on the Thailand side is imbricate cobble gravel overlain by 5-10 m of reddish-brown sandy silt. The silt section is composed chiefly of 1/2 to 2m thick layers of massive silt without paleosols interpreted as near-channel floodplain and gently-inclined levee deposits laid down by episodic, infrequent, large floods. The surface soil is dark-brown clay loam (b 1-m thick) with abundant brick fragments, pottery shards and charcoal of Lan Na time. Brick ruins of 14-16th Century Buddhist temples are crumbling into the river at Chiang Saen Noi, and formerly did so at Chiang Saen until banks were stabilized by rock walls. Bank retreat from river erosion has been N 20 m since Lan Na time, and has exposed a silt-filled moat. A radiocarbon age of 1475 cal yr AD was obtained from charcoal at the bottom of the moat, beneath 5.6 m of silt. Lag material from erosion of the silt banks contains Neolithic and Bronze Age artifacts out of stratigraphic context, as well as ceramics and bricks of Lan Na age. These artifacts as well Neolithic artifacts obtained from a 1972 excavation near the mouth of the Kham River indicate long human habitation of this riverbank area. In northern Thailand the Mekong is mostly in a bedrock canyon, but shifting topography along the active strike-slip Mae Chan fault has formed the upstream 2-5-km wide floodplain at Chiang Saen, and downstream has diverted the river into a broad S-shaped loop in the otherwise straight course of the river. A 1.7-Ma basalt within the bedrock channel 45-km downstream of Chiang Saen indicates little vertical incision by the river. Satellite images show former channels in the Chiang Saen area, meander-point-bar scrolls (radii of curvature N 1.2 km), and floodplain edges as arcuate cuts of similar curvature into the saprolite-mantled bedrock hills These features indicate channel avulsion occurred by meander loop cutoff in the past. Brick Buddhist monuments of the 14th-16th Century were built upon the floodplain with meander features on the Thai and Laos side of the river, indicating that these meandering channel features and the broader floodplain are mostly older than 600 years.

Research paper thumbnail of Seismic Expression and Geological Significance of a Lacustrine Delta in Neogene Deposits of the Western Snake River Plain, Idaho1

Research paper thumbnail of Northern Thailand Geothermal Resources and Development— A Review and 2012 Update

Northern Thailand has 16 hot spring systems with surface temperatures near or greater than 80°C w... more Northern Thailand has 16 hot spring systems with surface temperatures near or greater than 80°C with potential for binary plant power generation. Presently only Fang system generates power from wells flowing a total of 8.3 1/s of 116°C water to a 300 kW single module Ormat binary plant. Current production is 150-250 KW, which potentially can be increased by constructing new wells and increasing flow by pumping. Of the other 15 systems, 4 are in national parks and not considered for development. Several of the hot springs systems have silica geothermometry >130°C suggesting significant undeveloped resources exist in northern Thailand. Certainly the San Kamphaeng hot springs have the greatest known potential (estimated ~5MW) but like most of the systems it is associated with high-angle faulting and drilling has yet to find permeable zones yielding high flows (>11 l/s). The current project of the Thailand Department of Energy Development and Efficiency (DEDE) will survey these prospects with the intention of installing a small plant of 2-10 MW.

Research paper thumbnail of Geological Society of America Centennial Field Guide—Rocky Mountain Section, 1987 Geologic framework of the Boise Warm Springs geothermal area, Idaho

Research paper thumbnail of Geologic and Tectonic History of the Western Snake River Plain, Idaho and Oregon

Research paper thumbnail of Hydrology and Earth System Sciences Floodplain sediment from a 100-year-recurrence flood in 2005 of the Ping River in northern Thailand

The tropical storm, floodwater, and the floodplainsediment layer of a 100-year recurrence flood a... more The tropical storm, floodwater, and the floodplainsediment layer of a 100-year recurrence flood are examined to better understand characteristics of large monsoon floods on medium-sized rivers in northern Thailand. Storms producing large floods in northern Thailand occur early or late in the summer rainy season (May-October). These storms are associated with tropical depressions evolving from typhoons in the South China Sea that travel westward across the Indochina Peninsula. In late September, 2005, the tropical depression from Typhoon Damrey swept across northern Thailand delivering 100-200 mm/day at stations in mountainous areas. Peak flow from the 6355-km 2 drainage area of the Ping River upstream of the city of Chiang Mai was 867 m 3 s −1 (river-gage of height 4.93 m) and flow greater than 600 m 3 s −1 lasted for 2.5 days. Parts of the city of Chiang Mai and some parts of the floodplain in the intermontane Chiang Mai basin were flooded up to 1-km distant from the main channel. Suspended-sediment concentrations in the floodwater were measured and estimated to be 1000-1300 mg l −1 .

