Architecture, kinematics, and exhumation of a convergent orogenic wedge: A thermochronological investigation of tectonic–climatic interactions within the central St. Elias orogen, Alaska

Berger, A.; Spotila, James A.; Chapman, James B.; Pavlis, Terry L.; Enkelmann, Eva; Ruppert, N. A.; Buscher, Jamie T.

doi:10.1016/j.epsl.2008.02.034

Cited by 88 publications

(148 citation statements)

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“…Thermochronological research on the Neogene tectonic history of southern Alaska has led to the interpretation of exhumation pulses at approximately 25,23,20,18,16,11,6, 4 and 1 Ma (Plafker et al 1992;Fitzgerald et al 1995;O'Sullivan & Currie 1996;Berger et al 2008;Enkelmann et al 2008;Haeussler et al 2008;Spotila & Berger 2010). Palaeo-environmental analysis of Alaska's sedimentary basins also suggests that pulses of exhumation occurred during the Miocene -present (Lagoe et al 1993;Thoms 2000;Ridgway et al 2007;Haeussler et al 2008;Finzel et al 2009).…”

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confidence: 99%

Persistent long-term (c.24 Ma) exhumation in the Eastern Alaska Range constrained by stacked thermochronology

Benowitz

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VanLaningham

2013

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confidence: 99%

Persistent long-term (c.24 Ma) exhumation in the Eastern Alaska Range constrained by stacked thermochronology

Benowitz

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VanLaningham

2013

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“…To overcome this sampling obstacle, we analysed detrital zircons from rivers draining the main glacial systems to evaluate the cooling 1 Earth and Environmental Science, Lehigh University, 31 Williams Dr., Bethlehem, Pennsylvania 18015, USA, 2 Department of Geological Sciences, University of Texas at El Paso, 500 West University Ave., El Paso, Texas 79968, USA, 3 ages of these young exhumed parts of the orogen (Fig. 2).…”

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confidence: 99%

Intense localized rock uplift and erosion in the St Elias orogen of Alaska

et al. 2009

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The timing and role of exhumation in the St Elias orogen, the world's highest coastal mountain range, has been unclear. Sampling is limited to high mountain ridges that tower over widespread ice fields that sit in deeply eroded parts of the orogen. Existing bedrock studies 1-3 in the region are therefore prone to bias. Here we analyse detrital material of active sediment systems in the St Elias orogen to obtain age information from the inaccessible ice-covered valley bottoms. We present 1,674 detrital zircon fission-track ages from modern rivers that drain the glaciers. We find a population of very young ages of less than 3 Myr from the Seward-Malaspina glacier systems that is sharply localized in the area of the orogen's highest relief, highest seismicity and at the transition from transform to subduction tectonics. Our data provide evidence for intense localized exhumation that is driven by coupling between erosion and active tectonic rock uplift.The St Elias mountain belt originates from the collision of the Yakutat terrane with North America, at the corner formed by the dextral Fairweather transform and the Aleutian subduction zone (Fig. 1). Initiation of the Fairweather fault and northward transport of the Yakutat terrane started ∼30 Myr ago, but collision began at 10-5 Myr as the thickened crust of the Yakutat terrane accreted to the Aleutian trench 4,5 , stripping sedimentary cover from basement to construct a foreland fold and thrust belt 4,6 (Fig. 2). Along the orogenic belt, the youngest (5-0.5 Myr) low-temperature cooling ages of bedrock (60-110• C closure temperatures (T c ) for apatite (U-Th)/He (ref. 7) and fission track 8 ) are strongly correlated with those areas with the highest precipitation along the southern, seaward flanks of the orogen. Bedrock cooling ages are oldest in the drier northern side 1,2 (Fig. 2). Bedrock zircon fission-track (ZFT) ages (T c ∼ 250• C; ref. 9) give >10 Myr ages 3,10 ( Fig. 2), or are non-reset in the fold-thrust belt, because lateral transport of material into the orogenic wedge results in exhumation restricted to the upper 5 km (ref. 10). Similar to other active orogenic belts with high erosion rates, the St Elias range seems to have developed localized feedback between erosion and crustal strain [11][12][13] . Thus, it is puzzling that no evidence has emerged for locally enhanced exhumation and erosion in the form of localized young, higher-temperature cooling ages. However, the St Elias orogen is unique among active orogens in that more than 50% of its area is covered by glaciers hundreds of metres in thickness (Fig. 2). Besides reducing bedrock exposures in general, this glaciation also prohibits direct sampling of the low-elevation intensely glaciated valley bottoms where the most recently exhumed rocks and youngest cooling ages would be expected.To overcome this sampling obstacle, we analysed detrital zircons from rivers draining the main glacial systems to evaluate the cooling

