Deep-sea trace fossils controlled by palaeo-oxygenation and deposition: An example from the Lower Cretaceous dark flysch deposits of the Silesian Unit, Carpathians, Poland

Abstract

Trace fossil associations and ichnofabrics have been studied in three lithostratigraphic units of the Lower Cretaceous dark flysch deposits, i.e. within the Upper Cieszyn Beds (Valanginian-Hauterivian), the Verovice Shale (Barremian-lowermost Albian) and the Lgota Beds (Albian-Cenomanian). The associations differ from those of the Upper Cretaceous and Tertiary flysch deposits. The trace fossil association of the Upper Cieszyn Shale belongs to the Nereites ichnofacies, but the associations of the other two units do not; therein the trace fossil diversity is distinctly lower, and graphoglyptids or horizontal meandering pascichnia are absent or very rare. These trace fossil associations supposedly changed as a result of general evolutionary processes that influenced deep-sea trace makers after the Early Cretaceous, and which intensified the aforementioned differences. The composition of trace fossil associations and the vertical extent of the bioturbated zone in turbidite-hemipelagite beds were strongly affected by changing oxygenation on the deep-sea floor during the global Early Cretaceous anoxic events. The Verovice Shale is dominated by anoxic sediments interlayered with rare, thin, bioturbated horizons. In the Upper Cieszyn Shale and in the Lgota Beds, most tops of turbidite-hemipelagite rhythms are bioturbated. Non-bioturbated rhythms record anoxia, but their occurrence is influenced by the frequency of turbiditic deposition. Protovirgularia obliterata and Protovirgularia pennata occur in the Verovice Shale in the deepest tier below Chondrites. These trace fossils were probably produced below the redox boundary by chemosymbiotic bivalves. The studied associations show that the deep-sea environment is influenced by many factors that change with time, which records the large-scale dynamics of deep-sea ecological processes.

Full text

Deep-sea trace fossils controlled by palaeo-oxygenation and
deposition: an example from the Lower Cretaceous dark flysch
deposits of the Silesian Unit, Carpathians, Poland
ALFRED UCHMAN
Uchman, A. 2004 10 25: Deep-sea trace fossils controlled by palaeo-oxygenation and de
position: an example from the Lower Cretaceous dark flysch deposits of the Silesian Unit,
Carpathians, Poland. Fossils and Strata, No. 51, pp. 39–57. Poland. ISSN 0300-9491.
Trace fossil associations and ichnofabrics have been studied in three lithostratigraphic units of
the Lower Cretaceous dark flysch deposits, i.e. within the Upper Cieszyn Beds (Valanginian–
Hauterivian), the Verovice Shale (Barremian–lowermost Albian) and the Lgota Beds (Albian–
Cenomanian). The associations differ from those of the Upper Cretaceous and Tertiary flysch
deposits. The trace fossil association of the Upper Cieszyn Shale belongs to the Nereites
ichnofacies, but the associations of the other two units do not; therein the trace fossil diversity is
distinctly lower, and graphoglyptids or horizontal meandering pascichnia are absent or very
rare. These trace fossil associations supposedly changed as a result of general evolutionary
processes that influenced deep-sea trace makers after the Early Cretaceous, and which
intensified the aforementioned differences.
The composition of trace fossil associations and the vertical extent of the bioturbated zone in
turbidite–hemipelagite beds were strongly affected by changing oxygenation on the deep-sea
floor during the global Early Cretaceous anoxic events. The Verovice Shale is dominated by
anoxic sediments interlayered with rare, thin, bioturbated horizons. In the Upper Cieszyn Shale
and in the Lgota Beds, most tops of turbidite–hemipelagite rhythms are bioturbated.
Non-bioturbated rhythms record anoxia, but their occurrence is influenced by the frequency of
turbiditic deposition.
Protovirgularia obliterata and Protovirgularia pennata occur in the Verovice Shale in the
deepest tier below Chondrites. These trace fossils were probably produced below the redox
boundary by chemosymbiotic bivalves. The studied associations show that the deep-sea envi-
ronment is influenced by many factors that change with time, which records the large-scale
dynamics of deep-sea ecological processes.
Key words: Ichnology; bioturbation; tiering; anoxic events; turbidites.
Alfred Uchman [fred@ing.uj.edu.pl], Institute of Geological Sciences, Jagiellonian University,
Oleandry 2a; 30-063 Kraków, Poland
Introduction
Since the 1950s it has become clear that flysch trace fossil
communities are very diverse, even within basins and
between stratigraphic units (e.g. Ksia
pz
dkiewicz 1977;
Crimes et al. 1981; Uchman 1999). Data for some periods
are notably inadequate, especially for the Permian to
Jurassic (Uchman 2003), but it should also be noted that
data from the Lower Cretaceous flysch deposits are few in
comparison with the Upper Cretaceous or Palaeogene.
This gap can be partially filled by investigations of the
Lower Cretaceous flysch facies of the Silesian Unit in the
Polish Carpathians, which has a continuous record of
diverse facies throughout the Cretaceous and Palaeogene.
The flysch facies contain numerous trace fossils whose
taxonomy was partially investigated by Nowak (1957,
1959, 1961, 1962, 1970) and Ksia
pz
dkiewicz (1970, 1977).
Part of the Silesian flysch facies displays dark coloration
that is suggestive of the influence of Cretaceous anoxic
events. A lowered oxygenation during accumulation of
the Lower Cretaceous sediments of the Silesian Unit was
previously noticed by Ksia
pz
dkiewicz (1977), who did not

FOSSILS AND STRATA 51 (2004)
40 Alfred Uchman
discuss the details. The dark flysch facies is important
because literature on the relationship of flysch trace fossils
to oxygenation changes is rather sparse (but see
Leszczyn
aski 1991; Uchman 1991, 1999; Wetzel & Uchman
1998) in comparison with pelagic and hemipelagic,
fine-grained, post-Palaeozoic deposits (e.g. Bromley &
Ekdale 1984; Savrda & Bottjer 1989).
In this paper, dark flysch deposits of the Upper Cieszyn
Beds, Verovice Shale and Lgota Beds are considered
in four representative sections at Poznachowice Dolne,
Kaczyna, Zagórnik-Rzyki and Kozy (Fig. 1). Description
of the trace fossils and the interpretation of the associa-
tions are the main aims of this paper. Particular attention
is paid to the influence of oxygenation. Trace fossils
illustrated in this paper are housed at the Institute of
Geological Sciences of the Jagiellonian University (prefix
167P).
Geological setting and
stratigraphy
The Silesian Unit constitutes a large, complex nappe
in the Ukrainian, Polish and Czech Flysch Carpathians.
It contains thick, diverse deposits, mostly flysch, that
accumulated in a deep-sea basin (Silesian Basin) from the
late Kimmeridgian to the early Miocene. This basin, a part
of the Western Tethys, was at least a few tens of kilometres
wide and a few hundreds of kilometres long. Deposits
of the Silesian Basin were folded and thrust northward
during the Miocene.
The Lower Cretaceous deposits (Fig. 2) are represented
by the:
•Cieszyn Limestone (upper Tithonian–Berriasian),
100–250 m thick, dominated by turbiditic, commonly
Fig. 1. Map of the western part of the Polish Carpathians (top, with
inset location map) and detailed maps (below) showing the locations of
the study areas. A: Poznachowice Dolne. B: Kaczyna. C: Zagórnik-Rzyki.
D: Kozy. PKB, Pieniny Klippen Belt.
Fig. 2. Kimmeridgian–Palaeocene stratigraphy of the Silesian Unit
(based on S
a¢aczka, in S
a¢aczka & Kaminski 1998). The investigated units
are coloured grey.

