GeolCarp_Vol65_No6_433

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, DECEMBER 2014, 65, 6, 433—450 doi: 10.1515/geoca-2015-0004

Introduction

The  Skole  Nappe  is  the  most  external  nappe  of  the  Eastern
Outer  Carpathians  in  their  Polish  segment  (Fig. 1A,B).  It
comprises  a  3.0—3.8 km  thick  series  of  the  Lower  Creta-
ceous—Neogene flysch sediments (Poprawa & Nemčok 1998).
The  Lower  Cretaceous  strata  are  represented  by  silty  and
clayey turbidites, classified to the Bełwin Mudstones (Hau-
terivian) and Spas Shales (Hauterivian—Albian). They contain
sandy  turbidite  intercalations  of  the  Kuźmina  Sandstones
(Fig. 2 – Koszarski & Ślączka 1973; Kotlarczyk 1978; Gucik
1987; Gucik et al. 1991; Gedl 1999). This series is interpreted
as deposits of post-rift thermal subsidence in the Skole Basin,
which  was  a  part  of  the  external  basins  of  the  Outer  Car-
pathian  domain  (Książkiewicz  1962;  Oszczypko  2004),
formed  along  the  European  margin  in  Late  Jurassic—Early
Cretaceous times (Oszczypko 2006).

The younger succession (Cenomanian in age) contains a

series  of  deep-water  hemipelagic  non-calcareous  shales  with
calcareous  (biogenic)  and  siliciclastic  turbidites.  These  have
been  determined  as  the  Barnasiówka  Radiolarian  Shale  For-
mation (BRSF  –  Bąk  et  al.  2001,  2007b,c  –  Fig. 2).  Bio-
genic-rich-turbidites  precede  the  laminated  organic-rich
shales  and  mudstones,  which  were  deposited  in  the  latest

Cenomanian  in  response  to  progressive  eustatic  sea-level
rise and expansion of the oxygen minimum zone in the Outer
Carpathian  basins  (Bąk  K.  2006,  2007a—c).  These  organic-
rich  facies  record  an  oceanic  anoxic  event  (OAE-2),  docu-
mented by carbon isotope data (Bąk K. 2007b). Such facies
also  occur  in  other  Outer  Carpathian  basins  in  the  same
stratigraphic position representing a Bonarelli-equivalent ho-
rizon (cf. Bąk K. 2007d; Bąk M. 2011).

The OAE-2 sediments are replaced in the Skole Nappe by

a ferro-manganese carbonate layer. This layer is a chronoho-
rizon in the Outer Carpathian sediments corresponding to the
uppermost Cenomanian—lowermost Turonian (Bąk K. 2007d).
Its  occurrence  was  related  to  the  extremely  low  sedimenta-
tion rate in the basin and an increase in deep-water circula-
tion, causing basin oxygenation. This layer forms the base of
red  non-calcareous  shales  of  the  Turonian  age  (Variegated
shales  –  Fig. 2),  which  have  been  deposited  mostly  under
well-oxygenated  conditions  and  contain  numerous  biogenic
particles (Bąk K. 2006, 2007a—c; Okoński et al. 2014).

The above-mentioned Cenomanian succession, classified

as  the  BRSF,  reflects  the  diverse  environmental  conditions
in  the  Skole  Basin,  recorded  by  various  facies.  The  present
paper deals with the reconstruction of environmental condi-
tions  during  the  period  preceding  OAE-2,  recorded  as  the

Environmental conditions in a Carpathian deep sea basin

during the period preceding Oceanic Anoxic Event 2 – a case

study from the Skole Nappe

KRZYSZTOF BĄK

, MARTA BĄK

, ZBIGNIEW GÓRNY

and ANNA WOLSKA

Institute of Geography, Pedagogical University of Cracow, Podchorążych 2, 30-084 Kraków, Poland; kbak@up.krakow.pl

Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Mickiewicza 30,

30-059 Kraków, Poland; martabak@agh.edu.pl; a.wolska@gmail.com

Institute of Geological Sciences, Jagiellonian University, Oleandry 2a, 30-063 Kraków, Poland;

zbigniew.gorny@uj.edu.pl

(Manuscript received March 13, 2014; accepted in revised form October 7, 2014)

Abstract: Hemipelagic green clayey shales and thin muddy turbidites accumulated in a deep sea environment below the
CCD in the Skole Basin, a part of the Outer Carpathian realm, during the Middle Cenomanian. The hemipelagites
contain numerous radiolarians, associated with deep-water agglutinated foraminifera. These sediments accumulated
under mesotrophic conditions with limited oxygen concentration. Short-term periodic anoxia also occurred during that
time. Muddy turbidity currents caused deposition of siliciclastic and biogenic material, including calcareous foramini-
fers and numerous sponge spicules. The preservation and diversity of the spicules suggests that they originate from
disarticulation of moderately diversified sponge assemblages, which lived predominantly in the neritic-bathyal zone.
Analyses of radiolarian ecological groups and pellets reflect the water column properties during the sedimentation of
green shales. At that time, surface and also intermediate waters were oxygenated enough and sufficiently rich in nutri-
ents to enable plankton production. Numerous, uncompacted pellets with nearly pristine radiolarian skeletons inside
show that pelletization was the main factor of radiolarian flux into the deep basin floor. Partly dissolved skeletons
indicate that waters in the Skole Basin were undersaturated in relation to silica content. Oxygen content might have been
depleted in the deeper part of the water column causing periodic anoxic conditions which prevent rapid bacterial degra-
dation of the pellets during their fall to the sea floor.

Key words: Cenomanian Upper Cretaceous, Polish Outer Carpathians Skole Nappe, environment, Radiolaria,
Foraminifera, sponge spicules, pellets.

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green radiolarian shales with muddy turbidites. Here, we
document the micropaleontological record and discuss the
detected paleoenvironmental features of the Skole Basin.

Geological setting

The studied section is located in the inner part of the Skole

Nappe  (Poland),  within  one  of  the  tectonic  scales,  on  both
banks of the Trójca creek (Przemyśl Foothills), near Rybotycze
village, about 30 km south of Przemyśl (Fig. 1B—E). In this
area, the outcrops of the lower part of the BRSF are limited to
several sections, 0.5—4.5 m thick. Two of them (Fig. 1E) have
been studied and the results are presented in this paper. The
contact between the BRSF and the underlying Spas Shales is
tectonic  at  this  locality.  The  upper  and  middle  parts  of  the
BRSF  containing  the  organic-rich  sediments  of  OAE-2
(Bonarelli-equivalent  level  –  Fig. 2)  and  the  Turonian  red
non-calcareous  shales  overlying  the  BRSF  are  not  exposed
here. The BRSF is in tectonic contact with the Turonian sili-
ceous marls here.

Material and methods

A total of 14 samples were collected from the Trójca com-

posite  section,  with  an  average  sample  interval  of  30 cm
(Fig. 3). Microfossils were extracted by repeated heating and
drying of rock samples in a sodium carbonate solution. Resi-
dues were dried, washed through sieves with mesh in diame-
ters  of  63 µm.  Foraminiferal  and  radiolarian  specimens  and
sponge  spicules  were  manually  picked  from  the  fraction
0.063—1.5 mm. Microfacies and pellet analyses were carried
out in thin sections.

The microfossil slides and the residual rock samples are

housed in the Department of Geology and Geotourism, Fac-
ulty of Geology, Geosciences and Environmental Protection,

AGH University of Science and Technology (collection of
Marta Bąk).

Results

The studied section contains green non-calcareous clayey

shales,  a  few  black  clayey  shale  layers  (several  millimeters
thick) which are partly intercalated with green and grey, thin,
muddy turbidites (up to 5 cm thick), which contain siliciclas-
tic and calcareous (biogenic) particles. Among the siliciclastic
material, silt-sized quartz grains dominate, and are associated
with rare micas (Fig. 4J,K), glauconite (Fig. 4M,N) and Fe-Mn
oxides. Redeposited in turbidity currents biogenic particles in-
clude siliceous sponge spicules, calcareous benthic and plank-
tonic  foraminifers,  and  fragmented  otoliths  (Fig. 4C,D,F,G).
Biogenic  material  from  non-calcareous  hemipelagic  clayey
shale  consists  mainly  of  radiolarian  skeletons  (Fig. 3)  and
agglutinated foraminiferal tests. Fish teeth (Fig. 4A,B) were
also found sporadically.

Radiolarian assemblages

Radiolaria occur in most of the studied samples of the

Trójca section. They are frequent (Fig. 3) but poorly to mod-
erately  preserved.  Most  of  the  radiolarian  skeletons  are  re-
crystallized or replaced by pyrite and Fe-oxides, resulting in
destruction  of  external  and  internal  wall  structures.  With
such poor preservation, only 20 % of the skeletons were rec-
ognized  and  classified.  Identifiable  forms  were  found  in
samples Ryb-1, Ryb-3 and Ryb-9 (Fig. 5). As a general ten-
dency,  green  hemipelagic  shales  contain  higher  numbers  of
better  preserved  radiolarians,  while  in  dark-grey  and  black
shales,  the  radiolarians  are  usually  present  as  pyritized
moulds (Fig. 4I).

Eight radiolarian families, nine genera and twelve species

have been recognized in the studied material, according to

Fig. 4.  Organic  and  mineral  components  from  lower  part  of  the  Barnsiówka  Radiolarian  Shale  Formation  in  the  Trójca  section  (Skole
Nappe, Polish Outer Carpathians). A, B – fish teeth (A – Ryb-10), B – Ryb-1); C, D, F – otoliths (Ryb-1); E  – pyritized foraminiferal
tube (Ryb-2); G, H  – otoliths (Ryb-1); I  – Pyritized skeletons of radiolarians; J  – Muscovite grains (Ryb-1); K  – Biotite grain (Ryb-2);
L  – ?Magnetite grain (Ryb-1); M, N  – Glauconite grains (Ryb-6).

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radiolarian classification proposed by De Wever et al. (2001)
and adopted to Carpathian settings by Bąk M. (2011). In the
whole  section,  cryptothoracic  and  cryptocephalic  nasselari-
ans  are  the  main  components  of  radiolarian  assemblages.
The  species  from  the  family  Williriedellidae  prevail,  with
most  common  Holocryptocanium  barbui  Dumitrică  –
(Fig. 5F—I),  which  is  a  dominate  taxon  in  the  mid-  to  late
Cenomanian in Western Tethyan settings (Bąk M. 2011), as-
sociated with specimens of Holocryptocanium tuberculatum
Dumitrică  –  (Fig. 5J—L).  These  two  species  may  consist
even  70—100 %  of  the  whole  radiolarian  assemblage.  Other
nassellarian  species  belong  to  families  such  as:  Xitidae
(Xitus  spicularius  (Aliev)  –  (Fig. 5W),  Xitus  mclaughlini
(Pessagno)  –  Fig. 5S),  Eucyrtidiidae  (Stichomitra  stocki
(Campbell  &  Clark)  –  Fig. 5Y),  Stichomitra  communis
Squinabol  –  (Fig. 5T,X),  Pseudoeucyrtis  spinosa  (Squina-
bol)  –  Fig. 5M,N),  Syringocapsidae  (Squinabollum  fossile

(Squinabol)  –  Fig. 5O),  Pseudodictyomitridae  (Pseudodic-
tyomitra  pseudomacrocephala  (Squinabol)  –  Fig. 5U,V),
Archaeodictyomitridae  (Thanarla  veneta  (Squinabol)  –
Fig. 5P—R)  and,  Sethocapsidae  (Gongylothorax  siphonofer
Dumitrică – Fig. 5C,D).

Spumellarians are less common and less diversified. Spe-

cies recognized in the assemblages belong to two families:
Conocaryommidae (Praeconocaryomma lipmanae Pessagno
– Fig. 5A,B) and Dactyliosphaeridae (Dactyliosphaera
maxima (Pessagno) – Fig. 5E).

Foraminiferal assemblages

The studied section is dominated by deep-water aggluti-

nated foraminifera (DWAF – Table 1), moderately diversi-
fied. The Fischer alpha index ranges between 2.2 and 7.7
(calculated using the PAST software version 3.01; Hammer

Table 1: Foraminifera from the Middle Cenomanian sediments in the Trójca section, Skole Nappe, Outer Carpathians. Numbers of deter-
mined specimens are indicated.

b-14

b-12

b-11

b-10

b-8

b-7

b-6

b-5

b-4

b-3

b-2

b-1

Agglutinated

Ammodiscus cretaceous

(Reuss)

6 1

3 2 . . . 3 . . . .

Ammodiscus sp.

. . 2 . . 6

. . 2

. 1

Bulbobaculites problematicus

(Neagu)

17 1 . . 35 . 2 17 . . . 2

Caudammina ovula (Grzybowski)

1 2 . . 1 . . 1 1 . . .

Gerochammina stanislawi

Neagu

1 1 1 . 1 . 2 1 . . . 4

Gerochammina lenis

(Grzybowski)

11 2 6 . 9 . 14

11 1 2 . 2

Gerochammina obesa

Neagu

4 3 2 . 4 . 3 5 1 3 . .

Glomospira irregularis (Grzybowski)

Haplophragmoides sp.

. . . . . . . . . . . 1

Hyperammina sp.

1 1 . . . . . . 1 . . .

Psammosphaera sp.

. . 1 . 1

1 . . . . . .

Pseudonodosinella parvula

(Huss)

. . . . . . 2 . . . . .

Pseudonodosinella troyeri (Tappan)

15 6 4 . 29 . 50 13 . . . 1

Recurvoides contortus

Erland

. . . . 2 . . . . . . .

Recurvoides imperfectus

(Hanzlikova)

. . 2 . . . . . . . . .

Recurvoides sp.

Reophax sp.

. . . 1 . . . . . . . .

Repmanina charoides (Jones & Parker)

Rhabdammina sp.

. . . . . . . 1 1 1 . 2

Rhizammina sp.

2 2 1 1 4 . 3 6 . 3 . .

Rothina silesica

. 1 . . . . 2 . . . . .

Saccammina grzybowskii (Schubert)

1 . . 1 . . . . . . . .

Saccammina placenta

(Grzybowski)

2 . . . . 1 . 1 . . . 1

Thalm. meandertornata Neagu & Tocorjescu

Trochammina sp.

12 4 1 5 8 . 10

14 . . 5

Calcareous benthic

Berthelina baltica

Brotzen

. . . . . . . . . . 2 5

Berthelina cenomanica

(Brotzen)

. . . . . . . . . . 1 4

Globulina Prisca

Reuss

. . . . . . . . . . . 1

Pleurostomella sp.

. . . . . . . . . . 1 1

Valvulineria lenticularia

(Reuss)

. . . . . . . . . . 2 9

Planktonic

Hedbergella delrioensis

Casey

. . . . . . . . . . 85

Hedbergella planispira

(Tappan)

. . . . . . . . . . 6 3

Globigerinelloides ultramicra Subbotina

. . . . . . . . . . 7

Praeglobotruncana cf. delrioensis Plummer

. . . . . . . . . . . 2

Rotalipora (Th.) cf. appenninica

Renz

. . . . . . . . . . . 2

Rotalipora (Th.) sp.

. . . . . . . . . . . 2

Whiteinella archaeocretacea

Pessagno

. . . . . . . . . . 3 .

Whiteinella baltica Douglas & Rankin

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Fig. 7. Planktonic foraminifers from lower part of the Barnasiówka Radiolarian Shale Formation in the Trójca section (Skole Nappe, Polish
Outer Carpathians). A—C – Globigerinelloides ultramicra Subbotina (Ryb-1); D, E – Hedbergella delrioensis Carsey (Ryb-2); F, G – Ro-
talipora sp. (Ryb-1); H, I – Whiteinella baltica Douglas & Rankin (Ryb-2); J, K – Rotalipora (Th) cf. appenninica Renz (Ryb-1);
L, M – Praeglobotruncana cf. delrioensis (Plummer) (Ryb-1); N—P – Whiteinella archaeocretacea Pessagno (Ryb-2).

et al. 2001 – Fig. 3). Most of them represent flysch-type mi-
crofauna,  known  from  Cretaceous  and  Paleogene  bathyal—
abyssal  turbiditic  environments  (e.g.  Morgiel  &  Olszewska
1982;  Kuhnt  &  Kaminski  1989;  Kuhnt  et  al.  1990,  1992;
Bąk 2004; Kaminski & Gradstein 2005). Tubular specimens
belonging to a few genera (Rhizammina – Fig. 6A), Rhab-
dammina,  Psammosiphonella  –  (Fig. 6B)  and  Kalamop-
sis –  (Fig. 6C) are rare. The most frequent among them are
tiny rhizamminids (Table 1). The most abundant agglutinated
foraminifera, each with frequency exceeding 20 %, belong to
Bulbobaculites  problematicus  (Neagu)  –  (Fig. 6L,M),
Pseudonodosinella troyeri (Tappan) – (Fig. 6J,K) and gero-
chamminids  –  (Fig. 6U—X).  Recurvoides  –  (Fig. 6T)  and
Thalmannammina  –  (Fig. 6R,S)  are  also  abundant  through-
out the studied sections. However, their frequency is difficult
to measure, because many of them are not transparent and are
partly filled with pyrite. Some samples also contain numerous
completely pyritized large moulds of Recurvoides (Thalman-
nammina)-type  shapes.  Less  frequent  in  the  studied  sections
are  Ammodiscus  –  (Fig. 6D),  Saccammina  –  (Fig. 6H,I),

Caudammina  –  (Fig. 6E),  Repmanina  –  (Fig. 6F),  Glomo-
spira  –  (Fig. 6G),  Haplophragmoides  –  (Fig. 6N,O),  and
Spiroplectinella  –  (Fig. 6Y).  The  total  frequency  of  these
taxa  is  around  10 %  in  individual  samples.  Similarly,  small
trochamminids (Fig. 6P,Q) comprise nearly 10 % of the total
number of specimens in the samples.

Calcareous benthic foraminifera have been recorded in

only  two  samples  occurring  together  with  sponge  spicules
and  planktonic  foraminifera  (Table 1).  This  suggests  that
they constitute redeposited assemblages, transported by tur-
bidity currents. Only five species have been recognized that
belong  to  Valvulineria  lenticula  (Reuss),  Berthelina  ceno-
manica  (Brotzen),  Berthelina  baltica  Brotzen,  Globulina
prisca Reuss and Pleurostomella sp. All these taxa are well
known  from  the  Upper  Cretaceous  epicontinental  seas  that
surrounded  the  northern  basins  of  the  Western  Tethys  (e.g.
Gawor-Biedowa 1972; Heller 1975; Pożaryska & Wytwicka
1983; Peryt 1983; Hradecka 1993; Dubicka & Peryt 2012).

Numerous planktonic foraminifera are found in the topmost

part of the studied section (samples Ryb-1 and Ryb-2 – Fig. 3)

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with  numerous  forms  belonging  to  Globigerinelloides  ultra-
micra Subbotina – (Fig. 7A—C) and Hedbergella delrioensis
Carsey  –  (Fig. 7D,E).  Their  dimensions  do  not  exceed
150 µm  –  most  of  them  are  80—120 µm  in  diameter.  More-
over,  rare  and  small  (not  longer  than  200 µm)  specimens  of
Whiteinella  baltica  Douglas  &  Rankin  –  (Fig. 7H,I),
Whiteinella  archaeocretacea  Pessagno  –  (Fig. 7N—P),
Praeglobotruncana delrioensis Plummer – (Fig. 7L,M) and
Rotalipora (Th.) appenninica Renz – (Fig. 7J,K) have been
recorded from these sediments.

Sponge spicules

Loose sponge spicules have been found in six samples

(Fig. 3)  but  the  most  numerous  and  diversified  spicules  oc-
cur  in  a  turbidite  siltstone—claystone  layer  (Ryb-9).  All  of
them  belong  to  sponges  classified  as  Demospongiae
(Fig. 8G—Z) and Hexactinellidae (Fig. 8A—F). Practically all
the  spicules  are  broken  and  strongly  disintegrated.  The  spi-
cules represent choanosomal and dermal assemblages which
derived  from  various  sponge  species  (Fig. 8).  Spicules  of
Demospongiae are the most common. They consist of 64 %
of the whole assemblages and prevail over the spicules clas-
sified  to  Hexactinellidae  (21 %).  Various  types  of  oxea,
which may belong to both sponge groups, consist of 15 % of
the spicule assemblages.

Hexactinellidae spicules are represented only by hexac-

tines and pentactines (Fig. 8A—F). The hexactines are most
probably choanosomal spicules. Some fused spines present
in the studied material suggest that they were a part of solid
skeletons of Hexactinosa (Schrammen).

Demospongiae are represented mostly as loose and usually

strongly  articulated  tetraxial  and  monaxial  spicules.  The
most common spicules belong to the Lithistida. These are a
different  type  of  desmas  (Fig. 8G—O),  which  were  a  part  of
choanosomal skeletons, as well as different types of ectoso-
mal  phyllotriaenes  (Fig. 8U—V).  Tetraclone  desmas  and
phyllotriaenes  are  characteristic  of  lithistid  sponges  of  the
family  Theonellidae  Lendenfeld  (Pisera  &  Levi  2002a,b).
The  most  common  choanosomal  desmas  are  rhizoclones
(Fig. 8G—K).  Fossil  rhizoclones  are  usually  assigned  to  the
suborder Rhizomorina Zittel (Pisera 1997, 2002). The pres-
ence  of  various  types  of  triaenes  with  long  rhabdomes  may
indicate  the  presence  of  species  from  the  group  of  Astro-
phorida Sollas (Fig. 8R—T).

In addition to macroscleres, the microscleres are also

present in the material studied, represented by sterrasters
(Fig. 8Q). They are undoubtedly derived from species of the
family Geodiidae. A more precise assignment is not possi-
ble, because the shape and sculpture of singular forms have
no taxonomic value (Uriz 2002). Some of the oxeas found in
the material studied may also belong to geodiid sponges.

Pellets

Pellets are a common component of the green shales suc-

cession in the BRSF. Analysis of thin-sections shows that
pellets are one of the main constituents of silt and clay frac-
tions (Fig. 9). They vary in size and shape, which suggests

their  production  was  caused  by  both  micro-  and  mesozoo-
plankton. Most common are elliptical forms with the longer
axis  up  to  300 µm.  (Fig. 9A).  Semi-spherical  pellets  have
diameters  up  to  500 µm.  Longitudinal  forms  extend  along
the longer axis over 1 mm. Pellets contain large amounts of
undigested  or  partially  digested  material,  which  consists  of
complete  or  crushed  radiolarian  skeletons  (Fig. 9A—D),  as
well as planktonic foraminiferal tests (Fig. 9B). Some pellets
contain  homogenous  material  (Fig. 9A)  which  might  have
been  several  times  digested  by  different  consumers  during
their journeys through the water column.

Radiolarian biostratigraphy

There are no precise radiolarian age markers in the assem-

blage  investigated,  however,  the  radiolarian  species  occur-
ring  in  the  studied  section,  and  the  general  quantitative
composition  of  radiolarian  assemblages,  allow  us  to  make
some  observations  about  the  stratigraphy.  The  general  pic-
ture of nassellarian distribution in the Western Tethys is one
of high abundance in the middle and upper Cenomanian de-
posits below the onset of OAE-2 (Bąk M. 2011). This feature
of  radiolarian  assemblages  has  been  recognized  in  the  Um-
bria-Marche  and  the  Carpathian  basins.  In  the  Outer  Car-
pathian sediments, the most abundant are representatives of
the  family  Williriedellidae  (e.g.  Dumitrică  1975;  Bąk  M.
2000, 2004, 2011). The same trends have been observed here
in the sediments of the Skole Nappe.

The co-occurrence of two abundant radiolarian species –

Holocryptocanium  barbui  Dumitrică  and  H.  tuberculatum
Dumitrică  with  the  presence  of  Gongylothorax  siphonofer
Dumitrică indicate a middle to late Cenomanian age (Fig. 3),
based on correlation with the H. barbui—H. tuberculatum ra-
diolarian assemblage reported by Dumitrică (1975) from the
Romanian Carpathians and with comparison to previous data
obtained from the Polish Outer Carpathians and the Pieniny
Klippen  Belt  (Bąk  M.  1993a,b,  1996a,b,  1999,  2000,  2004;
Bąk M. & Bąk K. 1999).

On the other side, the studied sediments do not contain

radiolarian  species  such  as  Alievium  superbum  (Squinabol),
Crucella  cachensis  Pessagno,  Praeconocaryomma  universa
Pessagno,  Dictyomitra  napaensis  Pessagno,  Cavaspongia
antelopensis Pessagno, Patellula ecliptica O’Dogherty and P.
andrusovi  Ožvoldová,  which  are  common  in  the  uppermost
Cenomanian of the Outer and Inner Carpathian sections (e.g.
Górka  1995;  Bąk  M.  1996a,b,  2000,  2004,  2011;  Bąk  K.  &
Bąk  M.  2013).  Fortunately,  Cenomanian  species  as  Tanarla
veneta  (Squinabol)  and  Xitus  mclaughlini  (Pessagno),  which
finally  became  extinct  at  the  top  of  the  uppermost  Cenoma-
nian organic-rich facies of OAE-2, are present here (Fig. 3).

To refine the age assignment, an important observation is

that  these  sediments  lack  a  very  characteristic  radiolarian
zonal  marker  –  Hemicryptocapsa  prepolyhedra  Dumitrică
–  which  commonly  occurs  in  the  Carpathians  (Bąk  M.
1996b, 2000, 2004, 2011). The first appearance of this spe-
cies defines the lower boundary of the Hemicryptocapsa pre-
polyhedra Interval Radiolarian Zone in the Western Tethyan
sediments (Bąk M. 1999, 2011). It has been dated in the Polish

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Outer Carpathians to 1.0 Ma before the onset of OAE-2 (Bąk
M. 2011). The Middle/Upper Cenomanian boundary lies
within this radiolarian zone (Bąk M. 2011).

Another important species for stratigraphy is Stichomitra

stocki (Campbell & Clark), the first appearance of which is
known in the Carpathian basins earlier than H. prepolyhedra
but after the Mid-Cenomanian Event (MCE sensu Jenkyns et
al. 1994; Jarvis et al. 2006 – see discussion in Bąk M. 2011).

To summarize, all the presented data indicate that sedi-

mentation of the studied sediments began during the middle
Cenomanian (after the Mid-Cenomanian Event) and finished
earlier than 1.0 Ma before the onset of Oceanic Anoxic
Event 2, namely near the middle—upper Cenomanian bound-
ary taking into account the chronostratigraphy by Ogg &
Hinnov (2012).

Foraminiferal biostratigraphy

Planktonic foraminiferal assemblages are present only in

redeposited sediments of the topmost part of the studied sec-

tions.  The  Cenomanian  rotaliporid  index  species  are  absent
in  these  assemblages.  Relative  age  interpretation  can  be
made  on  the  basis  of  sporadic  forms  belonging  to  the
whiteinellids and rotaliporids (Fig. 3). The FOs of whiteinel-
lids  is  noted  from  the  Tethyan  realm  from  the  middle  Cen-
omanian  (Robaszynski  &  Caron  1995).  On  the  other  hand,
the  last  appearance  of  rotaliporids  was  diachronous  in  the
Tethys, related to the oxygen content in the water column. It
took place near the base of OAE-2, corresponding to the lat-
est Cenomanian.

The agglutinated assemblages from the whole studied suc-

cession  contain  numerous  specimens  of  Bulbobaculites
problematicus  (Neagu)  –  (Fig. 3),  an  index  species  in
benthic  zonations  of  the  Carpathian  basins  (e.g.  Geroch  &
Nowak 1984; Olszewska 1997; Bąk K. & Bąk M. 2013). Its
FO  was  precisely  documented  in  the  Pieniny  Klippen  Belt,
where it corresponds to the Rotalipora reicheli Zone (middle
Cenomanian) – (Bąk K. et al. 1995; Bąk K. 1998, 2000).

In conclusion, the datum events of foraminiferal species

show that the studied sediments represent the interval after
the first appearance of whiteinellids and B. problematicus

Fig. 9. Microfacies from black organic-rich mudstone layer of the Barnasiówka Radiolarian Shale Formation in the Trójca section (Skole
Nappe, Polish Outer Carpathians). A – Bioturbated organic-rich shale with different type of pellets. Elliptical forms (ep) prevail over lon-
gitudinal (lp). Small, rounded radiolarians (r), (probably williriedellids) are incorporated into the pellets or they are attached to pellet sur-
face; B – Flattened pellets with sharp boundaries in organic-rich shale. Pellets contain different organic particles such as fish bones (f),
agglutinated foraminifera (af) and radiolarians (r); C—D – Close up of pellet with microcrystal of quartz filled in moulds after complete (r)
and/or broken (rb) radiolarian skeletons. Most of the skeletons are spherical, resembling williriedellids.

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(Neagu) (Middle Cenomanian) and before the final extinc-
tion of the rotaliporids (uppermost Cenomanian). These data
confirm the radiolarian stratigraphy in the sense of determin-
ing the lower boundary of the studied succession. The upper
biostratigraphical limit is here less precise than that based on
the radiolarian biostratigraphy.

Environmental conditions at the floor

The lack of calcareous foraminifers in the hemipelagic lay-

ers indicates that the sedimentation of the deposits studied in
the  Skole  Basin  took  place  below  the  calcium  compensation
depth. The green claystone layers contain numerous radiolari-
ans with siliceous- and organic-walled benthic (agglutinated)
foraminifers typical of the Cretaceous bathyal and abyssal en-
vironments.  Planktonic  and  calcareous  benthic  foraminifera
are  redeposited  and  occur  only  in  clay-  and  silt-sized  turbid-
ites, where they are associated with siliceous sponge spicules.

The characteristic feature of these sediments is their green

colour (from pale-green in hemipelagic layers to dark-green
in  turbiditic  layers),  which  dominate  among  the  clayey  and
muddy shales, excluding a few very thin dark-grey and black
layers. The dominance of green colouration is characteristic
of  the  Upper  Albian—Cenomanian  deep-water  hemipelagic
sediments  in  all  the  Outer  Carpathian  tectonic  and  facies
zones (e.g. Książkiewicz 1962). These sediments significantly
differ in colour from the Lower Cretaceous hemipelagic strata
and  the  latest  Cenomanian  OAE-2  hemipelagic  sediments,
which  possess  dark-grey  and  black  colouration.  Because  of
the lack of chemical studies of these sediments, the interpre-
tation  of  this  fact  is  not  discussed  here.  However,  from  the
general point of view, using the published micropaleontolog-
ical  data  related  to  the  increase  in  diversity  of  deep-water
benthic  foraminiferal  assemblages  from  the  Aptian  to  Cen-
omanian in the Carpathian sediments (cf. Geroch & Nowak
1984;  Kuhnt  et  al.  1992;  Olszewska  &  Malata  2006),  the
change of sediment colour from black to green would be re-
lated to the increase in the oxygen content of deep water and
in the uppermost part of the sediment column in relation to
the pre-Cenomanian time period.

Such a conclusion also derives from features of the studied

benthic  microfossils.  The  DWAF  assemblages  are  low  to
moderately diversified. The Fisher alpha index, as a measure
of species diversity ranges from 2.2 to 7.7. These values of
diversity  are  comparable  to  the  values  of  the  Early  Creta-
ceous  assemblages  from  deep-water  oxygen-depleted  envi-
ronments  of  the  Tethyan  realm  (e.g.  Geroch  &  Koszarski
1988;  Decker  &  Rögl  1988;  Kuhnt  1995)  and  significantly
lower  than  the  values  in  Late  Cretaceous  (Turonian—Maas-
trichtian)  assemblages  from  oxygenated  deep  sea  basins  of
the same area (e.g. Kuhnt & Kaminski 1989; Bąk K. 2000;
Kaminski et al. 2008; Kaminski et al. 2011).

Environmental interpretation of the sea floor is also possi-

ble  using  paleoecological  interpretation  of  benthic  foramin-
ifera by means of morphogroup analysis. The morphogroup
concept refers to grouping of similar shapes and growth pat-
terns  of  foraminiferal  tests  using  the  idea  that  species  with
the  same  test  shape  have  the  same  preferred  life  habitats,

which can be related to feeding strategies, and that morpho-
groups distribution and abundance can reflect changes in se-
lected  environmental  parameters  (e.g.  Jones  &  Charnock
1985;  Nagy  1992;  Nagy  et  al.  1995;  Kaminski  et  al.  1995;
Peryt  et  al.  1997;  Preece  et  al.  1999;  Van  Den  Akker  et  al.
2000; Peryt et al. 2004; Bąk K. 2004; Kaminski & Gradstein
2005;  Kender  et  al.  2008a,b;  Cetean  et  al.  2011;  Murray  et
al. 2011; Mancin et al. 2013).

Fig. 10. Percentage content of foraminiferal genera in lower part of
the Barnasiówka Radiolarian Shale Formation in the Trójca section
(Skole Nappe, Polish Outer Carpathians). Tubular taxa have not been
included here due to their uncertain number, related to fragmentation
of the tests during fossilization and washing processes. Morphogroup
numbers (M2a to M4b) after Kaminski & Gradstein (2005).

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The assemblages studied are dominated by elongate subcy-

lindrical  and  elongate  tapered  forms  including  Pseudono-
dosinella, Gerochammina, and Bulbobaculites. They comprise
nearly 60 % of the total number of foraminiferal assemblages
(Fig. 10).  Using  the  definition  of  agglutinated  foraminiferal
morphogroups,  with  interpreted  life  habitat  and  feeding
strategy,  presented  by  Kaminski  &  Gradstein  (2005),  these
forms, representing morphogroups M4a and M4b, are inter-
preted as deep infauna living as active deposit feeders. The
deep infaunal forms are associated here with surficial epifau-
nal  taxa,  represented  by  rounded  trochospiral,  streptospiral,
and  planoconvex  trochospiral  forms  (morphogroup  M2b
sensu  Kaminski  &  Gradstein  2005)  including  Recurvoides,
Thalmannammina  and  Trochammina.  This  morphogroup
consists of nearly 30 % of the total number of foraminiferal
tests (Fig. 10). The tubular taxa (mostly tiny rhizamminids)
which are suspension feeders are rare in the sediments studied
(Table 1),  reaching  a  few  percent  in  total  numbers  of  fora-
minifers. Such a composition of the morphogroups points to
distinct  dominance  of  deep  infaunal  taxa,  however,  without
conspicuous domination by particular species.

As observed in modern deep-water environments (e.g. Joris-

sen  et  al.  1995;  Kaminski  et  al.  1995;  Gooday  &  Rathburn
1999; De Rijk et al. 2000; Gooday et al. 2000; Wollenburg
& Kuhnt 2000; Szarek et al. 2007; Murray et al. 2011), two
main factors control the structure of benthic foraminiferal as-
semblages: organic carbon flux to the sea floor, and the oxy-
gen concentration in the bottom waters and in the uppermost
part of the sediment. In deep sea basins, water depth is another
factor  affecting  the  benthic  foraminiferal  assemblages.  The
depth of the basin floor influences the reduction flux of or-
ganic matter from surface plankton production, which could
be several times lower if compared with marginal marine set-
tings (cf. Szarek et al. 2007; Murray et al. 2011). On the other
hand,  the  supply  of  organic  matter  can  be  occasionally  en-
hanced  in  deep  sea  environments  due  to  terrigenous  fluxes,
associated  with  turbidity  currents.  Both  sources  of  organic
matter on the deep sea floor of the Skole Basin are interpreted
here, based on observation of microfacies (Fig. 9). From one
side,  green  clayey  shales  contain  numerous  pellets,  which
could be one of the main sources of organic matter to the sea
floor.  At  the  same  time,  numerous  flakes  of  organic  matter
are dispersed in muddy and silty turbiditic material (Fig. 9D).

The occurrence of relatively numerous flakes of organic

matter  in  the  green  clayey  shales  points  to  another  conclu-
sion, related to the oxygen content at the sediment—water in-
terface. The low oxygen concentration that is here suggested
for  the  studied  sediments,  could  favour  the  preservation  of
organic matter. From another point of view, dysoxic condi-
tions could be the main factor which limited the number of
epifaunal forms within the foraminiferal assemblages thereby
providing an opportunity for exploitation of the sea floor by
deep infauna, composed of low-oxygen tolerant taxa. Similar
conditions occur recently in abyssal zones of the Sulu Sea, a
semi-enclosed,  meso-to-oligotrophic  basin  in  the  western
equatorial Pacic, characterized by warm (ca. 10 °C) and oxy-
gen-depleted  (dysoxic;  <1 ml/l O

) deep-waters (Szarek et

al. 2007). In such conditions, foraminiferal assemblages con-
sisted mainly of shallow infaunal agglutinated forms, with

dominant  species  belonging  to  Lagenammina  difugiformis
(Brady), Ammoscalaria tenuimargo (Brady), Ammobaculites
paradoxus  Clark  and  various  Reophax  species.  A  compari-
son  of  the  morphogroup  composition  from  the  sediments
studied (characterized by dominance of deep infaunal forms)
with  the  TROX  ecological  model  by  Jorissen  et  al.  (1995)
explaining  benthic  foraminiferal  microhabitat  preferences,
also suggests a mesotrophic environment with limited oxygen
concentration for the Skole Basin floor during the prevailing
time periods of the middle Cenomanian. Nevertheless, short-
termed  periodic  anoxia  also  occurred  during  that  time,  as
documented by the occurrence of several very thin (2—5 mm)
black organic-rich layers.

Concluding, the dysaerobic bottom water conditions with

a moderate rate of organic matter flux from surface plankton
production and from turbidity currents with short-term an-
oxia characterized the deepest part of the Skole Basin during
the Middle Cenomanian.

Source area of sponge spicules from turbidite

layers

Turbidite layers contain a rich assemblage of siliceous

sponge  spicules.  The  assemblage  indicates  that  the  sponge
fauna  was  dominated  by  lithistid  demosponges  represented
by  Theonellidae  and  rhizomorinids.  Demosponges  from
family Geodiidae (Astrophorida) are also common. Hexacti-
nellidae  spicules  are  rare;  only  spicules  derived  from  order
Hexactinosa were recognized.

Bathymetric reconstructions for the studied sediments,

based on sponges are imprecise because these organisms of-
ten have very wide bathymetric ranges. However, the studied
assemblage is neither characteristic of very shallow nor very
deep marine environments. Modern lithistid sponges prefer a
deep  water  environment  from  one  hundred  to  several  hun-
dred  meters  depth  (Vacelet  1988;  Maldonado  1992;  Pisera
1997). Species from the family Geodiidae are known to have
wide  bathymetric  ranges  from  intertidal  to  bathyal  depths,
however,  they  are  more  specific  to  the  bathyal  zone  (Uriz
2002).  In  contrast,  theonellids  might  occur  mainly  at  shal-
low-water  depths  (Vacelet  1988).  The  presence  of  hexacti-
nellid  sponges  indicate  deep  environments  (Reid  1968)
excluding the submarine caves and fjords where they could
thrive at shallower depths (Vacelet 1988; Vacelet et al. 1994).
Among  hexactinellids,  species  from  the  order  Hexactinosa,
from  which  spicules  are  present  in  the  turbiditic  layers,  are
known to have settled environments deeper than 100 meters,
preferring  a  stable  environment  with  low  water  turbulence
(Mehl 1992).

