Interaction of mantle dynamics, crustal tectonics, and surface processes in the topography of the Romanian Carpathians: A geomorphological approach

• Published in: Global and planetary change 2012-06, Vol.90-91, p.58-72
• Main Authors: Molin, P., Fubelli, G., Nocentini, M., Sperini, S., Ignat, P., Grecu, F., Dramis, F.
• Format: Article
• Language: English
• Subjects: Chains; Curvature; Dynamics; Fluvial terraces; Freshwater; Geomorphology; Mantle; Rivers; Romanian Carpathians; Tectonic geomorphology; Tectonics; Topography; Uplift
• ISSN: 0921-8181; 1872-6364
• DOI: 10.1016/j.gloplacha.2011.05.005

Tectonic processes and dynamic mantle flow impart a unique imprint on topography and geomorphic responses over time scales of 104 to 106yr. First-order topographic features in a tectonically active landscape represent ways to quantitatively characterise the interaction between crustal tectonics, mantle dynamics, and geomorphology, providing a basis for modelling landscape evolution. We analysed the topographic features of the Romanian Carpathians, a mountain range characterised by two straight segments connected by a narrow curvature zone. The deformation started in the Late Jurassic and includes two collisional phases during the Cretaceous and Miocene. We examined the tectonic geomorphology of the Romanian Carpathians focusing on regional and local topographic setting, drainage pattern, and river long profiles. Our main database is composed of DEM-based topographic analysis, supplemented with field investigations in the Slănic River basin, located in the Carpathian curvature zone. The longitudinal profiles of rivers draining the southern Carpathians are close to the equilibrium shape, in agreement with the older emersion of the chain. The longitudinal profiles of the rivers draining the eastern and southeastern Carpathians are in a transient state of disequilibrium as a consequence of a more recent emersion of the chain and of the Pliocene–Pleistocene tectonic activity in the Bend Zone. Filtering the topography at different wavelengths, we observe a relative depression in correspondence with the Carpathian Bend, where mantle seismicity and a high-velocity zone in tomography data are located and commonly interpreted as related to an almost inactive and dying subduction zone. Contrastingly, the filtered topography presents a high in the Transylvanian basin, where tomography data show a low-velocity area, interpreted as upwelling of hot asthenospheric materials. We hypothesise that local mantle convection generates positive and negative dynamic topographies. In the Slănic River basin, the foredeep deposits (Middle Miocene–Upper Pliocene) are folded and tilted, suggesting active compression beginning in the Lower Pleistocene. During the Middle–Late Pleistocene and Holocene, four terrace orders developed by the interaction between regional uplift and climate changes. The Carpathian topography results from a diachronous uplift superimposed on crustal tectonics. This diachronous uplift influenced the chain topography, the shape of river longitudinal profiles, an