Surface motions and intraplate continental deformation in Alaska driven by mantle flow

Abstract

The degree to which the lithosphere and mantle are coupled and contribute to surface deformation beneath continental regions remains a fundamental question in the field of geodynamics. Here we use a new approach with a surface deformation field constrained by GPS, geologic, and seismicity data, together with a lithospheric geodynamic model, to solve for tractions inferred to be generated by mantle convection that (1) drive extension within interior Alaska generating southward directed surface motions toward the southern convergent plate boundary, (2) result in accommodation of the relative motions between the Pacific and North America in a comparatively small zone near the plate boundary, and (3) generate the observed convergence within the North American plate interior in the Mackenzie mountains in northwestern Canada. The evidence for deeper mantle influence on surface deformation beneath a continental region suggests that this mechanism may be an important contributing driver to continental plate assemblage and breakup.

The August 2018 Kaktovik Earthquakes: Active Tectonics in Northeastern Alaska Revealed With InSAR and Seismology

“…The Brooks Range (Figure a) is underlain by a thick crustal root where the Moho is mapped to depths of 50 km (compared to 30–35 km in central Alaska) and the lithosphere is up to 200 km thick (Fuis et al, ; Jiang et al, ; Miller et al, ; O’Driscoll & Miller, ; Ward and Lin, ). Mantle flow or northward motion of the Yakutat indentor are thought to be driving current tectonic activity (Finzel et al, ; Mazzotti & Hyndman, ; Mazzotti et al, ). According to moment tensor solutions, the northeastern Brooks Range is currently dominated by a transtensional tectonic regime, in contrast to transpression south of the Brooks Range, where the lithosphere is weaker and deforming at a faster rate (Jiang et al, ; Leonard et al, ; O’Driscoll & Miller, ).…”

“…Despite widespread seismicity in Arctic Alaska, few active faults are mapped, and currently published GPS velocities are sparse (Snay et al, 2016). The current tectonic setting is equivocal (Finzel et al, 2015;Fuis et al, 2008;Haeussler, 2008;Koehler, 2013;Leonard et al, 2008;Mazzotti et al, 2008), but a relatively recent increase in seismic and geodetic data available from this area, with the deployment of the USArray in Alaska since 2014 and launch of the Sentinel-1 satellite pair in 2014 and 2016, permit a more detailed characterization of active tectonics in the Brooks Range.…”

Late Cretaceous‐Cenozoic Exhumation of the Western Brooks Range, Alaska, Revealed From Apatite and Zircon Fission Track Data

“…In Alaska, the zone of active deformation extends to the northern continental margin, and the width of the deforming zone was likely similarly vast throughout the Cenozoic (e.g., Blythe et al, 1996;Dinter, 1985;Moore & Box, 2016;O'Sullivan et al, 1997, and references therein). Numerous tectonic models have been proposed to account for both the modern (e.g., Finzel et al, 2014Finzel et al, , 2015Redfield et al, 2007) and the Cenozoic (e.g., Coe et al, 1989;Dumitru et al, 1995;Fuis et al, 2008) strain patterns. Elements of these models could be evaluated with better documentation of the Cenozoic kinematic history of the Alaskan interior.…”

Architecture of the crust and uppermost mantle in the northern Canadian Cordillera from receiver functions

“…In contrast with the orogenic float, Finzel et al . [, , ] propose an alternative tectonic model based on the net surface deformation produced by a combination of buoyancy forces due to gravitational potential energy, boundary forces from relative plate motions, and basal tractions caused by mantle flow. Their results suggest that present‐day deformation of the external domains (central, northern, and western parts of the Cordillera) result from a regional southward mantle flow deflected eastward into the northern Canadian Cordillera, with a flow rate decreasing toward the Cordilleran Deformation Front.…”

“…However, there are currently few constraints on seismic anisotropy of the crust in the northern Canadian Cordillera [e.g., Rasendra et al, 2014]. In addition, characterization of the anisotropy in the uppermost mantle beneath the Cordillera may help discriminate between small-scale convection, proposed as a mechanism for the orogenic float elevated geotherm [Currie and Hyndman, 2006], and large-scale mantle flow, resulting in crustal deformation [Finzel et al, 2015] and elevated geotherm at the edge of the craton [e.g., Bao et al, 2014].…”