The genesis of tempestite cycles

Abstract

At the boundary between the Late Maastrichtian Gulpen and Maastricht Formations, exposed in quarry ENCI (Maastricht, The Netherlands), rhythmically bedded coccolithic bioclastic siltstones with flint nodule layers (Chalk with Flint) are covered by rhythmically bedded coccolithic, phosphatic-glauconitic-pyritic bioclastic sandstones with carbonate cement (Tuffaceous Chalk). The rhythmic vertical variations of the grain size, depositional/bioturbational structures and authigenic mineral concentrations in Chalk with Flint and Tuffaceous Chalk with "protohardgrounds" were caused by the periodic variation of hydrodynamics and deposition rates. A numerical model enables the simulation of the genesis of rhythmically bedded (Tuffaceous) Chalk sequences as a function of deposition rates, bioturbative mixing, storm reworking and mineral authigenesis in redox zones of bacterial metabolism. The numerical model facilities the discussion of the relation between the variation of the lithology of (Tuffaceous) Chalk sequences and the variation of the dynamics of the depositional-early diagenetic environment in the subtropical shallow marine (Tuffaceous) Chalk sea.