Miocene to Pliocene vegetation and climate estimates in the Iberian Peninsula from pollen data
Résumé
Pollen analysis of Miocene and Pliocene sediments from the Iberian Peninsula shows a progressive reduction in plant diversity through time caused by the disappearance of thermophilous and high-water requirement plants. In addition, an increase in warm–temperate (mesothermic), seasonal-adapted “Mediterranean” taxa, high-elevation conifers and herbs (mainly Artemisia) occurred during the Middle and LateMiocene and Pliocene. This has mainly been interpreted as a response of the vegetation to global and regional processes, including climate cooling related to the development of the East Antarctic Ice Sheet and then the onset of the Arctic Ice Sheet, uplift of regional mountains related to the Alpine uplift and the progressive movement of Eurasia towards northern latitudes as a result of the northwards subduction of Africa. The development of steppe-like vegetation in southern Iberia is ancient and probably started during the Oligocene. The onset of a contrasted seasonality in temperature during the Mid-Pliocene superimposed on the pre-existing seasonality in precipitation, the annual length of which increased southward. The Mediterranean climatic rhythm (summer drought) began about 3.4Ma and caused the individualization of modern Mediterranean ecosystems. Quaternary-type Mediterranean climatic fluctuations started at 2.6Ma (Gelasian) resulting in repeated steppe vs. forest alternations. A latitudinal climatic gradient between the southern and the northern parts of the Iberian Peninsula existed since the Middle Miocene.