GeolCarp_Vol56_No1_57

GEOLOGICA CARPATHICA, FEBRUARY 2005, 56, 1, 57-65

The ichnological record across the Cretaceous/Tertiary

boundary in turbiditic sediments at Uzgruò (Moravia,

Czech Republic)

ALFRED UCHMAN

, MIROSLAV BUBÍK

and RADEK MIKULÁ

Institute of Geological Sciences, Jagiellonian University, Oleandry 2a, 30-063 Kraków, Poland; fred@ing.uj.edu.pl

Czech Geological Survey, branch Brno, Leitnerova 22, 600 00 Brno, Czech Republic; bubik@cgu.cz

Institute of Geology, Academy of Sciences of the Czech Republic, Rozvojová 135, 165 00 Praha 6, Czech Republic; mikulas@gli.cas.cz

(Manuscript received June 19, 2003; accepted in revised form March 16, 2004)

Abstract: The deep-sea, distal turbiditic deposits at Uzgruò have recorded no significant change of trace fossil diversity

and ichnofabrics across the Cretaceous/Tertiary (K/T) boundary interval. There is no evidence of any ecological catas-

trophe that can be related to the K/T event. The trace fossil association is rather poor in diversity. This can be related to

a general oligotrophy and poor preservation potential. The producers of the discussed trace fossils, dominated by Chon-

drites intricatus (Brongniart), Chondrites targionii (Brongniart), Ophiomorpha annulata (Ksi¹¿kiewicz), Ophiomorpha

rudis (Ksi¹¿kiewicz), Palaeophycus tubularis Hall, Planolites isp., Phycosiphon incertum Fischer-Ooster, Thalassinoides

isp. and Trichichnus isp. lived in a habitat, which had not been influenced by the event.

Key words: Cretaceous/Tertiary boundary, Western Carpathians, flysch, ichnology, ichnofabric.

Introduction

Trace fossils and ichnofabrics provide important data about the

paleoenvironment, especially about oxygenation, food supply,

rate of sedimentation, and paleodepth (Frey 1975; Ekdale et al.

1984a; Frey & Pemberton 1985; Pemberton 1992; Donovan

1994; Bromley 1996 and others). Therefore, they can be useful

for multivariate studies on the Cretaceous/Tertiary (K/T)

boundary. Examples already exist in the literature. In the Danish

chalk, they indicate upward shoaling across the boundary, a lo-

cal anoxia in the shallow part of the basin and oxygenated envi-

ronment in the deeper part recorded in bioturbated marls of the

Fish Clay (Ekdale & Bromley 1984). In Alabama, trace fossils

excluded that the clastic deposits at the K/T boundary are cata-

strophic tsunami deposits, but they indicate rather sea-level

changes (Savrda 1993). In the deep-sea (but above CCD) de-

posits in NE Mexico, Ekdale & Stinnesbeck (1998) recognized

at least three colonization episodes in clastics of the K/T bound-

ary layers in, which indicate a long period of time between the

possible extraterrestrial impact and extinction of the Cretaceous

plankton. According to preliminary analyses of ichnofabric at

the K/T boundary at Agost (SE Spain) by Rodríguez-Tovar

(2001), a tiered ichnoassemblage with Planolites, Thalassi-

noides, Chondrites and Zoophycos occur there.

In this study, trace fossils and ichnofabrics are used for bet-

ter understanding of paleoenvironment represented by the K/T

interval from the Uzgruò section in the Western Carpathians.

Previous work and geological setting

The K/T interval in the Uzgruò section is situated in the left

bank cut of an unnamed creek NNE of the Uzgruò settlement,

near Velké Karlovice close to the Czech-Slovak border

(Fig. 1). The K/T section consists of two isolated outcrops

close to each other (points No. 19 and 20 of Bubík et al.

1999). Correlation of both outcrops is easily possible because

of the overlap of a characteristic interval. The composed sec-

tion is about 9 m thick.

