ABSTRACT
155The Triassic of the Netherlands records a complex history of episodic tectonism, changing climate and marine flooding of a continental interior basin. The section is divided into two groups separated by the Base Soiling Unconformity: the latest Permian — Olenekian Lower Germanic Trias, and Olenekian — Norian Upper Germanic Trias. The lower group comprises a largely dryland continental succession of playa claystones, fluvial and eolian sandstones and lacustrine oolites that continued to fill the desiccated late Permian Zechstein sag basin. Conglomerates in the south of the Netherlands pass northwards into sandstones and offshore into claystones towards the basin centre. The section shows minor thickness changes and can be up to 800 m thick. The Upper Germanic Trias Group comprises Rat continental clastics and marine evaporites; Muschelkalk carbonate ramp and evaporite facies, and Keuper playa claystones with locally thick halite successions. The south of the Netherlands remained a fluvial clastic fringe throughout. The Upper Germanic Trias Group was profoundly influenced by Hardegsen and Cimmerian extensional events that facilitated marine ingress from the Tethys Sea, created fault-bounded depocentres for playa and evaporite accumulation and local uplift and erosion of older stratigraphy. Thickness changes are more dramatic in this interval, which can be up to 1750 m thick in the offshore Netherlands and up to 5000 m in the Gliickstadt and Horn grabens. The dryland continental character of the Triassic was a persistent feature, but brief episodes of environmental disruption and wetter climatic conditions also occurred. These were expressed by the establishment of perennial lakes and rivers, with the most prominent being in the mid-Carnian and late Ladinian. Widespread marine flooding of the basin began in the latest Triassic and was the precursor to the fully marine conditions that persisted through the Early Jurassic.