Most of the lithistids and species of the Hexactinosa group

formed rigid skeletons, which could be attached to a hard
substrate. However, some species from the family Geodi-
idae, could have been adapted to a soft substrate (Uriz 2002;
Pisera 2004).

The presented data show that the spicules from the studied

material came from disarticulation of moderately diversified
solid sponge assemblages, which lived mainly in the deeper
parts of the shelves and on the upper parts of the slopes (ner-

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itic—bathyal zones), generally, below the storm wave base
(100 m or more). However, some of them could have origi-
nated from shallow shelves. The poor state of preservation of
spicules and well sorted spicule material may indicate that
spicules were transported over a long distance, including not
only transport by turbidity currents, but also by bottom cur-
rents on the shelves.

Water properties based on radiolarians and pellets

analyses

The majority of radiolarians are indicators of nutrient-rich

surface waters, such as in upwelling areas (Casey 1977; De
Wever et al. 2001). Present day studies in the Equatorial Pa-
cific  region  show  that  total  radiolarian  standing  stocks  in-
crease in such regions, responding to a general increases in
nutrients,  chlorophyll-a,  and  diatom  occurrence  during  La
Niña periods (Yamashita et al. 2002). Studies of the equato-
rial region, Southern Ocean, and the Namibia upwelling re-
gime show that radiolarians are most abundant in the upper
50—150 m  of  the  water  column  within  the  mixed  layer,  but
also  occur  below  it  (Abelmann  &  Gowing  1996,  1997).  In-
tense  radiolarian  flux  subsequently  results  in  the  accumula-
tion  of  a  large  number  of  radiolarian  individuals  in
sediments,  which  enhances  the  organic  carbon  flux  and  in-
creases primary productivity (Wang et al. 2000; Chen et al.
2003).  The  lowest  abundances  occur  in  nutrient-poor  sub-
tropical  regions  and  close  to  the  Subtropical  Front  (Abel-
mann & Gowing 1996).

Although radiolarian assemblages in the studied deposits

are  strongly  influenced  by  sedimentary  and  diagenetic  pro-
cesses, some features of the living assemblages can be recog-
nized.  The  numerous  radiolarians  represent  two  ecological
supergroups,  “B”  and  “E”,  distinguished  for  the  Cenoma-
nian—Turonian  assemblages  in  the  Tethyan  realm  (Bąk  M.
2011).  Forms  assembled  in  supergroup  “B”,  which  are  the
most common, have been interpreted as living in the deeper
part of the water column. Among supergroup “B”, most spe-
cies belong to group “B3”, whose dominant taxon – Holo-
cryptocanium barbui  Dumitrică – was widely tolerant with
respect  to  nutrient  surplus  in  the  water  column,  and  could
live in the wide vertical range below the mixed surface layer.
Group “B2”, which is represented in the studied material by
Squinabollum fossile (Squinabol), assembled specimens that
lived  in  waters  with  an  increasing  amount  of  phosphorus,
characteristic  for  the  eutrophic  zone.  Other  species  (Xitus
mclaughlini  (Pessagno)  and  Thanarla  veneta  (Squinabol))
belong to the “B5” group, which comprises forms that lived
in oxygen depleted waters and/or close above the oxic/anoxic
interface.  The  “B6”  group  is  represented  here  by  Pseudo-
eucyrtis  spinosa  (Squinabol),  which  lived  below  the  mixed
layer in waters moderately rich in nutrients.

Radiolarian assemblages that belong to supergroup “E”

are  interpreted  as  an  association  living  in  surface  waters,
mostly in the mixed layer (Bąk M. 2011). Among these radio-
larian sets, Xitus spicularius  (Aliev), Stichomitra communis
Squinabol,  and  Holocryptocanium  tuberculatum  Dumitrică
(“E3”  group),  and  Pseudodictyomitra  pseudomacrocephala

(Squinabol) (“E4” group) were surface dwellers that lived in
very shallow waters, and possibly tolerated a wide range of
water temperatures and salinity. Species from group “E3”
(Xitus spicularius (Aliev), Stichomitra communis Squinabol,
Holocryptocanium tuberculatum Dumitrică) have been inter-
preted as living also in the surface mixed layer but with in-
creasing phosphorus content. They were more opportunistic
and more widely vertically distributed. These species pos-
sess skeleton shapes predestinated to a bacterivorous type of
feeding (Bąk M. 2011).

The radiolarian ecological groups presented above show

that  the  surface  and  intermediate  waters  were  well  enough
oxygenated and sufficiently rich in nutrients to enable plank-
ton  production,  however,  oxygen  content  might  have  been
depleted  in  the  deeper  water  column  or  waters  may  have
been  seasonally  anoxic  as  indicated  by  the  occurrence  of
species from group “B5”.

Another indicator of water properties might be pellets,

which occur in hemipelagic clayey shales. These pellets are
homogenous  inside  or  contain  undigested  or  secondary  di-
gested  radiolarian  skeletons  and  foraminiferal  tests.  The ra-
diolarian skeletons are present in various types of pellets in
different  positions.  Usually  small,  rounded  skeletons  (most
probably  forms  belonging  to  williriedellids)  are  located  in-
side pellets or they are attached to the pellets periphery. This
fact suggests that pellets are the main conveyor of radiolarian
skeletons from the water column into sea-floor sediment. In
this way, pellets could be the main source of siliceous skele-
ton flux from the upper water column, as previously suggested
for the Carpathian deposits (Bąk M. 2011). Thus sediments
enriched in siliceous skeletons might be a function not only
of  the  proliferation  of  silica-secreting  biota,  but  also  their
consumption  by  larger  zooplankton.  Pellets  came  from  un-
known  primary  radiolarian  consumers.  Where  such  pellets
are large (Fig. 9A,C), they might have been derived from the
epipelagic zone and have sunk fast enough to avoid re-pro-
cessing  by  other  zooplankton.  Crushed  and  strongly  pro-
cessed skeletons occurring inside pellets might be examples
of re-ingestion by other zooplankton (Fig. 9D).

