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Discussion on the Eocene–Oligocene boundary in the UK Journal, Vol. 163, 2006, pp. 401–415

^{1 1} Department of Palaeontology, Natural History Museum, Cromwell Road, London SW7 5BD, UK (e-mail: j.hooker@nhm.ac.uk)
^{2 2} N. P. Sille & D. P. Mattey, Department of Geology, Royal Holloway University of London, Egham TW20 0EX, UK
^{3 3} School of Earth, Ocean and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK
^{4 4} School of Earth and Environmental Sciences, University of Portsmouth, Portsmouth PO1 3QL, UK
^{5 5} Department of Mineralogy, Natural History Museum, Cromwell Road, London SW7 5BD, UK

The first 20% of the full text of this article appears below.

Jerry Hooker, Margaret Collinson, Stephen Grimes, Nick Sille & David Mattey write: Recognition of the Eocene–Oligocene boundary in the Hampshire Basin, UK, has been debated since naming of the Oligocene Epoch in 1854. Previously, this was because the boundary itself had not been stabilized and because the strata concerned are largely non-marine. A Global Boundary Stratotype and Stratigraphic Point (GSSP) was established at Massignano, Italy, in 1993 in marine strata. Recognition of the boundary on extinction of the planktonic foraminiferan family Hantkeninidae made boundary identification difficult in the continental realm. Correlation to marginal marine and non-marine strata is nevertheless possible via magnetostratigraphic and sequence stratigraphic studies and, importantly, biostratigraphically via dinocyst zones at Massignano (Brinkhuis & Biffi 1993; Brinkhuis & Visscher 1995). Therefore, recent publication of the magnetostratigraphy, sequence stratigraphy and orbital cyclicity of much of the Hampshire Basin Solent Group (Gale et al. 2006) is welcomed and substantially increases the number of correlation tools available in this area. Such cyclical phenomena, however, rely on absolute dating or biostratigraphy for calibration. No radiometric dates exist for the Solent Group, so biostratigraphy remains the best means of dating the succession.

There are, however, problems with the way Gale et al. (2006) have interpreted biostratigraphic markers and therefore with their placement of the Eocene–Oligocene boundary and associated events. The organisms concerned are calcareous nannoplankton (NP zones) and mammals (MP reference levels). Thus, the record by Aubry (1985) of NP22 in the Argiles Vertes de Romainville, Paris Basin, was subsequently qualified by her (Aubry 1986, p. 307) as ‘zone NP22 (not younger; possibly older: NP21?)’. This dating was based solely on the presence of rare Isthmolithus recurvus, which ranges from NP19/20 to NP22 (Aubry 1992), this being the real level of . . . [Full Text of this Article]