From Middle Jurassic extension to Late Jurassic obduction: sedimentary records from the Greater Adriatic margin of the Neotethys Ocean in NE Hungary

Abstract A displaced segment of the Late Triassic–Late Jurassic Greater Adriatic margin of the Neotethy Ocean was investigated in NE Hungary. In this area, the Mesozoic basement is largely covered by the Palaeogene—Miocene infill of the North Hungarian Palaeogene Basin and the Pannonian Basin. Micropaleontological, sedimentological and structural investigation of more than thirty wells resulted in the detailed characterisation and 3D depositional model of the area, which may have formed in the eastern continuation of the Slovenian Basin or in a similar sub-basin. The sedimentation in its Bajocian–early Callovian extensional half-grabens was characterised by pelagic limestones followed by dark shales with sandstone intercalations. Mass-flow deposits derived from both the footwalls of graben-bounding normal faults and the Adriatic Carbonate Platform were frequent. The most basin-ward segment of the latter one was penetrated by the south-westernmost well of the area. Both the Middle Jurassic extension of the formerly extended continental crust and the lower plate source of the sediments have great importance, while they change the tectonic interpretation of the basins. In the overlying Tarna olistostrome sedimentation lasted at least until the Tithonian, as indicated by nannofossils. This is the oldest possible age for the overthrusting of the ophiolite nappe over this segment of the Greater Adriatic continental margin. The now eroded ophiolite nappe is underlain by the Darnóhegy Mélange, a typical sub-ophiolitic mélange, which was formed further to the south-east during the Callovian–Oxfordian, at an earlier, intraoceanic stage of the Neotethyan subduction.