The history of the Lavanttal Basin and its surroundings was investigated using facies analysis, fault slip analyses, geochemical and geophysical methods. The c. 2000 m deep Lavanttal Basin has a gently dipping western flank and a steep fault-controlled eastern margin. Basin evolution commenced in Early Miocene times with the deposition of the fluviatile Granitztal Formation. Initially the Lavanttal and the Granitztal basins formed one combined depression with its western margin west of Griffen. In the Early Badenian W-E trending extension resulted in further basin subsidence. A contemporaneous sea level rise flooded the basin from the SE. The Mühldorf Fm., which was deposited in this period, consists of a transgressive, lacustrine part (fish shale) and an upper, marine part. The latter was dated as late Early Badenian (14.91-14.75 ma) and comprises a maximum flooding surface and a highstand systems tract. The marine sediments are overlain by lacustrine and fluviatile deposits of the Dachberg Fm. Brackish and lacustrine sediments prevail in the Lower Sarmatian succession. Moderate subsidence and sea level fluctuations favoured the formation of coal seams during Sarmatian times, which all are linked to non-marine transgressions. Detailed studies on the Stefaner seams indicate different depositional environments. The Lower Seam was deposited in a wet, nearly neutral swamp with a dominance of gymnosperms. In contrast the Upper Seam was formed in a relatively dry, more acidic swamp with a dominance of angiosperms. The Kuchl seams represent the youngest seams and are traditionally dated as Upper Sarmatian. However, palaeontologic evidence of this age is missing in the freshwater sediments. An alternation of gravel, sand and clay, deposited in a fluvio-lacustrine environment follow above the Upper Kuchl Seam. These sediments are considered as Pannonian in age and were deposited during a time with enhanced tectonic activity. NE-SW trending compression resulted in a reactivation of faults, which offset the Kuchl seams by 200 m. Thereafter a NW-SE trending extension was followed by a NNW-SSE trending compression. Resulting from a very young uplift, the western part of the basin was tilted towards the east and sediments c. 1000 m thick were eroded. Therefore, the original location of the western margin is disputed.