Terminal Palaeocene events in the North sea and Faeroe-Shetland basins

Abstract

To investigate the occurrence of these events in the North Sea and Faeroe-Shetland basins, wells 22/10a-4 in the Everest Field of the Central North Sea and 206/1-1A in the Faeroe-Shetland Basin were studied. These wells each yielded over 300' (100m) of near continuous core that was subjected to a high resolution sampling strategy (2' (60cm) sample frequency). The samples collected were subjected to a range of analyses which included biostratigraphic, palynofacies, microfaunal, TOC and d¹³C analyses.

The sparse palynofacies assemblages of Lista L3 were characterised by black wood, low TOC values, abundant bioturbation and diverse assemblages of agglutinated foraminifera: together indicative of deposition in a well-oxygenated environmental. A dramatic environmental change occurs at the Lista/Sele boundary where the palynofacies, microfaunal and geochemical evidence from Sele S1a, together with an absence of bioturbation and the dark grey, often pyritic nature of the sediment indicates a marked decrease in dissolved oxygen concentrations. This was probably due to the onset of basin restriction and concomitant decreases in circulation and dissolved oxygen concentrations. The data from Sele S1b show the dramatic appearance of the warm water dinocyst Apectodinium and an increase in the abundance of paratropical pollen such as Caryapollenites and Compositoipollenites at the base of this unit, indicating the development of warm climatic conditions associated with the widely documented late Palaeocene thermal maximum (LPTM). The disappearance of agglutinated foraminifera and deposition of finely laminated sediments at this point illustrates the development of truly hostile sediment conditions and anoxic bottom waters.

The data collected from 206/1-1A in the Faeroe-Shetland basin indicate that the vast majority of deposition occurred on a coastal alluvial floodplain that was periodically subjected to local marine incursions. The dinocyst assemblages recovered from this site are therefore allochthonous and provide little useful palaeoenvironmental information. However, although there is no evidence for the dramatic tectonic restriction observation in the North Sea Basin, as in 22/10a-4, the development of the LPTM is again indicated by the abrupt and coincident appearance of Apectodinium and paratropical pollen.

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