GEOLOGICA CARPATHICA, 51, 1, BRATISLAVA, FEBRUARY 2000
RECONSTRUCTION OF SYN- AND POSTSEDIMENTARY TECTONIC
EVENTS IN FLYSCH BASIN FROM LIMESTONE PEBBLES VARIATION:
DRAHANY CULM OF THE MORAVIAN RHENOHERCYNIAN ZONE
and JIØÍ KALVODA
Department of Geology and Paleontology, Faculty of Science, Masaryk University, Kotláøská 2, 611 37 Brno,
(Manuscript received June 19, 1998; accepted in revised form December 8, 1999)
Abstract: The microfacies of limestone pebbles from the Culm conglomerates of the Drahany Upland were examined
in this study. The established groups of microfacies with similar features have been interpreted in terms of sedimen-
tary environment and the content of facies of various age was analysed. For the pebbles of Upper Famennianbase of
Middle Viséan limestones, the ratio of those facies which are interpreted as calciturbidites, hemipelagites and pelagites
to the microfacies of shallower environments rises significantly in all Culm formations. No such facies were found in
the pebbles of the Givetian-Lower Famennian and Middle-Upper Viséan limestones. Comparison of the ratios of the
limestone pebbles of different ages in Culm formations shows the decrease of Upper Famennian-Middle Viséan
microfacies in the direction from the older part of the Culm (Protivanov Fm.) to its younger part (Myslejovice Fm.).
The analyses of the microfauna has shown that the pebbles of the Givetian-Lower Famennian and Middle-Upper
Viséan limestones occur in the eastern part of the Drahany Upland only. These trends in the content of the limestone
pebbles of various ages and sedimentary environments in individual formations and their areal distribution are inter-
preted as a result of two processes: 1) progressive erosion of the sedimentary cover of the basement unit from its distal
(pelagic and hemipelagic) through proximal (platform) parts due to foreward thrust propagation in the accretionary
wedge of the colliding terranes; 2) post-sedimentary tectonic juxtaposition of the western and the eastern parts of the
Drahany Culm. An advantage of the microfacial analysis of limestone pebbles is demonstrated for the regions where
source-rocks were tectonically modified after their erosion and/or where the source-area was covered with younger
Key words: Devonian, Lower Carboniferous, Rhenohercynian Zone, Drahany Culm, flysch, tectonic implications,
limestone microfacies, limestone pebbles.
The Moravosilesian Culm sediments are situated in the east-
ernmost part of the Bohemian Massif and are considered by
many authors (e.g. Dallmeyer et al. 1995) to be a part of the
southeastern branch of the Rhenohercynian and Subvariscan
Zone of the European Hercynides. They represent the sedi-
mentary cover of the Brunovistulicum which is regarded as the
continuation of the Eastern Avalonian group of terranes in-
volved in the oblique convergence with the southern peri-
Gondwana Lugodanubian group of terranes during the Her-
cynian orogeny (Kalvoda 1995). Tectonically juxtaposed
Devonian and Carboniferous carbonate and flysch sequences
are the remnants of different sub-basins developed on the
Brunovistulian passive margin.
The Drahany Culm represents the southern part of the fly-
sch development of the Moravosilesian Culm and includes
three formations: Protivanov Fm., Rozstání Fm. and Mysle-
jovice Fm. (Dvoøák 1973b; Figs. 1 and 2).
In the Protivanov Fm., which consists mainly of shales and
greywackes, the Koøenec Conglomerates and conglomer-
ates of the Bouzov Culm (Fig. 2) have been studied. These
polymict coarse-grained conglomerates are strongly de-
formed and crop out as oblong discontinuous bodies interca-
lated in greywackes. The Koøenec Conglomerates contain
pebbles of Brunovistulian granitoids, while Moldanubian
high-grade metamorphic rocks are absent (telcl 1965). The
content of the basement-derived pebbles is consistent with
Ar ages of some detrital micas which suggests Ca-
domian cooling of the source-rocks (Schneider et al. 1999).
According to Viséan foraminiferal fauna from limestone peb-
bles of the Koøenec Conglomerates (Kalvoda et al. 1995), we
estimate the age of the formation to be from Middle Viséan
to lower part of Upper Viséan.
The Rozstání Formation is composed mainly of siltstones
with intercalations of fine-grained greywackes and lenticu-
lar bodies of medium- to coarse-grained greywackes. Con-
glomerates are very scarce and crop out in two areas only.
Thin layers of deformed conglomerates occur close to lo-
calities 12 and 13 in the northern part of the Drahany Up-
land. Limestone blocks up to several meters in size (olis-
tolithes by Dvoøák 1987) are intercalated in shales at locality
15. The age of the formation is estimated to be Upper Viséan
according to fauna in the limestone pebbles and to its geolog-
ical position between the other two Culm formations.
In the Myslejovice Formation conglomerates constitute al-
most half of the lithology. They predominate in the south
while greywackes and shales prevail in the northern part. The
older, coarse-grained, polymict Raèice Conglomerates with
greywacke matrix contain pebbles of Moravian and Moldanu-
38 PAÈEK and KALVODA
bian metamorphites and magmatites, older Culm flysch sedi-
ments and limestones. This lithology crops out in the west (see
Fig. 1). In the top of the conglomerate sequence, a facies
known as the Luleè Conglomerates is distinguished which is
defined by the distinct content of Moldanubian granulites and
gneisses and less common pebbles of magmatic and sedimen-
tary rocks (telcl 1960). The transition of heavy minerals as-
semblages from low and medium grade metamorphic domi-
nant to high grade ultra-metamorphic dominant (Hartley &
Otava, in press) together with compositional differences be-
tweeen the pebble material of the Raèice and the Luleè types
correspond to progressive change in provenance.
The lower portions of the conglomerates contain boulders
up to 2 m in diameter, which in most cases are composed of
granulites and limestones. Pebbles of both types are mostly
well to perfectly rounded. According to the youngest fauna in
the limestone pebbles and to the goniatite fauna in the shales,
the age of the Myslejovice Formation is considered as Upper
goniatite zones; Kumpera & Lang 1975;
Inside the Culm flysch sequence, in the Rozstání Formation,
a group of several small bodies of pre-flysch rocks crops out
(Fig. 1). They are composed mainly of basic volcanites, oolitic
iron ores and shales with intercalations of the limestones. Ac-
cording to trilobite and graptolite fauna the shales have been
dated as Silurian (LandoveryLudlow) and Lower Devonian
(Emsian). This occurrence of pre-flysch rocks in the middle of
the Drahany Culm is interpreted as the boundary-marker of
two nappes in the Culm sequence (Chadima & Melichar 1996)
on the basis of the model suggested by Cháb (1986) for the
northern part of the Moravosilesian Culm.
No direct biostratigraphic data have been obtained from the
Rozstání Formation, and only a few data exist from the Proti-
vanov and the Myslejovice Formations. Thus, the limestone
pebbles provide a unique source of information on the age of
the fossil-free Culm formations which can be indirectly dated
by the age of the youngest pebbles. The limestone pebbles also
provide some information on the carbonate sedimentary envi-
ronments, especially on those destroyed during transpressional
tectonic phases of the Variscan orogeny. Until now the data on
the biostratigraphy and microfacies of the limestone pebbles in
the Moravosilesian Culm conglomerates have been rather
scattered and are insufficient. In the following pages we sum-
marize the results of our current three-year study on this topic.
Fig. 1. Stratigraphy of the Drahany Culm.
RECONSTRUCTION OF SYN- AND POSTSEDIMENTARY TECTONIC EVENTS 39
The research was based on detailed microfacial analysis of
the limestone pebbles from Culm conglomerates and com-
parison of their biostratigraphic and other microfacial prop-
erties in each formation.
About 140 thin sections from the pebbles of 29 localities
represent the input-set for the study (Fig. 2). We attempted to
cover the studied area as well as possible with the samples,
however, large parts of the Protivanov and the Rozstání For-
mations still remain without any data. These formations in-
clude only rare conglomerate outcrops which are strongly
weathered and carbonate pebbles are scarce and often
leached. In these two formations all known localities were
sampled. In the Myslejovice Fm. the limestone pebbles are
rather common and the localities were selected to cover the
studied area equally. In each locality all the types of macro-
scopically distinct limestones were collected, usually in sev-
eral samples to ensure the completeness of the study. At least
two thin sections from every pebble have been analysed.
The biostratigraphic data, ecology of fossils and the ratio
and type of clasts and matrix were used for the description
and comparison of the microfacies. An extended Dunhams
classification was used for the description of the microfacies
(Dunham 1962; Embry & Klovan 1971).