FOSSILS AND STRATA 51 (2004) Deep-sea trace fossils controlled by palaeo-oxygenation and deposition 41
sandy calcarenites and calcilutites interbedded with
marly shales;
•Upper Cieszyn Beds (Valanginian–Hauterivian), about
300 m thick, dominated by dark grey marly mudstones
alternating with regularly thin-bedded, calcareous
sandstones;
•Grodziszcze Beds (Upper Hauterivian–Barremian),
95–140 m thick, represented by grey marly shales
alternating with rare thin calcareous sandstone beds
and marlstones. Locally, sandstone beds are more
frequent. In some areas, these facies are replaced by
thick-bedded calcareous sandstones and debris-flow
deposits containing exotic pebbles and blocks;
•Verovice Shale (Barremian–lowermost Albian), about
200 m thick, composed of non-calcareous black mud-
stones interbedded with rare cross-laminated thin
sandstone beds and sideritic concretions;
•Lgota Beds (Albian–Cenomanian), 300–350 m thick,
dominated by thin- and medium-bedded, turbiditic
sandstones and greenish grey spotty mudstones (dark
spots are cross-sections of trace fossils visible on
parting surfaces). Locally, the lower part of the
unit exhibits thick-bedded sandstones, and the upper
part of the unit is composed of spongiolithic cherts
(Mikuszowice Cherts).
Upper Cieszyn Beds
The Upper Cieszyn Beds are about 300 m thick.
They are dominated by dark grey to black marly mud-
stones interlayered with numerous very thin to thin
layers (1–3 cm) of mostly cross-laminated turbiditic
fine-grained sandstones, rare sandy limestones, and local
sideritic claystones (e.g. Burtan 1978). The sandstones
display sharp erosive bases and transitional gradation to
overlying mudstones. These deposits are interpreted as
turbiditic sandstone–mudstone couplets capped by
hemipelagic mudstones. They are similar to the turbiditic
facies C2.3 of Pickering et al. (1986), but the muddy part
is thicker in the investigated deposits.
The Upper Cieszyn Beds are determined as having a
Valanginian–Hauterivian age based on the benthic
foraminiferids (Geroch & Nowak 1963; Nowak 1968).
The sandstone turbidites were transported from the
northwest and deposited at depths above the calcite com-
pensation depth (CCD). The Upper Cieszyn Beds were
investigated at Poznachowice Dolne (Fig. 1A), where a
section about 200 m thick is exposed along the stream.
This represents the longest section through the Upper
Cieszyn Beds exposed in the Polish Carpathians.
Verovice Shale
The Verovice Shale is about 200 m thick (Ksia
pz
dkiewicz
1951). It is composed of prevailing dark non-calcareous
mudstones and siltstones, which are intercalated irregu-
larly in thin- to medium-bedded fine-grained sandstones.
Locally, horizontal lamination occurs in the shales. The
sandstones display ripple cross-lamination. In places,
ferruginous concretions are present. The mudstones rep-
resent the E2 (locally C2) facies of Pickering et al. (1986),
which are typical of basin plains. Probably the sandstone
beds were deposited by episodic bottom currents. The
lack of calcium carbonate in the shales suggests deposi-
tion below the CCD. Lower bathyal depths are inferred on
the basis of foraminiferids (Szyd¢o 1997). Geochemical
analyses indicate both a high input of plant detritus from
adjacent lands and high phytoplankton production
(Gucwa & Wieser 1980).
The Verovice Shale is assigned a Barremian–earliest
Albian age (Szyd¢o 1996, 1997). The Verovice Shale has
been investigated at Zagórnik (Fig. 1), the best locality
being where about 70 m of the top of the unit is exposed
(Cieszkowski et al. 2001).
Lgota Beds
The Lgota Beds have been subdivided historically into the
Lower Lgota Beds, the Middle Lgota Beds and the Upper
Lgota Beds or Mikuszowice Cherts. The locally occurring
Lower Lgota Beds, generally 80 m thick, are composed
of thick-bedded, commonly amalgamated sandstones
interbedded with packages of thin- to medium-bedded,
commonly graded turbidites. This unit is characterised by
thickening-up sequences, with typically thick-bedded,
channelised sandstones in the upper part (facies C2.1,
C2.2 of Pickering et al. 1986).
Of the three units, the Middle Lgota Beds form the
dominant part. They are composed of thin- and medium-
bedded, mostly fine-grained sandstones with well-
developed Bouma (1962) intervals and interbedded dark
to green mudstones. Isolated thick sandstone beds are
locally present. The sandstone/mudstone ratio is approxi-
mately 1:1 (Unrug 1959). Facies C2.3 of Pickering et al.
(1986) prevails. The Middle Lgota Beds are 220 m thick in
the Kozy quarry.
The Upper Lgota Beds (Mikuszowice Cherts) are 50 m
thick, and occur only locally. They consist of thin-bedded
(rarely medium-bedded) sandstones that contain a con-
siderable amount of biogenic silica, mainly as opal and
chalcedony cement. In some beds, the silica predominates
and forms spongiolite chert bands. The sandstones are
regularly interbedded with mudstones. Facies C2.3 pre-
vails. In the northern marginal part of the Silesian Unit,
the Lgota Beds are replaced by the Geize Beds, which
consist mainly of thick-bedded siliceous sandstones with
spongiolites.
The Middle Lgota Beds are dominated by turbidites
(Unrug 1959). Lenticular, mainly cross-laminated, beds
of fine-grained, well-sorted sandstones beds intercalated

