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<br />~ <br />",'.,'t <br />t.., <br /> <br />Gosiute, within this intermontane basin. Fluctuations in the size of <br />the lake resulted in the intertonguing of the Green River Formation with <br />the Wasatch and Bridger Formations (see Figure 2-2). <br /> <br />During deposition of the Green River Formation, the climate fluctuated <br />from humid to arid and back to humid again. During the arid time, the <br />lake was much smaller and did not have an outlet which resulted in <br />saline conditions. The Wilkins Peak Member is a thick sequence of <br />carbonates with numerous occurrences of trona and saline evaporite <br />deposits. As the climate got more humid, fresh water conditions again <br />prevailed. Lake Gosiute reached its maximum size at that time and the <br />thick shale deposits of the Laney Member were deposited. <br /> <br />As sediments filled Lake Gosiute, fluvial deposits of the Bridger <br />Formation covered the Green River Formation. The environment during <br />deposition of the Bridger was such that gypsum and salt were deposited <br />in the contact zone with the Wilkins Peak Member of the Green River <br />Formation. <br /> <br />~' ~~ <br /> <br />Excessive irrigation from the project area results in deep <br />percolation in the contact zone of the Bridger and Wilkins Peak around <br />the margins of the prehistoric lake. This allows ground water recharge <br />that can not only interact with the salts in the Bridger Formation, but <br />can reach and interact with the saline facies in the Wilkins Peak <br />Member. This interaction can result in high salt loading to the <br />underground aquifer. The saline aquifer water is discharged into the <br />Big Sandy River via seeps, springs, and uncapped wells between the <br />irrigation project area and Gasson Bridge stream gauging station. <br /> <br />~~ <br />~:~ <br /> <br />Soils <br /> <br />A detailed soil survey was conducted on the original USBR withdrawal <br />area of the Eden Valley Irrigation Project during the early 1950's. <br />Detailed surveys were again completed on most of the deeded lands in the <br />1960's, which were revised and the area completely soils mapped during <br />1982-84. A soil survey publication of lands within the boundaries of <br />the Eden Valley Irrigation and Drainage District is at present in the <br />process of being published. A very general soils investigation of the <br />entire Big Sandy watershed was conducted during 1975-76 cooperatively by <br />the BLM and the SCS. <br /> <br />Discussion of soils in this report is limited to the Eden Valley <br />irrigation area. A General Soils Map with brief descriptions can be <br />found in Figure 2-3. <br /> <br />Most of the irrigated soils are alluvial deposits of sandy loams over <br />coarse sands or gravelly sands underlain by shale at depths mostly over <br />5 feet. Soils with shale at moderate depths occur in some areas. Small <br />areas of wind deposited sand dune soils and heavy clay soils also occur. <br />Also, soils shallow to shale bedrock occur in the surrounding uplands. <br /> <br />2~ <br />~-; <br /> <br />2-11 <br /> <br />~. 1 ~ , 3 <br />l> I ' " <br />J... J...J <br /> <br />t,-',< <br />