GEOLOGICA CARPATHICA, FEBRUARY 2005, 56, 1, 4155
Reconstruction of fluvial bars from the Lower Triassic
Buntsandstein Facies (Lúna Formation) in the Western
Carpathians (Slovakia)
ANNA VOZÁROVÁ
Department of Mineralogy and Petrology, Faculty of Natural Science, Comenius University, Mlynská dolina G,
842 15 Bratislava, Slovak Republic; vozarova@nic.fns.uniba.sk
(Manuscript received January 19, 2004; accepted in revised form September 29, 2004)
Abstract: The 50150 m thick Lower Triassic Lúna Formation quartzose sandstones and conglomerates are wide-
spread in the Tatricum, Northern Veporicum/Fatricum and Zemplinicum (Western Carpathians). Several braided
fluvial facies are well developed in the vertical sections from the Tribeè Mountains, the Èiera Mountains and the
Starohorské vrchy Hills. The channel lag and planar cross-bedded bar facies overlie major erosional surfaces and are
characterized by complex interlayering of planar cross-beds 25125 cm thick and trough cross-beds 1550 cm thick.
Paleocurrent data (both planar and trough cross-beds combined) indicate downcurrent, oblique or symmetrical accre-
tion of the bars with respect to the local channel direction and are inferred to document lateral or mid-channel braid
bar deposits. The thickness of the bar deposits suggests a shallow depth to the channels (~2 m). Paleohydrological
data for mean and bankfull channel depth and width, mean annual discharge and mean annual bankfull discharge,
paleoslope, drainage area and principal length of river are estimated. Paleoslope values estimated for the Lúna
Formation braid-channels lie between those generally found for alluvial fans and modern rivers (mean S=0.0099).
These higher paleoslopes, combined with shorter principal stream lengths, indicate a tectonically active, fault-seg-
mented margin of the source area, from which were derived braided fluvial wedges of clastic sediments on the pied-
mont braid-plain.
Key words: Western Carpathians, Lower Triassic, braided river, channel bar, paleohydrological data.
Introduction
Reconstruction of fluvial bars in ancient fluvial deposits is
crucial for interpreting channel pattern and paleohydraulics.
Exposures of the Lower Triassic deposits of the Tatric and
Northern Veporic Units of the Central Western Carpathians
provide an opportunity for such a reconstruction (Fig. 1).
Bars are the principal depositional elements within rivers.
Reconstruction of bars from ancient alluvium, therefore,
serves as an important tool for paleoenvironmental analysis
and paleochannel characteristics. A variety of bars, differing
in scale and morphology, have been documented from ancient
alluvium (Williams & Rust 1969; Rust 1972; Cant & Walker
1978; Haszeldine 1983; Kirk 1983; Miall 1985, 1994; Rust &
Jones 1987; Wizevich 1992; Willis 1993; Fergusson 1993).
This paper presents a detailed account of inferred bar deposits
from the Lower Triassic alluvial strata of the West Carpathian
Tatric and Veporic Units.
Previous authors considered the Scythian quartzites (de-
fined as the Lúna Formation by Fejdiová 1980), mostly as
marine littoral sediments (Zoubek 1930; Matìjka & Andrusov
1931; Andrusov 1959; Roniewicz 1966; Fejdiová 1980). Flu-
vial, lacustrine or deltaic environments were supposed by
some authors (Limanowski 1903; Passendorfer 1951; Dzulins-
ki & Gradzinski 1960). The only authors, who interpreted
them as continental sediments of ephemeral braided streams
on a piedmont plain were Miík & Jablonský (1978, 2000).
The Scythian quartzites occur within the several Central
Western Carpathians superunits. They developed from
the beginning of the Mesozoic sedimentary cycle with an un-
conformable position to the underlying polymictic Permian
sediments. The quartzites are conventionally attributed to the
Seis (probably Griesbachian) without any paleontological or
radiometric evidence. A continuous passage into overlying
Campilian strata can be observed (Andrusov 1959; Biely et
al. 1996).
Geological setting
The Western Carpathians have been traditionally divided
into external (Outer Western Carpathians) and internal struc-
tural zones (Inner Western Carpathians) since the 19
th
century
(túr 1860; Uhlig 1903; for summary Biely et al. 1996). Re-
cently a concept of triple division into Outer (external zone),
Central and Inner Western Carpathians (internal zone) has
been widely accepted (Miík et al. 1985). The internal part of
the Western Carpathians orogenic range is divided into the
pre-Gosau nappe system and an overlying post-nappe Upper
Cretaceous to Neogene sedimentary and volcanic formations.
The pre-Gosau nappe system comprises crystalline masses and
Upper Paleozoic-Mesozoic envelope formations, as a part of a
principal crustal-scale superunit and several cover nappe sys-
tems (Fig. 1). The Lúna Formation sediments are a character-
www.geologicacarpathica.sk
42 VOZÁROVÁ
istic feature of the Mesozoic sequence within the Central
Western Carpathians tectonic superunits (from N to S): the
Tatricum, Veporicum and correlational Zemplinicum, as well
the Fatricum and Hronicum cover nappe system (Fig. 2).
The Tatricum consists of crystalline cores and their Upper
Paleozoic (Permian) and Mesozoic sedimentary cover (Lower
Triassic to Lower Turonian). The Tatric crystalline basements
have generally well preserved Variscan structures without
a significant Alpine overprint. It is composed mainly of medi-
um to high grade metamorphic rocks (mostly paragneisses,
mica-schists, amphibolites) and several suites of Variscan
granitoids. The Mesozoic sedimentary envelope unit is typi-
cal of the Carpathian Keuper Formation, various Lower Juras-
sic successions (crinoidal limestones and marlstones with
cherty limestones) and Albian-Turonian flysch formations.
The Veporic Unit comprises: crystalline massifs and
overlying Upper Paleozoic-Mesozoic sequences, which form
an indigenous sedimentary envelope of crystalline massifs;
a nappe system composed of Mesozoic sedimentary rocks
(designated by Andrusov 1960 as the Lower Subtatricum or
Krína Nappe, and by Andrusov, Bystrický & Fusán 1973 as
the Fatricum). The internal structure of the Veporic crystalline
basement is complicated as it involves several lithotectonic
units, which are different in lithology, the grade of Variscan
metamorphism as well as its Alpine overprint and their Upper
Paleozoic-Mesozoic sedimentary envelope. The character and
evolution of the crystalline rocks in the Northern Veporicum is
similar to that in the Tatricum (the Tatra Terrane acc. to
Vozárová & Vozár 1996). In the Northern Veporicum, the Up-
per Paleozoic-Mesozoic sedimentary envelope constists of the
mostly anchimetamorphosed Ve¾ký Bok Group (Lower Trias-
sicNeocomian). Although different in detail, the Ve¾ký Bok
succesion is very similar to the Fatricum (Krína Nappe) Me-
sozoic sediments. In this respect, the Ve¾ký Bok suite was not
detached from its original basement and it is compared with
the Fatricum (Krína Nappe) root zone. This sedimentary com-
plex belongs to the Triassic facies area, characterized by the
Carpathian Keuper facies. The low-grade metamorphic rocks
and composite granitoids are common in the crystalline base-
ment of the Southern Veporic Unit. Its sedimentary envelope is
represented by the Stephanian-Permian continental sediments
as well as Mesozoic rocks of the low-grade metamorphosed
Foederata Group (Lower and Middle-Upper Triassic metacar-
bonates and rarely shales). The presence of the Stephanian
clastics as well as the missing Keuper facies is an essential dif-
ference from the Northern Veporic zone.
The Zemplinicum consists of the high- to medium meta-
morphosed crystalline complexes and its Upper Carbonifer-
Fig. 1. Tectonic sketch of the Slovak part of the Western Carpathians and location of individual sections.
