Miocene Forests in Volcaniclastic Landscapes: Lesvos, Greece
The island of Lesvos hosts the first UNESCO GeoPark—the Lesvos Global Geopark—and features impressive fossilized standing tree-trunks preserved to heights of 7 meters and prostrate trees with lengths > 20 meters. Volcanic eruptions over a 2 million interval, between ~18 and 16 million years ago, repeatedly covered mature forests that grew on previous ashfall (tephra) and debris-flow deposits. The debris flows, consisting of rock particles up to the size of boulders, flowed from east to west with considerable speed, engulfing the landscape of the western part of the island. Multiple forests are preserved one atop another, with many trees have retained their cellular details, allowing for their identification. Most trees are similar to those now living in other parts of the northern hemisphere, and include members of the Sequoia family, found today in northern California, as well as pines, oaks, conifers, and cinnamon trees. The preservation of wood anatomy also provides a means to reconstruct the climatic conditions under which each forest grew. The record of each tree’s rings may be our only insight into how the climate in the region changed in response to the increasing buildup of glacial ice at the poles during the Miocene.
Professor Gastaldo, working in collaboration with Dr. Nikolaos Zouros (University of the Aegean) and Dr. Carole Gee (Universität Bonn), have undertaken a pilot project to determine the number of buried, standing forests, their systematics, the heights to which these trees grew (calculated to have been up to 102 m!), and forest composition, in a 90 meter stratigraphic section in the Mpali Alonia Park.
Another UNESCO World Heritage site is Wadi Al-Hitan (Whale Valley) in the Western Desert of Egypt, where Professor Gastaldo, in collaboration with Prof. Philip Gingerich (University of Michigan) and Dr. Carole Gee (Universität Bonn), are searching for evidence of mangroves in this Eocene ecosystem. The locality preserves evidence of one of the iconic stories of evolution: the emergence of whales as ocean-going mammals from ancestors that were land-based animals. These are the youngest archaeocetes known in the fossil record and show last stages of losing their hind limbs. The animals display the typical streamlined body form of modern whales, but retain primitive anatomical aspects of both the skull and tooth structure. One question about the ecological setting in which these animals lived is whether or not they thrived along coastlines, under fluctuating freshwater and saltwater conditions, or lived in settings where there was little to no variation in salinity.