BRACHIOPOD RECORDS OF THE HANGENBERG AND EARLY TOURNAISIAN EXTINCTIONS AND POST-EXTINCTION RECOVERY IN THE UPPERMOST DEVONIAN - EARLIEST CARBONIFEROUS IN THE ILLINOIS BASIN, WESTERN LAURUSSIA

In the western Illinois Basin of North America, the Hangenberg Extinction (HE) and a regional Early Tournasian extinction is recorded in English River, Louisiana, Horton Creek and Glen Park Formations. The HE is marked by abrupt species extinctions and extirpations of 80% of the English River Formation fauna in the upper part of the Bispathodus utlimus Zone. It is replaced by the fauna of the Louisiana Limestone (lower Protognathodus kockeli Zone). The HE faunal turnover is associated with the onset of the Hangenberg δC¹³ Excursion (HIE) within the lower English River and abrupt shift to maximum values of the HIE within the Louisiana Limestone. These faunal and chemostratigraphic events are correlated globally and identify the HE interval and revised Devonian-Carboniferous boundary (base of P. kockeli Zone = former Upper praesulcata Zone) at the base of the Louisiana Limestone in the Illinois Basin. A second extinction is recorded by the near total extinction of the fauna of Louisiana Limestone in the upper P. kockeli Zone.

The English River fauna is comprised of over twenty species (Figs. 10-13) in the genera: Chonopectus, Mesoplica, Ovatia, Whidbornella, Sentosia, Plicohonetes?, Leptagonia, Schellwienella. Schuchertella?, Schizophoria, Paraphorhynhus, Kitakamathyris, Eudoxina, Syringothyris, Prospira, Hispidaria, Camarorphorella, Iniathyris and Eumetria. Four English River taxa that survive the Hangenberg Extinction include species of Chonopectus, Eudoxina, Kitakamathyris and Camarorphorella.

An earliest Tournaisian marine transgression initiated Louisiana Limestone deposition in the western Illinois Basin. The post-HE Louisiana brachiopod fauna includes 25 craniform and rhynchonelliform taxa in the genera: Anthocrania, Petrocrania, Rhipidomella, Schuchertella Plicochonetes, Rugosochonetes, Obinaria, Cyphotalosia?, Leptolosia, Paraphorhynchus, Cyrtina, Tylothyris, Acanthospirina, Syringothyris, Parallelora, Crurithyris, Lamellosathyris and Camarorphorella.

A sea level low-stand terminated Louisiana deposition and extinction of 22 of 24 species of the Louisiana fauna. Marine transgression in the upper P. kockeli Zone initiated deposition of the Horton Creek and Glenn Park formations. The fauna of these units include English River (9 species) and Louisiana (1species) holdovers. An additional 35 species (35 genera) have regional first occurrences in the Horton Creek-Glen Park marking the recovery following the Louisiana Extinction Event.