By: C. G. Oviatt, D. Sack, and T. J. Felger
Quaternary deposits were mapped at a scale of 1 :62,500 in an area of west-central Utah encompassed by nine 7.5-minute quadrangles. The area contains the threshold between the Sevier Lake basin and the Great Salt Lake basin, over which water flowed northward during Pleistocene episodes of high lake levels in the Sevier basin. Much of the Old River Bed, an abandoned river valley that fonned during the most recent episode of overflow, is within the map area. Lake Bonneville deposits first studied by G. K. Gilbert are well exposed along the Old River Bed. Quaternary deposits in the map area include alluvium in fans, channels, and floodplains; eolian deposits; Lake Bonneville marl, fine-clastic deposits, and gravel; pre-Bonneville lacustrine deposits; playa deposits, spring deposits; and basaltic lava flows. The Sevier Desert detachment fault underlies the map area and probably controls the locations and activities of Quaternary faults in near-surface deposits. The youngest faults in the map area cut deposits of late Pleistocene and Holocene age. The Old River Bed area contains an excellent stratigraphic record of Lake Bonneville, including fine-scale details of the lake history in the offshore marl deposits, and sediments de-posited near the lake's highest level that help demonstrate the timing of a major oscillation of the lake prior to the initiation of overflow.
The purpose of this report is to describe the Quaternary geology and Quaternary geologic history of the northern part of the Sevier Desert. This report extends the Quaternary mapping of Oviatt northward to and beyond the overflow threshold of the Sevier Lake basin.
Pages: 24 p.
Plates: 1 pl.
Location: Juab County, Millard County, and Tooele County
Media Type: Paper Map