Research Paper GEOSPHERE A Late Jurassic to Early Cretaceous record of orogenic wedge GEOSPHERE; v. 14, no. 3 evolution in the Western Interior basin, USA and Canada https://doi.org/10.1130/GES01606.1 Garrett M. Quinn1, Stephen M. Hubbard1, Peter E. Putnam2, William A. Matthews1, Benjamin G. Daniels1, and Bernard Guest1 1Department of Geoscience, University of Calgary, Earth Science 118, 2500 University Dr. NW, Calgary, Alberta, T2N 1N4, Canada 12 figures; 1 table; 1 supplemental file 2Osum Oil Sands Corp., Suite 1900, 255 5th Ave SW, Calgary, Alberta, T2P 3G6, Canada CORRESPONDENCE: garrett .quinn@ ucalgary.ca; gquinn7@ gmail .com ABSTRACT INTRODUCTION CITATION: Quinn, G.M., Hubbard, S.M., Putnam, P.E., Matthews, W.A., Daniels, B.G., and Guest, B., The Late Jurassic to Early Cretaceous fill of the Western Interior foreland Aggradation and denudation of proximal foreland basin deposits in the 2018, A Late Jurassic to Early Cretaceous record basin is characterized using geochronological data in order to assess the wedge-top depozone are first-order controls on sediment flux to more-distal of orogenic wedge evolution in the Western Interior stratigraphic expression of wedge-top geomorphology, as controlled by sedi- parts of foreland basin systems (Ben-Avraham and Emery, 1973; DeCelles, basin, USA and Canada: Geosphere, v. 14, no. 3, ment cover and denudation. In northern Montana, USA, and Alberta, Canada, 1994; DeCelles and Giles, 1996; Roddaz et al., 2005; Ross et al., 2005; Horton, p. 1187–1206, https:// doi .org /10 .1130 /GES01606.1. wedge-top deposits are poorly preserved; however, their former presence may 2018). Burial of the frontal toe of the orogen can heal complex topography Science Editor: Raymond M. Russo be inferred from the detrital record in the foreland basin. We present new U/Pb and enhance direct sediment transfer from the orogenic hinterland to a basin. detrital zircon data from nine samples collected near Great Falls, Montana, Conversely, denudation of these wedge-top sediments can lead to structural Received 24 August 2017 augmented with field data. The stratigraphy at Great Falls is characterized by control of river pathways; the process also can expose older stratigraphy in Revision received 21 February 2018 Late Jurassic marine and nonmarine deposits, which are truncated by a basin- the orogenic wedge, which can be reflected by provenance changes in the Accepted 16 April 2018 wide sub-Cretaceous unconformity. Aptian and lower Albian strata overlying adjacent foreland basin (Ross et al., 2005; Lawton et al., 2010). Published online 7 May 2018 the unconformity are dominated by nonmarine deposits, which transition Sediments in the wedge-top depozone accumulate on top of orogenic up-section into a predominantly marine succession related to a major trans- structures and are part of the frontal toe of the orogenic wedge (DeCelles and gression of the Boreal Seaway in the Albian. Giles, 1996). These synorogenic strata accumulate near the erosional/deposi- Detrital zircon grains from Great Falls strata yield age spectra that can be tional surface and are characterized by low preservation potential such that the subdivided into three groups using multidimensional scaling. Group 1 is char- history of sedimentation in this zone is difficult to discern (e.g., Coogan, 1992; acterized by diverse zircon populations, which are interpreted to record recy- Frisch et al., 2001; McMechan et al., 2018). More distal parts of the foreland cling of pre-Cordilleran sedimentary strata transported via foreland basin-axial basin contain well-established records of orogenic processes (e.g., Heller and river systems with headwaters in the southwestern United States. Group 2 is Paola, 1989; Ross et al., 2005; Quinn et al., 2016). Therefore, we hypothesize characterized by the dominance of Mesozoic detrital zircon grains, which are that the history of the wedge-top depozone can be elucidated by investigating interpreted to record sediment dispersal by fluvial systems with headwaters strata in more-distal parts of the foreland basin. This is particularly relevant to in the Cordillera. Group 3 is intermediate between groups 1 and 2, based on understanding topographic evolution in fold-thrust belts that have been deeply OLD G its proportion of Mesozoic zircon grains. This group records a diversification incised during subsequent orogenesis and glaciation (Osborn et al., 2006). of the provenance from one dominated by Cordilleran igneous rocks to include We present a detrital zircon data set from Western Interior basin strata ex- recycled sedimentary strata. posed near Great Falls, Montana, USA. The units provide a unique window New data are integrated with three other data sets from Montana and into the Late Jurassic–Early Cretaceous evolution of the foreland basin be- OPEN ACCESS Alberta such that stratal thicknesses (a proxy for accommodation devel- cause outcrops of these strata are rare except within the fold-thrust belt, which opment) and provenance evolution can be compared across the basin. The is ~100 km west of the study area. New data are integrated with previously pre- detrital record in each area, which transitions from diverse provenance to sented data sets from across the basin in order to consider the history of burial predominantly Cordilleran through the entire stratigraphic section, can be and exhumation of the frontal toe of the orogenic wedge (Fig. 1) ( Fuentes et al., linked to the burial of the pre-foreland strata in the wedge-top depozone. 