Development, Uplift, and Segmentation of the Kur Foreland Fold and Thrust Belt (Azerbaijan) as a Result of Multiple Convergent Events in an Oblique Continental Collision Zone During the Neogene–Quaternary

Session: Evolution of Orogenic Belts Through Time: Insights from Sedimentation, Deformation, Magmatism, and Metamorphism, Part I

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Abstract:

The NW–SE-trending Greater Caucasus Mountain belt between the Black and Caspian Seas in the Eastern Mediterranean region has been undergoing rapid uplift, and its Plio–Quaternary foreland basin (Kur Basin = KB) has been actively deforming during the past 5 m.y. This deformation and uplift result from the convergence between the Lesser and Greater Caucasus, and underthrusting of the former beneath the latter within the broad zone of continental collision between Arabia and Eurasia. Significant shortening of the KB has formed the Kur Fold and Thrust Belt (KFTB), displaying SW-vergent thrust faults and basin-parallel fold trains that collectively take up ~8 to 14 mm/yr of the Arabia–Eurasia convergence. The KFTB is a thin-skinned thrust wedge that is propagating SW into the modern KB along the gently NE-dipping Kur Fault. WNW–ESE–striking and SW–vergent thrust faults within the KFTB are moderately to gently dipping at the surface but become subhorizontal at depths of 5 to 7 km, soling into the décollement surface of the Kur Fault. ESE–WNW–trending, asymmetric open folds in Plio-Pleistocene flood plain and alluvial fan deposits are part of the structural architecture of the KFTB. A series of NE–SW–striking, oblique-slip fault systems dissect the KFTB, causing its segmentation and locally uplifting the older basinal strata to the surface. Syn-depositional uplifting of the Plio-Pleistocene strata due to the active and mainly sinistral oblique-slip faulting produced locally well-developed unconformities within the foreland basin stratigraphy. Rivers flowing in these NE–SW–oriented fault zones display ~5 to 10-m-thick fluvial–flood plain terraces, indicating their significant downcutting due to tectonic uplift. These oblique-slip faults played a major role in sediment dispersal in/across the KFTB and caused the segmentation of the entire thrust wedge. Synchronously with the late stages of deformation in the KFTB, dextral faults, which developed in NE Anatolia, Armenia, S Azerbaijan and NW Iran, facilitated crustal–scale extrusion reminiscent of escape tectonics. We propose that the KFTB development has been driven by the collision of the Lesser and Greater Caucasus, whereas the extrusion tectonics in the region is a result of the oblique continental collision between Arabia and Eurasia that began around 14 Ma.