Cretaceous to Miocene thrusting and wrenching along the central south Carpathians due to a corner effect during collision and orocline formation

Abstract

Field studies in the Romanian South Carpathians (longitude 22.5° to 24.2°E and latitude 45.2° to 45.6°N) demonstrate (1) Cretaceous top‐to‐NE shearing parallel to the present strike of the thrust system connected with coaxial flattening within the generally northwest dipping foliation, (2) Paleogene ductile‐brittle dextral wrenching, E‐W compression (σ1: 87±15°), and basin formation (Petroşani basin) along the Cerna‐Jiu fault system, (3) large‐scale Miocene dextral wrenching along the northern margin of Moesia (σ1: 143±16°), and (4) probably Pliocene–early Pleistocene N‐S compression (σ1: 205±25°). We discuss the tectonics of the South Carpathians stressing the corner effect of the Moesian foreland promontory during convergence and formation of the Carpathian orocline. Up to the late Early Cretaceous, subduction of oceanic crust was active between Europe‐Moesia on one side and East Carpathia‐Rhodopia on the other side. Collision and intracontinental deformation occurred during the late Early and Late Cretaceous. The pinning of the thrust front at the western tip of Moesia and the foreland recess north of it caused superposition of thrusting and wrenching during collision and lateral translation, tangential stretching during orocline formation, and spreading into the recess. Further convergence during the early Tertiary resulted in dislocation of the previously welded East Carpathian‐Rhodopian and Moesian fragments along the Cerna‐Jiu fault system and the further northeast translation of the western segment. The intramontane Petroşani basin opened as a northeasterly propagating, transient pull‐apart structure along the Cerna‐Jiu fault system, which acquired a curved, northwesterly convex, transtensional trace due to the shape of the Moesian promontory. Tightening of the Carpathian orocline and/or rearrangement of the microplate geometry during the formation of the Pannonian basin system led to large‐scale dextral wrenching along the northern margin of Moesia. Pliocene N‐S compression reflects final shortening in the Carpathian system before ongoing convergence between Europe and Africa was transferred to the Mediterranean. Rotation of material lines around the Moesian corner is corroborated by paleomagnetic studies.