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, DECEMBER 2014, 65, 6, 403—409 doi: 10.1515/geoca-2015-0001
Cambrian trace fossil Zoophycos from the Czech Republic
JAN DOUCEK
1
and RADEK MIKULÁŠ
2
1
Vodní zdroje Chrudim, s.r.o., U Vodárny 137, CZ-573 01 Chrudim, Czech Republic; Doucek@vz.cz
2
Institute of Geology, v.v.i., Academy of Sciences of the Czech Republic, Rozvojová 269, CZ-165 02 Praha 6 – Lysolaje,
Czech Republic; mikulas@gli.cas.cz
(Manuscript received January 15, 2014; accepted in revised form October 7, 2014)
Abstract: Lobate and helical ichnofossils attributable to Zoophycos found in Middle Cambrian shales of the Palác Hill in
the Železné Hory Mountains (eastern Bohemia) represent the oldest occurrence of this ichnogenus. Such a complex Zoophycos
became frequent during the Mesozoic but has been never recorded in strata older than the Ordovician. As such, they
represent the oldest occurrence of helical Zoophycos. Besides Zoophycos isp. there is also a 15 cm thick sandy siltstone
layer which is strongly bioturbated by Planolites isp., which seems unusual in a Lower Cambrian ichno-association.
Key words: Cambrian, Bohemian Massif, Železné hory, ichnology, marine settings, Zoophycos.
Introduction
The early Paleozoic, especially the Cambrian and Ordovi-
cian periods, was a time of very important and intensively
studied paleobiological events, which are reflected not only
by body fossils but also by trace fossils (for a review see
Buatois & Mangano 2011, p. 269—274). These events are
known as the Cambrian Explosion (Conway Morris 2000)
and the Agronomic Revolution (Seilacher & Pflüger 1994).
The ichnogenus Zoophycos Massalongo, 1855, is among
the first ichnotaxa to occur in the critical earliest Paleozoic
time (e.g. Sappenfield et al. 2012). It is an extremely com-
plex trace fossil with broad potential for behavioural inter-
pretation (e.g. Bromley 1991; Löwemark et al. 2007). For
these reasons, early Paleozoic occurrences of Zoophycos
should be thoroughly documented. Only a few reports of
Zoophycos in Cambrian strata have been published.
On a regional scale, the study of trace fossils can aid in the
interpretation of geological units that lack well preserved
body fossils. The paucity of body fossils may be caused by
partial metamorphism which is usually less destructive for
trace fossils than for body fossils (cf. Chlupáč 1997). This is
also the case for the lower Paleozoic of the Železné hory
Mountains, which are located in eastern Bohemia, about
100 km east of Prague (Chlupáč et al. 2002 – Fig. 1).
These rocks were intensively metamorphosed in places; at
other sites they were only anchimetamorphosed. As most of
the rock exposures are metamorphosed, though weakly, in
addition to a smaller number of exposures, few biostrati-
graphic data are available. Until now, paleo-ichnological
data from the Paleozoic complexes of the Železné hory
Mountains had not been systematically documented and in-
terpreted. However, it appears that the present record may
play an important role in the understanding of the paleo-en-
vironment of this region.
The aim of this work is to describe and interpret the most
interesting ichnological finds observed so far: the morpho-
logically complex trace fossils of the ichnogenus Zoophycos
in anchimetamorphosed Cambrian siltstones.
Geology of the study area
The Železné hory Mountains belong to the Bohemian
Massif which is a part of the Variscan (Hercynian) orogen
(Fatka & Mergl 2009). In the currently accepted concep-
tion, the Lower Paleozoic formations of the Železné hory
Mts are seen as the continuation of the well-known, inten-
sively studied Barrandian area to the east, showing a strong
affinity to the eastern part of the Barrandian area and also
to the so-called “metamorphic islets” of the Central Bohe-
mian Pluton (Chlupáč et al. 2002). In contrast to the faintly
metamorphosed to unmetamorphosed rocks of the Barran-
dian area, the Lower Paleozoic rocks of the Železné hory
Mountains have undergone faint contact and regional meta-
morphism (Mikuláš 1996). Recently, an alternative view on
the geological context of the Paleozoic of the Železné hory
Mountains has appeared; suggesting greater affinity with
the Saxo – Thuringian region (V. Kachlík, personal com-
munication, 2010).
