A vertical record of different tidal cyclicities: an example from the Miocene Marine Molasse of Digne (Haute Provence, France)



The Miocene marine molasse of Digne is thought to have been deposited in a structural embayment with a gulf-like morphology. This gulf was closed toward the alpine front and opened on to the Rhodano-Provençal gulf, part of the Tethys.

The outcrop of Auribeau, located on the northern margin of the gulf of Digne, displays a conspicuous vertical record of different tidal cyclicities indicating the importance of tidal dynamics on the Miocene marine molasse deposits. For the first time these tidal cyclicities are analysed from a vertical section (deposited by vertical accretion) and these are similar to the cyclicities described from megaripples or sand waves (deposited by lateral accretion). By means of thickness measurements and time series analysis, four main tidal cyclicities have been recognized: (1) the diurnal cyclicity (as it exists in the Atlantic Ocean); (2) the semi-lunar month cyclicity of neap to spring; (3) the lunar month cyclicity of neap, high spring, neap to low spring and (4) the semi-annual cyclicity of solstice to equinox.