The sediments in the Uzgruò vicinity belong to the Raèa

Unit of the Magura Group of Nappes in the Outer Flysch Car-

pathians. Sediments of the Uzgruò section can be assigned to

the Soláò Formation. Multistratigraphy of the K/T boundary

interval of the section was recently investigated and discussed

by Bubík et al. (2002).

Trace fossils from the K/T boundary interval of the Car-

pathians have not been studied in detail yet. Uchman (1991)

generally and briefly analysed the Incoceramian Beds (Senon-

ian to Paleocene) of the Polish Carpathians but the K/T

boundary has not been precised yet within this member. Ich-

Fig. 1. Location map. The Uzgruò locality is marked by an asterisk.

www.geologicacarpathica.sk

58 UCHMAN, BUBÍK and MIKULÁ

noassemblage of the Incoceramian Beds displays evidence of

environmental stress (possible oligotrophy) and limited pres-

ervation potential in comparison to the Eocene formations, but

this stress is not related to the K/T event. However, the trace

fossil association of the Incoceramian Beds is similar to that of

the Uzgruò section (see below).

The section shows characteristic flysch type lithology with

prevailing grey-green, grey, and dark grey mudstones over

siltstones and fine- to medium-grained greywacky sandstones.

Analysis of the mudstones from the K/T boundary interval re-

vealed quartz, plagioclase, mica, chlorite, kaolinite (and re-

spectively calcite in the calcareous turbidite layers). Less fre-

quently, thin layers of marlstones and rarely lutitic carbonates

occur. The marlstones contain up to 45 % of carbonate. Tur-

biditic mudstones usually have less than 10 % of carbonate.

Hemipelagic mudstones are solely non-calcareous. The lutitic

carbonates are close to dolomitic limestones or dolomites.

Carbonates and calcareous mudstones are restricted to the

Maastrichtian part of the section.

The sedimentary succession across the K/T near Uzgruò can

be characterized as alternation of thin-bedded muddy turbid-

ites and hemipelagites. A few thicker sandy turbidites (up to

40 cm thick) occur close to the K/T boundary. Most of the

sandstone beds show ripple-lamination and are up to few cm

thick. Commonly the beds pinch out after a short distance.

Silty-muddy turbiditic beds are very common. The coarsen-

ing-upward trend across the K/T boundary interval observed

by Bubík et al. (1999) also occurs in the section scale. Turbid-

ites consisting only of muddy intervals represent about 60 %

of the total number of the turbidites in the Maastrichtian part,

but only 30 % of the Paleocene part. Turbidites containing a

sandy interval are more frequent in the Paleocene (25 %) than

in the Maastrichtian part (7 %). Figure 6 contains a presumed

comparison of the Uzgruò turbidites to turbidite models by

Stow (1985), Piper (1978) and Bouma (1962).

In some thicker (510 cm thick) hemipelagites, thin silty

layers occur besides typical turbidites; they display no sharp

base but clear inverse gradation at the base and normal grada-

tion at the top. Such layers may represent the sediments of

bottom currents.

Relatively distinct erosion was observed in the upper part

of the section approximately 2 m above the base of the Pale-

ocene. On the distance of two meters, approximately 20 cm

of the deposit (two turbidite rhythms) were removed by ero-

sion.

The accumulation rate for the Uzgruò section cannot be cal-

culated precisely because the only chronometric datum refers

to the K/T boundary; but estimation can be made on the basis

of biostratigraphy. Sediments of the documented section are

separated from the underlying beds by a fault, which is cov-

ered by the stream bed as is evident from different successions

in the opposite creek banks. The Maastrichtian part of the sec-

tion is about 6 m thick. The segment of the section from the

opposite bank, which is assigned to the Micula prinsii Zone

(latest Maastrichtian), has the same or slightly greater thick-

ness. The next closely situated outcrop, but separated by a lo-

cal thrust, was dated to the older Nephrolithus frequens Zone.

