STRUCTURAL EVOLUTION OF THE TRANSYLVANIAN BASIN (ROMANIA) - A SEDIMENTARY BASIN IN THE BEND ZONE OF THE CARPATHIANS

The Transylvanian Basin with its up to l0-km-thick Upper Cretaceous to Pliocene fill is one of the most important sedimentary basins of sout heastern Europe. Upper Cretaceous coarse-grained clastics lie unconfor mably on basement strongly tectonized during Early Cretaceous and olde r stages. Upper Cretaceous sediments were mainly deposited along rough ly N-S-trending grabens and were subsequently folded before the end of the Paleocene. Eocene to Middle Oligocene rocks record mostly quiet s edimentation. N-S tension and extension took place in the Oligocene an d was followed by widespread NW-SE compression and contraction. Import ant thrusts are associated with this phase in the northwestern and sou theastern parts of the basin. Widespread N-S contraction followed duri ng the Early Miocene in association with S-vergent thrusting in the no rthern part of the basin. A southward thinning clastic wedge developed during this stage. The Badenian basal unconformity marked a major cha nge in the sedimentary and tectonic pattern of the Transylvanian Basin with new depocenters developing in the central parts of the present-d ay basin. Late Miocene E-W extension affected vast areas and caused so me important normal faulting in the southeast. The youngest deformatio n recorded is associated with E-W contraction and is of Pliocene or yo unger age.