Biostratigraphical dating of the Thornton Fossil Konservat-Lagerstätte, Silurian, Illinois, USA

Graptoloid graptolites, conodonts and chitinozoans from the lower part of the Racine Dolomite Formation at the Material Services Corporation quarry at Thornton indicate that the Fossil Konservat‐Lagerstätte here is of late Sheinwoodian (early Wenlock) age. It is thus of an age approximately midway between those of the other Midwest Lagerstätten: within the Brandon Bridge Formation at Waukesha (Telychian), and the Mississinewa Shale (Gorstian) and Lecthaylus Shale (Gorstian). Conodonts indicate that the Fossil Konservat‐Lagerstätte at Thornton corresponds to the ‘post Kockelella walliseri interregnum’ sensu Jeppsson (1997).