Upper Triassic continental margin strata of the central Alaska Range: Implications for paleogeographic reconstruction

Till, Alison B.; Harris, Anita G.; Wardlaw, Bruce R.; Müllen, Michael W.

doi:10.1130/2007.2431(08)

Cited by 4 publications

(16 citation statements)

References 13 publications

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“…Radiogenic 87 Sr/ 86 Sr ratios (N 0.725) in far east-central AK and relatively low ratios (b 0.709) in western AK reflect AK's progressive western growth along the ancestral North American miogeocline from the Precambrian to Mesozoic (Fig. 7) (Nelson et al, 2006;Colpron et al, 2007;Till et al, 2007;Trop and Ridgeway, 2007). Meybeck (1986): mafic silicates Ca/Sr = 167 mmol/mmol, felsic silicates Ca/Sr = 200 mmol/mmol, and pure carbonates Ca/Sr = 1428 mmol/mmol.…”

Section: Discussionmentioning

confidence: 99%

Strontium isotope variation and carbonate versus silicate weathering in rivers from across Alaska: Implications for provenance studies

et al. 2014

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Section: Discussionmentioning

confidence: 99%

Strontium isotope variation and carbonate versus silicate weathering in rivers from across Alaska: Implications for provenance studies

et al. 2014

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“…Upper Triassic marine slope and basinal strata are discontinuously exposed throughout the central and eastern Alaska Range on both sides of the Denali fault (Wilson et al, 2015). Similar Upper Triassic marine siliciclastic strata are exposed within klippen of weakly metamorphosed oceanic strata assigned to the Seventymile/Slide Mountain terrane in the Yukon-Tanana uplands and southwestern Yukon ( Csejtey et al (1986), Decker et al (1994), Hansen and Dusel-Bacon (1998), Dusel-Bacon and Harris (2001), Bradley et al (2003), Murphy et al (2006), Hampton et al (2007), Till et al (2007), Beranek, Mortensen, Orchard et al (2010), Malkowski and Hampton (2014), . Geologic time scale of Walker et al (2018).…”

Section: Coeval Stratigraphy In South-central and Eastern Alaska Southern Yukon And Northern British Columbiamentioning

confidence: 94%

“…These assemblages were first defined by initial geologic mapping studies in the central Alaska Range including areas east of the Nenana River in the Wood River drainage (e.g., Bultman, 1972; Hickman, 1974; Sherwood, 1973, 1979; Wahrhaftig, 1970a, 1970b, 1970c). These rocks have been interpreted to represent fault‐bounded slivers of the ancestral North American/Laurentian margin (e.g., Csejtey et al., 1992; Sherwood & Craddock, 1979; Till et al., 2007), and also comprise parts of the Yukon‐Tanana terrane of Foster et al. (1994).…”

Section: Geologic Backgroundmentioning

confidence: 99%

“…Similar Upper Triassic marine siliciclastic strata are exposed within klippen of weakly metamorphosed oceanic strata assigned to the Seventymile/Slide Mountain terrane in the Yukon‐Tanana uplands and southwestern Yukon (Figures 1 and 3; e.g., Dusel‐Bacon & Harris, 2001; Hansen & Dusel‐Bacon, 1998). Both Upper Triassic stratigraphic assemblages yield Carnian‐Norian conodonts and megafossils that suggest a shared depositional setting in a marine basin (Csejtey et al., 1986; Dusel‐Bacon & Harris, 2001; Sherwood & Craddock, 1979; Till et al., 2007; Umhoefer, 1984).…”

