Depositional features in Oligocene tidal sediments of Valkenburg, province of Limburg, the Netherlands, with the description of a new lithostratigraphical unit: Valkenburg Deposit

The Early Oligocene sands in Belgian Brabant and Limburg are devided into the Grimmertingen Sands, a shelf deposit, and the Neerrepen Sands, a nearshore, beach and barrier deposit. Both deposits represent a facies, that migrates with the coast; the regressive Neerrepen facies overlying the transgressive Grimmertingen facies. At Valkenburg the Neerrepen facies deposits overlying the Grimmertingen Sands are absent, but deposits with a distinct tidal influence are found instead. The term “Valkenburg facies” was introduced for this type of environment. For its sediments the name “Valkenburg Deposit” (new lithostratigraphical unit) is introduced. Stratotype is the part from 4.85 to 10.40 m of the description of Cadée & Vaessen (1975) of the Valkenburg sequence. The Grimmertingen Sands, the Neerrepen Sands and the Valkenburg Deposit are considered to be members of the Grimmertingen Formation. The Oligocene sequence consists of the following parts: – a transgression, characterized by the Grimmertingen facies shelf deposits (Grimmertingen Sands) – a regression, represented by Neerrepen near-shore and beach deposits (Neerrepen Sands) and overlying tidal deposits (gully systems and a silting-up sequence: Valkenburg Deposit) – a terrestrial phase, indicated by a fossil soil (Neerrepen Soil) – a transgression, that starts with supratidal sediments, grading into lagoonal deposits (Henis Clay and Sands and Marls of Oude Biezen).