Enhanced fracture permeability and accompanying fluid flow in the footwall of a normal fault: The Hurricane fault at Pah Tempe hot springs, Washington County, Utah
Stephen T. Nelson et al., Department of Geological Sciences, Brigham Young University, S-389 ESC, Provo, Utah 84602, USA. Pages 236-246.
The Pah Tempe hot springs near Hurricane, Utah, release large quantities of warm, CO2-laden water directly into the Virgin River. Geochemical analysis by Nelson et al. of these waters reveals several important features. First, they have circulated to great depths (more than 3 miles) and entered the subsurface anciently under colder climate conditions. This long and deep circulation has been enabled by fractures associated with the Hurricane Fault, a major active structure near the western margin of the Colorado Plateau. CO2 gas quantities released are quite large, including trains of CO2 bubbles rising through the Virgin River. However, the large majority of CO2 is released to the surface in the dissolved state, predominantly as carbonic acid and bicarbonate.
The paradox of minibasin subsidence into salt: Clues to the evolution of crustal basins
Michael R. Hudec et al., Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, University Station, Box X, Austin, Texas 78713-8924, USA. Pages 201-221.
Subsidence of sedimentary minibasins into salt is paradoxical, in that subsidence begins while minibasin fill is less dense than the fluid salt substrate. How can a light minibasin sink into a dense fluid? Hudec et al. identify five mechanisms to explain this anomalous subsidence, which are functions of tectonic environment, regional bathymetry, and sedimentation rate. Subsidence mechanisms control minibasin bathymetry, which
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