Ground-Water Hydrology of the Upper Klamath Basin, Oregon and California

Scientific Investigations Report 2007–5050

U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2007–5050
Version 1.1, April 2010

Table 1. Generalized hydrogeologic units in the upper Klamath Basin, Oregon and California.

Hydrogeologic unit	Map symbol	Lithologic and hydrologic characteristics
Quaternary sedimentary deposits	Qs	Fine- to coarse-grained sediments deposited in stream valleys and major lake basins. Permeable coarse-grained deposits occur in stream valleys and locally in the lake basins. The lake basin deposits are, however, predominantly fine grained and have low permeability.
Quaternary volcaniclastic deposits	Qvp	Pyroclastic flows and air fall material (pumice, ash, and lapilli) deposited during the climactic eruption of Mt. Mazama that formed Crater Lake, and debris avalanche deposits of the Shasta River Valley. Air fall deposits are highly permeable. Pyroclastic flows and debris deposits may have low permeability.
Quaternary volcanic rocks	Qv	Basaltic and andesitic lavas and vent deposits occurring in the Cascade Range and around Medicine Lake Volcano. These materials are generally highly permeable, but may not be saturated at high elevations.
Quaternary to late Tertiary sedimentary rocks	QTs	Fine- to coarse-grained unconsolidated to moderately indurated sedimentary deposits. The hydraulic characteristics of this unit are not well known but lithologic descriptions on maps suggest it may be moderately permeable at some locations. This unit has very limited distribution.
Late Tertiary sedimentary rocks	Ts	Predominately fine-grained continental sedimentary deposits including bedded diatomite, mudstone, siltstone, and sandstone. This unit has generally low permeability but contains permeable strata at some locations.
Late Tertiary volcaniclastic rocks	Tvpt	Palagonitized basaltic ash and lapilli deposits associated with eruptive centers. The hydrologic characteristics of this unit are not well known, but springs are known to emerge from basal contact with unit Ts. This unit is most prominent in the Sprague River valley.
Late Tertiary volcanic rocks	Tv	Predominantly basaltic and andesitic lava flows and vent deposits with lesser amounts of silicic domes and flows. This unit has moderate to high permeability and is by far the most widely developed aquifer unit in the study area. Permeability is locally diminished by hydrothermal alteration and secondary mineralization.
Older Tertiary volcanic and sedimentary rocks	Tovs	Miocene and older volcanic and volcaniclastic deposits. The permeability of this unit is generally low due to weathering, hydrothermal alteration, and secondary mineralization. This unit is generally considered a boundary to the regional ground-water system of the upper Klamath Basin.

Hydrogeologic unit

Map symbol

Lithologic and hydrologic characteristics

Quaternary sedimentary deposits

Fine- to coarse-grained sediments deposited in stream valleys and major lake basins. Permeable coarse-grained deposits occur in stream valleys and locally in the lake basins. The lake basin deposits are, however, predominantly fine grained and have low permeability.

Quaternary volcaniclastic deposits

Qvp

Pyroclastic flows and air fall material (pumice, ash, and lapilli) deposited during the climactic eruption of Mt. Mazama that formed Crater Lake, and debris avalanche deposits of the Shasta River Valley. Air fall deposits are highly permeable. Pyroclastic flows and debris deposits may have low permeability.

Quaternary volcanic rocks

Basaltic and andesitic lavas and vent deposits occurring in the Cascade Range and around Medicine Lake Volcano. These materials are generally highly permeable, but may not be saturated at high elevations.

Quaternary to late Tertiary sedimentary rocks

QTs

Fine- to coarse-grained unconsolidated to moderately indurated sedimentary deposits. The hydraulic characteristics of this unit are not well known but lithologic descriptions on maps suggest it may be moderately permeable at some locations. This unit has very limited distribution.

Late Tertiary sedimentary rocks

Predominately fine-grained continental sedimentary deposits including bedded diatomite, mudstone, siltstone, and sandstone. This unit has generally low permeability but contains permeable strata at some locations.

Late Tertiary volcaniclastic rocks

Tvpt

Palagonitized basaltic ash and lapilli deposits associated with eruptive centers. The hydrologic characteristics of this unit are not well known, but springs are known to emerge from basal contact with unit Ts. This unit is most prominent in the Sprague River valley.

Late Tertiary volcanic rocks

Predominantly basaltic and andesitic lava flows and vent deposits with lesser amounts of silicic domes and flows. This unit has moderate to high permeability and is by far the most widely developed aquifer unit in the study area. Permeability is locally diminished by hydrothermal alteration and secondary mineralization.

Older Tertiary volcanic and sedimentary rocks

Tovs

Miocene and older volcanic and volcaniclastic deposits. The permeability of this unit is generally low due to weathering, hydrothermal alteration, and secondary mineralization. This unit is generally considered a boundary to the regional ground-water system of the upper Klamath Basin.

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