Climate and vegetation during the Miocene - evidence from Danish palynological assemblages

Abstract: Several Danish exposures and one drill core spanning the upper Oligocene-upper Miocene interval of the Cenozoic (i.e., 24–5 Myr ago) were palynologically investigated. The sediments were deposited in alternating deltaic, marginal marine and fully marine settings, and reveal a rich and diverse miospore flora, associated with abundant dinoflagellate cysts. The results consistently demonstrate that coastal areas in what is now Denmark were inhabited by Taxodium swamp forests that also hosted a range of terrestrial angiosperms, such as Nyssa, Betula, Alnus and Myricaceae. Further inland, mixed deciduous-evergreen forests prevailed and in drained soils, or in elevated areas, conifer-forests dominated by Pinus, Sequoia and Sciadopitys thrived. By employing the Coexistence Approach, the mean annual temperatures were calculated to 15.5–21.1º C for the late Oligocene-late Miocene. The warmest periods occurred during the earliest Miocene and the middle Miocene, respectively. The latter period represents a prolonged climatic warming event approximately 17–14 Myr ago. This warming is globally recognized and referred to as the middle Miocene Climate Optimum. Following this event, a marked climatic cooling occurred at about 11 Ma, which coincides with the beginning of the globally identified late Miocene Cooling phase.