Publication details
Stratigraphy and petrophysical characteristic of Quaternary fluvial deposits in the Upper Morava pull-apart basin
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| Year of publication | 2014 |
| Type | Appeared in Conference without Proceedings |
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| Description | The Upper Morava Basin is a syndepositional pull-apart type basin, which developed at the contact of the Bohemian Massif with the Outer Western Carpathians. Tectonic forcing of the basin fill is documented by morphologically prominent normal faults, subsurface structure as indicated by gravity and seismic data, and the present-day seismicity. The basin system hosts several graben-like linear depocentres which accommodate Pliocene to Holocene lacustrine and fluvial deposits with maximum thickness of ~300 m. This study is focused on the Pleistocene to Holocene fluvial deposits, which are preserved in the active valley-floor terrace of the present-day River Morava and its tributaries, in the graben-like depocentres beneath the active terrace and in several terrace levels above the valley floor. Vertical offsets of coeval Pleistocene fluvial deposits may reach up to 100 m due to syndepositional normal faulting. Stratigraphic correlation of these deposits is therefore an extremely difficult task but, at the same time, the key to the Quaternary subsidence/uplift patterns of the basin. The original stratigraphic nomenclature of the fluvial deposits was established during 1960s and 1970s, based on morphological analysis of the terrace levels and heavy mineral spectra. However, in the light of the wealth of new geophysical data, geomorphologic interpretations, new petrophysical techniques available and several new AMS 14C ages, this model seems to be outdated. In this study, we provide the first results of the stratigraphic reassesment of the Quaternary fluvial deposits based on facies analysis, heavy-mineral provenance data, magnetic susceptibility and spectral reflectance (sediment colour), supported by AMS 14C ages. The data come from four drill cores, 11 to 25 m deep, which penetrated the active vally-floor terrace as well as the buried fluvial deposits beneath the active terrace. The results indicate that the terrace levels (layers) can be distinguished by changing heavy-mineral provenance from the crystalline rocks of the Silesicum, Lower Carboniferous siliciclastics of the Moravo.Silesian Culm basin and Upper Cretaceous deposits of the Bohemian Cretaceous Basin. Changing provenance across stratigraphy is nicely indicated by sediment colour data and, to a lesser extent, by magnetic susceptibility. The rate of aggradation in the buried Pleistocene terraces reached at least 0.5 m per kyr, which is consistent with the present-day aggradation rates in the Holocene valley floor terraces. Petrophysical parameters are suitable indicators of provenance in the fluvial deposits and can be used for stratigraphic correlation. This study was supported by the Czech Science Foundation project GAČR P210/12/0573. |