FOSSILS AND STRATA 51 (2004)
42 Alfred Uchman
in the shales have been interpreted as tractionites (Unrug
1959, 1977). Upper bathyal depths are proposed on
the basis of foraminiferids (Ksia
pz
dkiewicz 1975), but
deposition below the CCD is suggested because of non-
calcareous hemipelagites atop turbidite–hemipelagite
rhythms. The Lgota Beds were probably deposited in
distal, locally proximal, depositional lobes and fan fringe
settings.
Until recently, the Lgota Beds were assigned to the
Albian–?Cenomanian interval (Geroch & Nowak 1963).
The middle Cenomanian age of the top of this unit was
proved by Ba
pk et al. (2001) on the basis of foraminiferids
and radiolarians, and by Gedl (2001) using dinocysts. For
additional data based on dinocysts, see Jaminski (1995).
The Lgota Beds have been investigated at Kaczyna, Rzyki,
and the Kozy quarry (Fig. 1), where they are represented
by the lithofacies typical of the Middle Lgota Beds.
Synopses of ichnotaxa
Belorhaphe zickzack (Heer 1877) (Fig. 3I): hypichnial,
angular meanders with an apical angle of 45–85°, 7–9 mm
wide and 4–6 mm high, in some cases with short append-
ages at the apices. The apices are slightly rounded and
enlarged. Preserved as semi-reliefs. For a more complete
discussion of this ichnospecies, see Uchman (1998).
Chondrites intricatus (Brongniart 1823) (Figs. 3A, 4B):
occurs as a system of tree-like branching, downward-
penetrating, markedly flattened tunnels, 0.4 mm in
diameter. The tunnels form acute angles and show
phobotaxis. In cross-section it occurs as patches of
circular to elliptical spots and short bars. Commonly, the
fill of the trace fossil is darker than the host rock. For a
more extensive discussion of ichnogenus Chondrites, see
Fu (1991) and Uchman (1999).
Chondrites targionii (Brongniart 1828) (Fig. 4A):
endichnial, tubular, flattened tunnels branched in a
dendroid manner. Branches are commonly slightly
curved. The tunnels are 1.8–2.0 mm wide.
?Chondrites isp. (Fig. 3H): preserved as hypichnial,
horizontal, short, straight to slightly curved ridges that are
0.6–1.0 mm wide and up to 10 mm long. They densely
cover soles of sandstone beds. Most probably they are
washed out and cast Chondrites burrow systems.
Gordia isp. (Fig. 3B): represented by simple hypichnial
winding galleries; preserved in semi-relief, and shows
crossings. The galleries are 0.5 mm wide. For a discussion
of Gordia, see Fillion & Pickerill (1990) and Pickerill &
Peel (1991).
Helminthopsis abeli Ksia
pz
dkiewicz 1977 (Fig. 3C): simple,
cylindrical, irregularly winding, smooth tunnels
preserved in semi-relief; 5–10 mm wide.
Helminthopsis isp.: hypichnial winding, smooth gallery,
2.5 mm wide.
Helminthopsis hieroglyphica Wetzel & Bromley 1996
(Fig. 3F): hypichnial semicircular gallery that displays
first- and second-order windings. The second-order
windings are sharp but display low amplitude. The
string is about 1.2–2.0 mm wide, and constant within
individuals.
Helminthopsis tenuis Ksia
pz
dkiewicz 1977 (Fig. 3E): hypi-
chnial semicircular string, which displays alternating
wide and narrow irregular meanders. The gallery is
2.5–5.0 mm wide. The width of the gallery is constant in a
given specimen. For a discussion of Helminthopsis, see
Han & Pickerill (1995) and Wetzel & Bromley (1996).
Lorenzinia isp.: hypichnial form consisting of six ridges
radiating from a central flat area. The ridges are up to
4 mm long and about 1 mm wide. The trace fossil is about
13 mm wide.
Lorenzinia plana (Ksia
pz
dkiewicz 1968) (Fig. 3G): hypi-
chnial star-shaped trace fossil composed of straight or
slightly curved ridges radiating from a central flat area.
The ridges are semicircular, 5–30 mm long and 2–3 mm
wide. There are more than 20 ridges per trace fossil. The
central area is about 40 mm across, and the whole trace
fossil is about 110 mm across. For a discussion of
Lorenzinia, see Uchman (1998).
?Lorenzinia isp. (Fig. 4D): endichnial structure composed
of a semicircular wreath of short flattened cylinders,
2.5–4.0 mm wide, up to 7 mm long, radiating from an
indistinct area, and with dark infilling.
Megagrapton isp. (Fig. 5E): hypichnial irregular net, at
least 65 mm across. Individual galleries are 1.2–2.0 mm
thick. For a discussion of this ichnogenus, see Uchman
(1998).
Paleodictyon strozzii Meneghini in Savi & Meneghini 1850
(Fig. 5F): hypichnial hexagonal net, whose maximum
mesh size ranges from 3.0 to 5.5 mm; gallery diameter
from 0.8 to 1.0 mm. For a recent review of Paleodictyon,
see Uchman (1995).
Phycodes bilix (Ksia
pz
dkiewicz 1977) (Fig. 5A): hypichnial
trace fossil composed of a bunch of horizontal to sub-
horizontal flattened cylinders branching from one hori-
zontal to subhorizontal stem. The cylinders, 6–12 mm
wide, display a knobby wall, covered with small

FOSSILS AND STRATA 51 (2004) Deep-sea trace fossils controlled by palaeo-oxygenation and deposition 43
Fig. 3. Trace fossils from the Upper Cieszyn Beds at Poznachowice Dolne. Parting surface in shale in (A); soles of sandstone turbidites in (C)–(I). Scale
bars 10 mm in (A)–(F) and (H)–(I); 40 mm in (G). A: Chondrites intricatus. 174P19. B: Gordia isp. 174P12. C: Helminthopsis abeli. 174P11.
D: Protovirgularia pennata. 174P7. E: Helminthopsis tenuis; field photograph. F: Helminthopsis hieroglyphica. 174P12. G: Lorenzinia plana. 174P1.
H: ?Chondrites isp.; field photograph. I: Belorhaphe zickzack. 174P2.

