Tertiary Normal Faulting in the Canyon Range, Eastern Sevier Desert.

Area of Science:

• Structural geology
• Tectonic geomorphology
• Sedimentary geology

Background:

• The western Canyon Range contact was previously interpreted as a low-angle normal fault associated with the Sevier Desert detachment.
• This fault was hypothesized to be the breakaway zone for basin formation.

Purpose of the Study:

• To re-evaluate the nature of the contact between pre-Mesozoic and Tertiary rocks in the western Canyon Range.
• To investigate the tectonic history of the Sevier Desert basin and its bounding structures.

Main Methods:

• Detailed geological fieldwork and mapping in the western Canyon Range.
• Analysis of deformational fabrics and kinematic indicators.
• Reinterpretation of Tertiary conglomerate and gravity-slide deposit stratigraphy.
• Review of local seismic-reflection data.

Main Results:

• The contact is reinterpreted as largely depositional, not a major detachment fault.
• Deformational fabrics in the footwall are attributed to the Mesozoic Sevier orogeny.
• Kinematic indicators and dominant high-angle faults suggest block faulting and rotation, not low-angle normal faulting.
• Tertiary conglomerates are reclassified into three distinct units reflecting varied tectonic settings.

Conclusions:

• The Sevier Desert detachment hypothesis may not accurately represent the basin's evolution.
• High-angle faulting and block rotation are the dominant structural styles in the region.
• Alternative hypotheses for Sevier Desert basin evolution are warranted, potentially involving multiple fault generations.