Surface exposure dating of Holocene basalt flows and cinder cones in the Kula volcanic field (Western Turkey) using cosmogenic He-3 and Be-10

摘要

The Kula volcanic field in Western Turkey comprises about 80 cinder cones and associated basaltic lava flows of Quaternary age. Based on geomorphological criteria and K-Ar dating, three eruption phases, beta 2-beta 4, were distinguished in previous studies. Human footprints in ash deposits document that the early inhabitants of Anatolia were affected by the volcanic eruptions, but the age of the footprints has been poorly constrained. Here we use He-3 and Be-10 exposure dating of olivine phenocrysts and quartz-bearing xenoliths to determine the age of the youngest lava flows and cinder cones. In the western part of the volcanic field, two basalt samples from a 15-km-long block lava flow yielded He-3 ages of 1.5 +/- 0.3 ka and 2.5 +/- 0.4 ka, respectively, with the latter being in good agreement with a Be-10 age of 2.4 +/- 0.3 ka for an augen gneiss xenolith from the same flow. A few kilometers farther north, a metasedimentary xenolith from the top of the cinder cone Cakallar Tepe gave a Be-10 age of 11.2 +/- 1.1 ka, which dates the last eruption of this cone and also the human footprints in the related ash deposits. In the center of the volcanic field, a basalt sample and a metasedimentary xenolith from another cinder cone gave consistent He-3 and Be-10 ages of 2.6 +/- 0.4 ka and 2.6 +/- 0.3 ka, respectively. Two beta 4 lava flows in the central and eastern part of the volcanic province yielded He-3 ages of 33 +/- 0.4 ka and 0.9 +/- 0.2 ka, respectively. Finally, a relatively well-preserved beta 3 flow gave a He-3 age of similar to 13 ka. Taken together, our results demonstrate that the penultimate eruption phase beta 3 in the Kula volcanic field continued until similar to 11 ka, whereas the youngest phase beta 4 started less than four thousand years ago and may continue in the future. (C) 2016 Elsevier B.V. All rights reserved.