Palaeoenvironmental reconstruction of Triassic floras from the Central North Sea

Abstract

The Triassic sediments of the Central North Sea (CNS) are considered to have been deposited in a continental environment under a semi-arid climate. The Skagerrak Formation in particular comprises an alternation of sandstone and mudstone members, the development of which is considered to be climatically driven. However, conflicting models exist as to how climate influences member deposition. Here we analyse the climatic signal using a multivariate statistical approach in which detrended correspondence analysis (DCA) is applied to palynological observations to quantify environmental reconstruction. Using DCA it has been possible to define palaeoecological groups and construct a relative hydrological state trend showing hydrological conditions within the centre of the CNS basin during the Triassic. The resultant trends reveal that the relationship between hydrological conditions in the basin and the development of individual sandstone and mudstone members is perhaps not a simple as indicated by existing models. In particular, our data suggest that, although influenced by broader climate trends, in the basin centre there is no simple relationship between climate change and sandstone or mudstone development. The data also indicate that the Julius and Jonathan mudstone members were deposited under differing hydrological conditions. The DCA trends shown here also suggest that the Carnian Pluvial Episode documented from the South Permian Basin and Tethys is not expressed in the CNS.