Volcanic and deformation history of the Bodrum resurgent caldera system (southwestern Turkey)

Abstract

The volcanic rocks of the Bodrum Peninsula, in SW Turkey and NE of the Hellenic Arc, outcrop over an area of 138 km 2. A monzonitic intrusion is exposed in the western part of the peninsula. Upper Miocene volcanism is represented by high-K (HK)-andesitic, andesitic lava flows and pillows, sparse HK-andesitic and dacitic lava domes and associated block-and-ash flows. A HK-andesitic ignimbrite sequence with two stratigraphic units is associated with the collapse of a complex caldera system. Breccias, formed as a result of slumping of the caldera walls are observed inside the caldera. Post-caldera activity is represented by HK-andesitic, HK-basaltic andesitic lava flows, domes and associated block-and-ash flows. Numerous dykes, HK-andesitic and shoshonitic in composition cut all volcanic units. The structure of the Bodrum caldera was investigated using SPOT image, digital elevation model (DEM), aerial photographs as well as field data. The Bodrum caldera is a NE–SW-elongated, semi-elliptical, deeply eroded caldera with dimensions of 18.7×7.7 km. It is partly submerged in the SW part. The complex caldera system can be described in terms of two structural domains. The collapse of the Dagbelen domain is interpreted as a piston type subsidence, while the Karakaya domain represents a piecemeal collapse. Both domains exhibit two separate resurgence events. The elongation of the caldera may be related to pre-existing regional tectonic structures. The caldera is also affected and cut by late stage faults related to regional extensional events. Moreover, pre-caldera volcanism is dispersed and cannot be related to a pre-existing stratovolcano. Bodrum volcanism is therefore interpreted as a complex ignimbritic shield volcano.