Research paper thumbnail of Author's personal copy Floodplain deposits, channel changes and riverbank stratigraphy of the Mekong River area at the 14th-Century city of Chiang Saen, Northern Thailand A B

Riverbank stratigraphy and paleochannel patterns of the Mekong River at Chiang Saen provide a geo... more Riverbank stratigraphy and paleochannel patterns of the Mekong River at Chiang Saen provide a geoarchaeological framework to explore for evidence of Neolithic, Bronze-age, AD 5th Century Yonok and AD 14-16th Century Lan Na Cultures. Typical bank stratigraphy charted on the Thailand side is imbricate cobble gravel overlain by 5-10 m of reddish-brown sandy silt. The silt section is composed chiefly of 1/2 to 2m thick layers of massive silt without paleosols interpreted as near-channel floodplain and gently-inclined levee deposits laid down by episodic, infrequent, large floods. The surface soil is dark-brown clay loam (b 1-m thick) with abundant brick fragments, pottery shards and charcoal of Lan Na time. Brick ruins of 14-16th Century Buddhist temples are crumbling into the river at Chiang Saen Noi, and formerly did so at Chiang Saen until banks were stabilized by rock walls. Bank retreat from river erosion has been N 20 m since Lan Na time, and has exposed a silt-filled moat. A radiocarbon age of 1475 cal yr AD was obtained from charcoal at the bottom of the moat, beneath 5.6 m of silt. Lag material from erosion of the silt banks contains Neolithic and Bronze Age artifacts out of stratigraphic context, as well as ceramics and bricks of Lan Na age. These artifacts as well Neolithic artifacts obtained from a 1972 excavation near the mouth of the Kham River indicate long human habitation of this riverbank area. In northern Thailand the Mekong is mostly in a bedrock canyon, but shifting topography along the active strike-slip Mae Chan fault has formed the upstream 2-5-km wide floodplain at Chiang Saen, and downstream has diverted the river into a broad S-shaped loop in the otherwise straight course of the river. A 1.7-Ma basalt within the bedrock channel 45-km downstream of Chiang Saen indicates little vertical incision by the river. Satellite images show former channels in the Chiang Saen area, meander-point-bar scrolls (radii of curvature N 1.2 km), and floodplain edges as arcuate cuts of similar curvature into the saprolite-mantled bedrock hills These features indicate channel avulsion occurred by meander loop cutoff in the past. Brick Buddhist monuments of the 14th-16th Century were built upon the floodplain with meander features on the Thai and Laos side of the river, indicating that these meandering channel features and the broader floodplain are mostly older than 600 years.

Research paper thumbnail of Seismic Expression and Geological Significance of a Lacustrine Delta in Neogene Deposits of the Western Snake River Plain, Idaho1

Research paper thumbnail of Northern Thailand Geothermal Resources and Development— A Review and 2012 Update

Northern Thailand has 16 hot spring systems with surface temperatures near or greater than 80°C w... more Northern Thailand has 16 hot spring systems with surface temperatures near or greater than 80°C with potential for binary plant power generation. Presently only Fang system generates power from wells flowing a total of 8.3 1/s of 116°C water to a 300 kW single module Ormat binary plant. Current production is 150-250 KW, which potentially can be increased by constructing new wells and increasing flow by pumping. Of the other 15 systems, 4 are in national parks and not considered for development. Several of the hot springs systems have silica geothermometry >130°C suggesting significant undeveloped resources exist in northern Thailand. Certainly the San Kamphaeng hot springs have the greatest known potential (estimated ~5MW) but like most of the systems it is associated with high-angle faulting and drilling has yet to find permeable zones yielding high flows (>11 l/s). The current project of the Thailand Department of Energy Development and Efficiency (DEDE) will survey these prospects with the intention of installing a small plant of 2-10 MW.

Research paper thumbnail of Geological Society of America Centennial Field Guide—Rocky Mountain Section, 1987 Geologic framework of the Boise Warm Springs geothermal area, Idaho

Research paper thumbnail of Geologic and Tectonic History of the Western Snake River Plain, Idaho and Oregon

Research paper thumbnail of Hydrology and Earth System Sciences Floodplain sediment from a 100-year-recurrence flood in 2005 of the Ping River in northern Thailand

The tropical storm, floodwater, and the floodplainsediment layer of a 100-year recurrence flood a... more The tropical storm, floodwater, and the floodplainsediment layer of a 100-year recurrence flood are examined to better understand characteristics of large monsoon floods on medium-sized rivers in northern Thailand. Storms producing large floods in northern Thailand occur early or late in the summer rainy season (May-October). These storms are associated with tropical depressions evolving from typhoons in the South China Sea that travel westward across the Indochina Peninsula. In late September, 2005, the tropical depression from Typhoon Damrey swept across northern Thailand delivering 100-200 mm/day at stations in mountainous areas. Peak flow from the 6355-km 2 drainage area of the Ping River upstream of the city of Chiang Mai was 867 m 3 s −1 (river-gage of height 4.93 m) and flow greater than 600 m 3 s −1 lasted for 2.5 days. Parts of the city of Chiang Mai and some parts of the floodplain in the intermontane Chiang Mai basin were flooded up to 1-km distant from the main channel. Suspended-sediment concentrations in the floodwater were measured and estimated to be 1000-1300 mg l −1 .

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