GeolCarp_Vol60_No3_213

www.geologicacarpathica.sk

GEOLOGICA CARPATHICA, JUNE 2009, 60, 3, 213—232 doi: 10.2478/v10096-009-0015-2

The Brodno section – a potential regional stratotype of the

Jurassic/Cretaceous boundary (Western Carpathians)

JOZEF MICHALÍK

, DANIELA REHÁKOVÁ

, EVA HALÁSOVÁ

and OTÍLIA LINTNEROVÁ

Geological Institute of the Slovak Academy of Sciences, Dúbravská cesta 9, P.O.Box 106, 840 05 Bratislava 45, Slovak Republic;

geolmich@savba.sk

Department of Geology and Paleontology, Faculty of Natural Sciences, Comenius University, Mlynská dolina G-1, 842 15 Bratislava,

Slovak Republic; rehakova@fns.uniba.sk; halasova@fns.uniba.sk

Department of Economic Geology, Faculty of Natural Sciences, Comenius University, Mlynská dolina G-1, 842 15 Bratislava,

Slovak Republic; lintnerova@fns.uniba.sk

(Manuscript received May 7, 2008; accepted in revised form October 23, 2008)

Abstract: Compared to coeval successions from the Carpathians, the continuous Jurassic-Cretaceous (J/K) pelagic
limestone succession of the Brodno section offers the best possibility to document the J/K passage in a wide area. This
section comprises a complete calpionellid, and nannofossil stratigraphic record, that supports the older paleomagnetic
data. Moreover, the sequence stratigraphy and stable isotope (

C) data gave important results, too, enabling

comparison with known key sections from the Mediterranean Tethys area.

Key words: J/K boundary, Western Carpathians, regional stratotype, stable isotopes, biostratigraphy, microfossils,
pelagic carbonates.

Geological context of the Brodno section: an overview

The  Brodno  section  is  situated  in  an  abandoned  quarry  on
the  eastern  side  of  the  narrow  straits  of  the  Kysuca  River
Valley  north  of  the  town  of  Žilina  (known  as  the  “Kysuca
Gate”, Fig. 1). It yields a record of hemipelagic marine sedi-
mentation  in  a  marginal  zone  (the  Pieniny  Klippen  Belt)  of
the  Outer  Western  Carpathians.  The  lithology,  fossil  record
(including  ammonites  and  aptychi)  and  stratigraphy  were
studied  by  Andrusov  (1938,  1950,  1959),  Scheibner  (1961,
1962,  1967),  Borza  (1969),  Scheibner  &  Scheibnerová
(1969),  and  Samuel  et  al.  (1988).  A more  detailed  descrip-
tion of the Upper Jurassic and Lower Cretaceous litho- and
biostratigraphy was provided by Michalík et al. (1990), Re-
háková & Michalík (1992), and Vašíček et al. (1992). Houša
et  al.  (1996)  introduced  the  magnetostratigraphy  of  the  Ju-
rassic/Cretaceous  (J/K)  boundary  beds  correlated  with  the
microbiostratigraphic data.

This paper discusses the results of an integrated biostrati-

graphic study using three microplankton groups (calpionel-
lids, calcareous dinoflagellates and nannofossils), as well as
stable isotope data (

C) in the Brodno section, which

is proposed here as the candidate for a West Carpathian re-
gional  J/K  boundary  stratotype.  The  distribution  of  the
stratigraphically  important  planktonic  organisms  revealed
several coeval calpionellid and nannofossil bioevents record-
ed  in  the  pelagic  carbonate  sequence  of  the  Jurassic/Creta-
ceous  boundary  age.  The  stable  isotope  data  underline
environmental changes during the interval studied.

According to the International Commission on Jurassic

Stratigraphy, it is necessary to search for complete sections,
which can provide continuous records of both sedimentation
and biotic events across stage boundaries. Although the

Brodno section lacks ammonite record, it is presented here
as a potential candidate considering its continuously well ex-
posed and biostratigraphically properly documented succes-
sion, at least for the West Carpathian region.