FOSSILS AND STRATA 51 (2004)
44 Alfred Uchman
(1–2 mm) irregular mounds. For a discussion of this
ichnospecies, see Uchman (1998).
Phycodes isp. (Fig. 5B): hypichnial, semicircular straight
to curved ridges diverging from one area, spreading out in
the form of a fan, and then plunging into the bed, and
preserved as a full-relief. The ridges are 9–13 mm wide,
up to 90 mm long. Some of them are covered with
delicate longitudinal wrinkles.
?Phycodes isp. (Fig. 5C): epichnial system of semicircular
slightly curved grooves coming bilaterally out from a
central straight stem. The grooves are inclined in the same
direction in respect to the stem and ascend distally from
the stem. They are up to 60 mm long, and 10–15 mm
wide. Very probably this trace fossil is a preservational
variant of Phycodes isp.
Phycosiphon incertum Fischer-Ooster 1858 (Fig. 6A):
preserved as small horizontal lobes, up to 5 mm wide,
each encircled by a thin, less than 1 mm thick, marginal
tunnel. They occur on the upper surface of sandstone
beds. This trace fossil, produced by a deposit feeder, is
common in fine-grained deep-sea and deeper shelf
deposits. More information about Phycosiphon can be
found in Wetzel & Bromley (1994).
Planolites isp. (Figs. 4B–D, 6B): represented by two
morphotypes. Form A (Fig. 4B, C) is a variably oriented,
but mostly horizontal, cylindrical burrow without a wall,
Fig. 4. Trace fossils from the Lgota Beds. A: Chondrites targionii. Parting surface in a turbiditic sandstone. Kozy. 174P9. B: Thalassinoides isp. (T),
Planolites isp., form A (P) and Chondrites intricatus (C) against totally bioturbated background. Polished and oiled horizontal surface from shale.
Kaczyna. 174P44. C: Thalassinoides isp. (thick ridges) and Planolites isp. (thin ridges). Sole of a turbiditic sandstone bed. Kozy; field photograph.
D: ?Lorenzinia isp. (L) and Planolites isp., form B (P). Parting surface in shale. Kaczyna. 174P42. E: Taenidium isp. Parting surface in shale. Kaczyna.

FOSSILS AND STRATA 51 (2004) Deep-sea trace fossils controlled by palaeo-oxygenation and deposition 45
1–3 mm in diameter. In cross-sections it appears as oval
spots contrasting in colour against the surrounding rock.
It is also preserved on soles of sandstone beds in full-relief
as straight to slightly curved semicircular ridges. Form B
(Figs. 4D, 6B) is represented by straight to slightly curved,
strongly flattened endichnial cylinders with sharp
margins, 6–9 mm wide, filled with lighter sediment than
the surrounding rock in the Verovice Shale. In the Lgota
Beds, the cylinders are 3–5 mm wide, filled with darker
material that is locally burrowed preferentially by
Chondrites (composite trace fossil). Short ridges or knobs,
5–8 mm in diameter, preserved on the lower surfaces of
sandstone beds as semi-relief, probably belong to
Planolites (?Planolites isp.). For a discussion of Planolites,
see Pemberton & Frey (1982) and Keighley & Pickerill
(1995).
Protovirgularia obliterata (Ksia
pz
dkiewicz 1977): hypichnial
straight to slightly curved heart-shaped cylinder, 7–9 mm
wide, preserved in full-relief. It projects from the sole as
an angular ridge with indistinct median furrow and fine,
dense chevron ribs on the slopes. Locally, the ridge
displays primary successive branches sensu D’Alessandro
& Bromley (1987) that are probes plunging up into the
Fig. 5. Other trace fossils from the Upper Cieszyn Beds at Poznachowice Dolne. Soles of sandstone turbidites in (A), (B) and (D)–(F); top of sandstone
turbidites in (C). Scale bars 10 mm in (A), (B) and (D)–(F); 40 mm in (C). A: Phycodes bilix. 174P20. B: Phycodes isp. 174P22. C: ?Phycodes isp. 174P26.
D: Thalassinoides isp.; field photograph. E: Megagrapton isp. 174P10. F: Paleodictyon strozzii. 174P4.

FOSSILS AND STRATA 51 (2004)
46 Alfred Uchman
host bed. For a discussion of Protovirgularia, see Seilacher
& Seilacher (1994), Uchman (1998) and Mángano et al.
(2002).
Protovirgularia pennata (Eichwald 1860) (Figs. 3D, 6C,
D): hypichnial to endichnial straight to slightly curved,
almond-shaped cylinder preserved in full-relief, oriented
parallel or oblique to the bedding. It projects from the sole
as a triangular ridge, 5–12 mm wide, with an indistinct,
discontinuous, very narrow median furrow and fine,
dense, chevron ribs on the slopes. The ridges display
successive branches that are probes plunging up into the
host bed.
Protovirgularia isp.: hypichnial straight or curved
cylinder, almond-shaped in outline and preserved in full-
relief, and sticks out on the sole as an angular ridge. The
ridge is smooth, 3–4 mm wide.
Scolicia plana Ksia
pz
dkiewicz 1970 (Fig. 7A): epichnial
tripartite winding furrow, about 30 mm wide and 5 mm
deep. The furrow displays gentle slopes and slightly
elevated floor. The floor is covered with dense per-
pendicular thin ribs, and dissected by an indistinct
median furrow. This trace fossil represents the lower part
of an irregular echinoid burrow. For a discussion of
Scolicia, see Uchman (1995).
Scolicia strozzii (Savi & Meneghini 1850) (Fig. 7B): a
winding, bilobate smooth hypichnial ridge, which is
about 25 mm wide, up to 8 mm high. The ridge is
subdivided by a central, semicircular, furrow.
Taenidium isp. (Fig. 4E): a horizontal row of shallow
menisci, about 9 mm wide. They occur as black arcuate
strips, which are 1.0–1.5 mm wide and spaced 2–3 mm
apart. For a discussion of this ichnogenus, see
D’Alessandro & Bromley (1987).
Fig. 6. Trace fossils from the Verovice Beds at Zagórnik. A: Phycosiphon incertum. Parting surface in siltstone, top view; field photograph. B: Planolites
isp., form B. Parting surface in mudstone, top view; field photograph. C: Protovirgularia pennata. Sole of a sandstone bed. 174P27. D: Protovirgularia
pennata crossing sole of a sandstone bed. 174P50.