The age determination of limestone pebbles was based
mostly on foraminiferal fauna, while the zonation of the
Moravosilesian Devonian and Lower Carboniferous strata
(Kalvoda 1989) was used for biostratigraphic determina-
tions. Some Devonian microfacies were dated by J. Hladil
who analysed corals and stromatoporoids.
The established groups of microfacies with similar fea-
tures have been interpreted in terms of sedimentary environ-
ment and compared with the facies zones of Wilson (1975)
(see Fig. 3). This serves only for comparative purposes in the
present work and we do not attempt to reconstruct the car-
bonate platform from which the pebbles derived.
Only a general description of the main types of microfa-
cies is presented in this work. More detailed microfacial
characteristics, as well a list of identified fossils, are given in
a manuscript of paèek (1997).
On the basis of the evolutionary stages of foraminiferal as-
semblages, all the microfacies were classified into four broad
age groups (plus the group of uncertain age) and further sub-
divided into facies types according to structure and compo-
nent contents. The foraminiferal fauna in thin sections was
not always conclusive enough to enable exact identification
and often only the biostratigraphic assignment within the
range of more zones was possible.
The descriptions of microfacies are ordered according to
their importance within the age-based groups:
1) Givetian-Lower Famennian (Giv-Fa1) microfacies are
characterized by primitive foraminifers of the Nanicella
Zone, Multiseptida corallina-Eonodosaria evlanensis Zone,
Eonodosaria evlanensis-Quasiendothyra communis Inter-
zone. Stromatopors Amphipora sp., Dendrostroma sp.,
Stachyodes sp. and the coral Coenites sp. may be present.
Type 1A. Rudstones/floatstones with large clasts of stro-
matopors and corals. Matrices are wackestones or poorly-
washed grainstones composed of pelloids and bioclasts
which are often micritized. Primitive foraminifers, ostracods,
fragments of molluscs, crinoids and sponge-spicules are
present. Small subangular grains of quartz were found. Sort-
ing of these microfacies is usually poor. Stromatopors and
corals indicate Late Givetian to Middle Frasnian age (Pl. I:
Type 1B. Spongiostroms with micropellets and cal-
cisphaeres. Rare intraclasts and/or peloids may be present.
Fauna is very scarce and thus the age determination is diffi-
cult. Primitive foraminifers indicate Givetian to Frasnian age.
Type 1C. Coarse-grained packstones with bryozoans, fora-
minifers and micritized grains. Some peloids and cal-
Fig. 2. Schematic map of the studied area with the collection locali-
ties. 1 Vranová Lhota, 2 Hartinkov II, 3 Smolná, 4 Bou-
zov, 5 Hartinkov I, 6 Vìnice, 7 Trpín, 8 Koøenec III, 9
Koøenec II, 10 Koøenec I, 11 Okrouhlá, 12 Ptenský
Dvorek, 13 Stínava, 14 Køtiny, 15 Mokrá, 16 Èelechov-
ice (borehole HJ-3a), 17 árovice, 18 Obìený, 19 Hrádek,
20 Rakovecké údolí, 21 Luleè, 22 Bøezina, 23 Hádek II,
24 Hádek I, 25 Bìlkùv mlýn, 26 Muchova bouda, 27
Líeò, 28 Velatice, 29 Pindulka. Black body between the lo-
calities 12 and 13 pre-flysch rocks.
0 10 km
40 PAÈEK and KALVODA
cisphaeres may be present. The foraminifers are of Frasnian
to Lower Famennian age.
2) Upper Famennian-early part of Lower Viséan (Fa2-V1a)
microfacies contain foraminifers of the Quasiendothyra com-
munis-Q. regularis Zone, Q. kobeitusana-Q. konensis Zone,
Chernyshinella glomiformis Zone, Ch. tumulosaSpinobrunsi-
ina Zone, Paraendothyra Zone, Tetrataxis-Eoparastaffella sim-
plex Zone. Moravamminidae indet. is common and the coral
Ortholites sp. was found in locality 8.
Type 2A. Fine-grained limestones with alternating dark-
coloured layers containing radiolarians and packstones of
light-grey colours with considerable amount of shallow-wa-
ter derived bioclasts (mainly echinoderms, foraminifers and
green algae), peloids and small quartz clasts. Rarely erosion-
al surfaces of dark wackestones, sub-horizontal lamination
and less pronounced normal gradation can be observed. The
foraminifers of the packstone layers indicate Late Famennian
to latest Tournaisian age (Pl. II: Fig. C).
Fig. 3. Representation of the limestone pebbles of the different types of sedimentary environment in individual Culm formations. The ex-
pression of the sedimentary environment is simplified by dividing it into the three groups of facial zones of Wilson (1975). The values repre-
sent the fraction of localities with the content of microfacies of specific sedimentary environment on total number of localities in the forma-
tion. Explanation of abbreviations: Fa1, Fa2 Lower and Upper Famennian, V1a, V1b lower and upper parts of Lower Viséan, V2a,
V2b lower and upper parts of Middle Viséan, V3a lower part of Upper Viséan; P.Fm. Protivanov Formation, R.Fm. Rozstání For-
mation, M.Fm. Myslejovice Formation.
RECONSTRUCTION OF SYN- AND POSTSEDIMENTARY TECTONIC EVENTS 41
Plate I: Microfacies of limestone pebbles in the Drahany Culm. Scale 1 mm. A Floatstone/rudstone with broken stems of amphipors (Am-
phipora pervesiculata (Lecompte), A. laxeperforata (Lecompte)). In the micrite matrix foraminifers, Moravamminidae indet., sponge spi-
cules and the detritus of fine bioclasts occur. Middle Frasnian, loc. 25, Myslejovice Fm.; B Packstone with peloids, intraclasts, bioclast
and non-carbonate clasts (quartz, clastic sedimentary rocks). Moravamminidae indet., Dasycladaceae indet., conodonts? are present. Some
foraminifers occur within the intraclasts. Uppermost TournaisianLowermost Viséan (Tetrataxis-Eoparastafella simplex Zone), loc. 5, Proti-
vanov Fm.; C Grainstone with peloids and echinoderms. Well-sorted, well-washed with micritized bioclasts, rare quartz grains and fora-
minifers in sparite matrix. Upper FamennianLower Viséan (Quasiendothyra kobeitusana-Q. konensis Zone), loc. 5, Protivanov Fm.; D
Spongiostromes with small pseudopellets in thin laminar beds. Unknown age, loc. 27, Myslejovice Fm.
42 PAÈEK and KALVODA
Plate II: Microfacies of limestone pebbles in the Drahany Culm. Scale 1 mm. A Spiculite. The holes perforated by worms are filled with
sparite cement. Unknown age, loc. 24, Myslejovice Fm; B Radiolarian wackestone, tectonically deformed, darker domains are enriched
in clays due to solution at foliation surfaces. Unknown age, loc. 2, Protivanov Fm.; C, D Two examples of facies interpreted as calcitur-
bidites. Rapidly changing layers of darker wackestones with radiolarians and packstones with foraminifers, small peloids and fine-grained
debris of bioclasts. In some thin sections gradation is visible; C Upper FamennianLower Tournaisian, loc. 15, Rozstání Fm.; D upper-
most Lower Viséanlowermost Middle Viséan (Viseidiscus eospirillinoides-Glomodiscus oblongus Zone), loc. 15, Myslejovice Fm.
RECONSTRUCTION OF SYN- AND POSTSEDIMENTARY TECTONIC EVENTS 43
Plate III: Microfacies of limestone pebbles in the Drahany Culm. Scale 1 mm. A, B, C Examples of lagoonal packstones/rudstones/
floatstones with foraminifers, green algae Koninckopora sp., corals, echinoderms, bryozoans, brachiopods and other bioclasts, some
of which are covered and/or aggregated. Uppermost Middle Viséanlowermost Upper Viséan (Pojarkovella nibelis-Koskinotextularia
Zone), loc. 15 (A), 26 (B), 29 (C); D Typical tectonically deformed facies of Protivanov Fm., originally packstone with crinoids. Un-
known age, loc. 9.
44 PAÈEK and KALVODA
Type 2B. Packstones with intraclasts, ooids, peloids and
clasts of shallow-water biota. Bioclasts are represented by
echinoderms, bryozoans, foraminifers, green algae, corals,
gastropods and ostracods. In some microfacies clasts of
quartz, siliciclastic sediments and feldspar are of significant
content. Some microfacies with a lower content of bioclasts
(wackestones) of slightly different constitution (abundant os-
tracods and calcisphaeres) were added to this group. Foramin-
iferal assemblages indicate Late Famennian to latest Tournai-
sian or earliest Viséan age (Pl. I: Fig. B).
Type 2C. Mudstones and wackestones with scarce clasts of
sponge-spicules, thin-shelled bivalves, ostracods. Rare foramin-
ifers indicate Late Famennian to latest Tournaisian age.
Type 2D. Peloidal grainstones with micritized crinoids.
These grainstones are always well-sorted and well-washed.
In some grainstones of this type scarce foraminifers were
found, which indicate Famennian to earliest Viséan age (Pl.
II: Fig. C).
3) Lower Viséanbase of Middle Viséan (V1b-V2a) micro-
facies contain foraminifers of the Viseidiscus eospirillinoides-
Glomodiscus oblongus Zone. Moravamminidae indet., and
Koninckopora sp. are common.
Type 3A. In this group microfacies similar to those from
group 2B are incorporated. These are packstones/rudstones
and poorly washed grainstones with bioclasts of various main-
ly shallow-water organisms (echinoderms, foraminifers, cal-
cisphaeres, ostracods, green algae, bryozoans, brachiopods).
Frequently peloids and quartz clasts are present.
Type 3B. Limestones with alternating fine-grained dark-co-
loured layers and coarse-grained bioclast-rich layers. Micro-
structures and bioclastic content of these microfacies are very
similar to those of the type 2A (Pl. II: Fig. D).
The age of Lower Viséan to base of Middle Viséan was de-
termined on the basis of foraminiferal assemblages in both 3A
and 3B groups.
4) Upper part of Middle Viséanbase of Upper Viséan (V2b-
V3a) microfacies contain foraminifers of the Pojarkovella ni-
belis-Koskinotextularia Zone and abundant Koninckopora sp.,
Stacheiinae indet., Gigantoproductus sp.
Type 4A. Packstones, rudstones and wackestones with fora-
minifers and green algae predominating. In addition to the
main bioclastic constituents frequent crinoids, brachiopods,
bryozoans, trilobites, ostracods, corals, intraclasts and lumps
are present. No terrigenic material was observed in the micro-
facies of this type (Pl. III: Figs. A, B, C).
Type 4B. Algal coverstones. Irregular intercalations of
packstones contain scarce foraminifers, ostracods, crinoids
and bivalves. Sparite-filled fenestral vugs are frequent.
Type 4C. Grainstones with ooids, peloids and foraminifers.
Lumps, intraclasts and fragments of micritized crinoids, bra-
chiopods, algae, gastropods are present. Grainstones of this
type are well-washed and poorly sorted.
The age V2bV3a of all the specimens was determined on
the basis of foraminiferal assemblages.
5) Microfacies of unknown age were divided into three main
5A.Wackestones, packstones and poorly washed grainstones
with various components (ostracods, algae, intraclasts, micri-
tized grains, peloids, crinoids, foraminifers) (Pl. III: Fig. D).
5B. Spongiostroms with algal fabric, calcisphaeres, mi-
cropseudopellets, rare bioclasts and quartz (Pl. I: Fig. D).
5C. Dark mudstones and wackestones with calcified radi-
olarians and sponge spicules (Pl. II: Figs. A, B).
The interpretation of sedimentary evironment was limited
by the fact that pebbles always represent only a small part of
a sedimentary sequence, which is extracted from its context
and thus gives only limited information on sedimentological
aspects. It is then very difficult to determine the depositional
conditions of the rock. All the interpretations of the deposi-
tional environment given in the following paragraphs are
based on the comparison of the microfacies of pebbles with
those of better known sequences and should be considered as
the most probable alternatives.
The most shallow-water facies are spongiostromatic lime-
stones of the types 1B and 5B and the coverstones of the type
4B. They are interpreted as algal mats of peritidal environ-
ments. The activity of microbial organisms is apparent from
frequent micropellets. Fenestral vugs indicate dessication
processes and scarce biodetritic intercalations can be ex-
plained as a product of channel migration.
Facies of high-energy environments are represented by
grainstones of the types 2D and 4C. Constant wave and/or
current action is indicated by well to perfectly rounded
grains and lack of micrite in inter-grain space.
Packstones/rudstones of the types 1C, 2B, 3A, 4A and 5A
represent a widespread assemblage of deposits from protect-
ed lagoon environments. Abundant micrite indicates low dy-
namics of water, while common green algae, peloids and mi-
critized grains suggest a shallow-water origin for these types
of facies. Small transport is indicated by rather bad sorting of
Rudstones/floatstones of the type 1A have probably been
deposited in close proximity to a reef. The fossils are well
preserved and display short transport from their original po-
sition. Micrite matrix indicates low wave energy of the sedi-
Facies of the types 2A and 3B are interpreted as parts of
calciturbidite sequences. T
Bouma divisions were
observed. Generally, these facies types are very similar to
those described in well exposed outcrops of southern part of
the Moravian Karst (Kalvoda et al. 1996).
Pelagites are represented by radiolarian wackestones and
spiculites of 5C type. Mudstones/wackestones of the type 2C
with scarce thin-shelled bivalves are also interpreted as deep-
In view of the sedimentary environment of the limestone
pebbles, the wide spectrum of facies is characteristic of con-
glomerates of the Protivanov Formation.
RECONSTRUCTION OF SYN- AND POSTSEDIMENTARY TECTONIC EVENTS 45
Fig. 4. Representation of the limestone pebbles of the different time intervals in each formation. The values represent the fraction of lo-
calities containing pebbles of a specific age-range to the total number of localities in the formation. Localities which contained only the
pebbles of uncertain age were not included in the calculation. The pebbles of the age V2bV3a described by Dvoøák (1973a) is concluded
in the chart as well. For explanation of abbreviations see Fig. 3.
Deeper-water facies prevail mudstones and wacke-
stones with radiolarians and sponge-spicules are relatively
common (type 2C, 5C, localities 1, 2, 7 and 8). Microfacies
very similar to calciturbidites were found (type 2A, loc. 5).
Shallow-water microfacies are represented by spongios-
troms (type 5B, loc. 7), lagoonal packstones with foramini-
fers, peloids, echinoderms (types 2B and 3A, localities 5, 6,
7, 8 and 11) and by well-washed, well-sorted grainstones
(2D, loc. 5).
Generally, microfacies of limestone pebbles in the Proti-
vanov Fm. are very poor in foraminifers and they contain
no green algae at all. The pebbles of these conglomerates
were strongly deformed, which makes their analysis more
difficult. The age of the limestone pebbles in the Proti-
vanov Fm. ranges from Late Famennian to EarlyMiddle
Viséan (Fig. 4).
The Rozstání Formation is very poor in conglomerates.
Only five localities in the northern and southernmost parts of
the formation could be sampled.
In the northern part of the formation (locality 11) Frasnian
lagoonal facies of peloid-coral floatstones (type 1A) and la-
goonal facies of unknown age (type 5A) were found. Facies
from a deeper environment represented by radiolarian wack-
estones (type 5C) were found at locality 13.
In the southernmost part (loc. 15) calciturbidites and hemi-
pelagic microfacies of Upper Famennian to lowermost Mid-
dle Viséan age are characteristic (similar microfacies as in
the Protivanov Fm., alternating wackestones and packstones
with radiolarians, foraminifers etc., type 2A).
At locality 14 the pebbles of higher Middle Viséan to low-
er Upper Viséan were described by Dvoøák (1973a).
The pebbles studied in the conglomerates of the Rozstání
Formation are of FrasnianMiddle Viséan age; but Tournai-
sian limestone pebbles prevail (Fig. 4).
In the pebbles of the conglomerates of the Myslejovice Fm.,
microfacies interpreted as shallow-water platform sediments
of MiddleLate Viséan (V2bV3a) age are strongly preva-
lent. This group is represented by foraminiferal-algal pack-
stones, rudstones and floatstones with corals, intraclasts and
other bioclasts (type 4A, in less amounts types 4B and 4C,
localities 1518, 21, 23, 25, 27 and 29). Givetian to Frasnian
shallow-water facies of similar type are abundant as well:
foraminiferal-algal packstones, rudstones and floatstones
with stromatoporoids (1A, loc. 23 and 25), packstones with
bryozoans, foraminifers and micritized grains (1C, loc. 19),
spongiostroms (1B, loc. 16 and 27). Some of these microfa-
cies contain substantial amounts of nectonic fauna (trilobites,
conodonts) and could represent deeper-water sediments with
clasts partially resedimented.
Facies of the Famennian to Lower-Middle Viséan lime-
stones are more differentiated in terms of the depositional en-
vironment. Lagoonal packstones, grainstones and rudstones
with foraminifers and algae prevail (mainly types 2B and 3A,
loc. 15, 18, 22, 25, 28 and 29), but also facies interpreted as
calciturbidites are abundant (type 2A, loc. 15, 18 and 25). In
the microfacies of undetermined age both the shallow-water
(e.g. spongiostroms, type 5B, loc. 23) and deeper-water types
were found (e.g. spiculites, type 5C, loc. 24).
