Cenozoic tectonic and thermal history of the Nenana basin, central interior Alaska: new constraints from seismic reflection data, fracture history, and apatite fission-track analyses

Abstract

The Nenana basin of interior Alaska forms a segment of the diffuse plate boundary between the Bering and North American plates and is located within a complex zone of crustalscale strike-slip deformation that accommodates compressional stresses due to oblique plate convergence to the south. The basin is currently the focus of new oil and gas exploration.Integration of seismic reflection and well data, fracture data and apatite fission track analyses with regional data improves our understanding of the tectonic development of this continental strike-slip basin.The Nenana basin formed during the Late Paleocene as a 13-km-wide halfgraben, affected by regional intraplate magmatism and localized crustal thinning across the Minto fault in south-central Alaska. The basin was uplifted and exhumed along this faulted margin in Early Eocene through to Late Oligocene time in response to oblique subduction along the southern Alaska margin. This event resulted in the removal of up to 1.5 km of Late Paleocene strata from the basin. Renewed rifting and subsidence during Early Miocene time widened the basin to the west resulting in deposition of Miocene nonmarine clastic rocks in reactivated and newly-formed extensional half-grabens. In Middle to Late Miocene time, left lateral strike-slip faulting was superimposed on this half-graben system, with rapid subsidence beginning in Pliocene time and continuing to the present-day. At present, the Nenana basin is in a zone of transtensional deformation that accommodates compressional stresses due to oblique plate convergence and allows tectonic subsidence by oblique-extension along major basin-bounding strike-slip faults.

Shear Velocity Model of Alaska Via Joint Inversion of Rayleigh Wave Ellipticity, Phase Velocities, and Receiver Functions Across the Alaska Transportable Array

“…Journal of Geophysical Research: Solid Earth distribution (shown in cyan) of velocity models (Figures 4a and 4e-4h) that fit the data (Figures 4b-4d). Previous analysis of the Nenana Basin from well logs, gravity, and active-source seismic has mapped depth to basement below this station as~2 km depth, corresponding to Vp between 4.5 and 5.3 km/s, or Vs 2.67-3.15 km/s (Brocher et al, 2005;Dixit et al, 2017;Tape et al, 2015), which matches our result at this station. In order to analyze approximate sediment thickness from the surface across the entirety of Alaska, while accounting for potentially faster basin material at depth, we show maps to Vs 3.1 km/s across the region for both MCMC and final Vs results in Figure 8.…”

“…The long history of active tectonics in Alaska has led to the formation of several major basins, including the Mesozoic foreland Colville and forearc Cook Inlet Basins, Cenozoic backarc Bristol Bay Basin, and Cenozoic stepover basins, including transtensional-transpressional Bethel Basin and rift-transtensional Copper River, Nenana, Selawik, and Yukon Flats Basins (Coleman & Cahan, 2012). These basins have been previously analyzed by geological and geophysical surveys for hazard analysis (Bruhn & Haeussler, 2006;Haeussler et al, 2000), petroleum potential (Bird, 2010;Decker et al, 1988;Kirschner, 1994;Van Kooten, 2012), and relation to tectonic processes (Cole et al, 2004;Dixit et al, 2017;Moore & Box, 2016;Plafker & Berg, 1994). Our results include the first complete 3-D tomographic maps of every major basin in Alaska with high (Colpron et al, 2007) are shown as dashed black lines in (c) with terranes Arctic Alaska (AA), Yukon composite Terrane (YCT), Wrangellia composite Terrane (WCT), and southern margin composite Terrane (SMCT) labeled.…”

“…The Nenana Basin is primarily a transtensional basin related to the crustal extension and strike-slip faulting accommodated by the Denali fault to the south and Tintina-Kaltag system to the north (Page et al, 1995;Tape et al, 2015;Van Kooten et al, 2012). Sediments within the basin include lacustrine and fluvial deposits related to crustal extension during the late Paleocene (Dixit et al, 2017;Van Kooten et al, 2012), Eocene regional uplift (Dixit et al, 2017), and Miocene rifting and subsidence followed by Pliocene and Quaternary transtensional pull-apart processes. The Nenana Basin (Figure 10, B-B′ and Figure 11, E-E′) is…”

Deformation at the eastern margin of the Northern Canadian Cordillera: Potentially related to opening of the North Atlantic

“…Since the Eocene, several hundred kilometres of dextral motion occurred on these faults, which caused block rotation accompanied by sinistral strike‐slip and normal faulting, basin development, and magmatism (e.g. Dixit, Hanks, Rizzo, McCarthy, & Coakley, ; Dusel‐Bacon, Bacon, O'Sullivan, & Day, ; Dusel‐Bacon & Murphy, ). However, there is no record that convergent motion has crossed over the Tintina Fault to the east.…”