Alternating asymmetric topography of the Alaska range along the strike‐slip Denali fault: Strain partitioning and lithospheric control across a terrane suture zone

Abstract

Contrasting lithospheric strength between terranes often results in the concentration of strain and deformation within the weaker material. Dramatic alternating asymmetric topography of the central and eastern Alaska Range along the active Denali fault is due to contrasting lithospheric strength between terranes and a suture zone, controlled by fault location with respect to the irregular boundary of a relatively stronger terrane backstop. Highest topography and greatest Neogene exhumation in the central Alaska Range occur on the concave side of the arcuate Denali fault, yet to the north and on the convex side of the fault in the eastern Alaska Range. The Denali fault largely lies along a Mesozoic suture zone between two large composite terranes (Yukon and Wrangellia composite terranes: YCT and WCT), but the McKinley strand of the fault cuts across an embayment of weaker suture-zone rocks (Alaska Range suture-zone, ARSZ) within the irregular southern boundary of the YCT (Hines Creek fault). Deformation (and uplift of the Alaska Range) is driven by slip and partitioning of strain along the Denali fault, occurring preferentially in weaker rocks of the ARSZ against the stronger YCT. Where the YCT lies well north of the McKinley strand, deformation is primarily to the north of the fault (eastern Alaska Range). Where the YCT is close to the fault, deformation is primarily to the south (central Alaska Range). While the trace of the McKinley strand approximates a small circle, two restraining bends (McKinley and Hayes) pinned equidistant from the ends of this strand localize uplift and exhumation.

Slip partitioning along a continuously curved fault: Quaternary geologic controls on Denali fault system slip partitioning, growth of the Alaska Range, and the tectonics of south-central Alaska

“…For one, horizontal variations in lithospheric strength are likely on October 7, 2015 lithosphere.gsapubs.org Downloaded from what localizes the trace of the Denali fault due to the contrast between the relatively strong Southern Alaska block and the crustal-scale weakness associated with the Alaska Range suture zone to the north. Furthermore, Fitzgerald et al (2014) argued that significant contrasts in lithospheric strength in the Alaska Range allowed for the formation of asymmetric topography across the Denali fault. These strength contrasts potentially have multiple effects in both localizing the development of zones of high exhumation and extreme topography within the Alaska Range orogeny, as well as essentially dictating the side of the Denali fault on which the axis of deformation will occur.…”

“…The correspondence of topography and active faults in the Alaska Range ( Fig. 3) was established during the Quaternary and is viewed as a response to flat-slab subduction processes (Finzel et al, 2011b), local structural conditions of the Denali fault (Benowitz et al, 2011), and inherited crustal structures (Fitzgerald et al, 2014). Early low-temperature thermochronologic data in conjunction with the onset of widespread deposition of a coarse-grained foreland basin sequence on the north side of the Alaska Range have been interpreted to represent an orogen-wide pulse of exhumation at ca.…”

“…2; Fitzgerald et al, 2014). This topography is bounded on the north by a relatively continuous, abrupt range-front escarpment that separates the Alaska Range from the Tanana Basin ( Fig.…”

A new Triassic shortening-extrusion tectonic model for Central-Eastern Asia: Structural, geochronological and paleomagnetic investigations in the Xilamulun Fault (North China)

“…Consequently, the conjugate E-W trending dextral strike-slip faults and the NNE trending sinistral strike-slip faults may have resulted in the clockwise rotations of the parallelogram-shaped blocks between these faults (Fig. 8a), like the book-shelf-style or domino mechanism, which has been observed in numerous strike-slip fault zones, such as in the northern and southern Tibet (Armijo et al, 1989;England and Molnar, 1990), the Zagros belt (Mattei et al, 2012;Isik et al, 2014), and the Alaska range (Cole et al, 1999;Fitzgerald et al, 2013).…”

“…The procedures for isotope analyses and age calculations were controlled by MassSpec software. The parameters used for analyses and testing procedures can be found in Gong et al (2012).…”