Material and methods

The Jurassic/Cretaceous boundary succession was studied

using an integrated sequence-, bio- and isotope stratigraphy
approach from the detailed rock section sampled. A quantita-
tive microfacies analysis was carried in thin sections for the
sequence  stratigraphic  pattern  of  these  pelagic  limestones
(see Reháková 2000a; Michalík 2007). The calpionellids and
calcareous dinoflagellates were studied under a light micro-
scope  LEICA  DM  2500-P  in  96  thin  sections.  They  were
documented  by  a  LEICA  DFC  290  HD  camera.  Thin  sec-
tions are deposited in the Geological Institute of the SAS in
Bratislava.  Changes  in  the  distribution  of  these  organism
remnants  were  studied  aiming  at  their  correlation  with  the
nannoplankton associations.

The calcareous nannofossils were analysed in 40 smear

slides prepared from all the lithologies under a light micro-
scope at 1250

× magnification. The abundance was deter-

mined by counting all the specimens in at least 200 fields of
view in each sample. The preservation of the fossil material
could be characterized by a moderate to heavy dissolution
etching. The content of increased coccolite remnants in beds
C13 and C23B is interpreted as due to diagenetic alteration
of the calcareous nannofossils composition.

Carbon and oxygen isotope analyses were carried out on the

bulk carbonate fraction in 52 samples from the J/K boundary
interval in the Brodno section using a Finigan MAT-2 mass

214

MICHALÍK, REHÁKOVÁ, HALÁSOVÁ and LINTNEROVÁ

spectrometer. The values are reported in terms of Vienna-PDB
(V-PDB) in the standard

δ notation in ‰, with a precision of

0.01 ‰. The total organic (TOC) and inorganic carbonate
content (TIC) was measured on C-MAT 550. The paleotem-
perature calculation from calcite oxygen isotope (Epstein et al.
1953; Craig 1965; or Anderson & Arthur 1983) is as follows:

paleotemperature (°C) = 16.0—4.14 (

—

) + 0.13 (

—

)

. In

this equation, the calcite oxygen isotope (

) composition

with respect to V-PDB is directly related to the oxygen iso-
tope composition of seawater (

) from which the calcite has

precipitated with respect to V-SMOW. The value of —1.0 ‰
V-SMOW is characteristic of the post-Jurassic ice-free world
(Gröcke et al. 2003). The TIC values were recalculated to the
CaCO

content in order to assess the carbonate content of the

samples selected for isotope analysis. A lot of the geochemical
data have been presented previously (Michalík et al. 1995).

Results

Microbiostratigraphical remarks and reference scales

1. Calcareous dinoflagellate cysts. The distribution, abun-

dance and diversity of calcareous dinoflagellate cysts is im-
portant both from the stratigraphical and paleoenvironmental
points of view. Calcareous dinoflagellate cyst zonation sensu
Reháková (2000b) was followed (Fig. 11). These biomarkers
predominate in Lower Tithonian associations and are repre-
sented by: Cadosina parvula Nagy, Stomiosphaera molucca-
na  Wanner  –  (Fig. 3.1),  Parastomiosphaera  malmica
(Borza)  –  (Fig. 3.2),  Colomisphaera  pulla  (Borza)  –
(Fig. 3.3),  Colomisphaera  carpathica  (Borza)  –  (Fig. 3.4),
Colomisphaera  nagyi  (Borza)  –  (Fig. 3.5),  Carpistomio-
sphaera tithonica Nowak, Cadosina semiradiata semiradia-
ta  Wanner  –  (Fig. 3.6;  Fig. 4.3),  Cadosina  semiradiata

Fig. 1. Localization of the Brodno section in the Kysuca Gate (circle), north of Žilina.

Fig. 2. General view of the Brodno quarry. The sequence is over-
turned, the left upper side consists of the Czorsztyn Limestone For-
mation, and the right side is formed by the Pieniny Limestone
Formation. Lower right: a detailed view of the interval of the Juras-
sic/Cretaceous boundary with the Brodno Sub-magnetochron.

219

THE BRODNO SECTION – A POTENTIAL REGIONAL STRATOTYPE (WESTERN CARPATHIANS)

pathians by Borza (1984), Reháková (1995), and Reháková &
Michalík (1997a). These references are also considered in
this paper (Fig. 11).

3. Calcareous nannofossils form relatively low diversified

associations.  Eighteen  nannofossil  species  have  been  deter-
mined  in  our  sample  collection.  The  coccolitophorids  are
represented by Watznaueriaceae including Watznaueria bar-
nesae (Black) Perch-Nielsen (Fig. 6.7), Watznaueria britan-
nica (Stradner) Reinhardt (Fig. 6.6), Watznaueria manivitae
Bukry  (Fig. 6.8),  Watznaueria  ovata  Bukry,  Cycla-
gelosphaera  margerelii  Noël  (Fig. 6.9),  and  Cycla-
gelosphaera

deflandrei

(Manivit)

Roth

(Fig. 6.10).

