Triassic Sequence Stratigraphy of Western European Basins. An introduction.

The Triassic western European succession comprises at least four transgressive-regressive second order facies cycles which can be followed from the Boreal siliciclastic to the Tethyan carbonate settings. The exact timing of the peak transgression and maximum regression of these cycles vary slightly from basin to basin according to local physiographic conditions, tectonic behaviour and sediment supply. Up to twenty-four third order depositional sequences are the building blocks of the second order facies cycles. They form a good framework for correlation across basins and across facies belts. A major first order transgressive-regressive facies cycle also formed during Triassic time. Its lowermost and uppermost boundaries do not necessarily match with the Triassic system boundaries but, depending to the authors, with the P/T boundary or the Hardegsen unconformity (Late Scythian) for the lowermost one and with the Early Cimmerian unconformity (Late Norian) for the uppermost one.