The Quaternary thrust system of the northern Alaska Range

Bemis, Sean P.; Carver, Gary A.; Koehler, Richard

doi:10.1130/ges00695.1

Cited by 40 publications

(36 citation statements)

References 23 publications

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“…More recently, studies have documented the association of Quaternary-active thrust faults with the abrupt range front of the Alaska Range, and additional active faults lying within the foothills south of the range front (Bemis and Wallace, 2007;Carver et al, 2008Carver et al, , 2010. Bemis et al (2012) synthesized the record of Quaternary faulting in the northern Alaska Range and expanded the previously defined "northern foothills fold-thrust belt" (Bemis and Wallace, 2007) into the northern Alaska Range thrust system (Fig. 2).…”

Section: Quaternary Faults Of the Alaska Rangementioning

confidence: 99%

“…Along the length of this thrust system, there are four regions that have different structural styles, but in general, each region is dominated by basement-involved thrust faults, has clearly defined late Quaternary faults or folds associated with the northern topographic range front, and contains active faults that are predominantly parallel with the adjacent section of the Denali fault ( Fig. 3; Bemis et al, 2012).…”

Section: Quaternary Faults Of the Alaska Rangementioning

confidence: 99%

“…The structural style for this portion of the thrust system is characterized by left-stepping thrust fault segments connected by NE-trending strike-slip faults. These strike-slip faults do not extend significantly beyond the thrust faults to which they connect, and thus they appear to be tear faults within the larger thrust sheet (Bemis et al, 2012). Carver et al (2008) determined the slip rate for one of these NE-trending faults, the Canteen fault, based upon offsets of late Pleistocene moraines (Table 2; Fig.…”

Section: Quaternary Faults Of the Alaska Rangementioning

confidence: 99%

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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

2015

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Active transpressional fault systems are typically associated with the development of broad zones of deformation and topographic development; however, the complex geometries typically associated with these systems often make it difficult to isolate the important boundary conditions that control transpressional orogenic growth. The Denali fault system is widely recognized as transpressional due to the presence of the Denali fault, a major, active, right-lateral fault, and subparallel zones of thrust faults and fault-related folding along both the north and south flanks of the Alaska Range. Measured Quaternary and Holocene slip rates exist for the Denali fault system and portions of the adjacent thrust system, but the partitioning of fault slip between contractional and translational components of this transpressional system has not been previously studied in detail. Exploiting the relatively simple geometry of the Denali fault, we analyze the style and distribution of active faulting within the Alaska Range to define patterns of strain accommodation and determine how contractional and translational strain is partitioned across the Denali fault system. As the trace of the Denali fault curves by ~70° across central Alaska, the mean strike of the thrust system to the north remains subparallel to the Denali fault, while to the south, the few faults with known or suspected Quaternary offset are oblique to the Denali fault. This relationship suggests that as the Denali fault system accommodates local fault-parallel strike slip, it partitions the residual part of the regional NW-directed plate motion into NW-SE shortening south of the Denali fault and shortening perpendicular to the Denali fault to the north. The degree of slip partitioning is consistent with a balanced slip budget for the two primary faults that contribute displacement to the Denali fault system (the eastern Denali fault and Totschunda fault). The current obliquity of displacement south of the Denali fault is the result of the late Cenozoic development of the Totschunda fault, which provides a more direct connection for the transfer of strain from the Fairweather transform fault to the Denali fault system. The transmitted strain is partitioned into right-lateral slip on the Denali fault and into Denali fault-normal shortening that is accommodated by thrust faulting in the Alaska Range and distributed left-lateral slip faulting within interior Alaska to the north.

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Section: Quaternary Faults Of the Alaska Rangementioning

confidence: 99%

Section: Quaternary Faults Of the Alaska Rangementioning

confidence: 99%

Section: Quaternary Faults Of the Alaska Rangementioning

confidence: 99%

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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

2015

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“…Oblique underthrusting of the northern edge of the WCT in the late Cretaceous (Nokleberg et al, 1985) gave way to predominantly right-lateral motion in the Paleocene (Plafker et al, 1994). Slip rates peaked in the Holocene at approximately 15mm/yr, after which the slip has been consistent at the current rate of 10mm/yr (Matmon et al, 2006;Biggs et al, 2007;Freymueller et al, 2008;Bemis et al, 2012). Total horizontal displacement estimates range from 200km (e.g., Brogan et al, 1975) to 400km (e.g., Nokleberg et al, 1985).…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…Recent studies reveal some near-vertical offsets but no lateral offsets along the Hines Creek fault (Bemis et al, 2012;Bemis et al, 2015); the structure was considered for but omitted from the active fault map for Alaska . Active-source seismic and other combined geophysical methods used in the TACT (Trans-Alaskan Crustal Transect) deployment 150km to the east, near the junction of the Denali and Hines Creek faults, suggested a more gradual change in Moho depth north of the fault (Brocher et al, 2004;Fuis et al, 2008).…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Ten kilometer vertical Moho offset and shallow velocity contrast along the Denali fault zone from double-difference tomography, receiver functions, and fault zone head waves

et al. 2017

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Please cite this article as: A.A. Allam, V. Schulte-Pelkum, Y. Ben-Zion, C. Tape, N. Ruppert, Z.E. Ross , Ten kilometer vertical Moho offset and shallow velocity contrast along the Denali fault zone from double-difference tomography, receiver functions, and fault zone head waves, Tectonophysics (2017Tectonophysics ( ), doi: 10.1016Tectonophysics ( /j.tecto.2017 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.A C C E P T E D M A N U S C R I P T AbstractWe examine the structure of the Denali fault system in the crust and upper mantle using double-difference tomography, P-wave receiver functions, and analysis (spatial distribution and moveout) of fault zone head waves. The three methods have complementary sensitivity; tomography is sensitive to 3D seismic velocity structure but smooths sharp boundaries, receiver functions are sensitive to (quasi) horizontal interfaces, and fault zone head waves are sensitive to (quasi) vertical interfaces. The results indicate that the Mohorovičić discontinuity is vertically offset by 10 to 15km along the central 600km of the Denali fault in the imaged region, with the northern side having shallower Moho depths around 30km. An automated phase picker algorithm is used to identify ~1400 events that generate fault zone head waves only at near-fault stations.At shorter hypocentral distances head waves are observed at stations on the northern side of the fault, while longer propagation distances and deeper events produce head waves on the southern side. These results suggest a reversal of the velocity contrast polarity with depth, which we confirm by computing average 1D velocity models separately north and south of the fault. Using teleseismic events with M>=5.1, we obtain 31,400 P receiver functions and apply common- km to the north. To the east, this offset follows the Totschunda fault, which ruptured during the M7.9 2002 earthquake, rather than the Denali fault itself. The combined results suggest that the Denali fault zone separates two distinct crustal blocks, and that the Totschunda and Hines Creeks segments are important components of the fault and Cretaceous-aged suture zone structure.

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

et al. 2014

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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.

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The Quaternary thrust system of the northern Alaska Range

Cited by 40 publications

References 23 publications

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

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

Ten kilometer vertical Moho offset and shallow velocity contrast along the Denali fault zone from double-difference tomography, receiver functions, and fault zone head waves

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

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