Thermal history of Tertiary basins in Slovenia (Alpine–Dinaride–Pannonian junction)

Abstract

The transition zone between the Alps, the Dinarides, and the Pannonian Basin was affected by syn-collisional magmatism in Oligocene time and post-collisional lateral escape followed by extreme extension in early and middle Miocene times. Numeric heat flow models for sixteen sites and 650 vitrinite reflectance data from Paleogene and Neogene sediments were used to evaluate temporal and lateral heat flow variations related to these events.Oligocene. Oligocene (Smrekovec) volcanism is the main heat source for Paleogene sediments south of the Periadriatic Lineament. Vitrinite reflectance patterns suggest dextral displacement along the Donat Fault of the order of 50km. Coalification of Paleogene coal-bearing sequences south of the Pohorje is a result of the emplacement of the Oligocene Pohorje tonalite.Early/middle Miocene. Extremely elevated early/middle Miocene heat flow (>200mW/m2) occurred in the Styrian Basin, the Pohorje area, the Maribor–Radgona area, and along the Boč Anticline. It is partly a consequence of magmatic activity. However, no igneous rocks are known from the Maribor–Radgona area. A large shallow early Miocene pluton could explain the observed Miocene heat flow. Rapid uplift of hot basement rocks in the Pohorje/Kozjak region may have increased surface heat flow. Neither volcanic rocks nor metamorphic core complexes are known from the Boč area. The Ormož–Selnica Anticline was probably influenced by a middle Miocene heating event (∼150mW/m2). Coeval volcanism south of the anticline represents a potential heat source.Post-middle Miocene. The WSW–ENE-trending Ljutomer and Radgona Depressions are characterized by moderate Neogene heat flow (60–75mW/m2), whereas late Miocene to present-day heat flow in the Ormož–Selnica Anticline is 80–90mW/m2. A recent heat flow anomaly occurs in the Šomat-Benedikt area.