The age of the pebbles in the Myslejovice Fm. ranges from
Givetian to Late Viséan (Fig. 4).
An apparent divergence in the content of the limestone
pebbles of various ages in individual formations is illustrated
in Fig. 4. Comparing the relative amount of the pebbles of all
four time intervals in each formation, we can see the increase
in the number of Givetian-Lower Famennian and Middle-
Upper Viséan (V2bV3a) and the decrease of the Upper Fa-
mennian-Middle Viséan limestones in the direction from old-
er to younger formations (from the Protivanov Fm. to the
46 PAÈEK and KALVODA
Interpretation and discussion
A comparison of the content of the limestone pebbles of
various ages in individual formations illustrated in Fig. 4 in-
dicates that the erosional history of the source area of
Givetian-Lower Famennian (time interval 1) and Middle-
Upper Viséan limestones (time interval 4) was similar and
that the source area of the Upper Famennianbase of Middle
Viséan limestones had a different erosional development.
The areal distribution of the pebbles of the time intervals 1
(the oldest pebbles) and 4 (the youngest pebbles) is the same
and differs from that of the pebbles of the time intervals 2
and 3 (Fig. 5). The pebbles of Givetian-Lower Famennian
and Middle-Upper Viséan limestones occur in the eastern
part of the Drahany Upland only. This distribution shows
some differences in the source area of the western and the
eastern parts of the Drahany Culm.
A combination of the two possible interpretations can be
1) Assuming a simple model for the passive margin of the
Brunovistulicum and foreward thrust propagation in the ac-
cretionary wedge of the colliding terranes, the compositional
trend of the limestone-pebble material suggests progressive
erosion of the sedimentary cover of the basement unit from
its distal (pelagic and hemipelagic) to proximal (platform)
parts. Both the oldest (Giv-Fa1) and the youngest (V2b-V3a)
carbonates represent platform facies and thus their predomi-
nance in proximal parts of a passive margin is expected.
2) The correspondence of the westernmost external occur-
rences of the youngest and the oldest limestone pebbles with
the belt of the occurrence of pre-flysh Silurian and Devonian
rocks is apparent. The sharp compositional difference between
the both parts of the Culm can be therefore explained as a re-
sult of their different original position within the Culm basin
(Western and Eastern Culm units of Cháb 1986).
An insufficient volume of data can distort the statistical re-
sults, as in the case of localities 16 and 17. Here only a few of
the samples collected during former studies were analysed,
which is probably the reason why the Upper Famennian-Low-
er Viséan and Lower-Middle Viséan limestone pebbles do not
appear in the northeastern part of the Myslejovice Fm. (Fig. 5).
Provenance studies are complicated by the imperfect
knowledge of the tectonic development in the Variscan colli-
sional area. We suppose that the depositional area of the
main amount of limestones was situated on the Brunovistu-
lian passive margin. Paleocurrent analysis, which revealed
the main direction of transport from S-SW to N-NE in the
flysch basin (Kumpera 1966), supports the idea of dominant
supply from hinterland. Nevertheless, some features of the
Culm sediments seem to be in contrast to the hinterland-
1) dominant content of the pebbles of the youngest (V2b-
V3a) limestones in the Myslejovice Formation. These facies
are very scarce in a region, which is to the west (i.e. in the
hinterland part) of the Drahany Culm and they predominate
in the foreland of the Variscan orogeny (e.g. Dvoøák 1987).
2) the lack of the penetrative tectonic deformation of the
limestone pebbles. In the westernmost part of the Drahany
Culm the most of the limestone pebbles are ductily de-
formed, but this seems to be due to the strong post-Culm
dextral shear of the flysh rocks (paèek 1999). Even in the
youngest Culm conglomerates, the pebbles of the strained
limestones have never been found.
Another problem in the interpretations of provenance is as-
sociated with the significant content of the Cadomian clastic
material in the Protivanov Formation. The underplating base-
ment of the Brunovistulicum was probably the source of this
material. This fact can reflect that the tectonic imbrication of
the underthrusting plate was not strictly superficial and affect-
ed even deeper parts in a footwall of the sedimentary cover.
For the better understanding of the provenance, detailed
re-evaluation of the paleocurrent data and complex pebble
analysis must be carried out in the future research.
