Observations on Well-bedded Upper Jurassic Limestones

Abstract

Some studies of selected limestone beds in the Oxfordian of the northern and southern Franconian Alb again confirm the SEIBOLD-model: A continuous deposition of detrital clay is superimposed by a periodical changing calcium carbonate production. On this base, fused (i.e., doubled) limestone beds are recognizeable. Fusion or splitting of beds depends on the clay mineral association: where kaolinite is present, fusion occurs, and vice versa. In the northern region investigated, thickness of sequences and carbonate/non-carbonate ratio are positively correlated, in the southern area this correlation is negative. The lateral transition from a limestone/marl sequence into pure bedded limestones is a function of the thickness of individual limestone beds and their content of insoluble residues.