HR: 1340h
AN: T53A-0477    [Abstracts]
TI: Syn-tectonic sequence generation in low-gradient desert margin systems - the Lower Triassic Buntsandstein of the Central European Basin
AU: * Radies, D
EM: radies@geol.rwth-aachen.de
AF: Geological Institute RWTH Aachen University, Wuellnerstr. 2, Aachen, 52062 Germany
AU: Stollhofen, H
EM: stollhofen@geol.rwth-aachen.de
AF: Geological Institute RWTH Aachen University, Wuellnerstr. 2, Aachen, 52062 Germany
AU: Hollmann, G
EM: gregor.hollmann@gazdefrance-peg.com
AF: Gaz De France PEG, Waldstr. 39, Lingen, 49808 Germany
AU: Kukla, P
EM: kukla@geol.rwth-aachen.de
AF: Geological Institute RWTH Aachen University, Wuellnerstr. 2, Aachen, 52062 Germany
AB: The Late Permian/Early Triassic succession of the Central European Basin (CEB) was repeatedly affected by tectonic pulses associated with the earliest phases of Tethyan and Arctic-North Atlantic rifting. Effects of differential tectonic subsidence are particularly well recorded by unconformities, which form widespread sequence boundaries. In the lowermost Triassic the Hardegsen Unconformity (H-unconformity) represents the most prominent unconformity that can be traced over a distance of 1200 km from southern Germany as far north as the Irish Sea Basin. This hiatus is best expressed on intra-basinal highs that are associated with "stratigraphic losses" of whole formations down to Permian strata and a calculated erosional downcutting of up to several hundreds of meters. This study investigates the controlling mechanisms of unconformity development in a predominantly continental environment. 3D-seismic data from the eastern margin of the East-Netherlands Palaeo-High reveal that differential subsidence during the Middle and Upper Buntsandstein was induced by basement tectonics. Core- and log-based facies analysis of 18 cores from the Ems Area in northwestern Germany identifies the effects of differential subsidence and growth faulting on the generation of sedimentary sequences of the Middle Buntsandstein. Lineaments of synsedimentary tectonic movements are observed in seismic sections and drillcores. They originate from deep rooting, north-south extending basement faults in Upper Carboniferous strata that were decoupled by intercalated Permian evaporits. The sedimentary sequences of the Middle Buntsandstein Group are characterised by the fining upward sequences of the Volpriehausen-, Detfurth- and Solling Formations. Beginning with basal sandstone units that represent either fluvial or aeolian dune sandstones the depositional environment changes into ephemeral fluvial or playa type deposits. The H-unconformity is expressed by a stratigraphic gap underlying the Solling Formation. It comprises the entire Hardegsen Sequence and the upper Detfurth Sequence. Apart from these obvious "stratigraphic losses" the remaining sequences underlying the H-unconformity are characterised by a reduced thickness on the palaeo-high. The internal stratigraphical organisation of these continental sequences is characterised by the establishment of maximum flooding surfaces that can even represent short-lived marine ingressions. These flooding surfaces are traceable throughout the whole working area and they even occur twice in one unconformity bound main sequence. Such composite sequences give indication of previously unknown sequence boundaries of higher order. Throughout the CEB the H-unconformity is associated with palaeosoil developments, which show characteristic geochemical and textural finger prints, that allow regional correlations. The textural characteristics vary between vertisols (clay-rich types) and calcretes (carbonate-rich types). Analysis and correlation of these sequence boundaries is used to evaluate the relative importance of synsedimentary tectonism in the development of palaeo-topography and the provision of accommodation space.
DE: 9335 Europe
DE: 9609 Mesozoic
DE: 8105 Continental margins and sedimentary basins
DE: 8109 Continental tectonics--extensional (0905)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting