Middle to Late Miocene terrestrial biota and climate

The Middle to Late Miocene (15.97 – 5.33 Ma) is considered a time interval that was warmer than today. It is also a time interval of significant cooling. The aim of this study is to provide a new global view of this 10 Ma interval of global warmth and climate change, through the use of vegetation, mammals and modelling. The study begins in the UK and uses palynology to assign, the previously poorly constrained, Brassington Formation to the Tortonian. The pollen of the Brassington Formation shows the existence of a warm-temperate mixed forest in the UK with a mean annual temperature of 16°C – roughly twice the modern mean annual temperature. Using this fossil site, as well as 633 others, the global biome distributions are determined for the Langhian, Seravallian, Tortonian and Messinian stages. The data show that the Langhian represents a world significantly warmer than today. Cooling occurred through the Seravallian and Tortonian and by the Messinian, this cooling trend had eliminated warm – temperate mixed forests from the western USA and Australia and had formed mid – latitude deserts. Using the palaeobotanical data for the Tortonian age a data – model hybrid vegetation map has been made, suitable for use in palaeoclimate modelling studies. This is then used as a boundary condition in the HadAM3 climate model to show influence of vegetation on the Tortonian climate. Finally the palaeoecology of Late Miocene mammals is investigated to develop a new proxy for vegetation. The co–occurrence technique uses the biome tolerances of Late Miocene mammals to reconstruct regional vegetation. This has been successfully used to add further details to the vegetation maps from palaeobotanical data. This study presents a new approach to exploring vegetation and climate during the Miocene and provides novel details on this dynamic epoch.