Nevertheless, on the basis of this field situation, it was possi-

ble to conclude that the Micula prinsii Zone from the Uzgruò

section is at least 20 m thick. Relating this value to the dura-

tion of the M. prinsii Zone from the North Atlantic of about

220 ky (Henriksson 1993), the average sedimentation rate

reaches at least 9 cm/ky, and at least 3.6 cm/ky for hemipelag-

ites in the compacted shale. This estimation is very tentative,

but it implies relatively rapid deposition.

The completeness of the Uzgruò K/T section was evaluated

using trace fossils, which can help in recognition of erosion

(Wetzel & Aigner 1986). Foremost, an occurrence of trace

fossils preserved as semi-reliefs due to scouring and casting

indicate erosion at the base of turbidites. There are only a

small number of beds in the Uzgruò section, which contain

trace fossils of this sort. In most cases, the hemipelagic layer is

preserved below the sole of the turbidites. Consequently, ero-

sion has been relatively small on the deep-sea floor and the

section is almost complete. Thick sandstone beds with flute

casts may represent exceptions. Nevertheless, even in this

case, the underlying bed has been eroded only partly. It seems

that in most cases the erosion removed no more than a few

millimeters of sediment, which can be deposited approximate-

ly within several tens of years.

Material and methods

Trace fossils and ichnofabrics have been investigated in the

field and laboratory. Each bed has been examined. The soft

fine-grained parts of the beds have been polished in the field

using water-proof abrasive paper and running water. Differ-

ently oriented polished slabs have been easily obtained by

means of this method. Trace fossils have been also observed

on the parting and bedding surfaces. In this way, the ichnofab-

ric and its change within a bed was analysed. The material has

been documented in the field and later in the laboratory.

Synopsis of ichnotaxa

Twelve ichnospecies (see below) have been recognized in

the investigated section. Cross-sections of the trace fossils on

surfaces of the polished slabs are illustrated in Figs. 2 and 3.

Arthrophycus cf. tenuis (Ksi¹¿kiewicz 1977) occurs gregari-

ously as semi-reliefs of subhorizontal, hypichnial, convex

ridges. The ridges are 1.01.5 mm wide and up to 35 mm

long. They are straight, rarely branched and oriented in differ-

ent directions. Arthrophycus tenuis was previously described

under the ichnogenus Sabularia (Ksi¹¿kiewicz, 1977). Uch-

man (1998) recommended that this ichnogenus should no

longer be used and included Sabularia tenuis in the ichnoge-

nus Arthrophycus Hall on the basis of the very fine perpendic-

ular striae, which, however, are commonly not preserved. The

described form is smooth, but it displays the characteristic ge-

ometry and size of A. tenuis.

Chondrites intricatus (Brongniart, 1823) (Figs. 2C, 3B) oc-

curs as a system of tree-like branching, downward penetrating,

markedly flattened tunnels, less than 1.0 mm in diameter. The

tunnels form acute angles. In cross-sections it occurs as patch-

es of circular to elliptical spots and short bars. Commonly, the

fill of the trace fossil is darker than the host rock. For a more

60 UCHMAN, BUBÍK and MIKULÁ

extensive discussion of the ichnogenus Chondrites see Fu

(1991) and Uchman (1999).

Chondrites targionii (Brongniart, 1823) (Fig. 2A,B,E) is

represented by endichnial, tubular, flattened tunnels branched

in a dendroid manner. Branches are commonly slightly

curved. The tunnels are 12 mm wide. In cross-section it is

similar to C. intricatus, but distinctly larger.

Nereites irregularis (Schafhäutl, 1851) (Fig. 2D) is a tightly

to loosely meandering, rarely spirally coiled endichnial trace

fossil, 25 mm wide. It is composed of a central, light-co-

loured faecal string, and a dark envelope zone. The faecal string

occupies about 40 % of the width. For more information on

Nereites see Uchman (1995a) and Mángano et al. (2002).

