LOWER TO MIDDLE TRIASSIC SEQUENCE STRATIGRAPHY AND CLIMATOLOGY OF THE NETHERLANDS, A MODEL

The biostratigraphic framework for the Triassic used by the Nederlandse Aardolie Maatschappij in the Netherlands has been reviewed and updated. This resulted in the recognition of 5 palynological zones and 8 subzones. Northwest European palynological assemblages have been interpreted in terms of xerophytic and hygrophytic flora-elements, characterising dry and humid climatic conditions. The biostratigraphic zonation, the climatic fluctuations both in the Northwest European Basin and on the northwestern margin of the Tethys, and the cyclic lithostratigraphical development have been integrated. This leads to a climatological/sequence stratigraphical model for the Lower/Middle Triassic of the Netherlands. During the Late Scythian (Smithian-Early Spathian) monsoonal activity was responsible for the activation of an ephemeral drainage system on the northern side of the Central European Highland. Under the influence of sealevel highstands, the position of the monsoon belt shifted northwards and the northward flowing drainage system was most active, leading to mass transport of erosional products from the highlands into the Germanic Basin. Based on a combination of biostratigraphic data and climatic events, the Lower Triassic sedimentary cycles in the Netherlands can be linked indirectly with the "standard" sequence stratigraphy and to "Milankovitch" orbitally forced cyclicity. For the marine Middle Triassic sediments a more direct link is envisaged.