Northeastern (46th Annual) and North-Central (45th Annual) Joint Meeting (20–22 March 2011)

Paper No. 2
Presentation Time: 1:50 PM

DEVELOPMENT OF AN EPEIRIC SUBTROPICAL PALEOCLIMATE RECORD FROM WESTERN EURAMERICA: LATE FRASNIAN-EARLIEST TOURNASIAN STABLE CARBON ISOTOPE RECORD FROM THE YELLOW SPRING-NEW ALBANY GROUPS OF THE NORTHWESTERN ILLINOIS BASIN


DAY, Jed, Geography & Geology, Illinois State Univ, Normal, IL 61790-4400, WITZKE, Brian J., Department of Earth and Environmental Sciences, University of Iowa, 115 Trowbridge Hall, Iowa City, IA 52242 and ROWE, Harry, Earth and Environmental Sciences, University of Texas at Arlington, Box 19049, 500 Yates Street, Arlington, TX 76019, jeday@ilstu.edu

Sampling of a series of Iowa Geological Survey (IGS) cores was initated in 2006 to develop a single continuous biostratigraphic sequence stratigraphic, and chemostratigraphic record spanning the Middle Givetian to Early Tournasian for the subtropical ocean of western Euramerica. Here initial results are presented from the first-round sample suite in the IGS Sullivan Quarry and H-32 cores from southeastern Iowa that provide a near continuous record through the Upper Frasnian, entire Famennian, across the Devonian-Carboniferous (D-C) boundary interval in the northwestern margin of the Illinois Basin. Whole-rock geochemical samples were taken at mid-point positions within conodont sample intervals permitting calibration with the Upper Devonian conodont zonation in the IGS Sullivan Core. Large sample spacing (> 30 cm) in the lower part of the Sullivan core did not capture clear records of the Kellwasser excursions as documented in the Devonian composite records of Buggisch, and Joachimski and others. Numerous (>20) excursions are evident in the Famennian interval spanning the Middle triangularis through Middle exspansa zones. δ13Ccarb values within this long interval fall below maximum values of +0.3‰ and minimum values of -4.0 ‰, with certain excursions displaying maximum changes of δ13Ccarb values of up to 2‰. Positive δ13Ccarb values (up to +0.3‰) characterize the prolonged excursion within the interval of Middle-Upper triangularis Zone, that drop below +0.0‰ for the remainder of the Famennian through the interval of the Middle expansa Zone. Significant positive δ13Ccarb excursions commence in within the Upper expansa-Lower praesulcata? zones where an initial positive excursion reaches values of +2.0 ‰, succeeded by the onset of the Hangenberg Excursion signified by two initial excursions with peak values of +4.0 ‰ and +3.9‰ within the Middle praesulcata Zone. Values within the Upper praesulcata Zone are above +5.0 ‰ peaking at >+6.0 ‰ within the Louisiana Limestone carbonate platform. Louisiana Limestone platform deposition was terminated by a major sea level low-stand likely associated with onset of early Tournasian glaciation. Early Tournasian values are still at or above +4.0 ‰ in the Prospect Hill Formation.