In the Lesser Caucasus three main domains are distinguished from SW to NE: (1) the autochthonous South Armenian Block (SAB), a Gondwana-derived terrane; (2) the ophiolitic Sevan-Akera suture zone; and (3) the Eurasian plate. Based on our field work, new stratigraphical, petrological, geochemical and geochronological data combined with previous data we present new insights on the subduction, obduction and collision processes recorded in the Lesser Caucasus. Two subductions are clearly identified, one related to the Neotethys subduction beneath the Eurasian margin and one intra-oceanic (SSZ) responsible for the opening of a back-arc basin which corresponds to the ophiolites of the Lesser Caucasus. The obduction occurred during the Late Coniacian to Santonian and is responsible for the widespread ophiolitic nappe outcrop in front of the suture zone. Following the subduction of oceanic lithosphere remnants under Eurasia, the collision of the SAB with Eurasia started during the Paleocene, producing 1) folding of ophiolites, arc and Upper Cretaceous formations (Transcaucasus massif to Karabakh); 2) thrusting toward SW; and 3) a foreland basin in front of the belt. Upper-Middle Eocene series unconformably cover the three domains. From Eocene to Miocene as a result of the Arabian plate collision with the SAB to the South, southward propagation of shortening featured by folding and thrusting occurred all along the belt. These deformations are sealed by a thick sequence of unconformable Miocene to Quaternary clastic and volcanic rocks of debated origin.
The kinematics of the collision in Western Alps are investigated through five balanced cross sections of the whole external domain from the Oisans to the Mont Blanc massif. These cross sections were built using published data for the Jura and subalpine fold-and-thrust belts and new structural and field analysis for the External Crystalline Massifs. Five units are defined: the sedimentary nappes from innermost parts of the external zone (e.g., ultra-Dauphinois/Helvetic), the crystalline units with their dysharmonically folded cover (e.g., Morcles nappe), sedimentary nappes over the frontal parts of the crystalline massifs (the Aravis-Granier unit), the subalpine belts (e.g., Vercors, Chartreuse, Bauges, and Bornes), and the Jura. Except for the ultra-Dauphinois nappes, the shortening, including the cover shortening, always corresponds to basement shortening. The total amount of shortening increases from south (28 km, 20%) to north (66 km, 27%). Moreover, the shortening is slightly older in the south than in the north; deepwater turbidites (flysch) and shallow marine to freshwater clastics (molasse) basins are more developed in the north; pressure and temperature conditions are higher in the north; the average uplift rates are about 3 times higher in the north and more localized in space. We propose that these differences are due to along-strike variations in the structure of the European continental margin inherited from Mesozoic times. We then build five palinspastic maps: one at Cretaceous times showing the inherited European Mesozoic margin structure and four from Priabonian to upper Miocene times showing the collision kinematics and the related rotation of Adria.
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