Integrated Silurian conodont and carbonate carbon isotope stratigraphy of the east-central Appalachian Basin

Abstract The eastern and southeastern margins of the Appalachian Basin contain extensive exposures of Telychian through Pridoli (upper Silurian) strata. Litho- and biostratigraphic analyses of these strata over the last century provided a general means for their chronostratigraphic correlation to global series and stage boundaries. However, a rarity of zonally diagnostic fauna limited precise correlation both within and beyond the Appalachian Basin. Recent conodont biostratigraphic studies substantially revised the chronostratigraphic position of these strata by more than a series in some cases. Much of the interval, however, remained biostratigraphically unzoned and the precise position of series and stage boundaries remained tentative. To improve the chronostratigraphic correlation of these strata to global series and stage boundaries we provide new integrated conodont and high-resolution δ13Ccarb chemostratigraphic analyses from two outcrops located in West Virginia and Virginia, spanning the upper Rose Hill through Tonoloway formations (upper Telychian through Pridoli). These new data show that the Silurian carbon isotope record for this portion of the Appalachian Basin is shifted to more negative δ13Ccarb values than typical global data. However, the overall isotopic records appear correlative at least within the Appalachian Basin thereby providing a means for future correlation within the basin for intervals in which biostratigraphy is traditionally lacking. These coupled data demonstrate that the Ireviken and Mulde excursions are contained within our sections. The high-amplitude Lau Excursion was, however, not observed and the present biostratigraphic data suggest that a majority of the Ludlow Series was either not recorded or was later removed by erosion. These coupled analyses therefore indicate that the Ludlow-Pridoli boundary resides within the Wills Creek Formation and we propose that the overlying isotopic record presented here records the Late Ludlow Carbon Isotope Excursion (LLCIE) and Silale Low, previously identified only within the Baltic Basin.