Ophiomorpha annulata (Ksi¹¿kiewicz, 1977) (Figs. 2E,F, 4)

is an exichnial, hypichnial or rarely epichnial, straight to

slightly winding, vertical, oblique to horizontal, cylindrical,

walled trace fossil preserved in full-relief, 39 mm in diame-

ter. It is filled mostly with sandy material. In flysch deposits

this trace fossil rarely displays a wall covered with small oval

knobs, which are characteristic of the ichnogenus Ophiomor-

pha (Uchman, 1995a).

Ophiomorpha rudis (Ksi¹¿kiewicz, 1977) (Fig. 2G) is pre-

served as vertical to subvertical cylindrical, walled or un-

walled, sand-filled, rarely branched tunnels, 915 mm in di-

ameter. Some branches penetrate horizontally along bedding

surfaces. The exterior part of the tunnels is smooth or displays

indistinct, irregular sandy granules. Ophiomorpha rudis pene-

trates up to 30 cm through at least a few turbidites.

Palaeophycus tubularis Hall, 1847 is an endichnial horizon-

tal, branched, smooth, thinly lined, winding cylindrical bur-

row on the lower bedding surface, 310 mm in diameter. For

discussion of Palaeophycus see Pemberton & Frey (1982) and

Keighley & Pickerill (1995).

Planolites isp. (Fig. 2C) are variably oriented, but mostly

horizontal, cylindrical trace fossils without wall, 36 mm in

diameter. In cross-sections, they appear as oval spots contrast-

ing in colour against the surrounding rock. They are preserved

also on the soles of sandstone beds in full-relief. For discus-

sion of Planolites see Pemberton & Frey (1982) and Keighley

& Pickerill (1995).

Phycosiphon incertum Fischer-Ooster, 1858 (Fig. 3A) is ob-

served in horizontal polished slabs as curved endichnial lobes,

Fig. 3. Examples of trace fossils and ichnofabrics. A Phycosiphon incertum, turbiditic siltstone, ICH-2, horizontal section. B Plano-

lites isp. (P) and Chondrites intricatus (Ch), hemipelagic mudstone, ICH-81, slightly oblique section. C Taenidium isp. from a hemipelagic

mudstone, ICH-83, horizontal section. D Taenidium isp. (Ta) from a turbiditic laminated siltstone, ICH-92, slightly oblique section. E

Trichichnus isp. (Tr) against mottled background, hemipelagic mudstone, ICH-96, horizontal section. F Trichichnus isp. (Tr) against mot-

tled background, dark turbiditic siltstone to claystone, ICH-17, slightly oblique section. Scale bars = 1 cm.

THE ICHNOLOGICAL RECORD IN CRETACEOUS/TERTIARY TURBIDITIC SEDIMENTS (MORAVIA) 61

2 mm wide and up to 20 mm long, encircled by a marginal

tunnel, which is 0.71.0 mm wide. In vertical cross-sections it

occurs as patches of dark, elongated spots, about 1 mm in di-

ameter, surrounded by a light mantle. More information about

Phycosiphon can be found in Wetzel & Bromley (1994).

?Rotundusichnium zumayense (Gómez de Llarena, 1946)

consists of spirally coiled, partially overlapping endichnial

ribbons inclined toward the centre of the spiral. Only a single,

poorly preserved spiral, 3035 mm wide, has been found. For

discussion of this ichnospecies see Uchman (1998).

Taenidium isp. (Fig. 3D) is an oblique to horizontal, un-

walled, simple, tubular meniscate trace fossil, in which menis-

ci display different colour than the host rock. It is 10 mm

wide. Taenidium was discussed by DAlessandro & Bromley

(1987) and Keighley & Pickerill (1994), who regarded it as a

burrow of vagile deposit-feeding organisms, but Locklair &

Savrda (1998) suggested that at least some Taenidium were

produced by a sessile worm maintaining a connection to the

sediment surface or shallow subsurface and keeping pace with

sediment accumulation.

Thalassinoides isp. are walled or unwalled trace fossils

composed of cylindrical, mostly horizontal branched tunnels,

which are 1020 wide. They were observed mostly in vertical

or oblique cross-sections, where they occur as spots distinctly

larger than in the case of Planolites isp. For discussion of

Thalassinoides see Frey et al. (1984) and Ekdale (1992).

Trichichnus isp. (Fig. 3E,F) is a vertical to oblique, rarely

horizontal, straight to curved, simple or rarely branched, very

thin, cylindrical trace fossil, which is less than 1 mm in diame-

ter. It is filled with pyritic, commonly weathered material. For

discussion of Trichichnus see Fillion & Pickerill (1990) and

Uchman (1995a, 1999).

Zoophycos isp. (Fig. 4) was found only on the base of a

thick sandstone bed where it is preserved as a concave funnel

structure with radially arranged spreite. The funnel is about

40 mm wide. The spreite laminae are straight to slightly arcu-

ate. Zoophycos s.l. is generally assumed to be the trace of an

as yet undiscovered deposit-feeder. For discussion of this ich-

nogenus see Ekdale (1992) and Bromley & Hanken (2003).

The latest cited authors suggested that the upper helical part of

a large Pliocene Zoophycos from Rhodes, Greece, is a deposit-

feeding structure, and lateral lobes developing from its lower

part are sulphide wells for chemosymbiotic bacteria.

Form A is a simple horizontal tubular trace fossil with pel-

leted wall, 23 mm wide. It was ascertained in only one layer

of hemipelagic mudstone (ICH101).

Description of ichnofabrics

The ichnofabrics are mainly composed only by a few ichno-

taxa; they include Chondrites intricatus, Planolites isp. and

Trichichnus isp., whereas Ophiomorpha annulata, Phycosi-

phon incertum, and Chondrites targionii are a less common,

but still frequent and characteristic component of the ichnoas-

semblage. The remaining ichnotaxa are rare. They occur only

in single beds. Ichnofabrics occur in almost all beds. The dis-

tribution of trace fossils is shown in Fig. 5.

The green hemipelagites are totally bioturbated. Against

mottled background Planolites, Phycosiphon incertum, Chon-

drites intricatus and Trichichnus are visible. Planolites and

Phycosiphon incertum are cross-cut by Chondrites, and they

are all together penetrated by Trichichnus. Some Planolites

are densely reworked preferentially by Chondrites intricatus,

which follows exactly the Planolites filling. Rarely, Chon-

drites targionii, sand-filled Ophiomorpha annulata, or ?Ro-

tundusichnium zumayense are present.

Underlying grey turbiditic mudstones are also totally biotur-

bated at least in the upper part. Planolites and Phycosiphon in-

certum occur mostly in the upper part, and Chondrites intrica-

tus, Chondrites targionii and Trichichnus all over the layer,

including the lower part, where primary laminations may be

preserved. The latter three ichnotaxa can be found, but much

less abundant, in the underlying siltstones or even in the top of

turbiditic sandstones. In rare cases, Planolites occurs on the

soles of thin sandstone beds in full relief. In some beds, rela-

tively rare Nereites irregularis can be found. Thalassinoides

and Palaeophycus cross-cut by at least Chondrites and Tri-

chichnus occur most often in siltstones.

Ophiomorpha annulata is often present on soles of turbidit-

ic sandstones, but crosses also turbiditic and hemipelagic

mudstones cutting all other trace fossils. Commonly it pene-

trates through a few adjacent turbidites to a depth of at least

20 cm and occurs in full-relief along the base of a 40 cm-thick

sandstone bed. Ophiomorpha rudis occurs in the same way. In

one case (ICH55) O. annulata follows the fill of O. rudis. Rare

Arthrophycus cf. tenuis occurs exclusively on the sole of a

thin sandstone bed.