Historically, the Paleozoic complex of the Železné hory
Mountains is divided into two structural zones, called here
synclinoria, namely the Podol synclinorium in the south, and
the Přelouč synclinorium in the north. Recently, Vodička
(1997) put forth the idea that especially the Podol zone is
structurally close to a nappe structure and that therefore the
term synclinorium is inappropriate.
The age of deposits of the two so-called synclinoria is con-
siderably different. In the northern Přelouč synclinorium, the
stratigraphic sequence starts with the Seník Beds; these are
composed of silty and sandy shales, greywackes and con-
glomerates of Middle Cambrian age. The age of the se-
quence is confirmed only near the town of Heřmanův
Městec, where Havlíček (1949) found a trilobite fauna. Fiala
& Svoboda (1956) subsequently distinguished the so-called
“Sub-Cambrian complex” (currently ranked as Ediacaran)
and “Cambrian complex” in the Seník Beds. Quartz sand-
stones with intercalated silty shales of Ordovician (Tremado-
cian) age, the Lipoltice Beds (Burda 1989), overlie the
Cambrian strata there.
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The Podol synclinorium provides a stratigraphically more
complete set of strata. Ordovician, Silurian and Lower Devo-
nian deposits overlie the probable Cambrian rocks that were
discovered during uranium exploration (Urban 1972). The
Ordovician rocks are represented by very thick complexes
(Burda 1989). The Silurian sequence is represented by gra-
phitic schists and orthoceras limestones that belong to the
upper Llandovery to Ludlow; some authors place the upper
parts of these limestones in the Přídolí Stage (Schmidt et al.
1967; Vodička 1985). The youngest rocks (limestones) of
the Podol synclinorium are dated as early Devonian.
The locality
Palác Hill, near the town of Heřmanův Městec, from
which the described finds come, is located at the southeast-
ern margin of the Přelouč synclinorium. The bulk of the hill
is made of the Cambrian Seník Beds; only its northeastern
margin is built of Ordovician monomictic quartzites (Trema-
docian Lipoltice beds – Burda 1989). The Seník Beds pre-
dominantly consist of siltstones (at the small quarry 280 m
west-northwest of the spot height of 382 m – N 49°56’0”,
E 15°40’48”), sandy siltstones or sandstones. These pass
upward to quartz conglomerates.
Palác Hill, as a geological locality, was mentioned for the
first time by Havlíček (1949), who assigned its Middle Cam-
brian trilobite fauna to the Acadian Stage, which was used at
that time. He mentioned the following species: Ellipsoce-
phalus vetustus, Conocoryphe sulzeri, Ptychoparia sp., Para-
doxides minor, Lobocephalus marginatus, Lobocephalina
carinata and Skreiaspis spinosus. These finds confirmed the
Cambrian age of the eastern part of the Seník Beds. Havlíček
& Šnajdr (1951) subsequently depicted the specimens. The
existence of this trilobite fauna was later mentioned by nu-
merous authors who partly revised the faunal list according
to contemporary knowledge and understanding of the taxa
(e.g. Fatka & Mergl 2009).
In addition to debris and occasional small outcrops, three
small inactive quarries and five shallow boreholes with
core diameter 185 mm provided information on the geologi-
cal setting of Palác Hill. The most prominent quarry ap-
proximately 15 m long and 1.5 m high is located at
N 49°56’02”, E 15°40’28”. It is elongated in a north-
south direction; the inclination of bedding is 50° to east-
south-east. Of the five boreholes, three provided ichnological
data. The Hájovna borehole (N 49°56’01”, E 15°40’16”)
revealed several specimens of Zoophycos from the depth in-
terval 6.0—7.4 m, together with signs of plastic deformation
(boudins up to 4 cm in size) in the same interval. Lithologi-
cally, it is composed of grey to greyish-green siltstones,
finely fissured, and in places strongly limonitized. The Úvoz
borehole (N 49°56’61”, E 15°40’12”) exposed sandy silt-
stones and fine-grained sandstones alternating at centimetric
intervals that grade upward to quartzose sandstones and
greywackes. Planolites isp. was discovered in the drill core.
The Lavičky borehole (N 49°56’11”, E 15°40’13”) was
drilled in an area where Havlíček (1949) found a trilobite
fauna of Cambrian age. However, the borehole did not yield
Fig. 2. Location map. Position of boreholes: 1 – U Kóty, 2 – Pod
Lůmkem, 3 – Hájovna, 4 – Úvoz, 5 – Lavičky.
Fig. 1. Schematic map of Europe showing the location of the Czech Republic and the Lower Paleozoic of the Železné hory Mountains.