The size of the largest limestone pebbles in the Myslejov-
ice Formation is very similar to that of granulite pebbles,
which were undoubtedly transported from the hinterland.
These pebbles are up to 2 meters in diameter and their origin
surely required much higher elevations than can be expected
during forebulging. Generally well to perfectly rounded
limestone pebbles strongly prevail. Nevertheless, some large
limestone pebbles were found which have rather angular to
Fig. 5. Areal distribution of the limestone pebbles of different age.
The scatter-fields of localities with content of pebbles of specific
age-range are contoured by different lines. For explanations of the
map see Fig. 2.
RECONSTRUCTION OF SYN- AND POSTSEDIMENTARY TECTONIC EVENTS 47
subangular shape. These are, in contrast to the perfectly
rounded pebbles, always of Upper Famennianbase of Mid-
dle Viséan age, which supports the idea that the pebbles of
the two groups (time intervals 1+4 vs. 2+3) were derived
from different sources.
Provenance change related with the apparent petrographic
differences between the Raèice and the Luleè Conglomerates
of the Myslejovice Formation is not reflected in a composi-
tion of the limestone pebbles. Nevertheless, in these con-
glomerates the content of the limestone pebbles is very small
and the quick uplift of the hinterland source-area is apparent
from pebble lithology.
The latest research of the pebble material in the Luleè (J.
Leichmann, pers. comm.) reveals the presence of very high-
grade granulites with late Viséan cooling ages. Similarly,
Ar ages of the youngest detrital micas from the upper
portions of the Myslejovice Formation show the cooling of
their source-rocks through 350420 °C at 325 Ma (D.
Schneider, pers. comm.). The Luleè Conglomerates pass lat-
erally into fossiliferrous shales with goniatites of the Go
zone (Dvoøák 1987). This means that Moldanubian rocks
must have been uplifted, exhumed and eroded into Culm ba-
sin within extremely short time span, which does not allow
significant resedimentation process in the flysh basin, at least
for its youngest formation.
The content of the limestone pebbles of different sedimen-
tary environments in all the Culm formations shows a pro-
nounced change in the sedimentation regime of Rhenoher-
cynian carbonates in the Famennian. For the time intervals 2
and 3 (Late Famennianbase of Middle Viséan) the ratio of
facies which are interpreted as calciturbidites, hemipelagites
and pelagites to the other microfacies rises significantly in
all Culm formations of the Drahany Upland. The age of the
deep-sea facies of the pebbles correlates well with the inter-
val of maximum extension and the beginning of transtension
on the passive Brunovistulian margin when widespread cal-
citurbidite sedimentation occurred in this region (Kalvoda
1995, 1997). There were no such facies found in the pebbles
dated as GivetianEarly Famennian and MiddleLate
The analysis of the microfauna has shown that the pebbles
of Givetian-Lower Famennian and Middle-Upper Viséan
limestones occur in the eastern part of the Drahany Upland
only. Differences in the content of the limestone pebbles of
various ages in individual formations and their areal distribu-
tion are interpreted as a result of the two processes:
1) progressive erosion of the sedimentary cover of the
basement unit from its distal (pelagic and hemipelagic)
through proximal (platform) parts due to foreward thrust
propagation in the accretionary wedge of the colliding ter-
2) post-sedimentary tectonic juxtaposition of the western
and the eastern parts of the Drahany Culm. The border and
the extent of these two parts seems to correspond to the sup-
posed nappe units of Chadima & Melichar (1996).
In contrast to the distribution of the limestone pebbles, the
analysis of heavy minerals assemblages doesnt show any
distinctive differences between these two parts of the Culm
(Hartley & Otava, in press). Thus, microfacial analysis of
limestone pebbles seems to be very helpful, mainly for the
regions where crystalline rocks of the source-areas are of
similar mineralogical composition.
As far as the provenance is concerned, many features of
the Culm flysh basin are contrasting and even the basic ques-
tions as e.g. hinterland- vs. foreland-supply model can not be
answered unambiguously. In the future research, mainly the
source-model for the pebbles of the Cadomian granitoids and
for the youngest limestone pebbles should be presented.
Acknowledgements: The authors wish to express their grati-
tude to J. Leichmann for stimulating discussions and J.
Hladil for the determination of Devonian macrofauna. J.
Norris and all the reviewers are acknowledged for helping to
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