Publication details
Quantitative allochem composition analysis of Lochkovian-Pragian boundary sections of the Barrandian area (Prague Basin, Czech Republic)
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| Year of publication | 2016 |
| Type | Conference abstract |
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| Citation | |
| Description | The Lochkovian-Pragian boundary Event, connected to faunal and facies overturns accompanying global sea level fall, is the first in the series of global Devonian events defined in the classical Barrandian area (Prague Basin, Czech Republic). Carbonate compositional variations were studied on 148 samples from sections at Čertovy schody (257.5 m), Na Chlumu (96.5 m) and Na Branžovech (109.5 m) quarries. Raw quantitative data of determinable allochems (da) obtained by point-count method were used for correspondence, principal component and cluster analysis. The latter two were applied also on data transformed by the log-ratio methodology (clr) that was used to reduce biased patterns resulting from covariance structure of closed data. With the environmental gradient from shallow photic- to deep aphotic zones, several allochem categories were distinguished using the multivariate statistical analysis. The inferred curves of facies shifts show similar results for the raw and log-ratio transformed data. Stratigraphic distribution of the results indicates a lowstand- to transgressive- to highstand- succession in the Praha Formation with a prominent sequence boundary situated close to the Lochkovian/Pragian stage boundary. The heterotroph dominated associations with little contribution of phototrophs and peloids (supported by regional-scale facies architecture) suggest ramp topography. |
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