X-rays from a Central “Exhaust Vent” of the Galactic Center Chimney
Conodont diversity from Silurian/Devonian boundary interval from the Praha-Radotin section
1. CONODONT DIVERSITY FROM THE SILURIAN/DEVONIAN
BOUNDARY INTERVAL FROM THE PRAHA-RADOTÍN SECTION
Aneta Hušková & Ladislav Slavík
1,2 2
1
Institute of Geology and Palaeontology, Charles University, Albertov 6, 128 43 Praha 2, Czech Republic, huskovaa@natur.cuni.cz
2
Institute of Geology of the Czech Academy of Sciences, Rozvojová 269, 16500 Praha 6, Czech Republic, slavik@gli.cas.cz
Praha-Radotín
PRAHA-RADOTÍN SECTION:
N
Silurian
Devonian
Main faults
Cretaceous
5 km
CZECH
REPUBLIC
Fig. 1: Map of the Prague Synform with marked position of the section Praha-Radotín.
The section of Praha-Radotín is exposed in the northeastern part of
Prague Synform (see Fig. 1). The uppermost Pridoli is characterized by
dark grey thinly bedded limestones with shale intercalations. According
to Čáp et al. (2003), the base of the Devonian lies in Bed 9, which
records the FAD of the graptolite Monograptus u. uniformis. Typical
for the Silurian/Devonian boundary is the „Scyphocrinites horizon“
the limestones with the abundant amount of crinoids. The lowermost
Lochkovian limestones are coarser-grained than in the Pridoli but still
alternate with graptolitic shales. Dark grey calcisiltites with cherts are
common in the upper part of the section. Various faunal groups are
common: graptolites, cephalopods, eurypterids, ostracodes,
acritarchs, bivalves and also conodonts.
INTRODUCTION
The section was studied for conodont biostratigraphy and microfacies around the
Silurian/Devonian boundary. Sampled interval has 5.2 m, for lithology see Fig. 2.
Altogether, 13 samples for conodonts and 13 samples for the thin sections were
taken from the limestone beds of the uppermost Silurian and lowermost
Devonian interval from Praha-Radotín. The weight of each sample was
approximately 2.5 - 3.5 kg. The samples were processed in the laboratories using
standard processing techniques employing 8% solution of acetic acid. Dried
residues of the samples were then concentrated using separation in heavy liquids
(tribrommethane). Conodonts were obtained from nearly all samples (for taxa
ranges see Fig. 2). Representatives of other faunal groups (ostracodes,
brachiopods, bivalves, and gastropods) were commonly found in the conodont
samples. Only sample RAD03 was free of any bioclasts.Conodont material was
examined under the Leica MZ75 stereomicroscope. Selected conodont elements
were photographed by the Tescan Vega3 SEM. A collection of the obtained
conodonts is deposited at the Institute of the Geology of the Czech Academy
of Sciences.
MATERIAL AND METHODS
1 m
DEVONIAN
RAD8
RAD7
RAD6
RAD5
RAD4
RAD3
RAD2,5
RAD2
RAD1,5
RAD1
RAD01
RAD02
RAD037
8
9
10
11
12
13
14
Thinsections
Weosteinhornensiss.l.
Zieglerodinasp.
Zieglerodinacf.
Ozarkodinasp.indet.
Ozarkodinatypica
Ozarkodinaoptima
Wurmiellasp.indet.
Laneasp.indet.
Laneaplanilingua
Icriodussp.indet.
Icrioduscf.w.woschmidti
Zieglerodinapetreasp.n.
remscheidensis
Zieglerodinazellmeri
Wurmiellaexcavata
Laneaomoalpha
Pedavissp.indet.
Pedavisbreviramus
SILURIAN
PridoliLochkovian
Conodontsamples
Bednumber
Samplesnumber
Chronostr.units
Lithology
(simplified)
Ozarkodinacf.optima
Scyphocrinites Horizon
Bioclastic limestones
Limestones with cherts
Shales with limestone parts
Dark micritic/biomicritic limestones
Shales
Conodont samples
Thin sections
Icriodushesperius
This research was supported by the Czech Science Foundation (GA17-06700S) and
by the Grant Agency of the Charles University (GAUK no. 250252). In its final stages,
the study was also supported by the Research plan of the Institute of Geology of the
Czech Academy of Sciences by the Center for GeosphereRVO 67985831 and
Dynamics (UNCE/SCI/006).
ACKNOWLEDGEMENT:
For more information please see Hušková, A., & Slavík, L., 2019. In search of
Silurian/Devonian boundary conodont markers in carbonate environments of the
Prague Synform. Palaeogeography, Palaeoclimatology, Palaeoecology (in review).
Čáp, P., Vacek, F., Vorel, T., 2003. Microfacies analysis of Silurian and Devonian type
sections (Barrandian, Czech Republic). Czech Geological Survey Special Papers.
REFERENCES:
Fig. 2: Simplified lithology scheme of the Praha-Radotín section with the conodont data.
Diversity above the base of the Devonian is slightly higher compared to that in the
uppermost Silurian, and so is the abundance of conodont elements. Above,
it starts to gently decrease again it can be possibly explained by the fluctuation in
water depth in the depositional environment. According to the microfacies
analyses we have to point out the dominance of calciturbidite deposition is in the
Praha-Radotín section, where conodont elements including shallower-water
icriodontids were probably transported together with other faunas to deeper
parts of the slope.
RESULTS AND CONCLUSION
Abundant conodont material (more than one thousand elements) showed a high
diversity and disparity in both the family Spathognathodontidae and Icriodontidae
(see the Fig. 3). Altogether, 18 taxa were identified, but there are also many
unkown forms, which still require a formal description. Very interesting is the
co-occurence of the conodont Icriodus cf. w. woschmidti with the graptolite index
taxon Monograptus uniformis in the same bedding couplet.
Fig. 3: Examples of the different morphology of conodont elements. 1 - lateral
view, 2 - upper view. A - Ozarkodina typica, B - Lanea planilingua. C - Icriodus sp.
500 µm
B1
B2
A1
A2
C
