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NARROW
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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Africa
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North Africa
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Tunisia (1)
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West Africa
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Liberia (1)
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Antarctica
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Primates
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Invertebrata
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geochronology methods
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geologic age
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Cenozoic
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Quaternary
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Tertiary
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Neogene
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Miocene
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Astoria Formation (1)
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Columbia River Basalt Group (1)
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upper Miocene
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Messinian (1)
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Ogallala Formation (1)
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Pliocene (2)
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Mesozoic
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Cretaceous
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Cupido Formation (1)
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Jurassic
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Smackover Formation (2)
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Paleozoic
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sulfates
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Primary terms
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Africa
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North Africa
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West Africa
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Antarctica
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Asia
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Far East
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Japan
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Philippine Islands (1)
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Middle East
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carbon
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C-13/C-12 (5)
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organic carbon (1)
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Caribbean region
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Antilles
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Barbados (1)
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Bahamas (2)
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Cenozoic
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Quaternary
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Holocene (2)
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Pleistocene
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Blackwater Draw Formation (1)
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upper Pleistocene (1)
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Tertiary
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Neogene
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Miocene
-
Astoria Formation (1)
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Columbia River Basalt Group (1)
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upper Miocene
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Messinian (1)
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-
-
Ogallala Formation (1)
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Pliocene (2)
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-
-
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Central America
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Belize
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Maya Mountains (1)
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Chordata
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Vertebrata
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Tetrapoda
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Mammalia
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Theria
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Eutheria
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Primates
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Hominidae (1)
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climate change (3)
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continental shelf (1)
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Invertebrata
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Mollusca (1)
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isotopes
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limestone deposits (1)
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Mediterranean region (2)
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Mesozoic
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Cretaceous
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Lower Cretaceous
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Cupido Formation (1)
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Sligo Formation (1)
-
-
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Jurassic
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Upper Jurassic
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Smackover Formation (2)
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-
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Navajo Sandstone (1)
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Triassic
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Sherwood Sandstone (1)
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-
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metal ores
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copper ores (1)
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metals
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alkaline earth metals
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strontium
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Sr-87/Sr-86 (1)
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chromium (1)
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iron (1)
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metamorphic rocks
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marbles (1)
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metasomatic rocks
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skarn (1)
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metasomatism (1)
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Mexico
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mineral deposits, genesis (2)
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mineral exploration (2)
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nitrogen (1)
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North America
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Appalachian Basin (2)
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Appalachians
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Northern Appalachians (1)
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Piedmont (1)
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Great Plains
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Southern Great Plains (1)
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Gulf Coastal Plain (2)
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ocean floors (1)
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oxygen
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O-18 (1)
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O-18/O-16 (3)
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paleoclimatology (2)
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paleoecology (1)
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paleogeography (1)
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Paleozoic
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Berea Sandstone (2)
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Carboniferous
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Lower Carboniferous (1)
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Pennsylvanian
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Pittsburgh Coal (1)
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Upper Pennsylvanian
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Missourian (1)
-
-
-
-
Devonian
-
Lower Devonian
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Coeymans Formation (1)
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-
-
Permian (1)
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Silurian
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Lockport Formation (1)
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Middle Silurian (1)
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Niagaran (1)
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paragenesis (2)
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Plantae
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pollution (24)
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sea-level changes (5)
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sedimentary petrology (12)
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chemically precipitated rocks
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sedimentary structures
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springs (4)
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sulfur (2)
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tectonics (1)
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thallophytes (1)
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Amargosa Desert (2)
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Arkansas
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Columbia County Arkansas (1)
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Arkansas River (1)
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Atlantic Coastal Plain
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Southern Atlantic Coastal Plain (1)
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California
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Butte County California (1)
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Central California (1)
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Glenn County California (2)
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Inyo County California
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Owens Lake (1)
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Mono County California (1)
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San Joaquin Valley (1)
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Tulare County California (2)
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Eastern U.S.
