Landscape evolution and landform inheritance in tectonically active regions: The case of the Southwestern Peloponnese, Greece
Kleman, Johan; Borgström, Ingmar; Skelton, Alasdair; Hall, Adrian
published: Jun 1, 2016
manuscript accepted: Feb 16, 2016
manuscript received: Aug 13, 2015
ArtNo. ESP022006002006, Price: 29.00 €
Abstract The Peloponnese in southwestern Greece fronts the Hellenic Arc at the boundary between the European and African plates. The relief is developed across deeply eroded nappes and folds that represent the roots of Alpine mountains developed during Early Miocene collision. During the Plio-Pleistocene, the geomorphological development of the region was affected by both large-amplitude climatic swings and neotectonic uplift/subsidence of individual blocks. Combined tectonic and climatic forcing acting on existing mountain, piedmont and basin terrains developed across diverse low grade metamorphic and sedimentary rocks, including thick carbonate units, led to a geomorphological evolution that was both area-specific and highly variable over time. We here identify and analyse landforms of the southwestern Peloponnese and the climatic and tectonic events that have been driving the geomorphic evolution during the Plio-Pleistocene. The observational database consists of studies of river profiles, spatial landform distribution and genetic classification of landforms, some of them not previously described from the area. We observe that some important landforms and landscape elements can only be understood in the context of a long Plio-Pleistocene time perspective and reflect particular tectonic trends and events. We examine a partly dissected and southward-tilted pediment surface along the west side of the Mani Peninsula. The seaward truncation of this surface is interpreted to reflect Late Pliocene rifting and uplifting of the edge of Taygetos horst. Analysis of the spatial relations between landforms suggests that before the onset of rifting and the late-Pliocene-Pleistocene phase of uplift, a mature mountain-piedmont morphology already existed in the Taygetos-Mani block. The along-crest elevation differences were less pronounced than they are today, and the central part of the massif was fluvially dissected to a lesser depth than today. The pre-rifting elevation of the highest Taygetos summits is inferred to have been 1800–2000 m. Despite active neotectonics, the Peloponnese retains major landforms that have persisted through 1–3 Myr of slow erosion, due to partial exhumation, karstification and remoteness from drainage lines. A coherent inherited or relict surface comprising the highest summit of the Taygetos Mountains and a disjunct high-elevation, low-gradient valley is identified. We infer that this older morphology formed at considerably lower elevation and has since been uplifted to its present position. It is indicative of locally low summit erosion rates throughout Plio-Pleistocene uplift of the Taygetos horst. The impact of climate changes is most obvious at the lowest and highest elevations (<500 m and >2000 m). At the lowest elevations, eustatic sea-level changes influenced the spatial location of erosion and sedimentation, and ravine systems developed in uplifted marine sediments. At the highest elevations, glaciation has during the last few glacial cycles left a diagnostic imprint. At intermediate elevations, the landscape can be described as a continuously evolving fluvial landscape in which climatic changes have left few or no diagnostic landforms. Our results have implications for interpretation of other mountainous carbonate areas, particularly in the climatically distinctive Mediterranean region. Tectonics appears to have been the first-order driver for geomorphic evolution, the effects of which must be clarified before study of climate impact on landform development can be possible or meaningful. The Taygetos Mountains and Mani Peninsula provide a case study that illuminates how a multiple-age landscape can result from spatially extremely uneven erosional impacts, where tectonic isolation, remoteness from drainage lines, and karstification are important processes for creating inherited and only slowly changing landscape elements.