Anatomy of the southern Cordilleran hingeline, Utah and Nevada, from deep electrical resistivity profiling
- Univ. of Utah, Salt Lake City, UT (United States). Energy and Geoscience Inst.
- Johnston (Jeffery M.), Berkeley, CA (United States)
- Univ. of Washington, Seattle, WA (United States). Dept. of Geophysics
To address outstanding questions in Mesozoic-Cenozoic structure and present-day deep physicochemical state in the region of the southern Cordilleran hingeline, a detailed, east-west profile of magnetotelluric (MT) soundings 155 km in length was acquired. From these soundings, a resistivity interpretation was produced using an inversion algorithm based on a structural parameterization. In the upper ten kilometers of the transect, the interpretation shows two segments of low resistivity lying beneath allochthonous rocks of the Late Mesozoic, Sevier thrust sheet. Subsequent industry drilling motivated in part by this surveying confirms the existence and position of the eastern subthrust conductor and, more spectacularly, identifies the presence of yet deeper, autochthonous Mesozoic rocks. A simple structural interpretation is offered where one underthrust segment of low-resistivity sediments was created originally, but this segment was broken later into two major ones during higher-angle Tertiary extension. For the middle and lower crust, the MT data imply a nearly 1-D resistivity structure of remarkable uniformity across the entire transect. Pre-existing structural fabrics have had no measurable influence on localizing regions of high temperature fluids and melting in the lower crust, at least averaged over the scale of tens of kilometers. Given its uniformity over a distance of 155 km or more, the depth to the regional deep conductor does not appear related to the distribution of high-temperature geothermal resources.
- Sponsoring Organization:
- National Science Foundation, Washington, DC (United States); USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC07-90ID12929; AC07-95ID13274
- OSTI ID:
- 533069
- Journal Information:
- Geophysics, Vol. 62, Issue 4; Other Information: PBD: Jul-Aug 1997
- Country of Publication:
- United States
- Language:
- English
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