Tectonically-controlled Late Triassic and Jurassic sedimentary cycles on a peri-Tethyan ridge (Villány, southern Hungary)

Abstract

The article briefly summarizes the history of research of the Villány Mesozoic, with a focus on the Templom-hegy at Villány, and gives short descriptions of the important outcrops of the area. The geologic sketch of the Templom-hegy and concise descriptions of the Upper Triassic Mészhegy Formation, the Pliensbachian Somssichhegy Formation and the Bathonian-Callovian Villány Formation are also given. Several sedimentary cycles were recognized in the early Mesozoic formations exposed on the Templom-hegy. From among them, three fluvio-lacustrine, fining-upward cycles in the Late Triassic and one (or possibly two), marine, fining and deepening upward in the Early Jurassic, are demonstrated and evaluated in detail. The Late Triassic and Early Jurassic cycles at Villány were deposited in a westward-tilted half-graben structure, where repeated tectonic movements were responsible for the episodic and cyclic nature of the sedimentation. The finingupward trends within the three cycles probably reflect climatic changes from humid to arid conditions. For the Middle Jurassic the paleotectonic regime changed: faulting ceased and the territory began to sink uniformly. The Mesozoic subsidence history of the Villány area has close analogies in the contemporaneous blocks of the European inner shelf domain (Helvetic, Briançonnais, (central Penninic, Czorsztyn), and High Tatric Ridges, and the Bihor Autochthon). Their shared features are intensive subsidence in the Early and Middle Triassic, followed by a long interruption of subsidence in the Late Triassic to Middle Jurassic, then a renewed, rapid subsidence in the Late Jurassic. The interrupted subsidence was accompanied by erosion and formation of half-grabens, starting from the mid-Triassic. From this time on, these areas belonged to a transpression/transtension dominated zone for nearly 70 million years, until the Middle/Late Jurassic opening of the Valais-Magura oceanic belt.