RECONSTRUCTION OF FLUVIAL BARS FROM THE BUNTSANDSTEIN FACIES IN THE W CARPATHIANS 43
Fig. 2. Distribution of the Lower Triassic facies throughout the Western Carpathians. 1 Paleozoic crystalline basement; 2 Upper
Permian continental red-beds facies; 3 Lower Triassic continental gravel/sandy braidplain facies (the Lúna Formation Buntsand-
stein facies); 4 fine-grained sandstones; 5 alternation of sandy/shaly sediments; 6 silty shales; 7 marls; 8 evaporites; 9 rauh-
wackes; 10 dolomites; 11 calcarenites, oolitic limestones; 12 sandy limestones; 13 alternation shales and limestones, marly
limestones; 14 slope- and deep-water limestones; 15 epiplatform shallow-water limestones; 16 thin lenses of lacustrine phos-
phorites and phosphatic sediments.
ous-Permian and Lower- to Middle Triassic sedimentary en-
velope. Dominant paragneisses, amphibolites and migma-
tites in the Zemplinic crystalline basement and the Upper
Carboniferous to Middle Triassic sedimentary envelope cor-
respond very well to the Tatric and Northern Veporic tecton-
ic units.
The Scythian quartzose sediments are widespread within all
three above mentioned tectonic superunits as the basal part of
their Mesozoic envelope sequences. They are also an integral
part of the Fatric and Hronic Lower Triassic sedimentary
rocks (Fig. 2). The Scythian sediments transgressively overlie
their substratum, either consisting of coarse-grained Permian
clastic sediments or crystalline basement rocks.
General characteristics of the Lúna Formation
The Lúna Formation is a formal lithostratigraphic unit for-
merly defined by Fejdiová (1980) on the occurrences near
Liptovská Lúna village (Tatric Unit). A general feature is fin-
ing upward and graduate transition to fine-grained silty-shaly
sediments of the Werfen Formation, occasionally with carbon-
atic pedogenic horizons or evaporites. The Lúna Formation
mostly consists of relatively monotonous sediments, mainly
coarse- to fine-grained sandstones, with intercalation of con-
glomerates or gravelly sandstones and inferior thin layers of
silty/sandy shales (Fig. 3). Conglomerates are mainly concen-
trated in the basal part of the Lúna Formation as well as in the
form of thin layers at the lower part of small alluvial cycles.
The sandy sediments are cross-stratified, horizontal laminated
or in some cases also massive or only crudely bedded. They
are organized in multiplying smaller sedimentary cycles of al-
ternating gravel-bearing and gravel-free finer sandstones, or
thicker packages of multistorey sandstones. The boundaries
between individual sedimentary units of different grain size
are either erosional, sharp or gradual. Mudstone intercalations
are very subordinate and are in the most cases limited to thin
waning-flow drapes up to a few cm in thickness, whereas
thicker mudstone beds or lenses are very rare exceptions. In
the stratotype the Lúna Formation consists of three members
(Fejdiová 1980). The first member consists of coarse- to medi-
um-grained sandstones interlayered with fine-grained con-
glomerates and gravelly sandstones. The sediments are light-
pink and light-grey in colour, 1020 m thickness in range. The
second member (from 20 to 25 m in thickness) is character-
ized by the presence of green, occasionally red sandy shales.
44 VOZÁROVÁ
The lower part is composed of white to light-grey coarse- to
medium-grained sandstones displaying cross-bedding and cur-
rent lamination. Intercalations of shales range up to 5 cm in
thickness. There is an upward increase only in their frequency
and not in their thickness. The third member is violet and rela-
tively finer-grained (from 10 to 30 m in thickness), and con-
sists of medium- to fine-grained sandstones and silty/sandy
shales.
Principally, these sediments manifested their relatively high
grade of structural and mineralogical maturity. The dominant
mineral is quartz (8595 %, rarely 65 %), with less frequent
K-feldspars (in general 510 %, rarely 2025 %), fragments of
Fig. 3. Schematic lithostratigraphic section of the Lower Triassic
Buntsandstein lithofacies. 1 fine-grained conglomerates; 2
very-coarse grained sandstones; 3 coarse- to medium-grained
sandstones; 4 fine-grained sandstones; 5 siltstones, mud-
stones, shales; 6 calcretes and carbonatic nodules; 7 thin lay-
ers/laminae of pink dolomites.
acid volcanites, clastic micas and heavy minerals. Sandstones
predominantly belong to the group of quartzose arenites and
subarcoses, exceptional arcoses. Conglomerates are oligomic-
tic, with dominant quartz pebbles. Only a few pebbles of black
tourmalinites and acid volcanics were identified (for summary
see Miík & Jablonský 2000).
The depositional evolution of the Lúna Formation reflects
the trend of a highly to moderately-braided pebbly to sandy
fluvial system whith transition to sandy/muddy coastal flood-
plain. The fluvial braidplain was associated with intervals of
strong aeolian activity, documented by ventifacts, diagonally
cross-bedded sandstones and high degree of structural maturi-
ty. Semi-arid and arid climatic conditions are inferred from
horizons of pedogenic carbonate nodules as well as from tour-
maline rich-laminae (former boron-rich clays or primary bo-
rates), genetically associated with small arid endorheic water
reservoirs (Vozárová et al. 2003).
Reconstruction of bars in the Lúna Formation
quartzose sediments
The bars within braided streams include a hierarchy of indi-
vidual bedforms, small bars, bar complexes and mature vege-
tated islands. In view of the morphological complexities in-
volved and the difficulty of their recognition in the ancient
record, Miall (1978) proposed a simple classification consist-
ing of three categories: 1 gravelly, planar or massive bed-
ded bars; 2 sandy, simple foreset bars; 3 compound bars
of sand and gravel. The bars inferred in the basal part of the
Lúna Formation are mostly of the compound type as defined
above. Compared to this, sandy simple foreset bars are domi-
nant in the upper part of the sequence.
The following lithofacies were recognized in the Lúna For-
mation quartzose sediments:
1 Massive clast-supported pebble conglomerates (Gm):
Beds 23100 cm thick show upward-fining trend; some clast-
supported beds indicate crude horizontal stratification and
clast imbrication; the mean size of pebbles reaches 13 cm;
occasionally large imbricated pebbles attain 10 cm in size;
they form flat beds with erosional bounding surfaces; imbrica-
tions in a few beds generally show N-S transport. Interpreta-
tion: longitudal bars, lag deposits, sieve deposits.
2 Trough-crossbed fine-grained pebble conglomerates
and sandy conglomerates (Gt) with clast-supported struc-
tures: Set thickness is 3090 cm, 130390 cm wide in bed-
ding plane exposures; pebble size varies from 0.52 cm; occur
seldom as coset up to 5 m thick; paleocurrent mean direction
varies from NWNE to SESW, occasionally SWNE and E
W. Interpretation: minor channel fills.
3 Planar cross-bedded fine-grained pebble conglomer-
ates and sandy conglomerates (Gp): Beds 50125 cm thick;
1030 mm clasts dispersed throughout the cross-bedded units;
angular, occasionally gentle sigmoidal foresets; paleocurrent
mean direction generally varies from N-NW to S. Interpreta-
tion: rapid deposition from high velocity flow in shallow
channel; linguoid bars.
4 Coarse- to very coarse-grained sandstones locally with
granules and small (up 10 mm) pebbles (St, Sp, Sc): Trough-
RECONSTRUCTION OF FLUVIAL BARS FROM THE BUNTSANDSTEIN FACIES IN THE W CARPATHIANS 45
glomerates form only isolated irregular thin layers at the basal
part of bar successions. White to pinkish fine-grained sand-
stones, siltstones as well as purple-red and green silty shales
form highly eroded layers (27 cm to 15 cm thick) below first-
order bounding surfaces. They represent fillings of abandoned
channel sequences.
