EECO, LLTE and MECO events in the Eocene succession of the Isle of Wight and adjacent areas.

Abstract

The Eocene sediments of the London and Hampshire basins, which include the Isle of Wight, have long been a challenge for those interested in foraminifera and biostratigraphy. Despite many attempts at creating a viable zonation, this has proven impossible with Bowen (1954) stating that: “it is evident that no zonal scheme can be advanced for the [London Clay] formation base upon foraminifera”.           Here we present a zonation for the London Clay Formation based on smaller benthic foraminifera (SBF) and, in addition, indicate that the Early Eocene Climatic Optimum (EECO) event may have generated a glacio-eustatic signal. In the same way, using SBF and larger benthic foraminifera (LBF), the Late Lutetian Thermal Event (LLTE) and the Middle Eocene Climatic optimum (MECO) can also be identified, confirming the suggestion of Dawber et al. (2011). The LLTE and MECO events record the most northerly occurrence of numulitids in the UK, with the LLTE event particularly characterised by the northward limit of alveolinids and other LBF. Offshore Selsey Bill, which is east of the Isle of Wight, there is a distinctive carbonate-rich rock that is almost entirely formed of alveolinids and other bioclastic debris. Known since the 19th century it was, at one time, quarried as a building stone for local use. In the marine area around the Channel Islands, and on the Cotentin Peninsula, there are further occurrences of alveolinids, probably generated by a distinct glacio-eustatic event at this level in the succession. These Early and mid-Eocene glacio-eustatic events clearly pre-date the first, significant, glacio-eustatic event (Oi1) at the Eocene/Oligocene boundary (Westerhold et al., 2020). Bowen, R.N.C. 1954. Foraminifera from the London Clay. Proceedings of the Geologists’ Association, 65(2), 125–174. https://doi.org/10.1016/S0016-7878(54)80004-6 Dawber, C.F., Tripati, A.K., Gale, A.S., MacNiocaill, C., Hesselbo, S.P., 2011. Glacioeustacy during the Middle Eocene? Insights from the stratigraphy of the Hampshire Basin, UK. Palaeogeography, Palaeoclimatology, Palaeoecology, 300, 84–100. Westerhold, T., and 23 others, 2020. An astronomically dated record of Earth’s climate and its predictability over the last 66 million years. Science, 369(6509), doi: 10.1126/science.aba6853.