Print this pageCyclostratigraphy of Rupelian Clays, Belgium
VANDENBERGHE, NOEL,
The clay deposits along the Rupel river in Belgium were originally designed as the stratotype of the Rupelian.
The cyclic nature of the clay deposits is its most remarkable field aspect.
Grain size, bed thickness, organic matter and carbonates are the varying components. Grain size and organic matter, covary slightly out of phase, but the carbonate levels, are unrelated to the grain-size properties.
It can be demonstrated that the grain-size and organic-matter cycles correspond to Milankovitch cyclicity in which the 100000 year cycle is dominant. Grain-size, organic matter-properties, clay minerals and both organic and inorganic geochemical data allow to propose a model of climatically controlled sea-level fluctuations for these cycles.
The envelope of the high frequency Milankovitch orbital cycles shows two lower frequency cycles in grain size which are interpreted as 3th order eustatic sea level variations. The lateral continuity of the two sequences and local tectonics can be shown on subsurface logging data.
An even lower frequency cycle exists in the thickness distribution of the grain size cycles which is interpreted as a sediment supply-cycle and therefore as an indicator of tectonic activity in the area.