Fig. 4. Vertical section through profile T-11. Explanation: 1 vio-
let and green shale and mudrock; 2 violet siltstone; 3 fine-
grained sandstone; 4 medium-grained sandstone; 5 coarse-
grained sandstone; 6 very coarse-grained sandstone; 7
fine-grained conglomerate with grain supported structure; 8 part-
ing lamination and low-angle cross-bedding; 9 ripple lamination;
10 grain size in Φ
Φ
Φ
Φ
Φ units. The lithofacies symbols are from Miall
(1978). The rose diagram (A) shows paleocurrent data from cross-
beds and mean direction of channels (B) for both T-11 and T-12
sections.
or planar cross-bedded lenticular to tabular strata; solitary
(theta or alpha) or grouped trough/planar cross-bedding; sand-
stone bodies 2580 cm thick; cosets form sheet-like bodies
bounded by sharp or erosive surfaces; paleocurrent mean di-
rection varies from NE-SW. Interpretation: deposition from
small three-dimensional dunes in shallow, wide channels
(lower flow regime).
5 Medium- to coarse-grained tabular sandstones: Mas-
sive (Sm) with clast-supported, occasionally matrix-support-
ed, structure; very often with horizontal lamination, parting or
streaming lineation (Sh) and graded bedding (Sg); 1570 cm
thick. Interpretation: planar bed flow.
6 Very fine- to medium-grained sandstones with low an-
gle (<10°) or ripple lamination (Sl, Sr): 1530 cm thick; vari-
able ripple orientation. Interpretation: deposition in pools/
sluggish channels on bar tops or higher topographic levels of
braided streams; crevasse splays.
7 Coarse-grained sandstones with pebbles: Broad, shal-
low scours, occasionally including eta cross-stratification (Se).
Interpretation: scour fills.
8 Very fine-grained sandstones and siltstones with fine
lamination: Occasionally asssociated with very small ripples
(Fl). Interpretation: overbank or waning flood deposits.
9 Siltstones, mudstones with laminated to massive struc-
tures (Fm, Fcf, Fsc): Horizons with pedogenic calcrete soils
(P) or bioturbations (B).
The inferred bar succession of the Lúna Formation sedi-
ments consists predominantly of cosets of massive/graded
bedded or planar and trough cross-bedded conglomerates and
medium- to coarse-grained sandstones, with minor amounts of
very fine- to fine-grained sandstones, siltstones and mud-
stones (Figs. 411).
The fining upward succession is organized into several
channel-fill successions. Each channel-fill succession is
marked at its base by a major erosional surface that is flat to
concave-up and can be traced laterally. The most prominent
bounding surfaces are those marking the base of the channel-
fill successions. These are designated as first-order bounding
surfaces. The second-order bounding surfaces form the ero-
sional bases of the larger, solitary or compound cross-sets
(Fig. 7). These surfaces are irregular to flat and are subparallel
or at a low-angle to the first-order bounding surfaces. Internal
reactivation surfaces within the cross-sets or the intraset
boundaries constitute the third-order bounding surfaces. The
shape of the third-order surfaces (Fig. 7) is hardly variable and
has been found to change from convex-up to concave-up with-
in the same set.
Description of the sections
Tatric Unit
Section T-11
Loc. North of Baláe village, 580 m altitude, old abandoned
quarry, the Nízke Tatry Mountains (Fig. 4).
Light-grey to pink coarse-grained to very coarse-grained si-
liciclastic sandstones are the main lithology. Single sand-
stones strata are 660 cm thick. Fine-grained channel lag con-
46 VOZÁROVÁ
Fig. 5. Vertical section through profile T-12. Explanations as Fig. 4.
Active channel sediments mainly represented by the coarse-
to very-coarse-grained massive and trough- or planar cross-
bedded sandstones are dominant (lithofacies 4, 5 and 7 with
St, Sp, Sh, Sg, Sm, Se type of sandstones). The massive sand-
stones have a clast supported structure, very often with parting
or streaming lineation and graded bedding. Top part of indi-
vidual bars is proved by lithofacies 6 with ripples and low an-
gle crossbeds (Sr, Sl). The very scarce finer-grained sediments
(lithofacies 8, 9 with Fm, Fl siltstones and mudstones) are in-
terpreted as an ancient abandoned channel filling. Paleocur-
rent patterns (Fig. 4) indicate dominant accretion of the bars to
the north-east direction along the channels. The smaller cross-
beds show a more westerly flow direction.
The widths and depths of preserved channel fill structures in
the section T-11 indicates very narrow and shallow channels
(2 m wide and 0.20.3 m deep; Table 1). Comparing cross-
beds calculating values and their bankfull equivalents varies
significantly and their are noticeably greater (d
m
=0.493.12 m
and w=22140 m; d
b
=1.915.58 m and w
b
=2099 m; Ta-
ble 2). Estimated paleoslopes for the section T-11 are relative-
ly high, the average value for S=0.0137 mm
1
(total=13).
Calculated mean annual bankfull discharge (Q
b
=353.4 m
3
s
1
in average) and mean drainage area (A
d
=3249.7 km
2
) are ade-
quate to the calculated paleohydraulical data (Table 2).
Section T-12
Loc. Southwest from Niná Boca village, northern slope of
the Nízke Tatry Mountains (Fig. 5).
Fining-upward bars mostly consist of very coarse-grained to
coarse-grained sandstones. Clast-supported fine-grained con-
glomerates form only two layers (each of 23 cm thick) of
channel lag deposits at the basal part of the bar succession.
The thickness of individual bars is from 1.5 m to 2 m, rarely
up to 34 m. The massive conglomerates (lithofacies 1; Gm)
show horizontal bedding or inconspicuous streaming linea-
tion. They grade upward to lithofacies 4 (St, Sp), lithofacies 5
(Sh, Sg, Sm) or lithofacies 7 (Se). Sandy ripples occasionally
occur at the upper part of bar successsions (Sr). Remnants of
ancient abandoned channel sediments or overbank deposits
are only seldom preserved. They are represented by lithofacies
6 (Sl) and lithofacies 8 (Fm, Fsc). The azimuth of the planar
cross-beds shows a very consistent mean towards the north-
east (Fig. 4), conforming with section T-11.
As is shown in Table 1 the widths and depths of the pre-
served sandy and gravel channel fill in the section T-12 are
higher than those estimated for the section T-11. The real mea-
surements change from 1.3 m to 8.0 m for width and from
0.18 m to 0.70 m for depth. The calculated equivalent paleo-
hydrological values show approximately similar ranges
(d
m
=0.413.12 m;
w =18.4140.4 m;
d
b
=1.725.58 m;
w
b
=19.0298.78 m; Table 2). This, however, probably re-
flects an inability to measure a greater amount of real channel-
fill structures in the section T-11. The estimated paleoslope data
for section T-12 are a bit lower than those for the section T-11
(S=0.0103 mm
1
, total=21; Table 2). In contrast to this, the
Table 1: Width and depth of preserved gravel and sandy channel-
fill structures present in the Lúna Formation.
Locality No.
Width (m)
Depth (m)
3.5
0.9
3.0
0.8
2.0
0.5
4.0
0.8
section T-1
6.0
1.9
4.0
0.18
2.0
0.11
1.4
0.13
section T-5
1.5
0.09
2.0
0.22
section T-11
2.0
0.30
1.3
0.18
5.0
0.70
6.0
0.70
3.0
0.23
8.0
0.70
section T-12
5.0
0.45
RECONSTRUCTION OF FLUVIAL BARS FROM THE BUNTSANDSTEIN FACIES IN THE W CARPATHIANS 47
Fig. 6. Vertical section through profile T-1. Explanations as Fig. 4.
