GSSP for the Lochkovian - Pragian Boundary

Definition:

The base of the Pragian Stage is defined at the base of Bed 12 in Velká Chuchle Quarry, in the southwestpart of Prague, Czech Republic, where it coincides with the first occurrence of the zone conodont Eognathodus sulcatus sulcatus.

Location:

The Velká Chuchle section is located in southwestern Prague. It is in an old quarry on the road from Praha-Velká Chuchle to Slivenec on V Dolich Street (Přídoli), 8km southwest of the city center. The quarry is on the nature reserve called "Homolka", in the district of Prague5.		 click


Sedimentology:

The upper Lochkovian consists of gray, fine-grained, biodetrital, bituminous platy limestones with uncommon cherts and subordinate very thin intercalations of calcareous mudstone beds that are millimeters to a few centimeters thick. The Lochkovian - Pragian boundary, based on the first occurrence of conodont Eognathodus sulcatus, lies within this sequence, which shows no marked lithological change. Except for its lower part, the Pragian is represented by the Dvorce-Prokop Limestone. This is light gray, biomicritic to finely biodetrital in the lowest part and passes upward into darker gray micritic limestones. 		click


Primary Markers:

First occurrence of conodont Eognathodus sulcatus sulcatus at the base of bed 12.

Secondary Markers:

Tentaculites:
The boundary is above the Paranowakia intermedia Zone. The base of the subsequent Zone with Nowakia sororcula (possibly = Nowakia kabylica) lies just below the boundary, while the lowest occurrence of typical specimens of the worldwide Pragian index Nowakia acuaria s.s. is above the boundary.

Chitinozoans:
The boundary falls just below the lowest occurrence of the Pragian index Angochitina comosa, close to the first occurrence of Gotlandochitina philippoti, and close to the last occurrence of Eisenackia bohemica.

Other Locations around the World:

Eognathodus sulcatus sulcatus has been acceptedas part of the standard conodont zonal sequence. The name taxon and zone are now recognized in the Czech republic, Germany, Austria, China, Australia, Nevada, Alaska and Canada.

References:

Chlupác, I. and Oliver, W. A. 1989. Decision on the Lochkovian - Pragian Boundary Stratotype (Lower Devonian). Episodes, 12/2, p. 109-113.