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Florida (1)
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Idaho
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Ada County Idaho
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Idaho National Laboratory (1)
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Kansas
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Louisiana
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Madison Aquifer (1)
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Midcontinent (2)
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Midwest (2)
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Missouri River valley (1)
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Nevada
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Nye County Nevada
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Yucca Mountain (3)
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New Jersey (1)
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New York (2)
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Ogallala Aquifer (2)
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Pennsylvania
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chalk (1)
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dolostone (3)
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grainstone (3)
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limestone
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chemically precipitated rocks
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evaporites
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salt (1)
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clastic rocks
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arenite (1)
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black shale (1)
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red beds (1)
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shale (4)
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siltstone (1)
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coal (1)
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oil shale (1)
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turbidite (1)
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sedimentary structures
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sedimentary structures
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biogenic structures
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algal structures (1)
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planar bedding structures
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cyclothems (2)
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stratification (1)
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sediments
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oolite (5)
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sediments
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carbonate sediments (3)
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clastic sediments
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clay (1)
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cobbles (1)
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gravel (1)
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kaolin (1)
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loess (1)
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sand (10)
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silt (1)
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till (1)
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turbidite (1)
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soils
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soils
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Cambisols (1)
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loam (1)
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saturated zone
Abstract The Chalk is an unusual karst aquifer with limited cave development, but extensive networks of smaller solutional conduits and fissures enabling rapid groundwater flow. Small-scale karst features (stream sinks, dolines, dissolution pipes, and springs) are common, with hundreds of stream sinks recorded. Tracer velocities from 27 connections between stream sinks and springs have median and mean velocities of 4700 and 4600 m d −1 . Tests to abstraction boreholes also demonstrate very rapid velocities of thousands of metres per day. Natural gradient tests from observation boreholes have rapid velocities of hundreds of metres per day. There is strong geological control on karst with dissolution focused on stratigraphical inception horizons. Surface karst features are concentrated near the Paleogene boundary, or where thin superficial cover occurs, but rapid groundwater flow is also common in other areas. The Chalk has higher storage and contaminant attenuation than classical karst, but recharge, storage and flow are influenced by karst. Point recharge through stream sinks, dolines, losing rivers, vertical solutional fissures, and soakaways enables rapid unsaturated zone flow. Saturated zone networks of solutional fissures and conduits create vulnerability to subsurface activities, and enable long distance transport of point source and diffuse pollutants, which may be derived from outside modelled catchment areas and source protection zones.
Study of historical groundwater level changes in two Belgian chalk aquifers in the context of climate change impacts
Abstract In southern Belgium, 23% of abstracted groundwater volumes are from chalk aquifers, representing strategic resources for the region. Due to their specific nature, these chalk aquifers often exhibit singular behaviour and require specific analysis. The quantitative evolution of these groundwater resources is analysed for the Mons Basin and Hesbaye chalk aquifers as a function of past evolution, in the short and long term. Groundwater level time series exhibit decreases when analysed over different periods. This is particularly visible for the Hesbaye chalk aquifer when comparing the 1960–90 and 1990–2020 periods. Such decreases are associated with observed temperature increases and precipitation decreases, inducing a decrease of aquifer recharge, and a probable increase of groundwater abstraction in the adjacent catchment. Past evolution is also discussed considering recent winter and summer drought events. The aquifers exhibit long delays in response to recharge events, particularly where the thickness of the partially saturated zone plays a crucial role in observed delays. Regarding future evolution, simulations of the impact of climate changes using medium–high emission scenarios indicate a probable decrease of the groundwater levels over the Hesbaye chalk aquifer.
A GIS-based Methodology for Assigning a Flux Boundary to a Numerical Groundwater Flow Model and Its Effect on Model Calibration
Estimation of the top of the saturated zone from airborne electromagnetic data
300,000 yr history of water-table fluctuations at Wind Cave, South Dakota, USA—Scale, timing, and groundwater mixing in the Madison Aquifer
Groundwater recharge susceptibility mapping using logistic regression model and bivariate statistical analysis
Conceptualizing Groundwater-Surface Water Interactions within the Ogallala Aquifer Region using Electrical Resistivity Imaging
Antarctic subglacial groundwater: a concept paper on its measurement and potential influence on ice flow
Abstract Is groundwater abundant in Antarctica and does it modulate ice flow? Answering this question matters because ice streams flow by gliding over a wet substrate of till. Water fed to ice-stream beds thus influences ice-sheet dynamics and, potentially, sea-level rise. It is recognized that both till and the sedimentary basins from which it originates are porous and could host a reservoir of mobile groundwater that interacts with the subglacial interfacial system. According to recent numerical modelling, up to half of all water available for basal lubrication, and time lags between hydrological forcing and ice-sheet response as long as millennia, may have been overlooked in models of ice flow. Here, we review evidence in support of Antarctic groundwater and propose how it can be measured to ascertain the extent to which it modulates ice flow. We present new seismoelectric soundings of subglacial till, and magnetotelluric and transient electromagnetic forward models of subglacial groundwater reservoirs. We demonstrate that multifaceted and integrated geophysical datasets can detect, delineate and quantify the groundwater contents of subglacial sedimentary basins and, potentially, monitor groundwater exchange rates between subglacial till layers. The paper thus describes a new area of glaciological investigation and how it should progress in future.
