The Pannonian Basin took shape through Miocenian thinning and subsidence of crust structures formed during the Late Paleozoic Variscan orogeny. The Paleozoic and Mesozoic structures are visible in Papuk and other Slavonian mountains. The processes also led to the formation of a stratovolcanic chain in the basin 12-17 Mya; intensified subsidence was observed until 5 Mya as well as flood basalts at about 7.5 Mya. The contemporary tectonic uplift of the Carpathian Mountains severed water flow to the Black Sea and the Pannonian Sea formed in the basin. Sediments were transported to the basin from the uplifting Carpathian and Dinaric mountains, with particularly deep fluvial sediments being deposited in the Pleistocene epoch during the Transdanubian Mountains' formation. Ultimately, up to of sediment was deposited in the basin, and the sea eventually drained through the Iron Gate gorge.