TY - JOUR
T1 - A Middle Pennsylvanian macrofloral assemblage from below the Rock Island (No. 1) Coal Member, Illinois: Resolving the Bolsovian-Asturian boundary in the Illinois Basin
AU - Bashforth, Arden R.
AU - Nelson, W. John
N1 - Funding Information:
This project would not have happened without the continued support of William A. DiMichele at the National Museum of Natural History, Smithsonian Institution , which initially funded the Visiting Researcher posting of ARB at the ISGS. Prolongation of the temporary stay was made possible through the generous support of an Arthur James Boucot Research Grant from the Paleontological Society. ARB thanks the ISGS Coal Section staff, especially Scott Elrick and his co-author W. John Nelson, for their enthusiasm and continued encouragement. Access to plant-fossil collections in the ISGS Samples Library was facilitated by Bob Mumm, Rodney D. Norby, and Kristina Bruhn, who are gratefully acknowledged. Access to the photographic facilities of the Illinois Natural History Survey by Sam Heads and Jared Thomas also is appreciated. Hans-Dieter Sues is acknowledged for his assistance with translation, as are Claudine Delcambre Brousmiche, Christopher J. Cleal, and Josef Pšenička for their discussions about identifications. Alex Stuedemann, maintenance director of TPC Deere Run Golf Course, is thanked for facilitating access to collecting sites during a return visit by WJN. Finally, B. Mitch Blake and an anonymous reviewer are acknowledged for their constructive reviews.
Publisher Copyright:
© 2015.
PY - 2015/11/1
Y1 - 2015/11/1
N2 - 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.
AB - 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.
KW - ISGS
KW - Bolsovian
KW - Macroflora
KW - Asturian
KW - Desmoinesian
KW - Atokan
KW - Biostratigraphy
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U2 - 10.1016/j.revpalbo.2015.07.003
DO - 10.1016/j.revpalbo.2015.07.003
M3 - Article
VL - 222
SP - 67
EP - 83
JO - Review of Palaeobotany and Palynology
JF - Review of Palaeobotany and Palynology
ER -