Vertical motions in the Aegean volcanic arc: evidence for rapid subsidence preceding volcanic activity on Milos and Aegina

Late-orogenic extension in the Aegean region has been ongoing since the late Eocene or early Oligocene. Contemporaneously, numerous volcanic centres developed. In the south-central Aegean region, Plio-Pleistocene volcanism formed a number of islands. On two of these—Milos and Aegina—a sequence of late Miocene and Pliocene marine sediments underlie the oldest volcaniclastics. To determine whether extension of the Aegean lithosphere played a role in the formation and location of the early Pliocene volcanoes of the Aegean, we aimed to reconstruct the vertical motion history as it occurred prior to the onset of volcanism. To this end we reconstructed the paleobathymetry evolution using foraminifera recovered from sedimentary sections in the lower Pliocene of Milos and Aegina. Age dating on the Milos sections was based on bio-magneto- and cyclostratigraphy; from Aegina only bio- and magnetostratigraphy were available. The results show that prior to the onset of volcanism on both islands, many hundreds of metres of early Pliocene subsidence occurred—on Milos even 900 m between 5.0 and 4.4 Ma. It is unlikely that extension of the Aegean lithosphere led to melting of the underlying mantle. However, the extension probably did play a significant role in the timing of the onset of Pliocene volcanic activity in the Aegean. The position of the volcanic centres is probably the result of the depth of the subducted slab below the Aegean and the formation of a network of extensional faults in the overriding Aegean lithosphere.