The Frechi horizon (Humphriesianum Zone, Lower Bajocian) from the Oberrhein (South West Germany)

Abstract

New ammonite faunas were recently collected in the Humphriesi-Oolith member from the Oberrhein area between Bâle and Freiburg i.Br. A distinct biohorizon with predominant Stephanoceratidae was met within the basal Pinguis Subzone. This horizon corresponds to the frechi horizon of the type area of the Humphriesianum Zone on the Swabian Alb. The horizon at the Oberrhein contains Stemmatoceras frechi ( Renz)) M, including a remarkable variability, Gerzenites postrugosus ( Westermann)) m, Stemmatoceras sp. M, Stephanoceras rochei ( Maubeuge)) M+m, St. franconicum Schmidtill & Krumbeck M+? m, Stephanoceras lepsiusi ( Gillet)) M+m, several microconchs of Stephanoceras and Chondroceras cf. grandiforme Buckman.. They all are preserved with body chambers. This fauna can be correlated with similar faunal horizons in Swabia, Franconia, North West Germany and probably in South East France and Scotland.