Interpretation of the ichnofabrics

The cross-cutting relationships express a vertical partition-

ing of trace fossils in sediments, that is tiering, which can be

Fig. 4. Zoophycos isp. from the Uzgruò section. Hypichnial con-

cave form. The straight ridge in the upper left corner belongs to

Ophiomorpha annulata.

62 UCHMAN, BUBÍK and MIKULÁ

interpreted to some extent as for continuously deposited pe-

lagic sediments (e.g. Ekdale & Bromley 1991). According to

this scheme, Ophiomorpha annulata occupies the deepest tier.

Trichichnus can be placed in a shallower tier, but deeper than

the tier of Chondrites. Planolites and Phycosiphon occupy

further distinctly shallower tiers. The shallowest tiers are rep-

resented by a totally bioturbated zone produced by highly vag-

ile benthos; its activity is not recorded as trace fossils (Bro-

Fig. 5. Distribution of trace fossils in the investigated section. ICH

ichnologically investigated samples, housed in the Institute of Geolo-

gy, AS CR, Praha; 19D219F1 biostratigraphic samples as pub-

lished by Bubík et al. (2002), presented herein for the comparison to

the position of the ichnological samples.

mley 1996). Occurrence of crisp trace fossils such as Ophio-

morpha annulata, Chondrites or Trichichnus in hemipelagic,

totally bioturbated mud is an overprint of deep tiers from the

overlying beds (Fig. 6).

The above-outlined picture, however, is static and cannot be

explained by a simple shift of tiers in response to sediment ac-

cumulation. Foremost, the accumulation of sediment is mostly

incidental due to turbidity currents, which interrupt long peri-

ods of pelagic and hemipelagic sedimentation. The model of

sequential colonization can be applied for flysch deposits

(Wetzel & Uchman 2001), in which changes of the benthic

communities with time is stressed. Following that idea, after

deposition the turbiditic sediments contain the highest amount

of food and oxygen, which decrease with time. Firstly, they

are colonized by motile deposit feeders, which are represented

by Phycosiphon incertum and Planolites. In rare beds, they

are followed by Nereites irregularis, which is produced by a

more efficient and systematic bioturbator. In the meantime,

the near surface sediment is continuously reworked by several

animals, the activity of which produces only total bioturba-

tion, not recorded as distinct trace fossils, but as so-called bio-

deformational structures which only destroy pre-existing sedi-

mentary structures. At the beginning, they rework the top of

the turbiditic sediments, that is the turbiditic muds, and then

the settled pelagic and hemipelagic sediments, which are sub-

jected to long period of continuous reworking. When the food

content has been significantly exploited and oxygenation of

the sediment decreased as hemipelagic sedimentation is quite

rapid, the burrowers are followed by Chondrites, which is pro-

duced by opportunistic animals using chemoautotrophic mi-

croorganisms (Seilacher 1990; Fu 1991). They penetrated

deeply down into fine-grained sediment within the anaerobic

zone. Chondrites is followed by Trichichnus, which displays

similar, but even more opportunistic behaviour (Uchman

1995a). Ophiomorpha annulata is produced by a crustacean,

which does not depend on the change of food and oxygen con-

tent in fresh turbidites, but it exploits microorganisms and/or

organic matter maturated by microorganisms in buried turbid-

ites, especially along their sandy base, generally in the anaero-

bic zone. It maintains an open burrow for the supply of oxy-

genated water. They are typical multi-layer colonizers sensu

Uchman (1995b), which probably survive turbiditic flows. In

each stage, the near-surface sediment is reworked by different

bioturbators. The geometry of Chondrites, Trichichnus and

Ophiomorpha indicate that their producers are very inefficient

sediment reworkers, which, indeed, corresponds well to the pre-

sumed ethology of their traces.

The totally reworked zone at the top of turbidite-hemipelag-

ite couplets, contrasting in colour to surrounding rock, is dis-

tinguished in flysch deposits as a spotty layer (Uchman 1999).

