Reconstruction of land and freshwater palaeoenvironments near the Eocene–Oligocene boundary, southern England

摘要

Mammalian assemblages in the Bembridge Limestone Formation of late Eocene age, Headon Hill, Isle of Wight, England, indicate habitats ranging from open woodland to closed forest. Distinctive ‘lower’ and ‘upper’ mammalian faunas reflect different faunal provinces, probably in response to climatic fluctuations that foreshadowed the terminal Eocene event. In order to improve our understanding of these patterns, we have examined a variety of other palaeoenvironmental indicators from this section. These include palynological organic matter (POM), plant macrofossils, non-mammalian faunas, organic geochemistry and stable isotopes. The evidence shows that the depositional setting was a tranquil, shallow, freshwater lake, with a brief lagoonal interval. However, evidence for habitats surrounding the lake is contradictory, emphasizing the necessity for multidisciplinary approaches to palaeoenvironmental reconstruction. The mammal faunas give unequivocal evidence for woodland or forest, yet, apart from some of the land snails, there is no other indication of the presence of trees. Furthermore, according to the mammalian evidence the lake was bordered by distinctive vegetation at different times, with closed forest/woodland during marl deposition and open woodland during black mud deposition, but there are no parallel fluctuations in other biotic elements.