Burial and temperature evolution in thrust belt systems: Sedimentary and thrust sheet loading in the SE Canadian Cordillera

Abstract

[1] The southern Canadian foreland fold-and-thrust belt (FFTB) (SW Alberta -SE British Columbia) records the interplay between foreland basin evolution with the deforming wedge and thus controls the regionalscale overburden and exhumation history. Overburden estimates are typically based on the assumption that peak burials were reached by sedimentary burial prior to the emplacement of thrust sheets. This study combines organic maturity ranks from a newly compiled catalog with forward thermokinematic modeling to examine this assumption. The organic maturity rank trends correlate not only to sedimentary but also to tectonic burial histories. The forward thermokinematic modeling builds on this combined burial history scenario and shows how required peak burial and temperatures can be achieved with reduced sedimentary overburden when combined with tectonic loading. We thus consider that the overburden was reached during instead of prior to the contraction of the FFTB as result of an integrated sedimentary and tectonic burial history. Thermokinematic modeling also suggests that firstorder steady state temperature conditions prevail during the development of the FFTB. Differently from earlier findings that considered a drop in paleotemperature gradient during the belts growth, steady state conditions reduce the amount of regional overburden required and, consequently, of eroded sediments. Besides tracing the regional evolution, organic maturity ranks are also affected by more local phenomena such as thrust-scale denudation patterns and fluid flow. Citation: Hardebol, N. J., J. P. Callot, G. Bertotti, and J. L. Faure (2009), Burial and temperature evolution in thrust belt systems: Sedimentary and thrust sheet loading in the SE Canadian Cordillera, Tectonics, 28, TC3003,

Evolution of the Cordilleran foreland basin system in northwestern Montana, U.S.A.

“…Eroded proximal equivalents of the Fort Union and Wasatch Formations could have been much thicker. In Alberta, coal moisture, vit rinite refl ectance, and thermokinematic modeling indicates that 2-4 km of synorogenic Cenozoic strata have been erosionally removed (Beaumont, 1981;Hardebol et al, 2009).…”

“…Additional strata equivalent to the Fort Union and Wasatch Formations were probably deposited in the frontal thrust belt and proximal foredeep, but subsequent erosion has removed all traces of these deposits. The thickness of exhumed and removed Cenozoic synorogenic strata in Alberta has been estimated in the order of 2-4 km (Beaumont, 1981;Hardebol et al, 2009).…”

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“…The Middle Jurassic to Early Eocene foreland basin system (Fig. 4) preserves a thickness of strata of as much as 2.5-3 km, but a considerable thickness of Paleocene-Early Eocene proximal deposits was erosionally removed during the Cenozoic (Hardebol et al, 2009). Jurassic strata are characteristically thin and tabular, and possibly refl ect deposition in a distal, backbulge depozone (Fuentes et al, 2009).…”

Small‐scale convection at a continental back‐arc to craton transition: Application to the southern Canadian Cordillera

“…The position of the deflection corresponds to the location of the Canadian Foreland Belt (Figure 1a) and has a similar wavelength as lithosphere flexure and could have added to the strong flexural deflections from the build‐up and later removal of an orogenic surface load [ Beaumont , 1981]. The surface deflection in this study did not exhibit any >1000 km wavelength signals to explain post‐orogenic Eocene uplift and exhumation that not only affected the Cordillera, but also the adjacent craton at large distance [ Hardebol et al , 2009]. Beaumont [1981] already pointed out that the Cretaceous foreland subsidence in southern Canada was too wide in extent to be attributed only to continental flexure under the Cordilleran orogenic load (see also Peper , 1994and references therein).…”