The project CAUCA-Lift aimed at quantifying the orogenic growth of the Caucasus Mountains. The target area was the ESE- WNW oriented Caucasus range bordered by the Caspian and Black sea basins. It is a key natural laboratory: this region is characterized by spatially heterogeneous present-day plate tectonic movements along the chain (GPS and earthquakes) - pushed by the convergence between Arabia and Eurasia. The Main Caucasus (MCT) - South Caucasus (SCT) Thrust system together with the North Caucasus Front (NCF) and Thrust (NCT) accommodate much of the horizontal shortening and associated uplift of the Great-Caucasus (GC) over the Lesser-Caucasus and Scythian platform respectively. Phases of shortening, uplift and exhumation were poorly constrained, and there is little quantitative data available on the orogen itself that contrasts wit the wealth of subsidence analysis in the bordering oil-productive basins.
The presence of high topography in the GC was subject to debate because little is known about phases of uplift. Orography: there is a marked contrast in the slope gradient from one side to the other in the Greater Caucasus, at least in its easternmost segment where convergence reaches 14 mm/y, i.e. high towards the orogenic front to the SSW and lower on the other side of the range towards the NNW in Dagestan.
For all these reasons we determine rates of vertical movements along a transect across and along the Caucasus chain by the use of low temperature thermochronology (Fission-Track and (U-Th)/He dating). Our sampling profiles were selected across the main faults and the highest topographic elevations, in order to obtain the best controls on denudation histories and relief evolution within the different morpho-structural domains of the belt. Our results are derived from 25 samples and provide key elements for the quantification of denudationr rates. Apatite fission-Track ages span bewteen 120 and 15 Ma whereas U-Th/He dating on 1) apatite are all younger than 7 Ma while 2) zircon are comprised between 180 and 2 Ma. Contrasts are important and indicate that the Caucasus does not exhume as a whole. Once these three datasets combined together I can evidence that the active fault systems along which the Caucasus undergoes a recent phase of uplif are the South Caucasus Front and Fault. Additional thermal modelling is on its way to refine phases of iplift. I constrain denudation for the uppermost 1-8 km, i.e. rates of medium to long-term processes. U-Th/He data as young as 2 Ma suggest that rates reach 3 km/my which is very fast. This combination of methodologies allowed the detection of secular changes in denudation rates to be investigated from geological to sub-recent time and thanks to the prolongation I obtained I am convinced that I will be able to draw maps of rapid uplif.
Our dataset is the first one of this kind produced across the Caucasus chain. First order results constrain and distinguish phases of orogenic growth. For these rasons I also compared these thermochronlogical results to existing geological records such as foreland basin infillings provided by some of my local collaborators. The ultimate goal is partially attained, i.e. understand why the Great Caucasus undergoes today rapid uplift while sismic and GPS. The relevant tectonic processes that shaped the landscape of this mountain range in the frame of the Arabia-Eurasia convergence are the convergence itself that generated the thrusting of the Great Caucasus onto the foreland basins.