The rose diagrams show mean flow direction from planar cross-
beds (A) and mean directions of channels estimated from the T-1
and T-4 vertical sections.
Fig. 7. Detailed outcrop diagram of section T-1 (Fig. 6). Note pla-
nar cross-beds alternating with massive fine-grained conglomer-
ates and different order of bounding surfaces (e.g. second-order
between 21 and 19 beds; third-order betwen 22, 23, 24 beds).
mean annual bankfull water discharge value (Q
b
=616.5 m
3
s
1
;
total=21) as well as the mean drainage area value
(A
d
=5939.3 km
2
; total=21, Table 2) are higher.
Northern Veporic Unit
Section T-1
Loc. Upper part of the Kostolný potok Valley, about 200 m
SE from heights 844 m, the Èiera Mountains (Fig. 6).
The basal part of the Lúna Formation sequence in the
Northern Veporic Unit, merely 6 m from the underlying Per-
mian continental sediments. The surface exposures consist of
coarse quartzose sediments, grading from fine-grained con-
glomerates to very-coarse and coarse-grained sandstones, very
often with granules and pebbles (average size from 10 to
30 mm, locally at the basal part even 10 cm). Dominant are
the lithofacies 1 (Gm), prograding upward to the lithofacies 2
(Gt) and 4 (Sp, St, Sc) with distinct planar- and trough cross-
bedding. Relatively thick beds (from 50 to 80 cm, rarely up to
220 cm) are compound to the vertical succession of alternated
active braided bars (Fig. 7). Mean direction of transport varies
generally from NW to S in the planar cross-bedding and from
N or NNW to S in the trough cross-bedding. In the whole ver-
tical section the finer-grained sediments of abandoned chan-
nels are missing.
Azimuth of the planar and trough cross-beds in each of the
exposures shows a very consistent mean NWNSSE trend,
which is very consistent with the dominant direction of chan-
nels (Fig. 6).
The preserved gravel channel-fill structures range from 2 m
to 6 m in width and from 0.5 m to 0.9 m in depth (Table 1).
The calculated widths and depths estimated from the cross-
beds range from 1.35 m to 9.02 m for depth and from 60.7 m
to 405.9 m for width (Table 2). The mean paleoslope value is
lower than in the two sections above (S=0.007 mm
1
) and the
mean annual discharge as well as mean drainage area are ad-
equately higher (Q
b
=2023.5 m
3
s
1
, A
d
=33401 km
2
; total=8;
Table 2).
Section T-4
Loc. The right slope of the Kostolný potok Valley, 680 m
above sea level, 300 m SW from 844 heights, the Èiera
Mountains (Fig. 8).
Fine cyclicity in the framework of small braided bars (up to
5 m thick) is dominant. Individual bars are underlain by ero-
sive first-order bounding surfaces. Sediments are repeatedly
coarse-grained. The fine-grained conglomerates create thick
beds with low angle (up to 10°) streaming lineation and planar
cross-bedding, occasionally with trough cross-bedding (litho-
48 VOZÁROVÁ
Locality
h
(m)
d
m
(m)
w
(m)
Q
m
(m
3
s
1
)
d
b
(m)
w
b
(m)
Q
m
(1)
(m
3
s
1
)
S
(mm
1
)
S(1)
(mm
1
)
Q
b
(m
3
s
1
)
Q
b
(1)
(m
3
s
1
)
A
d
(km
2
)
A
d
(1)
(km
2
)
L
(km)
L(1)
(km)
0.07
2.87 129.15 278.0 5.30 91.91 61.48
0.0053
0.0095
1647.8
1940.3
19462.5
24200.2 524.4 597.6
0.04
1.64 73.8
90.8 3.84 58.54 28.43
0.0076
0.0165
795.1
858.5
6394.4
8540.5 268.9 319.9
0.04
1.16 73.8
90.8 3.84 58.54 28.43
0.0076
0.0165
795.1
858.5
6394.4
8540.5 268.9 319.9
0.04
1.64 73.8
90.8 3.84 58.54 28.43
0.0076
0.0165
795.1
858.5
6394.4
8540.5 268.9 319.9
0.076 3.10 139.5
324.3 5.56 98.29 68.95
0.0051
0.0088
1873.5
2182.7
23096.2
28313.2 588.1 656.6
0.033 1.35 60.7
61.5 3.34 48.15 20.35
0.0086
0.0199
493.6
623.3
3901.1
5336.0 199.9 241.2
0.033 1.35 60.7
61.5 3.34 48.15 20.35
0.0086
0.0199
493.6
623.3
3901.1
5336.0 199.9 241.2
T- 1
0.22
9.02 405.9
2745.9 10.33 233.95 303.78
0.0026
0.0031
9374.6
9847.8 197668.3 211083.9 2107.1 2191.8
0.06
2.46 110.7
204.2 4.86 81.40 49.95
0.0059
0.0110
1320.0
1571.6
14480.3
15716.0 439.1 461.3
0.02
0.82 36.9
22.7 2.57 33.37 10.87
0.0119
0.0325
252.6
334.7
1597.0
2323.9 116.9 146.5
T- 4
0.025 1.02 45.9
35.1 2.92 39.90 14.76
0.0103
0.0262
351.5
456.5
2480.7
3515.3 152.4 187.8
0.018 0.73 32.8
17.9 2.40 30.32 9.23
0.0129
0.0364
211.8
283.2
1262.7
1859.8 101.6 128.2
0.04
1.64 73.8
90.8 3.84 58.54 28.43
0.0076
0.0164
715.1
886.9
6394.2
8521.2 268.9 319.5
T- 5
0.013 0.53 23.9
9.5 2.00 23.49 5.96
0.0158
0.0497
132.0
181.9
672.4
1031.3 69.6 90.0
0.11
4.51 202.9
686.3 6.91 133.25 116.02
0.0040
0.0061
3290.4
3703.1
48940.7
57291.5 911.9 1002.3
0.09
3.69 166.0
459.4 6.15 113.19 87.78
0.0046
0.0074
2424.4
2786.7
32569.3
39215.3 714.2 798.4
0.36
14.76 664.2
7352.7 13.75 349.15 602.44
0.0019
0.0019 19701.6 19701.6 532111.1 532111.1 3817.1 3817.1
0.13
5.33 239.8
958.6 7.62 152.80 146.63
0.0036
0.0052
4244.4
4704.3
78807.7
78824.5 1213.6 1213.6
0.01
0.41 18.4
5.6 1.71 18.86 4.10
0.0186
0.0643
87.7
124.1
399.5
618.8 50.2 66.2
0.025 1.02 45.9
35.1 2.92 39.90 14.76
0.0104
0.0262
352.5
456.5
2489.6
3515.3 152.7 187.8
0.05
2.05 92.2
