New gravity survey in the SE part of the Bohemian Cretaceous Basin

 

Jiří Sedlák, Stanislav Zabadal, Ivan Gnojek, Zuzana Skácelová, Bedřich Mlčoch

Geoscience Research Reports 48, 2015 (GRR for 2014), pages 175–178

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Published online: 16 October 2015

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Abstract

New gravity survey at the scale of 1 : 25 000 was launched on the 571 km2 large segment of the SE part of the Bohemian Cretaceous Basin where this method has not been applied up to now. Much larger territory of 4200 km2 embracing both adjacent western and eastern territories was chosen for the geological interpretation of this survey (Fig. 3).
The Bouguer anomalies and several derived gravity maps, such as regional gravity, residual gravity, horizontal gradients, and Linsser density boundaries were calculated. The map of Bouguer anomalies (Fig. 1) did not show only density features of the adjacent crystalline units cropping out; it was able to indicate the continuation of these units partially buried under Cretaceous sediments. The residual anomalies (Fig. 2) predominantly showed the gravity effect of the thickness of the exposed near-surface structures of the occurring Permian to Neogene formations. Local gravity lows indicated the extent of depressions filled up by Cenozoic groundwater-bearing sediments.
Furthermore, 2.5D gravity model along the 100 km long W-E trending profile across the SE part of the Bohemian Cretaceous Basin was calculated (Fig. 4). The interpretation procedures disclosed the buried northern part of the Železné hory Pluton and the covered parts of the Polička unit granite bodies. The gravity cross-section suggested an extent and shape of the source of the prime „Svitavy gravity high“ within the Letovice unit. Then, the gravity response to the Zábřeh crystalline unit, the Mohelnice furrow, and the marginal part of the Moravo-Silesian unit on the East was shown.
The results of this gravity survey contribute to the ongoing geodynamic studies, and may also help to elucidate structures of crystalline units bellow the sediments of the Bohemian Cretaceous Basin.
 

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