Application of Multiple Criteria Decision Making Model For Evaluation of Levee Sustainability
Climate fluctuations recorded in phreatic and vadose calcretes of the Lower Carboniferous Clyde Sandstone Formation of Machrihanish, Kintyre Peninsula, SW Scotland
The Effect of Precipitation Pulses on Evaporation of Deeply Buried Phreatic Water in Extra-Arid Areas
Shaking water out of soil
Self-potential Inversion for the Estimation of Permeability Structure
An investigation of the basement complex aquifer system in Lofa county, Liberia, for the purpose of siting boreholes
Effect of pore-water chemistry on undrained shear behaviour of saturated loess
Gas generation and accumulation by aquifer drawdown and recharge in the London Basin
Pore-water extraction from the unsaturated and saturated zones
This hydrology and geochemistry volume is a companion volume to the 2007 Geological Society of America Memoir 199, The Geology and Climatology of Yucca Mountain and Vicinity, Southern Nevada and California , edited by Stuckless and Levich. The work in both volumes was originally reported in the U.S. Department of Energy regulatory document Yucca Mountain Site Description , for the site characterization study of Yucca Mountain, Nevada, as the proposed U.S. geologic repository for high-level radioactive waste. The selection of Yucca Mountain resulted from a nationwide search and numerous committee studies during a period of more than 40 yr. The waste, largely from commercial nuclear power reactors and the government's nuclear weapons programs, is characterized by intense penetrating radiation and high heat production, and, therefore, it must be isolated from the biosphere for tens of thousands of years. The extensive, unique, and often innovative geoscience investigations conducted at Yucca Mountain for more than 20 yr make it one of the most thoroughly studied geologic features on Earth. The results of these investigations contribute extensive knowledge to the hydrologic and geochemical aspects of radioactive waste disposal in the unsaturated zone. The science, analyses, and interpretations are important not only to Yucca Mountain, but also to the assessment of other sites or alternative processes that may be considered for waste disposal in the future. Groundwater conditions, processes, and geochemistry, especially in combination with the heat from radionuclide decay, are integral to the ability of a repository to isolate waste. Hydrology and geochemistry are discussed here in chapters on unsaturated zone hydrology, saturated zone hydrology, paleohydrology, hydrochemistry, radionuclide transport, and thermally driven coupled processes affecting long-term waste isolation. This introductory chapter reviews some of the reasons for choosing to study Yucca Mountain as a repository site.
In 2002, Yucca Mountain, Nevada, was selected as the proposed site for the U.S. high-level nuclear waste repository. Yucca Mountain lies within a large topographically closed basin, in which surface water is internally drained. Groundwater, however, can and does flow into and out of this basin at depth through a regional carbonate-rock aquifer (commonly referred to as the lower carbonate-rock aquifer). Most groundwater recharge (water infiltrating downward through the unsaturated zone into the water table) originates in the highlands north of Yucca Mountain and flows generally southward. Some groundwater discharges within the basin, as in Oasis Valley and the southern Amargosa Desert, but the ultimate discharge is in Death Valley, where water is returned to the atmosphere by evapotranspiration. Groundwater flows through a heterogeneous medium produced by a complex geologic history including both compressional and extensional tectonics. For hydrologic purposes, the rocks and alluvium are divided into 25 hydrogeologic units. Regionally, the most important unit for regional groundwater flow is composed of Paleozoic carbonate rocks, which are locally separated into two aquifers by an intervening shale. Rocks of the southwestern Nevada volcanic field form thick deposits in the northern part of the basin, and these rocks host both aquifers and confining units. The potentiometric surface of the site-scale flow system contains areas of large hydraulic gradient (as great as 0.13) and small hydraulic gradient (as small as 0.0001). Both extremes are found within the Yucca Mountain site area, where they are well constrained by numerous boreholes. At Yucca Mountain, a single borehole penetrates to the regional carbonate-rock aquifer, and, at this locality, the hydraulic head at depth is 20 m greater than in the overlying volcanic rocks. This head difference is likely widespread, as indicated by thermal highs at the groundwater table in the vicinity of block-bounding faults, where upward leakage of water from the regional carbonate-rock aquifer is