Combined tectonic-sediment supply-driven cycles in a Lower Carboniferous deep-marine foreland basin, Moravice Formation, Czech Republic

Abstract

The Lower Carboniferous Moravian-Silesian Culm Basin (MSCB) represents the easternmost part of the Rhenohercynian system of collision-related, deepwater foreland basins (Culm facies). The Upper VisØan Moravice Formation (MF) of the MSCB shows a distinct cyclic stratigraphic arrangement. Two major asymmetric megacycles bounded by basal sequence boundary, each about 500 to 900 m thick, have been revealed. The megacycles start with 50-to 250-m-thick, basal segments of erosive channels: overbank successions and slope apron deposits interpreted as lowstand turbidite systems. Up-section they pass into hundred metre-thick, finegrained, low-efficiency turbidite systems. Palaeocurrent data show two prominent directions, basin axis-parallel, SSW-NNE directions, which are abundant in the whole MF, and basin axis-perpendicular to oblique, W-E to NW-SE directions, which tend to be confined to the basal parts of the megacycles or channel-lobe transition systems in their upper parts. Based on the facies characteristics, palaeocurrent data, sandstone composition data and tracefossil distribution data, we suggest a combined tectonicssediment supply-driven model for the MF basin fill. Periods of increased tectonic activity resulted in slope oversteepening probably combined with increased rate of lateral W-E sediment supply into the basin, producing the basal sequence boundary and the subsequent lowstand turbidite systems. During subsequent periods of tectonic quiescence, the system was filled mainly from a distant southern point source, producing the thick, low efficiency turbidite systems. Consistently with the previous models, our own sediment composition data indicate a progressively increasing sediment input from high-grade metamorphic and magmatic sources up-section, most probably related to an uplift in the source area and progressive unroofing of its structurally deeper crustal parts. The first occurrence of the Cruziana-Nereites ichnofacies in sandrich turbidite systems in the youngest parts of the MF (Gobel to Gobspi Zone), supported by rapidly increasing quartz concentrations in sandstones, is thought to indicate a transition from generally underfilled to generally overfilled phase in evolution of the MSCB basin. This transition may be linked to the onset of Upper VisØan phase of northward basin-fill progradation assumed by previous authors.

Brunovistulian terrane (Bohemian Massif, Central Europe) from late Proterozoic to late Paleozoic: a review

“…Sandstone and conglomerate composition data from the foreland basin phase indicate increasing sediment supply from high-grade metamorphic and magmatic sources and decreasing supply from sedimentary, volcanic and low-grade metamorphic sources in upward and W-E directions. This trend is related to the uplift of the source area and the progressive unroofing of its structurally deeper crustal regions (Hartley and Otava 2001;Babek et al 2004 (Kotkova et al 2003(Kotkova et al , 2007Tajcmanova et al 2006). In late Viséan times, the basin started to become overfilled (Hartley and Otava 2001;Babek et al 2004), which eventually led to cessation of the deep-marine deposition and beginning of shallow-marine and continental sedimentation in the early Namurian time.…”

Rare earth elements and yttrium geochemistry of dolomite from post-Variscan vein-type mineralization of the Nízký Jeseník and Upper Silesian Basins, Czech Republic

“…In the siliciclastic host rocks, only alteration of biotite, K-feldspar and plagioclase was documented (Table 4). Although these minerals have low REY contents, their occurrence in large amounts in the greywackes (Bábek et al, 2004) Taylor and McLennan (1985). Data for crystalline basement after Kus et al (1987), Souček et al (1988), Jelínek and Dudek (1993), data for Devonian limestones after J. Hladil (unpublished data), for Lower Carboniferous siliciclastics after Pouba (1984) and Dolníček et al (2003) and for Upper Carboniferous siliciclastics after Pouba (1984).…”

Clasts of Variscan high‐grade rocks within Upper Viséan conglomerates – constraints on exhumation history from petrology and U‐Pb chronology

“…Hartley & Otava (2001) presented a concept of point‐source‐derived axial system without a tectonic control for the southern part of the Culm basin. In contrast, Bábek et al. (2004) found evidence for lateral sediment supply in the northern part of the basin, reflecting increased tectonic activity.…”