FOSSILS AND STRATA 51 (2004) Deep-sea trace fossils controlled by palaeo-oxygenation and deposition 47
barren of distinctive trace fossils. Only locally less than
1 cm thick bioturbated horizons occur. The horizons
are slightly lighter in colour and occur at the top of
some depositional event beds. Phycosiphon incertum,
Chondrites intricatus, and Planolites are the dominant,
albeit usually poorly visible, ichnotaxa. Below some
of the bioturbated horizons, Protovirgularia pennata
and Protovirgularia obliterata occur in a zone a few
centimetres thick, especially below sandstone beds, where
they can be abundant (Fig. 9).
In the upper few metres of the section of the Verovice
Shale at Zagórnik, a few centimetre thick layers of
greenish, bioturbated, spotty shales occur. They contain
Planolites, Chondrites and Thalassinoides. The appearance
of the layers is typical of the overlying Lgota Beds.
These occurrences would seem to indicate a general
improvement in oxygenation.
The Lgota Beds contain a trace fossil assemblage of
low diversity, dominated by Planolites, Chondrites and
Thalassinoides. The oldest occurrence of Scolicia in the
Flysch Carpathians was noted here by Ksia
pz
dkiewicz
(1977), but this and other trace fossils are rare.
Distinct spotty layers of totally bioturbated greenish-
grey, non-calcareous mudstones occur at the top of
turbidite–hemipelagite couplets (Fig. 10). Cross-sections
of Chondrites, Planolites, and Thalassinoides are com-
monly visible against a totally bioturbated background.
The last two ichnotaxa are commonly preserved in semi-
reliefs on the lower surface of turbiditic sandstone beds.
The spotty layer is absent in some couplets; instead dark
mudstones occur, which are barren of trace fossils.
Discussion
The described trace fossil assemblages are markedly
different from those of the younger deposits of the Alpine
Fig. 7. Scolicia from the Lgota Beds. A: Scolicia plana. Upper surface of a turbiditic sandstone bed. Rzyki. UJ TF 621. B: Scolicia strozzii. Sole of a
turbiditic sandstone bed. Kaczyna. UJ TF 898.
Thalassinoides isp. (Figs. 4B, C, 5D): hypichnial,
horizontal, straight to slightly curved and branched
cylinders without a wall, preserved in full-relief, 6–10 mm
wide. In cross-section in the shale beds, it appears as oval
spots. For a further discussion of this ichnogenus, see
Ekdale (1992).
Trichichnus isp.: straight to winding, rarely branched,
steeply vertical to oblique, thin cylinders filled with iron
sulphides or oxides. The cylinder is about 1.0 mm in
diameter. For a discussion of this ichnogenus, see
Uchman (1999).
Trace fossil assemblages and
ichnofabrics
Trace fossils of the Upper Cieszyn Beds are relatively
abundant and diverse (Table 1). Most are preserved in
semi- or full-relief on the lower surfaces of turbiditic
sandstones. Chondrites intricatus, Helminthopsis, and
Planolites are the most abundant ichnotaxa. Among the
graphoglyptids, which are diverse, Belorhaphe zickzack,
Megagrapton isp., and Lorenzinia ispp. are the most
abundant. Common occurrence of Protovirgularia
obliterata is characteristic. Other trace fossils are rare.
Totally bioturbated light layers (spotty layers sensu
Uchman 1999) occur at the top of dark turbidite–
hemipelagite couplets (Fig. 8). The couplets average
3 mm; most are less than 1 cm thick. This layer contains
mostly Planolites cross-cut by very thin Chondrites
overprinting a totally bioturbated background. In at least
a few of the beds, the spotty layer does not occur at all.
In contrast, deposits of the Verovice Shale are
dominated by laminated mudstones and siltstones nearly

FOSSILS AND STRATA 51 (2004)
48 Alfred Uchman
Table 1. Occurrence of trace fossils in the studied sections.
Upper Cieszyn Shale Verovice Shale Lgota Beds
Poznachowice Dolne Zagórnik Kaczyna Rzyki Kozy
[Arthrophycus strictus Ksia
pz
dkiewicz]*X
Arthrophycus tenuis (Ksia
pz
dkiewicz)*X
Belorhaphe zickzack (Heer) R
Chondrites intricatus (Brongniart)
[Chondrites aequalis Sternberg] C R C C C
Chondrites targionii (Brongniart)
[Chondrites furcatus (Brongniart)] R R
?Chondrites isp. R C C C
Gordia isp. R
Helminthopsis abeli Ksia
pz
dkiewicz
[Helminthopsis hieroglyphica Ksia
pz
dkiewicz] C
Helminthopsis hieroglyphica Wetzel & Bromley R
Helminthopsis isp. R
Helminthopsis tenuis Ksia
pz
dkiewicz R
Lorenzinia isp. R
Lorenzinia plana (Ksia
pz
dkiewicz)
[Sublorenzinia plana Ksia
pz
dkiewicz] R
?Lorenzinia isp. R
Megagrapton isp. R
Paleodictyon strozzii Meneghini R
Phycodes bilix (Ksia
pz
dkiewicz) R
Phycodes isp. R
?Phycodes isp. R
Phycosiphon incertum Fischer-Ooster C
Planolites isp. C R C C F
Protovirgularia isp. R
Protovirgularia obliterata (Ksia
pz
dkiewicz) C C
Protovirgularia pennata (Eichwald) R
Scolicia plana Ksia
pz
dkiewicz X
Scolicia strozzii (Savi & Meneghini)
[Taphrhelminthopsis vagans Ksia
pz
dkiewicz] X
Taenidium isp. R
Thalassinoides isp.
[Sabularia rudis Ksia
pz
dkiewicz;
Buthotrephis aff. succulens Hall] C C C F
Trichichnus isp. R
X, data by Ksia
pz
dkiewicz (1977) (his original ichnotaxonomic determinations are revised here, and included in square brackets); C, common; F,
frequent; R, rare (present author data).
*According to Seilacher (2000) and Rindsberg & Martin (2003), the flysch Arthrophycus is indeterminate because of a lack of evidence of an internal
structure.

FOSSILS AND STRATA 51 (2004) Deep-sea trace fossils controlled by palaeo-oxygenation and deposition 49
region (e.g. Crimes et al. 1981; Leszczyn
aski & Seilacher
1991; Tunis & Uchman 1996a, b; Uchman 1995, 1999,
2001). Their diversity is lower and they do not contain
some trace fossils, based on the detailed documentation
of other formations, as might be expected, for instance
Scolicia, Nereites irregularis or Ophiomorpha rudis.
Most probably these differences resulted from lowered
oxygenation and evolutionary processes (Uchman 2004).
Ichnofacies problem: some evolutionary
aspects and specificity of the trace fossil
assemblages
The classical ichnofacies model (Seilacher 1967; Frey &
Seilacher 1980) can only be applied to the investigated
deposits to a certain extent. The Upper Cieszyn Beds
contain the typical Nereites ichnofacies with a significant
contribution of graphoglyptids (about 20% of ichno-
taxa), typical of the Paleodictyon ichnosubfacies Seilacher
1978).
Fig. 8. A short sedimentological log with the vertical extent of trace
fossils from the Upper Cieszyn Beds at Poznachowice Dolne. Grain-size
scale: m, mud; s, silt; vf, very fine sand; f, fine sand; m, medium sand; c,
coarse sand. Samples (P1–P20) are also shown.
Fig. 9. A short sedimentological log with the vertical extent of trace
fossils from the Verovice Shale at Zagórnik, where Protovirgularia
obliterata is exceptionally abundant. Grain-size scale as in Fig. 8.

