Abstract
AbstractThe Ancestral Rocky Mountains system consists of a series of basement-cored uplifts and associated sedimentary basins that formed in southwestern Laurentia during Early Pennsylvanian–middle Permian time. This system was originally recognized by aprons of coarse, arkosic sandstone and conglomerate within the Paradox, Eagle, and Denver Basins, which surround the Front Range and Uncompahgre basement uplifts. However, substantial portions of Ancestral Rocky Mountain–adjacent basins are filled with carbonate or fine-grained quartzose material that is distinct from proximal arkosic rocks, and detrital zircon data from basins adjacent to the Ancestral Rocky Mountains have been interpreted to indicate that a substantial proportion of their clastic sediment was sourced from the Appalachian and/or Arctic orogenic belts and transported over long distances across Laurentia into Ancestral Rocky Mountain basins. In this study, we present new U-Pb detrital zircon data from 72 samples from strata within the Denver Basin, Eagle Basin, Paradox Basin, northern Arizona shelf, Pedregosa Basin, and Keeler–Lone Pine Basin spanning ∼50 m.y. and compare these to published data from 241 samples from across Laurentia. Traditional visual comparison and inverse modeling methods map sediment transport pathways within the Ancestral Rocky Mountains system and indicate that proximal basins were filled with detritus eroded from nearby basement uplifts, whereas distal portions of these basins were filled with a mix of local sediment and sediment derived from marginal Laurentian sources including the Arctic Ellesmerian orogen and possibly the northern Appalachian orogen. This sediment was transported to southwestern Laurentia via a ca. 2,000-km-long longshore and aeolian system analogous to the modern Namibian coast. Deformation of the Ancestral Rocky Mountains slowed in Permian time, reducing basinal accommodation and allowing marginal clastic sources to overwhelm the system.
Highlights
Over the last several decades, increasing attention has been focused on the importance of treating sediment production, transport, and storage processes within an integrated source-to-sink framework (e.g., Allen, 2008; Tinker et al, 2008; Covault et al, 2011; Romans et al, 2016; Wang et al, 2019)
All zircon samples collected from the Lone Pine Formation and sedimentary rocks of Santa Rosa Flat (Keeler and Lone Pine Basins) were analyzed at the University of California–Santa Barbara (UCSB) Laser Ablation Split Stream (LASS) facility using a Nu Plasma high resolution multi-collector–inductively coupled plasma mass spectrometer (HR MC–ICPMS), a Nu AttoM single collector ICPMS, and an Analyte 193 excimer ArF laser-ablation system equipped with a HeLex sample cell using a 24 μm beam
Detrital zircon spectra from the Upper Mississippian Surprise Canyon Formation through the Leonardian Coconino Sandstone are composed of largely similar age spectra
Summary
Over the last several decades, increasing attention has been focused on the importance of treating sediment production, transport, and storage processes within an integrated source-to-sink framework (e.g., Allen, 2008; Tinker et al, 2008; Covault et al, 2011; Romans et al, 2016; Wang et al, 2019) Vital to this approach is the determination of both the spatial and temporal extent of the source-to-sink system, or alternately stated, it is imperative to understand the degree to which the source is separated from the sink, both by physical distance and by the time elapsed between erosion and deposition. Recent work has demonstrated that transport by longshore current can result in mixing of provenance signals at long spatial and temporal wavelengths (e.g., Liu et al, 2007; Garzanti et al, 2014; Sickmann et al, 2016), but these processes are not as well considered in deep-time provenance records
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