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any new finds of body fossils. Greenish siltstones contain
layers of fine-grained bioturbated sandstones up to one centi-
meter thick.
From the cores and outcrops it is possible to reconstruct
the schematic lithostratigraphic profile of Palác Hill (Fig. 3).
The Seník Beds are heterolithic; they are represented by
greenish grey siltstones, which are overlain by anchimeta-
morphosed silty shales and greywackes, quartzose sand-
stones and conglomerates. In the lower part of the profile,
sandy siltstones with varying proportions of sand occur.
Rocks of the Seník Beds, attributable to the Cambrian, are
overlain by the monomictic, quartz-cemented conglomerates
of the Lipoltice Beds (Tremadocian – Burda 1989).
To summarize, the rocks studied on Palác Hill represent
several stratigraphic levels and different depositional environ-
ments. Except in the sandy greywackes to conglomerates in
the upper part of the section, primary sedimentary structures
Fig. 3. Tentative lithostratigraphic profile on the rocks of Palác Hill
based on geological mapping, outcrops and cores. Overall thickness
of the depicted profile is more than 500 m.
Fig. 4. Zoophycos isp. (specimen No. 1) in sample P1H; oblique
section. Scale bar = 1 cm.
are well-preserved. The structures in the siltstones in the mid-
dle part of the section (coarse, irregular parallel laminae; bio-
turbation) suggest deposition below the storm wave base. The
lower and upper parts of the section represent shallow water,
probably a shoreface environment with a sandy bottom.
Systematic ichnology
Zoophycos
Massalongo, 1855
Zoophycos isp.
Fig. 4—6
M a t e r i a l : 3 specimens, Seník Beds, Hájovna Borehole;
depth: 6.0 to 7.5 m.
D e s c r i p t i o n : Fragments of horizontal to subhorizontal
laminae of spreiten that repeat vertically in the sediment,
suggesting the helical shape of the whole structure. The
lobes may be connected with horizontal or subhorizontal
tunnels showing a meniscate fill. Spreite structures are com-
posed of the same material as the surrounding rock or with
slightly darker material with higher clay admixture.
Sample P1H displays two specimens. Specimen No. 1
(Fig. 4) has six oblique laminae that are 3.0—4.0 mm thick;
width of primary lamellae ranges from 0.3 to 0.5 mm. The
diameter of the specimen cannot be precisely measured be-
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cause the cross-section of the specimen obviously does not
reach its central portion. The presumable depth can be esti-
mated as several centimeters; more precise estimation would
be speculative.
The specimen No. 2 from the P1H sample (Fig. 6) consists
of two aligned subhorizontal lamellae, 2.5 to 3.0 mm thick.
Measurable horizontal extent is 51.0 mm. The specimen
from the P2H sample (Fig. 5A) consists of three or four pre-
sumably lobed, subhorizontal structures. Width of each lobe
is approximately 55.0 mm; laminae are 2.3 to 3.9 mm thick.
Individual lamellae, 0.5 to 0.6 mm thick, are easily visible in
places. Spreite-structures are mostly composed of the same
material as the surrounding rock; only in places are they
darker, with the clay admixture.
The specimen from the P3H sample (Fig. 5B) is also ob-
servable in a transverse section steeply oblique to bedding.
The three subhorizontal, joined or tightly aligned laminae
are 3.6 to 4.8 mm thick; lamellae are 0.4 to 0.9 mm thick.
Spreite-structures are composed of the same material as the
surrounding rock.
R e m a r k s : Using specimen No. 1 on sample P1H
(Fig. 4), which is best accessible for observation, we can
identify which morphotype of the ichnogenus Zoophycos is
probably present. The described specimen evidently has a
helical spreite and reaches the depth of several centimeters.
This description fits the morphotype described by Olivero &
Gaillard (2007) well. The specimen in the sample P3H en-
ables the determination of the spiralling direction of the spre-
ite-structure; this can be described as sinistral-upward.
Planolites
Nicholson, 1873
Planolites isp.
Fig. 7—8
M a t e r i a l : Several dozen specimens. Seník Beds, Úvoz
and Lavičky Boreholes, and outcrops at the Palác Hill.
D e s c r i p t i o n : In the cores, the material attributable to
Planolites consists of flattened, originally presumably circu-
lar to oval cross-sections of horizontal to subhorizontal tun-
Fig. 5. A – Zoophycos isp. in sample P2H, vertical cross-section;
B – Zoophycos in the sample P3H, vertical cross-section. Scale
bar = 1 cm.