FOSSILS AND STRATA 51 (2004)
50 Alfred Uchman
There is an obvious difficulty in the application of the
ichnofacies model to the Verovice Shale and Lgota Beds.
The Verovice Shale, although deposited in the deep sea,
contains no graphoglyptid or meandering trace fossils,
which are the index forms of the Nereites ichnofacies.
Protovirgularia obliterata, Chondrites intricatus, Planolites,
and Phycosiphon incertum are most common. This
ichnoassemblage differs significantly from most of the
modern deep-sea ichnofacies of pelagic muds at depths
exceeding the CCD. The latter, apart from rare
Chondrites, contain common Teichichnus and Zoophycos
(Ekdale et al. 1984; Wetzel 1991), but these do not occur
in the Verovice Shale.
The trace fossil association of the Lgota Beds is
dominated by Chondrites, Planolites and Thalassinoides.
The occurrence of meandering forms (Scolicia, Helmin-
thopsis) and graphoglyptids (?Lorenzinia) is poorly
documented. This ichnoassociation can only provision-
ally be ascribed to a very impoverished version of the
Nereites ichnofacies.
The studied trace fossil assemblages do not contain
Scolicia ispp., Ophiomorpha rudis, or numerous
graphoglyptids, which are common in Upper Cretaceous
and Tertiary flysch deposits. This can be explained by
the fact that Scolicia, which is produced by irregular
echinoids, and Ophiomorpha rudis, which is produced by
a relatively large crustacean, only appeared in the
Tithonian (latest Jurassic) for the first time, and remained
very rare in the Early Cretaceous, probably because of
widespread anoxia (Tchoumatchenco & Uchman 2001).
Many graphoglyptids, which are characteristic trace
fossils of the archetypal Nereites ichnofacies, had their
first occurrences after the Late Cretaceous (Uchman
2003).
Trace fossil assemblages and
oxygenation
Oxygenation on the deep-sea floor fluctuates. In an
oxygen-restricted setting, it increases after turbiditic
flows, which introduce oxygenated water (Dz
du¢yn
aski &
S
ala
pczka 1958), and decreases between turbiditic events.
This is considered as the crucial phenomenon that,
together with changes in benthic food supply, governs the
sequential colonisation of thin turbiditic beds by
bioturbating organisms (Wetzel & Uchman 2001).
The general oxygenation level of the deep-sea floor can
be considered on the scale of lithostratigraphic units.
The oxygenation level is reflected by the diversity and
composition of the trace fossil assemblages, and by the
vertical extent of the bioturbated zone in turbidite–
hemipelagite couplets. However, each of these parameters
is partially problematic for flysch deposits. The diversity
of trace fossil assemblages corresponds to the diversity of
infaunal organisms, but it is also influenced by preserva-
tion potential. In thin- and medium-bedded flysch, where
delicate scouring and casting are common during deposi-
tion, the preservational potential is higher than in shaly or
thick-bedded flysch.
In this study, the highest preservational potential is
inferred for the Upper Cieszyn Beds, which have the
greatest total number and frequency of deposition of
thin-bedded turbidites. The lowest preservational poten-
tial is inferred for the Verovice Beds, where the number of
sandstone beds is comparatively small. In the Lgota Beds,
the total number and frequency of turbidites are lower
than in the Upper Cieszyn Beds. However, a few thousand
thin turbidites in the former unit should enable preserva-
tion of all burrow systems, which are normally scoured
and cast.
The composition of trace fossil assemblages can also be
taken into account. Assemblages dominated by ichnotaxa
Fig. 10. A short sedimentological log with the vertical extent of trace
fossils from the Middle Lgota Beds at Kaczyna. Grain-size scale as in
Fig. 8.

FOSSILS AND STRATA 51 (2004) Deep-sea trace fossils controlled by palaeo-oxygenation and deposition 51
related to opportunistic r-selected organisms are typical
of stressed environments, commonly related to lowered
oxygenation (Ekdale 1985a, 1988). Indeed, the contribu-
tion of graphoglyptids, which are related to the K-selected
organisms (Ekdale 1985a), is relatively low in the investi-
gated sediments. It is highest in the Upper Cieszyn Beds.
In the Lgota Beds, the presence of graphoglyptids is
problematic and in the Verovice Shale they are absent.
According to the model of sequential colonisation of
turbidites (Wetzel & Uchman 2001), a newly deposited
turbiditic bed contains the maximum content of oxygen
and benthic food, which decreases during subsequent
colonisation. In the middle and shallow tiers, the bed is
colonised at first by less efficient mobile deposit feeders
producing Phycosiphon, which exploit small areas
encircled by marginal tunnels. They are followed by
larger, more efficient, trace makers of Nereites irregularis,
which produce tight meanders. When benthic food is
exploited, the bed is colonised by stationary, possibly
chemotrophic forms producing Chondrites (Wetzel &
Uchman 2001). Such a succession is expressed by the
cross-cutting relationships between trace fossils, which
enables reconstruction of the tiering pattern (Fig. 11).
The mobile deposit feeders do not have a permanent
connection to the sea floor, and therefore they need
oxygenated sediments.
It is intriguing that in the Upper Cieszyn Beds and
Lgota Beds, Nereites and Phycosiphon do not occur at
all. Phycosiphon only occurs in some horizons of the
Verovice Shale. The absence of Nereites irregularis may be
an evolutionary effect. It occurs more abundantly after
the Lower Cretaceous, and is rare or problematic in
older sediments (Uchman 2004). Alternatively, another
explanation might be that Nereites follows the redox
boundary (Wetzel 2002) and the redox boundary in the
studied sediments was too shallow or too unstable for
the Nereites producers to become active. The absence or
rarity of Phycosiphon, which is abundant in older and
younger sediments, may be caused by a low oxygen
content within the middle and shallow tiers of the
turbiditic beds. Probably, the sediment was only biotur-
bated in a very thin near-surface layer, where no distinct
trace fossils could be preserved owing to the low shear
strength caused by the high water content. In the Lgota
Beds, the middle tier is commonly occupied by small
Thalassinoides, which was an open-burrow system, into
which the crustacean trace maker may have pumped
oxygenated water (cf. Ekdale 1988).
Scolicia, a trace fossil produced by irregular echinoids,
occurs in a few beds in the Lgota Beds for the first time in
the Carpathian Flysch (Ksia
pz
dkiewicz 1977). Echinoids
usually burrow close to the redox boundary (Bromley
et al. 1995). The absence of their burrows could indicate a
Fig. 11. Tiering pattern of the commonest trace fossils in the
investigated units. The shaded area corresponds to the totally
bioturbated sediments. Note that the dashed horizontal line depicts
the occurrence of Phycosiphon incertum.
very shallow redox boundary that does not allow
echinoids to completely bury themselves.
Thus, the absence of mainly horizontal trace fossils,
which are not interpreted as open burrows, may have
been caused by the poor oxygenation of the shallow and
middle tiers. This is in basic agreement with the model by
Ekdale & Mason (1988), who considered sediments with
pascichnial Phycosiphon and Scalarituba (=Nereites) as
better oxygenated than sediments with fodinichnial
Chondrites and Zoophycos. This model, however, does not
explain the absence of Zoophycos in the investigated
sections.