The studied pellets do not possess an organic membrane,

which  usually  surrounds  their  modern  counterparts.  In  this
study,  boundaries  with  surrounded  material  represent  two
types:  sharp  or  with  boundaries  weakly  visible.  Sharp
boundaries  suggest  that  pellets  might  have  retained  a  chiti-
nous  membrane  much  longer,  during  sinking,  than  pellets
whose outer boundaries are difficult to determine (Fig. 9A).

Analogous pellets, most probably deriving from copepod

grazing activity, are the main components of the green clay-
stones from the younger part of the BRSF (not studied here),
and green claystones from the Variegated Shale in the Silesian
and Subsilesian units of the Outer Carpathians (Bąk M. 2011).

One of the important factors for the contribution of pellets

to transport of particles is the mineralization of pellet material
during  sinking.  Non-mineralized  pellets  can  be  rapidly  de-
graded  by  bacterial  activity  on  the  sea  floor  (Hansen  et  al.
1996)  and  destroyed.  This  process  is  much  faster  at  higher
water temperatures and during higher rates of biogenic pellet
accumulation (Hansen et al. 1996). The degradation processes
lower the particulate organic carbon value without changing

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the biogenic silica flux (Dagg et al. 2003), however, released
skeletons  are  more  sensitive  to  dissolution  in  water  under
saturated with respect to silica. Pellets in the material inves-
tigated  possess  their  original  intact  and  not  compacted
shapes. In the case of such pellets, the degradation processes
must  be  arrested  before  final  bacterial  decomposition.  Such
preservation of pellets would suggest the presence of water-
column  anoxia  which  prevented  secondary  digesting  and
rapid disintegration by microbial and faunal activity.

Water saturation with respect to silica

The radiolarian content and preservation of skeletons may

approach  the  saturation  of  sea  water  with  respect  to  silica.
Similar  processes  are  observed  in  modern  counterparts,
which are sensitive to dissolution during settling through the
water column and within the bottom sediment (Takahashi &
Honjo 1983) because modern sea water is Si-under saturated
from the surface layer to the bottom. In such conditions, the
pelletization  process  is  very  important  for  the  radiolarian
flux and their further preservation within the sediment.

The radiolarians in the hemipelagites of the middle Cen-

omanian  sediments  of  the  Skole  Unit  are  characterized  by
the dominance of thick-walled, siliceous skeletons, resistant
to dissolution and skeletons replaced by pyrite or ferrous ox-
ides.  Most  of  the  radiolarian  skeletons  that  occur  in  the
whole  studied  succession  are  partly  dissolved.  Moreover,  a
part of the planktonic foraminifers together with radiolarians
have been transported in pellets, as observed in thin sections
of the sediment. Complete, undigested pellets contain better
preserved  skeletons,  while  crushed  and  partly  dissolved
radiolarian skeletons are visible in thin sections as surrounded
by the remnants of disintegrated remains of the pellet. This
suggests  that  more  complete  and  better  preserved  skeletons
were protected by fecal mass, while partly dissolved skeletons
have been temporary exposed to aggressive waters undersatu-
rated in respect to silica. This means that the number of radio-
larian individuals is a function of production vs. resistance in
the upper part of the Si-undersaturated water column.

Conclusions

Hemipelagic green clayey shales with associated thin

muddy  and  clayey  turbidites,  such  as  the  lower  part  of  the
Barnasiówka Radiolarian Shale Formation, were accumulated
in a deep sea environment, below the CCD. The radiolarians
and foraminifers from these sediments show that their sedi-
mentation  took  place  during  the  middle  Cenomanian  and
continued at least until the middle—late Cenomanian bound-
ary, namely near 1.0 Ma before the onset of OAE-2. Conse-
quently,  these  sediments  reflect  a  record  of  environmental
conditions in the Skole Basin during the period between two
oceanic  anoxic  events,  the  Mid-Cenomanian  and  the  latest
Cenomanian (OAE-2).

The taxonomic composition and low to moderate diversity

of benthic foraminifers (deep-water agglutinated foramin-
ifera) from hemipelagic shales suggests mesotrophic condi-

tions with limited oxygen concentration for the Skole Basin
floor  during  the  prevailing  time  periods  of  the  middle  Cen-
omanian.  Additionally,  short-term  periodic  anoxia  also  oc-
curred during that time, as documented by the occurrence of
several  very  thin  black  organic-rich  layers.  Comparison  of
the  DWAF  assemblages,  dominated  by  infaunal  taxa,  with
their  modern  counterparts,  and  using  the  TROX  ecological
model, enabled us to assess the rate of organic matter fluxes
from  surface  plankton  production  as  moderate,  but  the  flux
was periodically enhanced by turbidity currents.

Muddy turbidity currents transported to the seafloor silici-

clastic and biogenic material, including calcareous foramini-
fers and numerous sponge spicules. The composition of the
spicules, dominated by spicules of demosponges (lithistids),
suggests that they originated from the disarticulation of
moderately diversified solid sponge assemblages, which
lived mainly in the neritic—bathyal zone, but, some of them
could have come from shallower parts of the shelves. Their
poor state of preservation and high rate of disintegration in-
dicate that spicules were transported over a long distance, in-
cluding transport by bottom currents on the shelves.

Analysis of radiolarian assemblages in the studied sedi-

ments, in comparison to ecological groups distinguished for
the Cenomanian—Turonian taxa in the Tethyan realm (Bąk
M. 2011) allowed us to interpret the conditions in the water
column. The investigated taxa live in a surface mixed layer
with increasing phosphorus content and also in intermediate
waters, well-enough oxygenated and sufficiently rich in nu-
trients to enable plankton production. However, the oxygen
content might have been depleted in deeper parts of the wa-
ter column by periodic anoxia, as indicated by the occur-
rence of species that lived in oxygen depleted waters and/or
close above the oxic/anoxic interface.

The studied hemipelagic green shales contain numerous

undigested radiolarian skeletons inside pellets. This fact sug-
gests that pellets are the main conveyor of radiolarian skele-
tons from the water column into the sea-floor sediment. The
occurrence of numerous uncompacted pellets with well-pre-
served radiolarians inside them also indicates water anoxia
which impeded the rapid bacterial degradation of the pellets.

Acknowledgments: This paper was supported by Funds of
the Pedagogical University of Kraków and AGH University of
Science and Technology awarded to K. Bąk (DS-UP-WGB-4n)
and to M. Bąk (DS-AGH WGGiOŚ-KGOiG No.11.11.140.173).
Michael A. Kaminski (King Fahd University of Petroleum and
Minerals, Saudi Arabia), Špela Goričan (Slovenian Academy
of Science and Arts) and Claudia Cetean (Babe -Bolyai Uni-
versity, Romania) are thanked for comments on the manu-
script and improving the English.

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