141.8 4.38 70.38 38.95
0.0066
0.0132
1007.2
1223.0
10096.5
13078.4 353.7 413.1
0.02
0.82 36.9
22.7 2.57 33.37 10.87
0.0119
0.0325
252.6
334.7
1597.0
2323.9 117.0 146.5
0.05
2.05 92.2
141.8 4.38 70.38 38.95
0.0066
0.0132
1007.2
1223.8
10096.5
13078.4 353.7 413.1
0.07
2.87 129.1
277.9 5.32 92.40 62.04
0.0053
0.0095
1666.0
1961.7
19749.6
24557.6 529.0 602.9
0.17
6.97 313.6
1639.3 8.98 192.30 217.25
0.0030
0.0040
6497.3
7042.3 121239.4 134985.2 1571.5 1653.6
0.05
2.05 92.2
141.8 4.38 70.38 38.95
0.0066
0.0132
1007.2
1223.0
10096.1
13078.8 353.7 413.1
0.05
2.05 92.2
141.8 4.38 70.38 38.95
0.0066
0.0132
1007.2
1223.0
10096.1
13078.8 353.7 413.1
0.06
2.46 110.7
204.2 4.86 81.41 49.96
0.0059
0.0111
1320.2
1575.8
14482.8
18337.3 439.2 505.9
0.02
0.82 36.9
22.7 2.57 33.37 10.87
0.0119
0.0325
252.6
334.7
1596.8
2323.8 117.0 146.5
0.02
0.82 36.9
22.7 2.57 33.37 10.87
0.019
0.0325
252.6
334.7
1596.8
2323.8 117.0 146.5
0.05
2.05 92.2
141.8 4.38 70.38 38.95
0.0066
0.0132
1007.2
1223.0
10096.1
13078.8 353.7 413.1
0.025
1.02 45.9
35.1
2.92
39.90
14.76
0.0103
0.0262
351.5
456.5
2480.6
3514.9
152.3
187.8
0.03
1.23 55.3
51.0
3.25
46.35
19.07
0.0092
0.0218
464.7
591.7
3599.4
4967.5
190.5
231.1
0.02
0.82 36.9
22.7
2.57
33.37
10.87
0.0119
0.0325
252.6
334.7
1596.8
2323.8
117.0
146.5
0.028
1.15 51.7
44.6
3.25
46.35
19.07
0.0096
0.0333
470.3
666.2
3657.3
5818.4
192.3
254.1
0.016
0.66 29.7
14.7
2.27
28.04
8.07
0.0137
0.0402
183.2
247.6
1040.5
1554.7
90.5
115.1
T- 9
0.016
0.66 29.7
14.7
2.27
28.04
8.07
0.0137
0.0402
183.2
247.6
1040.5
1554.7
90.5
115.1
0.046
1.88 84.6
119.3
4.16
65.48
34.43
0.0070
0.0144
881.6
1078.9
8453.3
11065.6
317.9
373.7
0.012
0.49 22.0
8.1
1.91
20.02
5.34
0.0166
0.0539
117.3
162.8
572.9
889.9
63.2
82.3
0.016
0.66 29.7
14.7
2.27
28.04
8.07
0.0137
0.0402
183.2
247.6
1040.5
1554.7
90.5
115.1
0.015
0.61 27.4
12.5
2.16
26.16
7.17
0.0144
0.0435
160.8
219.2
874.4
1321.7
81.5
104.4
0.01
0.41 18.4
5.7
1.72
19.02
4.16
0.0186
0.0643
89.2
126.2
398.5
633.0
50.9
67.1
0.014
0.57 25.6
10.9
2.08
24.81
6.55
0.0151
0.0465
165.6
200.1
909.4
1170.4
83.4
97.1
0.025
1.02 45.9
35.1
2.92
39.90
14.76
0.0104
0.0262
352.5
456.5
2490.1
3514.9
152.7
187.8
0.076
3.12 140.4
328.5
5.58
98.78
69.54
0.0051
0.0088
1893.0
2205.4
23417.7
28706.7
585.9
662.1
0.02
0.82 36.9
22.7
2.57
33.37
10.87
0.0119
0.0325
252.6
334.7
1596.8
2323.8
117.0
146.5
0.013
0.53 23.8
9.5
2.00
23.49
5.96
0.0158
0.0500
132.0
182.3
672.1
1033.7
69.6
90.1
0.012
0.49 22.0
8.1
1.91
22.02
5.34
0.0166
0.0540
117.1
162.9
572.9
889.7
63.2
82.3
0.013
0.53 23.8
9.5
2.00
23.49
5.96
0.0158
0.0500
132.0
182.3
672.1
1033.7
69.6
90.1
T- 11
0.012
0.49 22.0
8.1
1.91
22.02
5.34
0.0166
0.0540
117.1
162.9
572.9
889.7
63.2
82.3
0.04
1.64 73.8
90.8
3.84
58.54
28.43
0.0076
0.0165
715.1
988.9
6394.7
9852.3
268.9
348.5
0.027
1.11 49.9
41.5
3.06
42.60
16.51
0.0098
0.0242
397.1
511.5
2918.8
4090.7
167.9
205.7
0.01
0.41 18.4
5.7
1.72
19.02
4.16
0.0186
0.0643
89.2
126.2
398.5
633.0
50.9
67.1
0.06
2.46 110.7
204.2
4.86
81.41
49.96
0.0059
0.0111
1320.2
1575.8
14482.0
18337.3
439.2
506.0
0.06
2.46 110.7
204.7
4.86
81.41
49.96
0.0059
0.0111
1320.2
1575.8
14482.8
18337.3
439.2
506.0
0.03
1.23 55.3
51.0
3.25
46.35
19.07
0.0092
0.0237
464.7
605.7
3599.4
5124.8
190.5
235.5
0.025
1.02 45.9
35.1
2.92
39.90
14.76
0.0103
0.0341
351.5
491.5
2480.6
3878.8
152.3
199.2
0.011
0.45 20.25
6.8
1.81
20.42
4.69
0.0175
0.1705
101.6
192.3
474.1
1109.9
56.4
94.0
0.015
0.61 27.4
12.5
2.16
26.16
7.17
0.0144
0.0939
160.8
292.0
874.4
1937.2
81.5
131.3
0.016
0.66 29.7
14.7
2.27
28.04
8.07
0.0137
0.0801
183.6
300.4
1040.5
2011.8
90.5
134.4
0.013
0.53 23.8
9.5
2.00
23.49
5.96
0.0158
0.1229
132.0
234.5
672.1
1446.1
69.6
110.2
0.045
1.84 82.8
114.3
4.11
64.38
37.08
0.0071
0.0107
854.6
958.6
8109.9
9451.8
310.1
340.0
0.017
0.70 31.5
16.5
2.34
29.26
8.68
0.0132
0.0715
198.5
317.8
1154.0
2168.7
96.3
140.5
0.037
1.52 68.4
78.0
3.68
55.15
25.67
0.0080
0.0156
641.0
772.8
5526.8
7091.8
246.4
286.1
0.056
2.30 103.5
178.5
4.68
77.22
45.64
0.0062
0.0069
1199.7
1236.2
12747.6
13267.4
406.8
416.7
0.047
1.93 86.85
125.6
4.22
66.81
35.63
0.0069
0.0098
915.4
1009.9
8888.2
10132.2
327.6
354.4
0.047
1.93 86.85
125.6
4.22
66.81
35.63
0.0069
0.0098
915.4
1009.9
8888.2
10132.2
327.6
354.4
0.028
1.15 51.7
44.6
3.13
43.97
17.42
0.0096
0.0270
421.6
563.2
3161.3
4651.0
176.2
222.1
T- 12
0.076
3.12 140.4
328.5
5.58
98.78
69.54
0.0051
0.0087
1893.0
2198.4
23417.2
28585.3
585.9
660.4
0.033
1.35 60.7
61.5
3.43
49.98
21.69
0.0087
0.0197
539.0
672.6
4343.2
5893.1
213.2
256.0
0.013
0.53 23.8
9.5
2.00
23.49
5.96
0.0158
0.1229
132.0
234.5
672.1
1446.1
69.6
110.2
x
0.05
1.84 82.78
268.4
3.74
60.59
42.01
0.0099
0.0319
1180.7
1336.9
19444.1
21039.9 345
382
Sx
0.07
2.15 96.85
938.8
2.07
52.42
82.54
0.0045
0.0304
2653.9
2691.3
68069.7
68377.6 540
545
n =
71
Table 2: Estimations of paleohydraulic data from the Lúna Formation on the basis of thickness of planar and trough cross-beds.