FOSSILS AND STRATA 51 (2004)
52 Alfred Uchman
Protovirgularia as a burrow of
chemosymbiotic bivalves
Protovirgularia is supposedly produced by vagile bivalves
(Seilacher & Seilacher 1994). Its occurrence in the studied
deposits is intriguing. In the Verovice Shale it occurs in
the lowest tier, distinctly below Chondrites. Such a deep
location suggests Protovirgularia as a trace of chemo-
symbiotic bivalves that could burrow in anoxic sediment,
like the solemyacid bivalve Solemya (Seilacher 1990), or
certain lucinid and thyasirid bivalves (Powell et al. 1998,
and references therein). The occurrence of Protovirgularia
is also relatively common in the Upper Cieszyn Beds,
where it occurs on the soles of beds, certainly in a very
deep tier.
Relatively abundant Protovirgularia is unusual and
specific to the Lower Cretaceous of the Silesian Unit.
Protovirgularia also occurs in younger deposits of the
Carpathian Flysch, where it is very rare and never consti-
tutes a significant component of trace fossil associations.
It is probable that abundance of this ichnogenus in the
Lower Cretaceous sediments is an adaptation of the
bivalve producer or producers to the long-term oxygen
deficiency common during the Early Cretaceous. Unfor-
tunately, recurrence of the Lower Cretaceous associations
with abundant Protovirgularia remains unknown,
because Lower Cretaceous flysch deposits are poorly
known.
Vertical extent of the bioturbated zone
In flysch deposits, totally bioturbated sediments occur at
the top of turbidite–hemipelagite couplets, where they
form the so-called spotty layer (Uchman 1999). This layer
embraces sediments deposited between the turbiditic
events in hemipelagic environments and sediments from
the top of the turbiditic mudstones in the turbiditic beds.
Part of the hemipelagic sediment is intermixed with
turbiditic sediment by bioturbation. The thickness of the
spotty layer was related to oxygenation, i.e. a thicker
spotty layer could indicate better oxygenation (Uchman
1999). This view is reconsidered and corrected here.
Owing to their low depositional rate, hemipelagic
sediments are usually completely bioturbated even where
bioturbating action is neither strong nor deep (Berger et
al. 1979). All background sediments have a relatively long
residence time on the sea floor and can be biologically
disturbed several times. Therefore, the thickness of
hemipelagic sediments cannot be related to the thickness
of the oxygenated zone because the thickness depends
mostly on the time of deposition (see the discussion by
Wetzel 1991). In contrast, rapidly deposited siliciclastic
turbiditic mud is colonised from the top down, and
the thickness of a totally bioturbated layer in such a
mudstone bed can be related to oxygenation. Often it is
difficult to delineate macroscopically between pelagic and
turbiditic mud because of negligible contrast between the
grain sizes. However, changes in colour and calcium
carbonate content can help to distinguish them.
When the bioturbated spotty layer is absent, several
possibilities can be invoked. One is that there was not
enough time for colonisation, as when turbidites were
deposited frequently one after another. However, deposi-
tion of two or more turbiditic beds one after another is
generally quite rare and cannot explain the common
absence of the spotty layer in many depositional rhythms.
Another possibility is that erosion of the turbiditic flow
removed the spotty layer. This should be indicated by
common erosional structures. Moreover, some remnants
of the spotty layer would be expected, because erosion
usually acts unevenly. Where such features are lacking,
the absence of the spotty layer can be explained by anoxic
conditions on the sea floor, especially in dark sediments
(cf. Bromley & Ekdale 1984). Similar interpretations
were proposed previously for the Albian–Eocene flysch
of northern Spain (Leszczyn
aski 1991, 1993) and for the
Upper Cretaceous Inoceramian Beds of the Polish
Carpathians (Uchman 1992).
The spotty layer is common in the Upper Cieszyn
Beds, absent from the Verovice Shale, and relatively
uncommon in the Lgota Beds. Erosional structures, such
as small flute casts or groove marks, occur in the Upper
Cieszyn Beds and in the Lgota Beds, but are the same on
the soles of sandstone beds above the couplets regardless
of the presence or absence of a spotty layer. Therefore,
the absence of couplets with a spotty layer in these
units is referred to anoxic conditions. At first glance, the
frequency of the couplets without a spotty layer could be
related theoretically to the frequency or the duration of
anoxic events, but the frequency of the turbidites seems to
be the foremost influence. For the Upper Cieszyn Beds,
the turbidites are almost 10 times more frequent than in
the Lgota Beds (Table 2). In other words, it appears that
10 turbidites were deposited in the Upper Cieszyn Beds
while only one accumulated in the Lgota Beds during an
anoxic episode of the same duration. If this is true, then
the spotty layers of the Lgota Beds should be on average
10 times thicker than those of the Upper Cieszyn Beds
because the duration between turbiditic events was on
average 10 times longer. In fact, the spotty layers are only
five times thicker (on average 15 and 3 mm, respectively).
This might be caused by differences either in the rate of
accumulation of hemipelagic mud or in the depth of total
bioturbation in the turbiditic mud. Because distinguish-
ing between turbiditic and hemipelagic mudstones in
these units is problematic, the issue remains unresolved.
However, the overall evaluation of the trace fossil associa-
tion in these units favours the second possibility, i.e. that
the smaller thickness of totally bioturbated turbiditic
muds in the Lgota Beds is recording lower oxygenation
than in the Upper Cieszyn Beds.