Section: Geologic Backgroundmentioning

confidence: 99%

“…Regional Permo-Triassic stratigraphic assemblages in the western Alaska Range, southern central Alaska Range/Talkeetna Mountains, central Alaska Range (this study), Yukon-Tanana Uplands/southwest Yukon, and southeast Yukon. Stratigraphic information and age ranges were synthesized from Csejtey et al (1986), Decker et al (1994), Hansen and Dusel-Bacon (1998), Dusel-Bacon and Harris (2001), Bradley et al (2003), Murphy et al (2006), Hampton et al (2007),Till et al (2007), Beranek, Mortensen, Orchard et al (2010,Malkowski andHampton (2014), and. Geologic time scale ofWalker et al (2018).…”

mentioning

confidence: 99%

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Tectonic Growth of the Late Paleozoic‐Middle Mesozoic Northwestern Margin of Laurentia and Implications for the Farewell Terrane: Stratigraphic, Structural, and Provenance Records From the Central Alaska Range

Keough

Ridgway

2021

Tectonics

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Suture Reactivation, Slip Partitioning, and a Protracted Strike‐Slip Rate Gradient in the Denali Fault System, Southern Alaska, USA

Waldien,

Roeske,

Chatterjee

et al. 2023

Tectonics

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Active strike‐slip fault systems commonly display along‐strike Quaternary slip rate gradients associated with fault bends and splay faults, which generate surface uplift by dip‐slip faulting or distributed “off fault” deformation. By analogy, the documentation of long‐term (107 yr) slip gradients on some continental strike‐slip fault systems implies long‐term coevolution of strike‐slip and dip‐slip fault systems. Here we leverage the observed ≥33 Myr right‐lateral slip gradient on the Denali fault, Alaska, USA to investigate the role of splay thrust systems in accommodating the slip gradient. We focus on the Broxson Gulch thrust system, which splays southwestward from the Denali fault in the eastern Alaska Range. Apatite and zircon (U‐Th)/He and fission‐track cooling ages from metasedimentary and metaplutonic rocks intersected by the thrust system record an along‐strike decrease in cooling ages commensurate with an increase in late Oligocene‐Neogene bedrock exhumation and shortening with proximity to the Denali fault. The dominant structure in the Broxson Gulch thrust system is the Valdez Creek fault, which is an upper crustal reactivation of the Valdez Creek shear zone–the main Late Cretaceous suture between western North America and outboard accreted arc terranes. After reactivation of the Valdez Creek shear zone at ca. 30 Ma, the thrust system grew by south‐vergent imbrication of the upper crust along thrust and reverse faults until at least 6 Ma. Incorporating results from the Broxson Gulch thrust system into the regional structural evolution of the Denali fault system reveals significant spatiotemporal heterogeneity in shortening adjacent to the Denali fault. Moreover, nearly all of the late Oligocene‐Neogene shortening south of the Denali fault was focused along reactivated terrane boundaries inherited from Mesozoic assembly of the North American Cordillera, and the spatial distribution of the inherited structures appears to control slip partitioning behavior of the Denali fault system across time scales ranging from 101 (historic seismicity) to 107 yr. The slip partitioning behavior of the Denali fault system highlights the mechanical importance of inherited structures leading to protracted shortening on splay thrust systems, which siphon slip from the master strike‐slip fault. We contend that the weakness of nearby reactivated terrane boundaries should be considered among other mechanisms commonly evoked to explain the partitioning behavior of continental strike‐slip fault systems (e.g., stress field rotation, obliquity angle, and strength of master strike‐slip fault).

show abstract

Upper Triassic continental margin strata of the central Alaska Range: Implications for paleogeographic reconstruction

Cited by 4 publications

References 13 publications

Strontium isotope variation and carbonate versus silicate weathering in rivers from across Alaska: Implications for provenance studies

Strontium isotope variation and carbonate versus silicate weathering in rivers from across Alaska: Implications for provenance studies

Tectonic Growth of the Late Paleozoic‐Middle Mesozoic Northwestern Margin of Laurentia and Implications for the Farewell Terrane: Stratigraphic, Structural, and Provenance Records From the Central Alaska Range

Suture Reactivation, Slip Partitioning, and a Protracted Strike‐Slip Rate Gradient in the Denali Fault System, Southern Alaska, USA

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