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Fig. 6. Zoophycos isp. (specimen No. 2) in sample P1H (lower
left); oblique cross-section. Scale bar = 2 cm.
Fig. 7. Cross-sections of Planolites isp. A, B, D – Úvoz borehole, C – Lavičky borehole. Scale bar = 2 cm.
nels, 2.0—4.0 mm in diameter. The fill contrasts with the
surrounding rock that is sandy or clayey. The material
from the outcrop shows predominantly simple horizon-
tal tunnels with diameters of 0.7—1.5 mm. The tunnels
are unlined, unbranched, straight or more often curved
(exceptionally even strongly curved to twisted), com-
monly intersecting each other. In comparison to the sur-
rounding rock, the fill is finer, more clayey and more
greenish.
O c c u r r e n c e : The burrows were recorded in the
Úvoz and Lavičky boreholes (depth 5.5 and 4.0 m, re-
spectively). The highest amount of specimens was found
in a fox hole (N 49°56’04”, E 15°40’48”) next to the
largest quarry, in a 15 cm thick layer. All the occurrences
belong to the lower part of the Seník Beds (Fig. 3).
Discussion and conclusions
Finds of helical Zoophycos from the Hájovna borehole
on Palác Hill are unique in regard to their age. Thus far,
the oldest specimens of Zoophycos come from the lower
Cambrian member of the Wood Canyon Formation in
California (Sappenfield et al. 2012) and from the Early
Cambrian Rusophycus avalonensis trace fossil zone
from Sweden (Jensen et al. 2001). The oldest known
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Fig. 8. Planolites isp. from the fox hole near the small quarry. Scale
bar = 1 cm.
Zoophycos is a shallow burrow, constructed about 1—2 cm
deep in the mixed layer (Sappenfield et al. 2012).
Among other notable finds of early Zoophycos, one comes
from the Buen Formation of North Greenland (Bryant &
Pickerill 1990). Stratigraphically, it is placed in the second
Stage of the Cambrian Series. The morphology of this trace
is simple: a straight tunnel 52 mm long and 3—6 mm wide,
showing internal lamination. Laminae are alternately light
and dark (Bryant & Pickerill 1990). Its architecture and
structure indicate that it is a simple sinistral morphotype of
Zoophycos (Olivero & Gaillard 2007).
All other specimens so far reported from the Cambrian are
similar, planar forms. Jensen (1997) described such a find
from the Lower Cambrian Mickwitzia Sandstone of Sweden.
Yang & Wang (1991) described a planar Zoophycos from the
Middle Cambrian beds of the North China Platform. De
(1993) reported Zoophycos from the Lower Cambrian strata of
Kashmir, India. Goldring & Jensen (1996) noted Zoophycos
from Cambrian Stage 2(?) in western Mongolia. Potentially
the oldest find of Zoophycos, as reported by Alpert (1977)
from the Campito Formation of southern California, proba-
bly does not represent the ichnogenus Zoophycos; moreover,
its stratigraphic position is questionable (S. Jensen, personal
communication 2012).
The above data show that Zoophycos from the Železné
hory Mts is unique among the Cambrian occurrences of the
ichnogenus for its complex, non-planar, probably helical
structure. No examples of helically coiled Zoophycos have
previously been reported before the Ordovician (e.g.
Mikuláš 1995).
Planolites is, in its most typical form, a horizontal to sub-
horizontal tunnel which can be common on bedding planes
as semi-reliefs or within a substrate in full relief (Häntzschel
1975). In the Cambrian, dense Planolites ichnofabric is nota-
bly rare. The layer described here shows such an infrequent
case, namely a modest mixed layer showing an even degree
of bioturbation throughout its thickness of ~ 15 cm; the ichno-
fabric index (Droser & Bottjer 1986) is 3. Surrounding layers
show no bioturbation. It can be presumed that Planolites rep-
resents in this case a true feeding trace; the bioturbated bed
might have been well oxygenated and rich in nutrients.
Acknowledgments: This study was partly supported by the
Science Foundation of Charles University through the
Project No. 66709 and by the Czech Science Foundation
through Project No. 205/09/1521. Thanks go to the Vodní
zdroje Chrudim Company for financial and material support.
The authors are obliged to Sören Jensen (Badajoz) and Dirk
Knaust (Stavanger) for critical reading of an earlier version
of the manuscript.
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