FOSSILS AND STRATA 51 (2004) Deep-sea trace fossils controlled by palaeo-oxygenation and deposition 53
The spotty layers from the younger Godula Beds
(Turonian), which accumulated in the same basin, are
much thicker than those from the Upper Cieszyn Beds.
However, the frequency of turbidites in these units
is almost the same. The expected thickness of the
bioturbated hemipelagic sediments deposited at the same
rate would be about 20 times greater in the Verovice Shale
than in the Upper Cieszyn Beds, but in reality it is less
in the Verovice Shale than in the Upper Cieszyn Beds
(Table 2). Most probably, the original vertical extent of
bioturbation in the Verovice Shale was much less than for
the Upper Cieszyn Beds.
Table 2. Some sedimentological parameters for the lithostratigraphic units studied plus the Godula Beds (Turonian). The expected thickness of the
hemipelagite layer is calculated for a sedimentation rate of 1 mm/1000 years.
Average number
Thickness and of turbidites/m and Frequency of Expected thickness Average thickness
Lithostratigraphic duration of approximate total turbiditic events of the hemipelagite of the spotty
units accumulation number of turbidites (years/turbidite) layer (mm) layer (mm)
Godula Beds 2000 m 10 275 0.3 30
5.5 Myr 20,000
Lgota Beds 250 (locally 450) m 15 4800
18 Myr 3750 (locally 6750) (locally 2666) 2.5–5 15
Verovice Shale 300 m 5 10,000 10 0.5
15 Myr 1500
Upper Cieszyn Beds 300 m 65 487 0.5 3
9.5 Myr 19,500
Fig. 12. Relationships between trace fossil diversity, frequency of turbidites and oxygenation in the investigated units. The frequency of turbidites is
expressed by an average number of years per each turbidite flow (e.g. one turbidite flow/5000 years). The expected thickness is a theoretical thickness of
the hemipelagic layer based on a sedimentation rate of 1 mm/1000 years (=1 mm/1 ka). The average thickness refers to the hemipelagic layer measured
in the field. The arrows show the direction of increasing values of the various parameters employed.
In summary, there was a gradation of generalised
oxygenation of the deep-sea floor during deposition of
the investigated units (Fig. 12). Sediments of the Verovice
Shale were deposited mostly in anoxic conditions with
short oxic events that enabled colonisation of the
deep-sea floor by burrowers. The trace fossil assemblage
of this unit shows the lowest diversity. The thicker layers
of greenish, bioturbated, spotty shales at the top of this
unit indicate a general improvement in oxygenation.
The Lgota Beds were deposited in relatively more oxic
conditions than in the Verovice Shale. Most couplets
contain the spotty layer, but their trace fossil diversity is

FOSSILS AND STRATA 51 (2004)
54 Alfred Uchman
relatively low. The Upper Cieszyn Beds were deposited in
even more oxic conditions than the Lgota Beds, apart
from the higher number of rhythms without the spotty
layer. The latter pattern resulted from about 10 times
higher frequency of turbiditic deposition. The trace fossil
assemblage of this unit shows the highest diversity.
Cretaceous anoxic events
The decrease in deep-sea floor oxygenation during
sedimentation of the discussed deposits can be related to
the widely known Early Cretaceous anoxic events (e.g.
Arthur & Schlanger 1979; Jenkyns 1980). Periods of true
anoxia are mostly short episodes (Ekdale 1985b), less than
one million years in duration (Bralower et al. 1994). This
is confirmed by the investigations presented here. Only
the Verovice Shale contains evidence of longer anoxic
periods, as indicated by the presence of thicker non-
bioturbated units separated by thin bioturbated horizons.
Verovice and Lgota deposition roughly corresponds to
the Oceanic Anoxic Event 1 (OAE 1) of Arthur &
Schlanger (1979). Longer oxygen deficiency intervals in
the deep ocean during the late Barremian–early Aptian,
i.e. during the deposition of the Verovice Shale, are
a world-wide phenomenon (Bralower et al. 1994).
Improvement in the oxygenation after the deposition of
the Verovice Shale may be related to the late Aptian
drop in global temperature (Scott 1995; Price et al.
1998), which may have resulted in acceleration of
oceanic circulation. The Early Cretaceous anoxic events
probably delayed the colonisation of deep-sea floor
environments by irregular echinoids producing Scolicia
(Tchoumatchenco & Uchman 2001). Thus, the trace
fossil associations were apparently influenced by world-
wide phenomena related to the Cretaceous anoxic events.
General remarks
In the 1970s and beginning of the 1980s, the deep sea was
commonly considered as a stable habitat influenced only
by long-term probabilistic linear evolutionary processes
without rapid changes. This view was formulated as the
time-stability hypothesis by Sanders (1968), and was
invoked by Seilacher (1976, 1978) and Frey & Seilacher
(1980) to explain the evolution of deep-sea communities.
Subsequent research proved the deep-sea floor to be
influenced by many factors that changed through time,
for example, the anoxic events. These factors influenced
the deep-sea organisms (e.g. Gage & Tyler 1992), some of
which were trace makers. The evolutionary trends in
graphoglyptids are an example of the changes that do
not fit the time-stability hypothesis (Uchman 2003).
The trace fossil associations discussed in this paper are
influenced by many factors, such as oxygenation changes,
preservation potential, frequency of turbiditic deposition,
and evolutionary changes in trace makers, which cause
significant disturbances through time, and influence
changes in the trace fossil record from unit to unit.
Conclusions
1. Trace fossil associations from the Lower Cretaceous
dark flysch deposits of the Upper Cieszyn Beds,
Verovice Shale, and Lgota Beds differ from most trace
fossil communities known from Upper Cretaceous
and Tertiary flysch successions. Only the trace fossil
association of the Upper Cieszyn Shale (Valanginian–
Hauterivian) can be ascribed to the Nereites ichno-
facies. In the other two studied units, graphoglyptids
and horizontal meandering pascichnia, the typical
components of this ichnofacies, are absent or rare.
2. The composition of the trace fossil communities
and the vertical extent of bioturbation in the
turbidite–hemipelagite couplets were strongly affected
by lowered oxygenation on the deep-sea floor. The
lowered oxygenation appears to correspond to global
Early Cretaceous anoxic events.
3. The Verovice Shale is dominated by anoxic strata
interlayered with rare, thin bioturbated horizons.
In the Upper Cieszyn Shale and Lgota Beds, most
tops of turbidite–hemipelagite rhythms are biotur-
bated. Unbioturbated couplets record anoxia. Their
frequency is correlated with that of turbiditic
deposition.
4. The differences between the Upper Cretaceous and
younger trace fossil communities were also influenced
by evolutionary processes involving trace makers, such
as those that resulted in increasing diversity of the
graphoglyptids, and a greater abundance of Scolicia
and Nereites irregularis since the Late Cretaceous.
5. Protovirgularia obliterata and Protovirgularia pennata
from the Verovice Shale and probably the Upper
Cieszyn Beds occur in the deepest tier below Chon-
drites. They were probably produced below the redox
boundary by chemosymbiotic bivalves.
Acknowledgements
This research was sponsored by grant 6 PO4D 002 19 from
the Polish Science Committee (Komitet Badana Naukowych).
Additional support was provided by the Jagiellonian University.
W. Miller III (California), A. K. Rindsberg (Alabama), A. Wetzel
(Basel) and B. D. Webby (Macquarie, Sydney) improved the
English and provided helpful comments.
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