A Middle Pennsylvanian macrofloral assemblage from below the Rock Island (No. 1) Coal Member, Illinois: Resolving the Bolsovian–Asturian boundary in the Illinois Basin

Abstract

A taxonomic, quantitative, and biostratigraphic analysis is presented for a macrofloral assemblage collected from below the Rock Island (No. 1) Coal Member at the historical Friendship Farm locality in Rock Island County, on the northwestern margin of the Illinois Basin. The Middle Pennsylvanian (middle Moscovian) fossiliferous strata involve the middle Tradewater Formation, and are situated a short distance below the Atokan-Desmoinesian Stage boundary as defined by marine microfossils and palynology. The assemblage of 14 fossil-taxa is overwhelmingly dominated by pteridosperms, including Laveineopteris rarinervis, Neuropteris flexuosa, Alethopteris serlii, Macroneuropteris scheuchzeri, and Mariopteris nervosa, whereas lycopsids, sphenopsids, and ferns are comparatively rare. Homotaxial comparison with the macrofloral biozonation scheme established in Europe indicates an Asturian age for the assemblage, in all likelihood early Asturian (Linopteris obliqua Biozone). Similar comparisons with range limits documented in the Appalachian Basin yield a more ambiguous age, but an early Asturian age is equally probable. These findings indicate that the Bolsovian-Asturian Substage boundary of western Europe lies below the Atokan-Desmoinesian Stage boundary in the Illinois Basin, boundaries that have traditionally been correlated by palynology. The Middle Pennsylvanian interval near these boundaries is being increasingly recognized as one of significant environmental change, reflected in marked lithological and biological modifications throughout tropical Euramerica. However, the fact that the Bolsovian-Asturian and Atokan-Desmoinesian boundaries are not synchronous, albeit being broadly equivalent, suggests that the environmental perturbation was a protracted event that may have had global consequences.

A revision of <em>Annularia</em> and <em>Asterophyllites</em> species from the lower Westphalian (Middle Pennsylvanian) of the Maritime Provinces of Canada

“…from Asturian strata of the Shelburn Formation, Indiana. Lesquereux's (1870) type material as well as that figured Canright's (1959) specimens are also from Indiana; these are by Noé (1925) and Darrah (1969) are from uppermost from the Lower Block Coal, lower Brazil Formation of late Asturian and/or lowermost Cantabrian strata at Mazon Bolsovian age according to Bashforth and Nelson (2015). Creek, Illinois, U.S.A. White (1880) Bell (1938): locality 513 (GSC 2269); locality 556 (GSC 3107).…”

Plant Fossils from the Pennsylvanian–Permian Transition in Western Pangea, Abo Pass, New Mexico

“…Quantitative assessments of each flora were carried out using a modification of the hand-sample/quadrat method of Pfefferkorn et al (1975), as described by Bashforth and Nelson (2015). In this method, top and bottom surfaces of each hand sample are treated as separate sampling quadrats.…”

Palaeobotanical experiences of plant diversity in deep time. 2: How to measure and analyse past plant biodiversity

“…Alternatively, standard-size samples are measured, such as using botanical survey quadrats (Scott, 1978), or pseudo-quadrats created by exposing rectangular areas of bedding plane (Gastaldo et al 2004a) or bringing together specimens until a quadrat-sized area is filled (Iwaniw 1985;Bashforth et al 2010Bashforth et al , 2011. Alternatively, proxy quadrats have been based on "normal size" hand-specimens (Pfefferkorn et al 1975;Wing and DiMichele 1995;Uhl and Lausberg, 2008;Barbacka 2011Barbacka , 2016DiMichele et al 2016DiMichele et al , 2021Cleal et al 2012;Bashforth and Nelson 2015;DiMichele et al 2019a,b;Koll and DiMichele 2021) or borehole cores of a set diameter (DiMichele et al 2000). Various counting strategies have been used, with either all specimens in a quadrat being counted (Drägert 1964;Oshurkova 1967;DiMichele et al 2007;8.…”