Vegetation and climate changes at the Early-Late Pliocene Transition around the Mediterranean basin: A case from the Burdur Basin in Southwestern Anatolia

Abstract. The Pliocene (5.33–2.58 Ma), particularly the Early-Late Pliocene transition (~3.6 Ma), is a key period for understanding future climate change linked to increases in greenhouse gases. Around the Western Mediterranean basin, the Early-Late Pliocene transition was marked by the establishment of a Mediterranean climate with summer droughts, cool/wet winters and latitudinal gradients. However, environmental changes in the eastern part of the Mediterranean area during the Early-Late Pliocene transition have rarely been documented. Here, we propose to reconstruct the environmental and climate changes during the Early-Late Pliocene transition from the Lake Burdur sequence, located in Southwestern Türkiye. The aim of this study is to characterize the vegetation, lake dynamics, and water level changes based on pollen and Non-Pollen Palynomorph (NPP) proxies, to quantitatively reconstruct climate changes using a multimethod approach (Modern Analogue Technique, Weighted Averaging Partial Least Squares regression, Random Forest, and Boosted Regression Trees and Climatic Amplitude Method) and morphologically characterize the large pollen grains of Poaceae (Cerealia-type).

The results indicate that, during the Early-Late Pliocene transition at Burdur, the vegetation was dominated by steppes with Poaceae, Artemisia, and Amaranthaceae. Subsequently, arboreal taxa decreased and a alternation between steppe grasslands with deciduous Quercus and steppes dominated by Amaranthaceae became evident. Large Poaceae pollen grains (Cerealia-type) are recorded in the Burdur sequence, but their percentages are lower than those at Acıgöl, a nearby record dated to the Pleistocene. The morphological characteristics of these large Poaceae pollen grains from Burdur are similar to those of domesticated cereals from recent periods, preventing a clear distinction between wild and domesticated Poaceae pollen. The lacustrine ecosystem was characterized by semi-aquatic vegetation and freshwater algae, exhibiting alternating oligotrophic and eutrophic conditions. Climate reconstructions of Burdur show similar trends across different methods, with reconstructed values during the Early-Late transition being close to present-day values. Following a climatic optimum in precipitation and temperature, climate reconstructions indicate an alternation between cool, wet conditions and warmer, drier conditions during the Late Pliocene in Southwestern Anatolia. Around the Mediterranean Basin, climate reconstructions during the Early Pliocene show warmer conditions compared to modern values and a north-south gradient in terms of precipitation, with wetter conditions in the north in comparison to the south. The Late Pliocene is characterized by colder conditions, and more humid conditions in the Western Mediterranean, while Türkyie and Central Asia experienced more arid conditions.