2011; Leier and Gehrels, 2011; Raines et al., 2013; Benyon et al., 2014; Blum and This record elucidates a period of evolution of the western margin of North Pecha, 2014; Quinn et al., 2016). This study emphasizes the potential impact This paper is published under the terms of the America to a more Andean-type system with primary input to the basin from of wedge-top dynamics on sediment dispersal across foreland basins and the CC‑BY‑NC license. an active magmatic arc. structural evolution of the orogen. © 2018 The Authors GEOSPHERE | Volume 14 | Number 3 Quinn et al. | A record of orogenic wedge evolution 1187 Research Paper A 55°0′0″N W WHR TH ALBERTA GC CLSASKATCHEWAN AA′ AC G GR GF C Fold-Thrust Belt YM AFB Belt-Purcell JE Basin GRP A MONTANA N Great Falls v v v v v v v 1000 km v v v YC v v 25°0′0″N vv 110°0′0″W v 80°0′0″W vv EM Figure 1. (A) Modified geological map of Montana, Little Belt USA, which highlights the Great Falls outcrop belt (af- Mountains ter Garrity and Soller, 2009). The inset shows the set- ting of the Great Falls and other areas with detrital zir- con data sets relative to the major bedrock provinces of North America (modified after Dickinson and Gehrels, 2009b). Inset: A—Appalachian Orogen; AC—Archean Craton; AFB—Appalachian Foreland Basin; C—Cordi- Idaho lleran magmatic arc and accreted terranes; CL—Cold Batholith 100 km Lake; EM—East Mexico Arc; G—Grenville Orogen; GC—Grande Cache; GF—Great Falls; GR—Gibson Res- ervoir; GRP—Granite–Rhyolite Province; JE—Jurassic eolianites; TH—Trans-Hudson Orogen; YC—Yucatan– SedimentaryVolcanic Intrusive Campeche Terrane; W—Wopmay Orogen; WHR—Wyo- ming–Hearne–Rae cratons. (B) Balanced cross section Late Cretaceous to Quaternary Late Cretaceous Late Cretaceous showing a reconstruction of the Early Cretaceous oro- Cretaceous Early to Middle Cretaceous Early to Middle gen–foreland basin system of the southern Canadian Cretaceous Cordillera (after Price, 1994). Line of section is shown in Great Falls outcrop belt Jurassic the inset of Figure 1A. (Jurassic to Early Cretaceous) Jurassic Paleozoic Proterozoic A B A′ km 0 50 km 50 Foreland basin Late Proterozoic to Middle Jurassic sedimentary rocks Mesozoic intrusions Mid-Proterozoic sedimentary rocks Allochthonous terranes Basement GEOSPHERE | Volume 14 | Number 3 Quinn et al. | A record of orogenic wedge evolution 1188 Research Paper STUDY AREA AND STRATIGRAPHY Groff, 1966; Suttner, 1969; Brenner and Davies, 1974; Walker, 1974; Hayes, 1983). Jurassic strata are truncated by the basin-wide sub-Cretaceous uncon- The outcrops of interest to this study are within 30 km of Great Falls, Montana formity (Fig. 2). The overlying Kootenai Formation is dominated by fluvial (Fig. 1). This location is ideal for the study of basin evolution in the Late Jurassic deposits, with marine influence interpreted by some workers (Glaister, 1959; to Early Cretaceous because of the unique access to outcropping undeformed Oakes, 1966; Shelton, 1967; Walker, 1974; Mudge and Rice, 1982; Hopkins, 1985; strata of this age exposed in the distal foreland plains. Because the stratigraphy Hayes, 1986; Farshori and Hopkins, 1989; Hayes, 1990). Two major flooding can be correlated into western Montana and the Alberta foreland basin to the events are evident in Lower Cretaceous strata, recorded by (1) the lacustrine north, the Great Falls area is key for integrating data across the region. or restricted marine Ostracod Member of the Kootenai Formation, and (2) the The stratigraphic nomenclature for this study (Figs. 2, 3) is mostly based marine shale and shoreface deposits of the Flood Member of the Blackleaf For- on the convention defined by Walker (1974); however, we refer to the basal mation, which overlies the Kootenai Formation (Cannon, 1966; Fox and Groff, sandstone of the Kootenai Formation as the Cut Bank Member (Glaister, 1959; 1966; Finger, 1983). Hopkins, 1985) and the Quartzose Sandstone unit as the Sunburst Member (Glaister, 1959; Hopkins, 1985; Hayes, 1990). The Upper Jurassic–Lower Creta- ceous stratigraphy is more than 200 m thick in the study area (Figs. 2 and 3). METHODS Sedimentological characteristics and the interpreted depositional environ- ments for individual units are summarized in Table 1. Measured stratigraphic sections totaling ~290 m were used to compile Jurassic deposits transition from the marine Swift Formation to the non- sedimentological data.