Lithostratigraphy and Permeability of Neogene Deltaic, Lacustrine and Fluvial Sediments Along the Northwestern Margin of the Western Snake River Plain, Emmett and Boise, Idaho

Publication Date

7-2000

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Geology

Department

Geosciences

Supervisory Committee Chair

Tamra Schiappa

Abstract

Neogene fluvial, deltaic and lacustrine sediments are found along the northeastern margin of the Western Snake River Plain (WSRP) and are used as outcrop analogs to the down-faulted sediments below the Boise Valley. Sequence stratigraphy determined that the arkosic sediments In the Boise Foothills were deposited during a transgressive phase of Pliocene Lake Idaho. Lacustrine sediment gravity flow and deltaic foreset sediment deposits underlain and overlain by Donjek type braided stream sediments are recognized at Freezeout Hill, Emmett and delta foreset beds separated by lacustrine sediment gravity flow deposits were found at Military Reserve, Boise, Idaho. Detailed stratigraphy showed that the sediments exhibit characteristic facies with unique hydraulic conductivity values. The, hydraulic conductivity values were determined using an air mini-permeameter (AMP). The use of the AMP has shown that lithostratigraphic facies have specific hydraulic permeabilities, signifying that aerial expressions of subsurface aquifers can be studied to help characterize ground water flow parameters. These parameters will be useful in the further understanding contaminant plume behavior and water yield of the aquifers. Permeability of the sediments range from a high 1.4X10-3 meters/second in the pebble sand facies to a low of 9.2X104 m/s in the silt facies. The detailed facies analysis and lithostratigraphy of the sediments outcropping along the Boise Front in conjunction with calculated hydraulic conductivity values provides more information toward the development of a better understanding of the depositional system and aquifer parameters in the Boise Valley.

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