Between the Alb and the Alps – The fauna of the Upper Cretaceous Sandbach Formation (Passau region, southeast Germany)

Situated halfway between the Franconian Alb and the Northern Calcareous Alps, the uppermost Turonian to basal Middle Coniacian sediments of the Sandbach Formation (Ortenburg–Passau area, Lower Bavaria) provide valuable information on an area largely devoid of Cretaceous sediments at the surface. Based on the rediscovered classic collection of Gustav von Stockheim, the facies and fauna of the two subunits of the Sandbach Formation, i.e., the Marterberg and Buchleiten members, are described, illustrated, and evaluated with regard to palaeoecology. The fauna comprises 53 taxa in total. Almost two-thirds of these are bivalves, which also dominate the eutrophic distal inner shelf assemblage of the Marterberg Member. Conversely, the mid- to outer shelf fauna of the Buchleiten Member is dominated by siliceous sponges, which flourished on account of continuous deepening and decline of terrigenous input during transgression.