Biostratigraphy and sequence stratigraphy of the Toarcian Ludwigskanal section (Franconian Alb, Southern Germany)

Extensive construction work at the canal cutting of Ludwigskanal near Dörlbach, Franconian Alb, provided opportunity to re-investigate a scientific-historical and biostratigraphically important reference section South-German Toarcian. The 16 m thick section, described bed by with respect lithology macrofossils, starts within Upper Pliensbachian Amaltheenton Formation, covers Toarcian Posidonienschiefer Jurensismergel ends in basal parts Opalinuston Formation. Carbonate contents are high successively decline Opalinuston. carbonate associated comparatively low organic carbon contents. However, normalized silicate fraction similarily if compared other regions Germany. Only persistence levels into middle differs from those most central Europe. Ammonite biostratigraphy indicates thickness >9 for Pliensbachian, 1.15–1.20 Lower Toarcian, 5.04 >0.5 Aalenian. Despite sediment thickness, all ammonite zones almost subzones present, except major Tenuicostatum Zone Fallaciosum Subzone. On basis discontinuities, condensed beds, correlations neighbouring sections Southern Germany, sequence stratigraphic interpretation is proposed this region: (i) Formation corresponds one 3 rd order T-R sequence, top Hawskerense Subzone fucoid Variabilis Subzone, maximum flooding surface Falciferum Zone. (ii) exhibits two sequences: first ranges Illustris (i.e., Intra-Variabilis-Discontinuity) Thouarsense Zone, “belemnite battlefield” reflects transgressive “ravinement surface” Sequence, not regression its basis. second extents erosive Dispansum Aalensis Pseudoradiosa-Aalensis boundary. Finally, new Torulosum Transgressive system tracts these sequences commonly phosphoritic, while some regressive show pyrite preservation ammonites. surfaces reflect significant submarine erosion relief formation seawater currents, effect less pronounced boundary Jurensismergel-Opalinuston Formation).