Anthony Butcher

The lower Williamson Shale (Silurian) of New York: a biostratigraphical enigma

The lower Williamson Shale at Tryon Park, Rochester, New York State is unique in the co-occurrence of Stimulograptus clintonensis (Hall), previously recorded only from the middle Telychian, and Pterospathodus amorphognathoides amorphognathoides Walliser, previously recorded only from the upper Telychian ( Cyrtograptus lapworthi Biozone and higher). These two co-occurring fossils are clearly providing contradictory ages for the lower Williamson Shale. The incorporation of chitinozoan data from both the Williamson and Willowvale shales does not support unequivocally either the graptolite- or conodont-derived biostratigraphy and thus the age of the lower Williamson Shale remains problematical.

A new high-resolution δ13Ccarb isotope curve through the lower Wenlock Series of Buttington Quarry, Wales

New high-resolution δ13Ccarb isotope data are presented through the lower part of the early Sheinwoodian carbon isotope excursion from a section in Buttington Quarry, Wales. The graptolite biostratigraphy of the section is established, with the base of the measured section within the Cyrtograptus murchisoni Biozone. The first appearance datums of the biozonal indices Monograptus firmus and Monograptus riccartonensis are recorded. The new isotope curve will provide the basis for future studies, particularly on the palynology of the section.