It contains mostly hemipelagic or pelagic sediments, which,

however, are mixed together with turbiditic sediments by bio-

turbation. Below, where distinct trace fossils typically occur,

the elite layer is distinguished (Uchman 1999). The totally

bioturbated top of turbiditic mudstone is separated as the up-

per elite layer. The upper elite layer and the spotty layer can be

regarded as equivalent of the mixed layer from Recent deep-

sea pelagic sediments (Ekdale & Berger 1978; Berger et al.

1979). The zone with distinct trace fossils in turbiditic deposits

THE ICHNOLOGICAL RECORD IN CRETACEOUS/TERTIARY TURBIDITIC SEDIMENTS (MORAVIA) 63

with primary lamination is distinguished as middle elite layer,

and the exichnial elite layer is distinguished for trace fossils

penetrating in buried turbidites (Uchman 1999). The middle and

exichnial elite layers are an equivalent of the transitional layer

in the recent pelagic sediments (Ekdale et al. 1984b).

The thickness of the mixed layer in the Recent deep-sea sed-

iments of the Atlantic and Pacific ranges from 3 to 8 cm, and

the transitional layer is 2035 cm thick (Ekdale & Berger

1978; Berger et al. 1979; Ekdale et al. 1984b). Taking into ac-

count compaction, the thickness of the spotty layer from

Uzgruò corresponds to these values.

Discussion and conclusions

The described and interpreted ichnofabrics indicate long,

changing in time colonization of the deep-sea floor after depo-

sition of each turbidite. A layer of oxygenated sediment of

Fig. 6. Models of ichnofabrics and tiering pattern. Left column contains a presumed comparison to turbidite models by D.A.V. Stow (1986;

T6-T8), D.J.W. Piper (1978; E1-E3) and A.H. Bouma (1962; TdTe).

changing thickness existed after each turbidite event. There is

no evidence of anaerobic or dysaerobic environment in the

shallow subsurface layer or on the sea-floor. The trace fossil

association is rather poor in diversity. This can be related to a

general oligotrophy and poor preservation potential. The latter

can be caused by the small number of turbiditic sandstone

beds; their deposition pre-requisite to scour and cast and,

hence, preserve pre-depositional burrows formed in the mixed

layer. The oligotrophy is probably indicated by a small num-

ber of true deposit-feeders, represented in most beds only by

Planolites and Phycosiphon incertum. Amount of benthic

food is not equal to the organic matter content, because some

of it is refractory.

There is no significant change of diversity or ichnofabric

across the K/T boundary beds. Above, Nereites irregularis oc-

curs for the first time in the studied section in a few single

beds, and ?Rotundusichnium zumayense in one bed (Fig. 5).

Nereites irregularis is very common in the Carpathian flysch

64 UCHMAN, BUBÍK and MIKULÁ

in the Upper Cretaceous-Paleogene units (e.g. Ksi¹¿kiewicz

1977 under Helminthoida labyrinthica) and Rotundusichni-

um zumayense is common in some Paleocene units (Uchman,

unpublished). Their occurrence in the Uzgruò section is rather

incidental than related to any event around the K/T boundary.

In any case, there is no evidence of any ecological catastrophe

that can be related to the K/T event. The producers of the dis-

cussed trace fossils are rather independent of ecosystems that

were influenced by the event.

Acknowledgments: Andreas Wetzel (Basel), Paolo Monaco

(Perugia) and Ján Soták (Banská Bystrica) are acknowledged

for helpful reviewers comments. The research has been sup-

ported by the Grant No. 205/00/0218 of the Grant Agency of

the Czech Republic. The paper is a part of the research pro-

gramme of the Institute of Geology, Academy of Sciences of

the Czech Republic (No. AV0Z30130516). A.U. was spon-

sored by the Jagiellonian University, Kraków, and the CEE-

PUS Academic Exchange Programme, which enabled his visit

to the Czech Republic.

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