HR: 0800h
AN: T11B-0382    [Abstracts]
TI: Coupled Subduction Evolution - an Exemplifying Model on a Mesozoic Subduction in the Alpine-Carpathian Belt
AU: * Schuller, V
EM: volker.schuller@uni-tuebingen.de
AF: University of Tuebingen, Institute for Geosciences, Sigwartstr. 10, Tuebingen, 72076 Germany
AU: Frisch, W
EM: frisch@uni-tuebingen.de
AF: University of Tuebingen, Institute for Geosciences, Sigwartstr. 10, Tuebingen, 72076 Germany
AB: Both, advancing and retreating subduction, were described on various modern and ancient subductions, each on separate subduction zones and cycles. On the base of several investigation methods, this study tries to integrate both subduction types within one subduction cycle. In the Apuseni Mts. (Romania) - a section of the Alpine-Carpathian belt - a Mesozoic subduction was active. During the first period, without subduction related magmatism, a shallow marine forearc basin with sedimentary supply from both, the crystalline hinterland and the forearc ridge, evolved. The following period, accompanied by subduction related magmatism, was characterized by rapid basin subsidence and increased uplift rates in the crystalline hinterland as evidenced by zircon fission-track (FT) and heavy mineral provenance analysis, and thermal modelling on apatite FT length. As well during the second stage, sediments derived from a forearc ridge and the crystalline hinterland. The sedimentary succession - regionally described as Gosau type deposits - is characterized by a sudden change from a shallow marine facies, linked to the first period, and a rapid change to a deep marine environment starting with the second period. Basin modelling proved that during the Upper Cretaceous, apart form a forearc basin, a deep ocean trench basin evolved, which accumulated thick turbidite deposits. Such basins are typically known from active margins with retreating subduction. Several models tried to explain the rapid basin subsidence, for instance with subduction erosion. However, our model proposes a switch of the subduction type as being the responsible mechanism for the sudden and increased subsidence and the late onset of the subduction related magmastism. The first period of advancing subduction, with low-angle dip of the slab, was followed by a retreating subduction due to dehydrating processes in the subducting slab. The onset of retreating subduction is responsible for the installation of a corner flow. A second consequence is the abrupt basin subsidence, which is caused by the slab pull of the backwards moving subducted slab. This model explains an initially missing subduction related magmatism, as well as the generation of a forearc basin with a shallow marine sedimentation followed by a rapid subsidence.
DE: 3060 Subduction zone processes (1031, 3613, 8170, 8413)
DE: 8104 Continental margins: convergent
DE: 8169 Sedimentary basin processes
SC: Tectonophysics [T]
MN: Fall Meeting 2005