RECONSTRUCTION OF FLUVIAL BARS FROM THE BUNTSANDSTEIN FACIES IN THE W CARPATHIANS 49
facies 3, rarely 2). This coarse basal part of the bar progrades
upward through very coarse to medium-grained sandstones
(with parting lineation or low-angle cross-lamination) in its
upper part (lithofacies 5). Abandoned channel or overbank fa-
cies are also absent.
The paleocurrent pattern is consistent with those in the sec-
tion T-1. The calculated flow depth and width based on cross-
beds range between 0.82 and 2.46 m (d
m
) and from 45.9 to
110.7 m (w). Corresponding are values for bankfull channel
depth and bankfull channel width (d
b
= 2.574.86 m,
Explanations to Table 2: h thickness of cross-beds (m); d
m
wa-
ter depth (m); w channel width; Q
m
maximum instantaneous wa-
ter discharge; d
b
bankfull channel depth; w
b
bankfull channel
width; Q
m
(1) average daily discharge; S stream paleoslope (eqn
8a); S(1) stream paleoslope (eqn 8b); Q
b
bankfull water dis-
charge (using S values); Q
b
(1) bankfull water discharge (using S(1)
values); A
d
drainage area (using Q
b
values); A
d
(1) drainage area
(using Q
b
(1) values); L principal stream length (using A
d
) values;
L
(1) principal stream length (using A
d
(1) values).
Fig. 8. Vertical section through profile T-4. Explanations as Fig. 4.
Fig. 9. Vertical section through profile T-5. Explanations as Fig. 4.
The rose diagram indicates mean flow direction from planar cross-
beds.
w
b
=33.3781.40 m; Table 2). The estimated paleoslope values
(S=0.0060.012 mm
1
) as well as bankfull water discharge
(Q
b
) and drainage area (A
d
) data are adequate to the others
North Veporic sections (Table 2).
Vertical section T-5
Loc. The right slope of Drahoná Valley, 312 m above see
level, the Tribeè Mountains (Fig. 9).
Sandy sediments with different size grades, from coarse-
grained through medium- to fine-grained sandstones, prevail.
I
50 VOZÁROVÁ
The first-order erosive bounding surfaces are overlain by rela-
tively thin layers of pebble sandstones (up to 30 cm thick).
They represent channel lag deposits and scour fills occasional-
ly with intraclasts in basal part of braided bars. The whole se-
quence is well differentiated into small bars with distinct up-
ward fining. Clast-supported massive or graded-bedded
sandstones sometimes with streaming lineation are dominant
(lithofacies 5; Sm, Sg, Sh). The lithofacies 5 progrades up-
ward into the planar cross-beds, associated seldom with the
wide and shallow trough cross-beds (lithofacies 4; Sp, St).
Medium-grained rippled sandstones were locally identified in
the upper part of bars (lithofacies 6; Sr). Purple to green-grey
fine-grained sandstones, mudstone and silty shales are subor-
dinate (lithofacies 9; Fl). They usually comprise fine horizontal
lamination and occasionally small scale ripple marks. Paleo-
current patterns indicate dominant flow directions from the
north to the south (Fig. 9).
The widths of the preserved sandy channel fill structure
fluctuate between 1.4 and 4.0 m. The depth is very shallow,
ranging from 0.09 to 0.18 m (Table 1). Compared to this the
calculated values of depth and width and their bankfull equiv-
alents are higher (d
m
=0.531.64 m, w=23.973.8 m, d
b
=2.0
3.84 m, w
b
=23.4958.54 m; Table 2). Paleoslope data indi-
cate steeper slope (S=0.008-0.016 mm
1
) with adequate
fluctuating bankfull water discharge (Q
b
=132715 m
3
s
1
) and
drainage area (A
d
=6726394 km
2
; Table 2).
Section T-8
Loc. Haliar Valley, E of the Staré Hory village, the Staro-
horské vrchy Hills (Fig. 10).
This vertical section represents a fragment of fine-grained
abandoned channel deposits or erosional remnants of backwa-
ters or floodplain depression deposits. The prevailing sedi-
ments are purple siltstones intercalations of light-grey fine-
and very fine sandstones and purple to green shales. The indi-
vidual layers (2 to 10 cm thick) are uniform, with flat and
sharp contacts between them. A very fine horizontal lamina-
tion is dominat, passing rarely into moderate oblique (lithofa-
cies 8; Fl). Some laminated to massive siltstones, mudstones
and shales (lithofacies 9; Fm, Fcf, Fsc) contain carbonate pe-
dogenic (P) or bioturbation (B) horizons. The medium-grained
sandstones form only two low angle cross-beds (up to 12 cm
thick).
Vertical section T-9
Loc. The left slope of the Jelenská dolina Valley, SE from
700 m above sea level, the Starohorské vrchy Hills (Fig. 11).
Active braided channel deposits are dominant (up to 5 m
thick, rarely more). They cyclically alternate one above the an-
other in the whole vertical sequence. They are mostly repre-
sented by the fine-grained conglomerates of the lithofacies 1,
3 and rarely 2 (facies Gm, Gp, Gt) and very coarse to coarse-
grained sandstones of the lithofacies 4 and 5 (facies St, Sp,
Sm, Sh) with planar and small trough cross-bedding as well as
parting lineation. Medium- to fine-grained sandstones with
low angle planar or small trough cross-bedding were identi-
fied as bar-top finer sediments. Fine backwater or abandoned
channel fill deposits form only scarce erosional remnants in
the second half of the vertical section. The whole T-9 vertical
section shows a very moderate upward fining, similar to that
within the individual bars.
The paleoflow directions of the smaller cross-beds show a
divergent pattern (Fig. 11), to the NE and to the W. These
measurements probably reflect flow divergence with respect
to mean channel direction.
Estimated flow depths vary overall between 0.66 m and
6.97 m and width values range from 29.7 m to 313.6 m. Their
bankfull equivalents indicate similar variability (Table 2). The
mean paleslope value (S=0.009 mm
1
; total=23) is higher
than the maximum known from the recent river (0.007; Blair
& McPherson 1994). The bankfull water discharge fluctuates
similarly to the drainage area in dependence of bankfull great-
ness and changes of paleoslope (Table 2). The relatively high
mean bankfull water discharge is also reflected in the high mean
drainage area (Q
b
=2055.8 m
3
s
1
, A
d
=39977.2 km
2
; Table 2).
Interpretation of the vertical sections and
paleohydrological data
Planar cross-beds that dominate the bar succession were
probably deposited by migrating dunes. Similar planar cross-
Fig. 10. Vertical section through profile T-8. Explanations as Fig. 4.
RECONSTRUCTION OF FLUVIAL BARS FROM THE BUNTSANDSTEIN FACIES IN THE W CARPATHIANS 51
Fig. 11. Vertical section through profile T-9. Explanations as
Fig. 4. The rose diagram shows divergent flow directions estimat-
ed from smaller cross-beds.
bedded successions were described in many modern and an-
cient braided fluvial deposits (Smith 1970; Rust 1972; Miall
1978, 1994; Ashley 1990; Selley 1996). Bedforms were both
simple and compound types, the latter with superposed small-
er bedforms. The paucity of fine-grained sediments and low
directional variability of the planar cross-beds supports depo-
sition in low-sinusoity bedload streams. Reactivation surfaces
indicate frequent fluctuation of flow depth and velocity.
