Paleoseismic patterns of Quaternary tectonic and magmatic surface deformation in the eastern Basin and Range, USA

Abstract

The competing contributions of tectonic and magmatic processes in accommodating continental extension are commonly obscured by a lack of on-fault paleoseismic information. This is especially true of the Sevier Desert, located at the eastern margin of the Basin and Range in central Utah (USA), where surface-rupturing faults are spatially associated with both regional detachment faults and Quaternary volcanism. Here, we use high-resolution topographic surveys (terrestrial lidar scans and real-time kinematic GPS), terrestrial cosmogenic nuclide (10Be and 3He) exposure dating, 40Ar/39Ar geochronology, and new neotectonic mapping to distinguish between modes of faulting and extension in a transect across the Sevier Desert. In the western Sevier Desert, the House Range and Cricket Mountains faults each have evidence of a single surface-rupturing earthquake in the last 20–30 k.y. and have time-integrated slip and extension rates of <0.1 and ∼0.05 mm yr−1, respectively, since ca. 15–30 ka. These rates are similar to near-negligible modern geodetic extension estimates. Despite relatively low geologic, paleoseismic, and modern extension rates, both faults show evidence of contributing to the long-term growth of topographic relief and the structural development of the region. In the eastern Sevier Desert, the intrabasin Tabernacle, Pavant, and Deseret fault systems show markedly different surface expressions and behavior from the range-bounding normal faults farther west. Pleistocene to Holocene extension rates on faults in the eastern Sevier Desert are >10× higher than those on their western counterparts. Faults here are co-located with Late Pleistocene to Holocene volcanic centers, have events temporally clustered around the timing of Pleistocene volcanism in at least one instance, and have accommodated extension ∼2×–10× above geodetic and long-term geologic rates. We propose a model whereby Pliocene to recent extension in the Sevier Desert is spatially partitioned into an eastern magma-assisted rifting domain, characterized by transient episodes of higher extension rates during volcanism, and a western tectonic-dominated domain, characterized by slower-paced faulting in the Cricket Mountains and House Range and more typical of the “Basin and Range style” that continues westward into Nevada. The Sevier Desert, with near-complete exposure and the opportunity to utilize a range of geophysical instrumentation, provides a globally significant laboratory for understanding the different modes of faulting in regions of continental extension.

Diffuse Tectonic Deformation in the Drum Mountains Fault Zone, Utah, USA: Testing the Utility of Legacy Aerial Photograph-Derived Topography

“…Near the southern terminus of the Wasatch fault, within the Sevier Desert of central Utah (Figure 1), the spatial distribution of extension becomes more complex. An array of range-bounding and intrabasin normal faults with <1 mm yr −1 slip rates contribute to the extensional budget in this region, in addition to a minor contribution from local magmatism (Stahl and Niemi, 2017;Stahl et al, 2020). The Sevier Desert has been seismically quiescent over the last c. 150 years with no > M4 earthquakes and few other instrumentally recorded events (Pankow et al, 2020).…”

“…The third model proposes that late Pleistocene and Holocene faulting in the eastern Sevier Desert is associated with coeval volcanism, subsidence, and dike-injection (Wannamaker et al, 2008;Stahl and Niemi, 2017;Stahl et al, 2020). This model was put forward on the basis of (i) spatial coincidence of faults with volcanic centers, highheat flow, and near-vertical low resistivity anomalies that extend to depths below the Sevier Desert detachment; (ii) temporal coincidence of some faulting events with the volcanism; (iii) surface expression of faulting and far-field displacements consistent with dike-induced faulting; and (iv) adequate elastic dislocation model fit to GPS velocities with a purely tensile dislocation located at the zone of recent volcanism (Stahl and Niemi, 2017).…”

“…The Wasatch fault zone accommodates the majority of the c. 4 mm yr −1 westward motion of the Basin and Range relative to the Colorado Plateau from continuous GPS measurements. Extension rates of Quaternary faults near Delta, Utah, are <1 mm yr −1 and < 0.1 mm yr −1 to the west in the House Range (HR) (Stahl et al, 2020). Seismic lines of Allmendinger et al (1983) and Crone and Harding (1984), referred to in text, are shown as "Line U1" and "CH", respectively.…”

“…Shoreline features such as wave cut benches and depositional gravel bars, the most prominent of which formed during the Bonneville (c. 18.5 ka) and Provo (c. 15-18.5) highstands (Oviatt, 2015), are present around the Sevier Desert. The Bonneville and Provo shoreline elevations, formed during highstands of the same name, represent originally horizontal datums that have been deformed by isostatic rebound, faulting, volcanism, and/or other mechanisms of local subsidence (Currey, 1983;Chen and Maloof, 2017;Stahl et al, 2020). Between these two shorelines, more subtle depositional shorelines mark the rise of Lake Bonneville between about 30 and 20 ka (e.g., Oviatt, 2015).…”

Unusual Seismic Signals in the Sevier Desert, Utah Possibly Related to the Black Rock Volcanic Field

“…In addition to volcanism, it is possible that a low angle normal fault is located beneath the Sevier Desert (Allmendinger, 1983; Coogan & DeCelles, 1996; Yuan et al., 2018). Faults local to the Black Rock volcanic field (Figure 1b) are spatially coincident with volcanic edifices, are typically short (<5 km) in length, and show fault‐normal motion (Stahl et al., 2019). Understanding how the Basin and Range accommodates and partitions extension is a key question in modeling continental dynamics (Colgan et al., 2006).…”