A Cordatum Zone ammonite assemblage from a condensed stromatolitic bed of the Sengenthal Formation (Lower Oxfordian) at Wolfsbach, Southern Germany

For the first time, a large assemblage of uncompressed ammonites from the Cordatum Zone (Lower Oxfordian) has been collected from the top of the Sengenthal Formation, Franconian Alb. The ammonites were recovered from a condensed iron-oolitic and glauconitic conglomeratic bed, here designated the Wolfsbach-Bank, which unconformably overlies Bathonian iron-oolitic marls. The bed contains Cardioceras cordatum (Sowerby), Proscaphites paturattensis (Greppin), Neocampylites delmontanus (Oppel), Euaspidoceras freii (Jeannet), Mirosphinctes niedzwiedzkii (Siemiradzki), Protophites christoli (Beaudouin) and further perisphinctid ammonites, which have previously not or rarely been described from Southern Germany. One Macrocephalites sp. indicates additional reworked components from Lower or Middle Callovian sediments. This condensed bed, characterized by iron-rich stromatolitic crusts devoid of cyanobacteria, bears a resemblance to the Schellenbrücke-Bank in N Switzerland, with respect to its ammonite assemblage and sedimentology. The uppermost part of the overlying bed represents a discontinuity widespread in Europe and may have been formed during transgression and lag sedimentation following a sea-level lowstand during that submarine erosion took place.