This paper is part of the special publication No.156, The Mediterranean basins: Tertiary
extension within the Alpine Orogen. (eds B.Durand, L. Jolivet, F.Horvath and M.Seranne).
The structure of the Pannonian basin is the result of distinct modes of Mid-Late Miocene
extension exerting a profound effect on the lithospheric configuration, which continues
even today. As the first manifestation of extensional collapse, large magnitude, metamorphic
core complex style extension took place at the beginning of the Mid-Miocene in certain
parts of the basin. Extrapolation of the present-day high heat flow in the basin,
corrected for the blanketing effect of the basin fill, indicates a hot and thin lithosphere
at the onset of extension. This initial condition, combined with the relatively thick
crust inherited from earlier Alpine compressional episodes, appears to be responsible
for the core complex type extension at the beginning of the syn-rift period. This
type of extension is well documented in the northwestern Pannonian basin. Newly obtained
deep reflection seismic and fission-track data integrated with well data from the
southeastern part of the basin suggests that it developed in a similar fashion. Shortly
after the initial period, the style of syn-rift extension changed to a wide-rift style,
covering an area of much larger geographic extent. The associated normal faults revealed
by industry reflection seismic data tend to dominate within the upper crust, obscuring
pre-existing structures. However, several deep seismic profiles, constrained by gravity
and geothermal modeling, image the entire lithosphere beneath the basin. It is the
Mid-Miocene synrift extension which is still reflected in the structure of the Pannonian
lithosphere, on the scale of the whole basin system. The gradually diminishing extension
during the Late Miocene/Pliocene could not advance to the localization of extension
into narrow rift zones in the Pannonian region except some deep subbasins such as
the Mako/Bekes and Danube basins. These basins are underlain coincidently by anomalously
thin crust (22-25 km) and lithosphere (45-60 km). Significant departures (up to 130
mW m -2) from the average present-day surface heat flow for the initiation of two
newly defined narrow rift zones (Tisza and Duna) in the Pannonian basin system. However,
both of these narrow rifts failed since the final docking of the Eastern Carpathians
onto the European foreland excluded any further extension of the back-arc region.