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“…2.2 we calculated the depth to a closure isotherm from a one-dimensional model that assumed an isothermal boundary condition at the mean topographic elevation. However, if we are to extend the analysis to investigate exhumation rates across a larger region, the topography of Earth's surface needs to be included (Lees, 1910;Bullard, 1938;Jeffreys, 1938;Birch, 1950;Werner, 1985).…”

Section: The Effects Of Topography On a Closure Isothermmentioning

confidence: 99%

“…In this case, ages are calculated by tracking material paths through space and time and using the resulting temperature-time (T − t) paths. Various analytical solutions have been presented to account for heat advection in response to erosion (e.g., Zeitler, 1985;Mancktelow and Grasemann, 1997;Brandon et al, 1998;Moore and England, 2001;Willett and Brandon, 2013) as well as the perturbation of the thermal field by topography (e.g., Lees, 1910;Birch, 1950;Stüwe et al, 1994;Mancktelow and Grasemann, 1997;Braun, 2002). Otherwise, numerical thermo-kinematic models have been used, in which spatial variations in rock uplift due to differential tectonic movements may be specified by structural or tectonic models combined with a surface erosion model (e.g., Grasemann and Mancktelow, 1993;Batt and Braun, 1997;Harrison et al, 1997;Batt and Braun, 1999;Stüwe and Hintermuller, 2000;Ehlers et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

“…An alternative to these computationally expensive threedimensional thermo-kinematic inverse models is to simply map spatial patterns in exhumation by converting isolated ages into time-averaged exhumation rates (e.g., Van den Haute, 1984;Omar et al, 1989;Brandon et al, 1998;Berger et al, 2008;Thomson et al, 2010). Vernon et al (2008) computed the difference in elevation of isoage surfaces, which are interpolated from the data distributed in three dimensions, to estimate variations in exhumation rate.…”

Section: Introductionmentioning

confidence: 99%

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A linear inversion method to infer exhumation rates in space and time from thermochronometric data

et al. 2014

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Abstract. We present a formal inverse procedure to extract exhumation rates from spatially distributed low temperature thermochronometric data. Our method is based on a Gaussian linear inversion approach in which we define a linear problem relating exhumation rate to thermochronometric age with rates being parameterized as variable in both space and time. The basis of our linear forward model is the fact that the depth to the "closure isotherm" can be described as the integral of exhumation rate,ė, from the cooling age to the present day. For each age, a one-dimensional thermal model is used to calculate a characteristic closure temperature, and is combined with a spectral method to estimate the conductive effects of topography on the underlying isotherms. This approximation to the four-dimensional thermal problem allows us to calculate closure depths for data sets that span large spatial regions. By discretizing the integral expressions into time intervals we express the problem as a single linear system of equations. In addition, we assume that exhumation rates vary smoothly in space, and so can be described through a spatial correlation function. Therefore, exhumation rate history is discretized over a set of time intervals, but is spatially correlated over each time interval. We use an a priori estimate of the model parameters in order to invert this linear system and obtain the maximum likelihood solution for the exhumation rate history. An estimate of the resolving power of the data is also obtained by computing the a posteriori variance of the parameters and by analyzing the resolution matrix. The method is applicable when data from multiple thermochronometers and elevations/depths are available. However, it is not applicable when there has been burial and reheating. We illustrate our inversion procedure using examples from the literature.

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Architecture, kinematics, and exhumation of a convergent orogenic wedge: A thermochronological investigation of tectonic–climatic interactions within the central St. Elias orogen, Alaska

Cited by 88 publications

References 59 publications

Persistent long-term (c.24 Ma) exhumation in the Eastern Alaska Range constrained by stacked thermochronology

Persistent long-term (c.24 Ma) exhumation in the Eastern Alaska Range constrained by stacked thermochronology

Intense localized rock uplift and erosion in the St Elias orogen of Alaska

A linear inversion method to infer exhumation rates in space and time from thermochronometric data

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