MIOCENE VOLCANIC LANDSCAPES OF THE EASTERN MEDITERRANEAN: THE FOSSIL FORESTS OF LESVOS, GREECE

The island of Lesvos, Greece, is located in the NE Aegean Sea south of the North Anatolian fault that lies between the Arabian and Eurasian plates. Active Miocene (~18 Ma) volcanism associated with the strike-slip boundary and subduction left tephra, debris flow, and mudflow deposits across the western part of the island built over a late Paleozoic to Triassic and an ophiolite suite of basement rocks in the east. Volcanic activity emanating from the Vatoussa stratovolcano is believed to be responsible for deposition of the ~350 m thick volcaniclastic sequence on its western flanks, known as the Sigri Pyroclastic Formation, over a relatively short interval of time. Some estimates of this center's pyroclastic activity are as short as 50 ka, during which time in situ trees that grew on these volcanic landscapes are preserved.

The Lesvos Global Geopark, centered around the Protected Natural Monument of the Petrified Forest, consists of four sites in which autochthonous, silicified trees are preserved and exposed: Mpali Alonia Park, Sigri Park, Plaka Park, and Nisiopi Island. A preliminary survey of the stratigraphy, sedimentology, taphonomy, and wood systematics in the Mpali Alonia park was undertaken to determine the number of forest horizons and character of the Miocene landscapes on which the trees grew.

At the Mpali Alonia Park, permineralized trunks in growth position are found on two major levels in approximately 90 m of stratigraphic section. Standing trunks, ranging in preserved heights from <0.4 to 7.1 m, are buried in fine-grained debris flows and exhibit slight inclinations toward the southwest. Forests are rooted in poorly developed paleosols in the debris flows. As was determined by previous workers, the forested landscapes are dominated by Pinoxylon paradoxum and Taxodioxylon gypsaceum, with a minor component of various broad-leaved angiosperms, Taxodioxylon albertense, and Tetradinoxylon velitzelosii. Trunks display well-developed growth rings, where preserved, and climatic conditions were such that some individuals attained stem diameters of nearly 3 m. Reconstructed tree heights using standard allometric equations show that individuals can be interpreted as either canopy emergents (65-102 m), canopy (55-65 m), or subcanopy (<50 m) forest elements.