Change in the shape of the reactivation surfaces from convex-
up to concave-up probably represents a progressive lowering
of the flow stage (Fig. 7). Erosional truncation of the planar
cross-beds by lenticular, trough cross-bedded units is inferred
to represent a shallow, low-stage channel which dissected the
bar tops. The point bar within vertical sections T-11 and T-12
as well as T-5 (Figs. 4, 5 and 9) can be 3 to 5 m thick. The
point bar sequence from the bottom to the top is made up of
sandy and pebble sandy megaripples. Internally, cross-bedded
units (10 to 50 thick) are present, laminae show high angles of
dip (>30°). Horizontal bedding of the upper flow regime is
also present. This type of sequence most probably represents
the mid-bar facies (Levey 1978). The finer sediments of aban-
doned channel fills are present only in some erosive remnants.
The bars within sections T-1 and T-4 (Figs. 6 and 8) can be
interpreted as gravelly stream deposits. Fine-grained conglom-
erates associated with pebble sandstones are the prevailing
type of sediments. The bedding is often massive with clast-
supported structure and often streaming lineation. The basal
part of bars is made up of coarse channel lag deposits with
erosive bounding surfaces. Those prograde to trough cross-
bedded unit, made by migrating megaripples. This unit is
overlain by the coset of planar cross-beds of transverse bars.
This subfacies corresponds to the upper part of the point bar.
The upper half of the section T-1 (Fig. 6) contains a very well
preserved channel and bar sequence. This bar sequence is
characterized by sinuous trend and steep foreset cross-stratifi-
cation.
The vertical profile T-9 represents a fully developed braided
bar sequence with gravel-sandy mixed sediments. Within the
schematic vertical sequence, low-angle planar cross-bedded
fine conglomerates alternate with trough cross-bedded ones.
The bar top sediments are formed by massive or horizontal
and rippled sandstones. In the upper part of the profile the
coarse-grained sandstones are dominant. They are character-
ized by mainly horizontal bedding (parting lineation), low-an-
gle planar cross-bedding (<10°), and trough cross-bedding.
Paleohydrological data were estimated for the braided fluvi-
al system of the Lúna Formation using different formulas for
the estimation of hydrological parameters in the ancient river
system, proposed by various authors. The width and depth of
the preserved channel-fill structure in the Lúna Formation are
presented in Table 1. A comparison of those results with cal-
culated values (Table 2) indicates large and significant differ-
ences. Dimensions measured in the field are considerably
smaller. This probably reflects an inability to recognize, and
thus also measure, greater channel-fill structure in the field
due to strongly forested surface area. Outcrops of the exposed
Lúna Formation sediments exceed several tens of meters in
width and a few or tens of meters in height.
Table 2 provides various hydrological data parameters esti-
mated in this study for the Lúna Formation sediments (includ-
ing mean and one standard deviation). The estimation of hydro-
logical parameters was made on the basis of the thicknesses
measured from cross-bed structures (e.g. Ethridge & Schumm
1978). Standard errors in their application are often significant
and vary depending on the applied formula and the number of
data points used to derive the equations (Miall 1976; Turner
1980; Van der Neut & Eriksson 1999). The set thickness of pre-
served cross-beds was used to obtain a mean water depth (d
m
) in
meters by applying the Allens (1968) formula:
h=0.086 (d
m
)
1.19
(1)
where h is the thickness of cross-beds in meters, and d
m
is the
mean water depth over the sedimentary structure, in meters.
The ratio between channel width and depth (F) may be esti-
mated by:
52 VOZÁROVÁ
Fig. 12. Binary plot of paleoslopes (S) and mean annual bankfull
discharge (Q
b
) values estimated for the Lúna Formation rivers. The
maximum gradient (0.007) calculated for modern rivers and that as-
sociated with modern alluvial fans (0.026) are taken from Blair &
McPherson (1994).
F=225 M
1.08
(Schumm 1968) (2)
where M is the percentage of silt and clay in the channel pe-
rimeter. According to Schumm (1968), coarse bedload streams
have M values of less than 5 %. The paleostreams of the
Lúna Formation drainage system generally fall into this cate-
gory, as the sedimentary sequences have low matrix content,
and M is, therefore, assumed to be 5 % in this study. Substitut-
ing this value in the equation (2) gives a channel width to
depth ratio of F=45. This value enables us to estimate of the
width of channel, w (in meters), by calculating:
w=45 d
m
(Schumm 1968). (3)
From this equation is possible to assess the average daily dis-
charge (approximation of mean annual discharge), Q
m
(m
3
s
1
),
by calculating:
Q
m
=vA (4)
where A is the mean cross-sectional surface area of the chan-
nel (m
2
), approximated by multiplying the water depth (d
m
) by
channel depth (w). The mean bankfull channel depth (d
b
), in
meters, can be calculated from:
d
b
=0.6 M
0.34
Q
0.29
(Schumm 1969) (5)
and then the bankfull channel width to calculate (w
b
) from
w
b
=8.9 d
b
1.40
(Leeder 1973). (6)
According to Van der Neut & Eriksson (1999), this value
enables a more realistic estimation of an average daily dis-
charge (Q
m
) than eqn (4), when it is applied to the formula of
Osterkamp & Hedman (1982):
Q
m
=0.027w
b
1.71
(7)
as eqn (4) reflects the maximum instantaneous discharge and
eqn (7) the average daily discharge. The gradient or slope of
the river is one of the fundamental hydraulic parameters con-
trolling channel morphology. The estimation of the stream pa-
leoslope (S), in mm
1
, was calculated by formulas:
S=60 M
0.38
Q
m
0.32
(Schumm 1968) (8a)
S(1)=30 (F
0.95
/w
0.98
) (Schumm 1972) (8b)
as the second estimation of Q
m
(eqn 7) it is applied to eqn (8a).
These two values provide an approximate range of possible
paleoslope values for the Lúna Formation braided channels.
The boh S values enable to estimate two bankfull water dis-
charge values, using:
Q
b
=4.0 A
b
1.21
S
2.28
(Williams 1978) (9)
where A
b
=d
b
×w
b
. Similar to this, Leopold et al. (1964) pro-
vide an estimation of the probable drainage area for river sys-
tem by the formula:
Q
b
=(A
d
)
b
(10)
where A
d
is drainage area (km
2
). This value was used for cal-
culation of supposed stream length. According to Leopold et
al. (1964), the principal stream length has a stable and con-
stant relationship to the drainage area and is approximated by
the formula:
L=1.4 (A
d
)
0.6
(11)
where L is the stream length (km).
The set of the above mentioned formulas was used by Turn-
er (1980) for determination of the paleohydrological data of
the Upper Triassic Molteno Formation as well as by Van der
Neut & Eriksson (1999) for the fluvial river system of the Pro-
terozoic Wilgerivier Formation. Both the Molteno and
Wilgerivier Formations are inferred to reflect predominantly
braided-river deposition systems (l.c.). Compared to the Lúna
Formation data (n=71) the previous authors supported their
results by the much greater set of paleohydrological data, for
the Wilgerivier Formation of a total of 810 set thicknesses and
for the Molteno Formation of a total of 137. Table 2 shows
that all except two mean hydrological parameter estimated for
the Lúna Formation river deposits are a bit lower than their
equivalent values derived from the Wilgerivier Formation (Ta-
ble 3). The exceptions are the mean S(1) value and both A
d
pa-
rameters, which are relatively higher for the Lúna Formation.
