The Glenwood Shale as an example of a Middle Ordovician condensed section

A Middle Devonian basin-scale precious metal enrichment event across northern Yukon (Canada)

“…Condensed sections form in response to shoreline transgressions that form during late transgressive to early highstand systems tracts (Loutit et al, 1988). They are clastic sediment-starved, such that thin (centimeter-scale) beds represent relatively long durations (Schutter 1996). Several criteria are used to identify condensed sections (cf.…”

“…Several criteria are used to identify condensed sections (cf. Schutter, 1996), and relevant ones present within the HEBS are high abundances of authigenic 1 GSA Data Repository item 2020063, Figures DR1 and DR2 (supplemental photographs and photomicrographs of HEBS from the Peel River showing and the Nick prospect, respectively), Table DR1 (estimated modal mineralogy of mineral separates produced for this study), Table DR2 (Re-Os data), and Table DR3 (supplemental information regarding specific conodont taxonomic data and metadata), is available online at http://www.geosociety.org/datarepository/2020/, or on request from editing@geosociety.org. minerals (e.g., sedimentary sulfides), abundant biogenic debris, high abundances of metals, and widespread geographic distribution.…”

High-resolution sequence stratigraphy and detrital zircon provenance of the Ordovician Ancell Group in the Iowa and Illinois Basins

“…The Glenwood Shale is composed of light green and gray to black organic-rich mudrock, ferroan ooid grainstone, poorly sorted quartz arenite, argillaceous dolostone, and blue-green clay and siltstone (Schutter, 1992(Schutter, , 1996. The Glenwood Shale was first described in and named after the Glenwood Township, Winneshiek County, Iowa (Calvin, 1906).…”

“…The Glenwood Shale was locally deposited disconformably on the Tonti Member of the St. Peter Sandstone and is disconformably overlain by the Platteville Group with laterally gradational contacts into the Starved Rock Formation and Platteville Formation (Templeton and Willman, 1963). The Glenwood Shale was assigned to the lower part of Platteville Formation (Choi et al, 1997), whereas it was interpreted as a distinct unit marking a condensed section associated with a widespread transgressive event in Early Mohawkian (Schutter, 1992(Schutter, , 1996.…”

“…Sequence stratigraphy was developed using siliciclastic shelf-to-basin profiles of divergent continental margins (e.g., Vail et al, 1977;Van Wagoner et al, 1988), but this methodology has had little impact on understanding intracratonic basins due to their low sedimentation rates, low depositional relief and difficulty in defining the sedimentary packages geometries in these basins (Vecsei and Duringer, 2003). Adapting sequence stratigraphy methods and nomenclature to intracratonic basins may be possible if relative sea-level fluctuation records longer term subsidence, and different shelf-margin geometries are envisioned as implied by lowstand wedge deposits (Witzke and Bunker;1996).…”