Geographic and temporal patterns in the late Neogene (12–3 Ma) aridification of Europe: The use of small mammals as paleoprecipitation proxies

Abstract

Present-day relations between small-mammal community structure and rainfall are used to predict late Neogene (12–3 Ma) precipitation patterns in Europe and Anatolia. New proxy methods are developed which include regressions of mean annual and minimum monthly precipitation on diet (Invertivory Index) and locomotion/habitat (Arboreality Index). A series of precipitation maps and a set of regional precipitation curves through time at 1 Myr resolution are presented. Precipitation curves at a higher temporal resolution are constructed for the region of central Spain. The Miocene results show the existence between 12 and 9 Ma of a large wet (800–1200 mm/yr) zone, extending from northern Spain to the Ukraine, and characterized by the whole-year penetration of large amounts of moisture far into the continent. Between 10–9 and 5 Ma, this European Temperate Wet Zone (ETWZ) shrinks and/or moves northward, resulting in diachronous aridification. A coeval northward migration of the Subtropical High Pressure Zone (SHPZ) is hypothesized, which is also consistent with the predicted onset of seasonal (summer) dryness between 10 and 8 Ma. The maximum extension of the ETWZ at 12–9 Ma temporally correlates with Northern Hemisphere cooling, suggesting that climate zonation rather than the global amount of atmospheric moisture controlled European climate at this time. The main aridification at 9–8 Ma could best be explained by a northward extension/shifting of the Subtropical High Pressure Zone, and a transition towards less zonal circulation, processes which ultimately could have been triggered by uplift of the Tibetan plateau. A temporary increase of precipitation at 7–6 Ma is associated with renewed global cooling. The lowest precipitation values (less than 400 mm/yr) occur during the Pliocene in Southern and Eastern Europe. Uplift in Eastern Europe (Carpathians, shrinking of the Paratethys) could well explain the aridification in this area and the associated sharpening of east–west precipitation gradients across the continent.