Emplacement and Denudation History of the Lewis-Eldorado-Hoadley Thrust Slab in the Northern Montana Cordillera, USA: Implications for Steady-State Orogenic Processes

Sears, James W.

doi:10.2475/ajs.301.4-5.359

Cited by 38 publications

(37 citation statements)

References 38 publications

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“…1A), suggest that a foredeep zone was developed in western Montana and eastern Idaho during the middle Cenomanian. Owing to the northeast-southwest shortening of the Rocky Mountains during Late Cretaceous-Paleocene time (Price and Sears, 2000;Sears, 2001;Ross et al, 2005), the foredeep deposits in southeastern British Columbia, eastern Idaho, and northwestern Montana were uplifted and cannibalized.…”

Section: Middle Cenomanianmentioning

confidence: 98%

Evolution of the northern Cordilleran foreland basin during the middle Cretaceous

Yang

Miall

2009

Geological Society of America Bulletin

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A detailed study of the middle-late Cenomanian Belle Fourche Formation in southern Alberta helps to elucidate the evolution of the Cordilleran foreland basin during the middle Cretaceous. By combining isopach data from the study area with previously published research on middle Cretaceous stratigraphy in adjacent areas of northern Alberta and Montana, it is possible to defi ne the position of the proximal foredeep, forebulge, and backbulge depozones from late Albian to Cenomanian time.The foredeep probably lay to the west of the present fold-thrust belt in western Montana from the late Albian to middle Cenomanian, with the forebulge extending northwestward through the northwest corner of Wyoming and curving northeastward through the present-day location of Calgary. Thick Dunvegan deposits (middle Cenomanian) of northwestern Alberta are interpreted as foredeep deposits. Palinspastic reconstruction of the southern Rocky Mountains of Alberta is consistent with a location of the foredeep within the area of the present fold-thrust belt. At the end of the middle Cenomanian the forebulge retreated westward within Alberta, defi ning a nearly straight northwest-southeast trend through the present position of the Foothills and Front Ranges of Alberta and northwestern Montana. The change in trend of the foreland basin at the end of the middle Cenomanian may refl ect the change of convergence vectors along the western margin of North America during the middle Cretaceous.

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Section: Middle Cenomanianmentioning

confidence: 98%

Evolution of the northern Cordilleran foreland basin during the middle Cretaceous

Yang

Miall

2009

Geological Society of America Bulletin

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“…The flexural curvature of the basement transfers the subsidence from the basin to the FFTB. The kinematic model (Figure 9) depicts clearly how the strong subsidence in the foredeep implies also the preservation of a thick wedge in the foothills, thus preventing significant synorogenic exhumation [Sears, 2001;Osadetz et al, 2004;Hardebol et al, 2007]. As a result, substantial tectonic overburden from thrust sheet stacking can pile up and be preserved (Figure 9; stage V at 45 Ma).…”

Section: Considerations On Out-of-sequence Thrusting and Postorogenicmentioning

confidence: 99%

“…In addition, erosional products from Blairmore strata are found in the Eo-Oligocene basin fill of the Flathead valley graben. Assuming the Clark Range as its most likely source, this suggests that a 5 -6 km thick Lewis thrust sheet inclusive of the Blairmore Formation, remained preserved from erosion till the formation of the Flathead valley graben in Eo-Oligocene times [Sears, 2001;Osadetz et al, 2004].…”

Section: Eo-oligocene Half Grabensmentioning

confidence: 99%

“…This forward deformation sequence is also followed in our kinematic modeling, and more details are given by Hardebol et al [2007]. Contractional deformation started post-80 Ma farther to west, constrained by the dating of decollement level to polydeformed sillimanite-orthoclase paragneisses [Parrish, 1995;Carr, 1992], and overall shortening ceased at $58 Ma [Fermor and Moffat, 1992;Sears, 2001;van der Pluijm et al, 2006]. Cooling curves suggest rapid uplift and erosion of the Purcell Anticlinorium (just west of the study area) between 65 and 55 Ma [Archibald et al, 1984] and FT T-t modeling for Lewis thrust hanging wall cooling 110-60°C between 75 and 35 Ma.…”

Section: Tc3003mentioning

confidence: 99%

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

Hardebol¹,

Callot

Bertotti

et al. 2009

Tectonics

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[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,

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“…According to Sears (2001), emplacement of the Lewis-Eldorado-Hoadley (LEH) thrust slab ended bỹ 59 Ma, based on dated porphyritic dykes cross-cutting faults at the leading edge of the thrust. But Hoffman et al (1976) concluded that progressive burial of footwall sediments by the LEH slab continued until 57 Ma, as recorded by potassium metasomatism in bentonite beds.…”

Section: What and When Was The Bend Of The Laramide (Eol)q?mentioning

confidence: 99%

Emergence of the Canadian Rockies and adjacent plains: A comparison of physiography between end-of-Laramide time and the present day

2006

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Emplacement and Denudation History of the Lewis-Eldorado-Hoadley Thrust Slab in the Northern Montana Cordillera, USA: Implications for Steady-State Orogenic Processes

Cited by 38 publications

References 38 publications

Evolution of the northern Cordilleran foreland basin during the middle Cretaceous

Evolution of the northern Cordilleran foreland basin during the middle Cretaceous

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

Emergence of the Canadian Rockies and adjacent plains: A comparison of physiography between end-of-Laramide time and the present day

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