The reconstruction of the vegetation and climate history of the Marmara region in northwestern Turkey is of particular interest due to its key role for migration routes of modern men and its location between different vegetation zones. Geochemical and mineralogical investigations of the largest lake in the region, Lake Iznik, already registered striking changes during lake’s history (Roeser et al. 2012). However, a palynological investigation encompassing the late Pleistocene to Holocene transition was still missing. Here, the first pollen record of the last 31 ka cal BP from Lake Iznik sediments as an independent proxy for paleoecological reconstructions is presented.
Sediment samples were taken in a resolution of 50 cm along 13 m of the composite profile. The sampling resolution was increased along the Pleistocene-Holocene boundary. For the preparation of the pollen samples, a standard protocol described in Faegri and Iversen (1989) was followed. A biome reconstruction following the method described in Prentice et al. (1996) was performed.
Lake Iznik’s catchment area is located in a climatic transition area between the Mediterranean and Pontic climate zones. Today, the region is highly influenced by (sub-) Euxinian temperate deciduous and mixed forests dominated by deciduous oak (Quercus) and beech (Fagus). Coastal areas of the southeastern Marmara Sea and the Aegean Sea are dominated by (sub-) Mediterranean woods and shrubs with sclerophyllous and evergreen elements. Towards the southeast, the annual precipitation decreases and steppe-forests followed by dwarf-shrub steppe form the vegetation (Zohary, 1973).
The pollen record of Lake Iznik reflects typical pattern in vegetational and climatic changes of the Eastern Mediterranean with some regional variations. It illustrates the shift from steppe forest during the end of Marine Isotope Stage 3 and steppe vegetation during the Last Glacial Maximum towards an oak dominated mixed forest with Mediterranean elements. The steppe is dominated by grasses, Chenopodiaceae, Artemisia, and other Asteraceae indicating cool and/or dry conditions. A change in steppe components and a higher vegetation density suggest milder climate conditions since ca. 18 ka cal BP. This goes along with an increase of summer insolation (Berger, 1978; Berger et al., 2007). Deciduous oaks increase remarkably since the Late Glacial Interstadial indicating warmer temperatures. A short period of dryer and/or cooler climate (Younger Dryas) is marked by an increase of Artemisia and a decrease of several trees. Deciduous oaks predominate the vegetation since the early Holocene, and they are accompanied by other temperate trees like hazel (Corylus) and elm (Ulmus). The pollen record shows a typical pattern known from the Eastern Mediterranean: the Sarcopoterium spinosum pollen type and Pistacia occur constantly for the first time at the early Holocene. The increase of Fagus and Abies suggests moister conditions since the early Holocene. During an early settlement phase near Lake Iznik beginning ca. 8 ka cal BP (Roodenberg, 2012), only minor changes in the pollen assemblage are registered. Still, the occurrence of anthropogenic indicator species and the ongoing degradation of oak forests indicate human activity around 4 ka cal BP.
Local pollen assemblage zones are in accordance with previously defined sedimentary units (Roeser et al., 2012; P. A. Roeser, unpublished data). In addition, several prominent changes in pollen and non-pollen palynomorph ratios coincide with changes in the aragonite precipitation of Lake Iznik (P. A. Roeser, unpublished data).
Lake Iznik sediments have the potential for further detailed palynological investigations to improve the vegetation and climate reconstruction for the Marmara region. A higher resolution and extension of the present pollen record could reflect the implication of rapid climate changes and human influences on the local and regional environment more precisely.
Unknown Author (2013): Vegetation and climate history of the Marmara region during the last ca. 30,000 years based on lacustrine sediments from Lake Iznik (NW Turkey).
|Title||Vegetation and climate history of the Marmara region during the last ca. 30,000 years based on lacustrine sediments from Lake Iznik (NW Turkey)|