The Neogene stratigraphy of the glaciated European margin from Lofoten to Porcupine

The Neogene succession is here divided into two megasequences, which represent the Miocene–lower Pliocene and lower Pliocene–Holocene intervals. This two-fold subdivision is based largely on a combination of seismic-sequence stratigraphy and biostratigraphy; the latter linked to the various chronostratigraphic boundaries, as defined by Berggren et al. (1995). The proposed new scheme is summarised in Fig. 6 and Table 1. This section provides a summary of all of the information that underpins the unified stratigraphic scheme (Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11, Fig. 12, Fig. 13), whilst a full definition, discussion and illustration of the individual megasequences is given in subsequent sections.

Seismic-sequence stratigraphy is the main tool used in this study, and has enabled the recognition and mapping of several key reflectors, which represent regional unconformities of latest Oligocene–early/mid-Miocene and early Pliocene age. From a database that consists of a total of 76 Neogene sample sites (see catalogue of boreholes in the preface), 13 key boreholes were chosen as important sources of stratigraphic information, enabling these Neogene megasequence boundaries to be calibrated and regionally correlated. These key boreholes are depicted in Fig. 7, which indicates the reliability and resolution of the stratigraphic data that help to constrain the age of the megasequence boundaries. The seismic-stratigraphic expression of the megasequence boundaries is illustrated and described in Fig. 8, Fig. 9 and Fig. 10. The age assignment of the key reflectors is further supported by the remaining sample sites, which are summarised in stratigraphic-range charts (Fig. 11, Fig. 12 and Fig. 13). In addition to stratigraphic information, these charts depict summary lithological information as well as an indication of the stratigraphic reliability of each sample. The charts also provide the basis for future potential subdivision of the megasequences, particularly related to the effects of glaciation (Fig. 8, Fig. 9 and Fig. 10).

All biostratigraphic information has been referred to the nannoplankton zonation scheme of Martini (1971) as a common reference for stratigraphic correlation. This scheme has been used in previous studies of Neogene strata off NW Britain (Stoker 1999), and is retained here for purposes of consistency and cross-referencing. 

The final part of this section presents an initial attempt to establish a Neogene event stratigraphy (Fig. 14). The megasequence boundaries are likely to represent major phases of continental margin evolution. Thus, it is necessary to explore any potential linkages between tectonics, relative sea level, palaeoceanographic circulation, and climate change.

References

Berggren, W.A., Kent, D.V., Swisher, III, C.C. & Aubry, M-P. 1995. A revised Cenozoic geochronology and chronostratigraphy. In: Berggren, W.A., Kent, D.V., Aubry, M-P. & Hardenbol, J. (eds), Geochronology, Time Scales And Global Stratigraphic Correlation: Framework For An Historical Geology. Society of Economic Geologists and Palaeontologists, Special Publication 54, 129-212.

Martini, E. 1971. Standard Tertiary and Quaternary calcareous nannoplankton zonation. In: Farinacci, A. (ed), Proceedings of the Second Planktonic Conference, Rome 1970, (Roma: Tecnoscienza), 739-785.

Stoker, M.S. 1999. Stratigraphic nomenclature of the UK North West Margin. 3. Mid- to late Cenozoic stratigraphy. British Geological Survey, Edinburgh.

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