There is a strong dependence between the values of mean
annual bankfull discharge (Q
b
) as well as paleoslope (S) and
drainage area (A
d
) (Table 2). The paleoslope values (S) esti-
mated for the Lúna Formation braid-channels lie between
those generally found for alluvial fans (>0.026) and for rivers
(<0.007) (Blair & McPherson 1994), since the Lúna Forma-
tion mean value are for S=0.0099 and for S(1)=0.0319 (Ta-
ble 2). Blair & McPherson (1994) ascertained a distinct break
in nature in the longitudinal slopes of fluvial distributary sys-
tems, between those found on alluvial fans (slopes ranging
from 0.026 to 0.466) and those characteristic for river fluvial
systems (maximum slope approx. 0.007). Paleoslopes estimat-
ed for the Lúna Formation (in spite of a bit higher S(1) value)
fall mostly into the gap discussed above (Fig. 12), indicating
RECONSTRUCTION OF FLUVIAL BARS FROM THE BUNTSANDSTEIN FACIES IN THE W CARPATHIANS 53
Wilgerivier
Formation
h
(m)
d
m
(m)
w
(m)
Q
m
(m
3
m
1
)
d
b
(m)
w
b
(m)
Q
m
(1)
(m
3
m
1
)
S
(mm
1
)
S(1)
(mm
1
)
Q
b
(m
3
m
1
)
Q
b
(1)
(m
3
m
1
)
A
d
(km
2
)
A
d
(1)
(km
2
)
L
(km)
L(1)
(km)
mean
0.23 2.23 100.57 198.32 4.50 74.19
45.44
0.01
0.02
1378.19 1564.77 16760.77 19624.53 440.42 489.29
stand. deviation
0.12 0.94 42.25 191.90 1.05 24.81
27.76
0.00
0.01
967.64 1015.29 17005.64 18250.84 237.56 244.96
Table 3: Mean paleohydrological data estimated for the Wilgerivier Formation (Van de Neut & Eriksson 1999).
Fig. 13. Binary plot of mean annual bankfull discharge (Q
b
) and
drainage area values (A
d
) estimated for the Lúna Formation rivers.
braided channels different in character to either modern fans
or bedload fluvial systems. The inferred values also corre-
spond very well with paleoslope parameters estimated for the
Wilgerivier ancient braided alluvia (Table 3). The direct de-
pendence of discharge values on the size of the drainage area,
applicable to river systems in general, is also reflected in the
paleohydraulic estimates for the Lúna Formation, as illustrat-
ed in the binary plot of Q
b
again A
d
(Fig. 13).
Evidence for a braided stream interpretation for the Lúna
Formation includes the predominance of cross-bedded (main-
ly planar) medium- to coarse-grained sheet sandstones, subor-
dinate imbricated conglomerate beds, finer pebble and more
common sandy channel-fill structure, consistently oriented N-
S paleocurrent trends exhibiting only a small variation in di-
rection and scarcity of mudrocks. The hydrological data from
the Lúna Formation reflect braided-river setting, with no evi-
dence of significant suspended load or floodplain influences.
Generally, the Lúna Formation it thought to have been deposit-
ed within an active tectonic setting, following after a relatively
short period of pre-Triassic tectonic stabilization linked with
rapid weathering. The Lower Triassic mature sediments were
deposited along a linear steep and faulted margin, bordered by
a number of alluvial draining system. A predominant braidplain
environment, with subordinate abandoned channels and small
endorheic basins, proceeded to lagoonal and shallow water con-
ditions in its distal part. An active tectonic faulting in the prove-
nance area led to the origin of segmented depositional margins
and thus, to a number of alluvial drainage areas of varying size.
A semi-arid climate is inferred for the Lúna Formation in gen-
eral, owing to the presence of alluvial and aeolian deposits (e.g.
presence of ventifacts, layers of sandstones with a high degree
of sorting and mudrocks with carbonate nodules).
Concerning basin paleogeography, distributions of the
Lúna Formation facies give evidence of the development of
a broader braidplain in the foreland of the erosional highlands
(Fig. 14). The main reasons for the origin of this extensive
braidplain were the frequency and intensity of ephemeral at-
mospheric precipitation to provide high-capacity discharge
rates and volumes in the streams and tectonic rejuvenation of
the relief in the provenance area to enable steep slopes. These
factors together with aggressive weathering and a very rapid
rate of erosion in the absence of land vegetation in the prove-
nance area resulted in origin of an extensive braidplain, which
was covered by a network of a highly- to moderately-braided
river system. Thin aeolian sheet and dune sandstones repre-
sent separate intervals within the braided fluvial sediments.
The Lúna Formation upward fining is associated with decline
in the sinusoity of watercourses. Moderately- to weakly braid-
ed sandy river system passed upward to sandy/muddy inland
floodplain. Scarse bioturbation horizons were occasionally
recognized in the upper part of shallow channels or thin sheet-
flood sandy/silty sediments as well as the playa mudstone as-
semblage. These indicate low-energy or stagnant conditions
which led to installation of endofauna and organogenic re-
working of sediments. Upward decreasing of sedimentary sup-
ply and basin energy was connected with increasing of aridity.
This is documented by the presence of pedogenic horizon with
carbonate nodules, laminae of dolomites and lenses of evapor-
ites in places.
In terms of general depositional modelling, the Lúna For-
mation Buntsandstein facies sedimentary area passed through
a broad braidplain river system and inland floodplain from the
north to a coastal floodplain in front of the invading carbonat-
ic sea to the south.
Conclusions
The common features that characterize the bar succession in
the Lúna Formation are:
1. the presence of succession of planar cross-beds above
a major erosion surface and paucity of fine-grained sediments
in the succession;
Fig. 14. Scheme of paleoenvironmental evolution of the Lúna
Formation sedimentary system.
54 VOZÁROVÁ
2. transition of the solitary planar cross-beds into compound
cross-beds or into cosets of smaller trough cross-beds;
3. the presence of shallow channels that cut down into the
top of large beds and are filled with small trough cross-beds;
4. the bar succession of the Lúna Formation were formed
during rapidly fluctuating flow conditions; bars were mostly
of mid-channel type;
5. the channels had a low sinusoity;
6. the fluvial system was characterized by the contempora-
neous existence of both shallow and deeper channels;
7. low dispersion of paleocurrents measured from large pla-
nar cross-beds.
The vertical profiles of the Lower Triassic Lúna Formation
sediments indicate a sand-dominant braided stream model.
The basal, more proximal sequence contains mixed sandy-
gravel material and no or a few mudrock layers. The upper
part of the Lúna Formation clastic succession is sand domi-
nated, with some often thin mudrock intercalations and better
developed fining upward cyclicity within bars. Inland flood-
plain facies with bioturbations and pedogenic horizons as well
as playa evaporite intervals occur only in its uppermost part.
The paleohydrological data from the Lúna Formation re-
flect a braided river setting, which is characterized by rapid
and large fluctuations in river discharge (Q
m
and Q
b
variables;
Table 2). Paleoslopes are close to the maximum known from
modern rivers (0.007), but those estimated for the Lúna For-
mation (0.0099) (Table 2) fall between this maximum and val-
ues corresponding to modern fans (>0.026). The faulted mar-
gins of the Lúna Formation depositional area provided
a number of smaller drainage areas and aggressive weathering
and high erosion rates promoted formation of sandy detritus
close to the former source area. High-gradient braided and in-
termittent torential storms played an important role on these
braided floodplains.
Acknowledgments: This research was supported by Grant
Project No. 1/8205/01 of the Scientific Grant Agency of Edu-
cation of Slovak Republic and Slovak Academy of Sciences,
Commission VEGA No. 3., on Science of Earth and Cosmos.
The author is grateful to P. Karnkowski (Warszawa), T. Peryt
(Warszawa) and G.H. Bachman (Halle) for their stimulating
and valuable comments and careful review of the manuscript,
to R. Vojtko for assistance with paleocurrent diagrams and E.
Petríková for graphic demonstrations of figures.
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