Detrital zircons and sediment dispersal in the eastern Midcontinent of North America

Abstract

Results of detrital-zircon analyses (U-Pb ages and initial Hf values, εHft) of Mississippian–Pennsylvanian sandstones in the Michigan, Illinois, and Forest City basins are remarkably similar to data for coeval sandstones in the Appalachian basin, indicating dispersal of sediment from the Appalachian orogen through the Appalachian basin to the eastern Midcontinent during the late Paleozoic. The similarities of results include matches of the two most prominent age groups (1300–950 Ma and 490–350 Ma), as well as matches of the less abundant age groups. Comparisons of the data are from observations of probability density plots and multidimensional scaling of U-Pb age data and of εHft values. Despite the dominance of an Appalachian signature in all samples, some samples contain grains with ages that suggest intermittent additional sources. Four samples (three ranging in depositional age from Morrowan to Atokan–Desmoinesian in the Illinois basin, and one of Desmoinesian age in the Forest City basin), in addition to typical Appalachian age distributions, have prominent age modes between 768 and 525 Ma, corresponding in age to Pan-African/Brasiliano rocks in Gondwanan accreted terranes in the Appalachian orogen, suggesting intermittent dispersal from the Moretown terrane of the northern Appalachians. Sandstones in the Appalachian basin and those in the Midcontinent basins have very few grains with ages that correspond to the Alleghanian orogeny in the Appalachian orogen. Nevertheless, three sandstones each in the Illinois basin and Forest City basin with depositional ages of 312–308 Ma have a few zircon grains in the age range of 321 ± 5 to 307 ± 4 Ma. The nearly identical crystallization and depositional ages suggest reworking at the depositional sites of air-fall volcanic ash from the Alleghanian orogen, rather than fluvial transport from the orogen. The basal Pennsylvanian sandstones lap onto a regional unconformity around the northern rims of the Illinois and Forest City basins, suggesting sources for recycled grains. Along the northern edge of the Illinois basin, Ordovician sandstones beneath the unconformity may have contributed minor concentrations of Superior-age zircons in the basal Pennsylvanian sandstones. Basal Pennsylvanian sandstones in the Forest City basin lap onto Mississippian strata, suggesting possible recycling of zircons from eroded Mississippian sandstones.

Detrital-zircon analyses, provenance, and late Paleozoic sediment dispersal in the context of tectonic evolution of the Ouachita orogen

“…12E). The detrital-zircon distributions are generally similar to those in the stratigraphically lower Pennsylvanian and Mississippian sandstones in the Forest City basin, which are characteristic of an Appalachian provenance (Kissock et al, 2018;Chapman and Laskowski, 2019;Thomas et al, 2020). In contrast, the Middle Permian Whitehorse sample includes a secondary group with ages of 638-519 Ma and a minor mode of 576 Ma (Fig.…”

“…1B and 5; Tables 1 and 2; Supplemental Tables S1 and S2) represent the sedimentary cover over the Wichita and Arbuckle uplifts, in contrast to the conglomerates that rest unconformably on the Precambrian-Cambrian crystalline rocks in the uplifts (Thomas et al, 2016). Published U-Pb and Hf data from a Permian sandstone (Thomas et al, 2020) on the divide between the Anadarko basin and the intracratonic Forest City basin on the north (Figs. 1 and 5B) provide a test of regional dispersal systems.…”

“…A sample from the Middle Permian Whitehorse Group (KS-5-WH; Fig. 10G; Thomas et al, 2020) on the structural divide between the Anadarko basin and the Forest City basin on the north (Fig. 1) suggests distant transport from the Ouachita-Marathon orogen onto the craton (Fig.…”

U-Pb geochronology and paleogeography of the Valanginian–Hauterivian Neuquén Basin: Implications for Gondwana-scale source areas

“…This drainage system, with an area of ~900,000 km 2 , represents the main sediment outfall for southern Africa (Bremner et al, 1990). In North America, several detrital-zircon studies have now demonstrated far-flung sediment delivery systems that spanned the entire width of the continent during the peak assembly of the Pangean supercontinent (Pennsylvanian-Permian) (Gehrels et al, 2011;Kissock et al, 2017;Thomas et al, 2020), and the same would remain true for the source-tosink delivery system that would have connected Patagonian source rocks with the Karoo basin during the late Paleozoic (Johnson, 1991;Sato et al, 2015;Gomis-Cartesio et al, 2018).…”

Two‐Dimensional Quantitative Comparison of Density Distributions in Detrital Geochronology and Geochemistry

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Detrital geochronology has transformed the way geologists approach many Earth Science questions. Research incorporating detrital geochronology is wide ranging, from standard application in studies of sediment provenance and dispersal patterns (e.g., Thomas et al, 2020), determination of the maximum depositional age of stratigraphy (e.g., Dickinson & Gehrels, 2009; Vermeesch, 2020), and reconstructing paleogeography and landscape evolution (e.g., Roberts, 2012), to recent novel applications in determining controls on paleoclimate modulations (e.g., McKenzie et al, 2016), placing temporal constraints on floral and faunal continental ecosystems (e.g., Tucker et al, 2013), and estimating the age of early hominins (e.g., Böhme et al, 2017).Zircon is the mineral of choice in detrital geochronology as it is physically and chemically robust, refractory, can survive multiple erosional and/or tectonic cycles, and incorporates abundant U with little initial Pb (Cherniak et al, 1997;Speer, 1980;Stacey & Kramers, 1975). In addition to being a useful mineral for geochronology, zircon can also be paired with secondary information such as (U-Th)/He or fission track thermochronometry for determining thermal histories (e.g.

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