postulated. Since the early 1980s, numerous two- and three-dimensional flow models have been developed to depict regional groundwater flow. A 2004 transient flow model of the Death Valley region has 16 layers and a 1500 m/side horizontal grid; it is composed of 194 rows and 160 columns. The model was first calibrated to a steady-state condition and then to transient conditions. The model matches observed flow patterns well, and it generally agrees with measured water levels except in areas of large hydraulic gradient. The regional model provides the boundary conditions for a detailed site-scale flow model. The finite-element heat and mass transfer code, FEHM v2.24, was used to simulate flow through the saturated zone at Yucca Mountain. Cells in the site-scale model are 250 m/side in the horizontal grid; it is composed of 181 rows and 121 columns. The model may use as many as 67 layers, but the framework model allows a stair-stepped ground surface, so the number of layers is variable. Layer thickness ranges from 600 m at the bottom of the model to 10 m south of Yucca Mountain. The site-scale flow model was constructed and calibrated, matching observed hydrologic data well. The site-scale flow model provides a means for assessing the hypothetical flow path for any radioactive materials originating from the proposed repository.
The paleohydrology of unsaturated and saturated zones at Yucca Mountain, Nevada, and vicinity
Surface, unsaturated-zone, and saturated-zone hydrologic conditions at Yucca Mountain responded to past climate variations and are at least partly preserved by sediment, fossil, and mineral records. Characterizing past hydrologic conditions in surface and subsurface environments helps to constrain hydrologic responses expected under future climate conditions and improve predictions of repository performance. Furthermore, these records provide a better understanding of hydrologic processes that operate at time scales not readily measured by other means. Pleistocene climates in southern Nevada were predominantly wetter and colder than the current interglacial period. Cyclic episodes of aggradation and incision in Fortymile Wash, which drains the eastern slope of Yucca Mountain, are closely linked to Pleistocene climate cycles. Formation of pedogenic cement is favored under wetter Pleistocene climates, consistent with increased soil moisture and vegetation, higher chemical solubility, and greater evapotranspiration relative to Holocene soil conditions. The distribution and geochemistry of secondary minerals in subsurface fractures and cavities reflect unsaturated-zone hydrologic conditions and the response of the hydrogeologic system to changes in temperature and percolation flux over the last 12.8 m.y. Physical and fluid-inclusion evidence indicates that secondary calcite and opal formed in air-filled cavities from fluids percolating downward through connected fracture pathways in the unsaturated zone. Oxygen, strontium, and carbon isotope data from calcite are consistent with a descending meteoric water source but also indicate that water compositions and temperatures evolved through time. Geochronological data indicate that secondary mineral growth rates are less than 1–5 mm/m.y., and have remained approximately uniform over the last 10 m.y. or longer. These data are interpreted as evidence for hydrological stability despite large differences in surface moisture caused by climate shifts between the Miocene and Pleistocene and between Pleistocene glacial-interglacial cycles. Secondary mineral distribution and δ 18 O profiles indicate that evaporation in the shallower welded tuffs reduces infiltration fluxes. Several near-surface and subsurface processes likely are responsible for diverting or dampening infiltration and percolation, resulting in buffering of percolation fluxes to the deeper unsaturated zone. Cooler and wetter Pleistocene climates resulted in increased recharge in upland areas and higher water tables at Yucca Mountain and throughout the region. Discharge deposits in the Amargosa Desert were active during glacial periods, but only in areas where the modern water table is within 7–30 m of the surface. Published groundwater models simulate water-table rises beneath Yucca Mountain of as much as 150 m during glacial climates. However, most evidence from Fortymile Canyon up gradient from Yucca Mountain limits water-table rises to 30 m or less, which is consistent with evidence from discharge sites in the Amargosa Desert. The isotopic compositions of uranium in tuffs spanning the water table in two Yucca Mountain boreholes indicate that Pleistocene water-table rises likely were restricted to 25–50 m above modern positions and are in approximate agreement with water-table rises estimated from zeolitic-to-vitric transitions in the Yucca Mountain tuffs (less than 60 m in the last 11.6 m.y.).