Western Snake River Plain, Idaho, Fluvial-Lacustrine Sediments: Exhumation Estimates from Mudstone Compaction, Unconformity Identification by Buried Soil Carbonate, Hydraulic Conductivity Estimates from Well Cuttings

Publication Date


Type of Culminating Activity


Degree Title

Master of Science in Geology



Major Advisor

Spencer Wood


Selected density and sonic-porosity data of mudstones from six deep wells in the western Snake River Plain are compared to a normal compaction trend using the Magara (1976a) method for estimating exhumation. A normal trend is best represented by data from the Anschutz Federal # 1 well west of Grandview, Idaho (SW¼ SW¼, sec. 13, T., 2 N., R., 3 E.). The interval between 1,000 and 2,200 feet appears normally compacted with respect to other wells in the basin. Other wells appear over-compacted with respect to their current burial depths and are compared to this normal compaction curve. Estimates of exhumed overburden range between 200 feet to 1,600 feet.

A carbonate layer found in the recently drilled City of Boise geothermal re-injection well located in Julia Davis park Boise is interpreted as a caleche layer based on carbon-13 isotope analysis. The carbon-13 isotope analysis indicates the carbonate coatings on pebbles is derived from soil water and not groundwater or lake water. Seismic profile data is interpreted in light of this new data depicting a time when lake level dropped allowing for vegetation to flourish.

Transmissivity values for the Micron No.4 well located in Boise, Idaho (sec. 7 NE ¼, SW ¼, T. 2 N., R. 3 E.) determined from hydraulic testing are compared to hydraulic conductivity estimates from empirical formulas, and permeameter tests. Constant rate pump test data calculates a transmissivity value of 34,000 g/d/ft2. Hydraulic conductivity values from Terzaghi, Kozeny, and Hazen-type equations estimate aquifer transmissivities between 900 and 818,650 g/d/ft2 for the cumulative screened section in the well.

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