The Transylvanian basin is a major sedimentary basin located in the eastern part of the European Alpine orogenic system. It has a sedimentary fill more than 5 km (up to 8 km in some small areas) thick of Upper Cretaceous to upper Miocene deposits. It represents the main gas-producing province in Romania and central, eastern Europe.
In this article we analyze seismic lines and structural data from the basin as well as from its northern, eastern, and southeastern borders. These data indicate a tectonic origin for the Neogene structures from the Transylvanian basin. These structures include (1) northeast- and southwest-dipping thrust faults, and (2) east-northeast- and west-northwest-striking strike-slip faults having normal or reverse slip. Secondary structures such as salt diapirs and folds are related to these faults.
Structural data from the basin and its border indicate a Neogene overall compressional/transpressional regime having maximum principal stress oriented north to northeast.