Zeugrhabdotus embergeri (Noël) Perch-Nielsen (Fig. 6.2) is
another  frequent  constituent.  Dissolution-resistant  coccolith
taxa Helenea chiastia Worsley (Fig. 6.5), Cruciellipsis cuvil-
lieri (Manivit) Thierstein (Fig. 6.4) dominate among others,
such  as  Zeugrhabdotus  erectus  (Deflandre)  Reinhardt
(Fig. 6.1), Diazomatholithus lehmannii Noël (Fig. 6.11), and
Discorhabdus ignotus (Górka) Perch-Nielsen (Fig. 6.3). The
last  group  is  indicative  of  eutrophic  environments,  and  oc-
curs less frequently. Nannoliths represented by Conusphaera
mexicana Trejo subsp. mexicana Bralower et al. (Fig. 6.12—
14),  Conusphaera  mexicana  Trejo  subsp.  minor  Bown  &
Cooper  (Fig. 6.15),  Polycostella  beckmannii  Thierstein
(Fig. 6.25—28),  Assipetra  spp.,  Hexalithus  noeliae  Loeblich
&  Tappan  (Fig. 6.29),  Litraphidites  carniolensis  Deflandre,
Nannoconus  infans  Bralower  (Fig. 6.23—24),  Nannoconus
wintereri  Bralower  &  Thierstein  in  Bralower  et  al.
(Fig. 6.21—22),  Nannoconus  steinmanni  minor  Deres  &
Achéritéquy  (Fig. 6.18),  Nannoconus  globulus  Brönnimann
ssp.  minor  Bralower  in  Bralower  et  al.  (Fig. 6.16—17),  and
Nannoconus  kamptneri  minor  Bralower  in  Bralower  et  al.
(Fig. 6.19—20)  are  abundant.  Abundance  fluctuation  of  dis-
solution-resistant nannoliths (Conusphaera spp., Polycostel-
la  spp.,  and  Nannoconus  spp.)  and  that  of  coccoliths
(Cyclagelosphaera  margerelii,  Watznaueria  barnesae,  and
Watznaueria  manivitae)  has  been  detected  by  quantitative
analysis.  The  nannofossil  zonations  of  Bralower  et  al.
(1989), and Tavera et al. (1994), was used and slightly modi-
fied (Fig. 11).

Sequence stratigraphy and biostratigraphy

The succession starts with red nodular marly limestones of

the  “Ammonitico  Rosso”  lithofacies,  known  as  the  Czorsz-
tyn Limestone Formation (Birkenmajer 1977). According to
an  analysis  of  the  microfacies  distribution  (see  Michalík
2007), several cyclical repetitions of the microfacies parame-
ters were recognized in part of the sequence appearing on the
left side of the quarry wall (Figs. 2, 7). These cycles are 0.5
to  1.6 m  thick.  Considering  an  average  sedimentary  rate  of
2 mm/kyr, which results from microbiostratigraphical analy-
sis of the formation, their duration should be roughly equal
to  400  kilo-years  (800  or  2400 kyr,  respectively).  As  phe-
nomena  proving  the  condensation  and  amalgamation  of  cy-
cles  are  generally  common  in  this  facies,  these  oscillations
evidently had the character of Milankovich long eccentricity
cycles.  The  architecture  of  these  cycles  seems  to  be  con-
trolled  by  eustatic  sea-level  changes.  The  sequence  is  ar-

ranged into inexpressive low frequency (40 kyr, i.e. obliqui-
ty)  cycles  expressed  by  an  alternation  of  limestone  layers
and  more  marly  insertions.  The  origin  of  these  cycles  was
probably  ruled  by  climatic  (humidity  driven)  oscillations.
The  biostratigraphic  boundaries  are  usually  not  identical
with  the  sequence  ones,  the  former  usually  running  within
the highstand part of the underlying cycle.

1. The lowermost first cycle is represented by beds L51 to

L58  (Fig. 7).  It  consists  of  pale  greenish  to  rosa-coloured
limestones  (Saccocoma  to  Globochaete  wackestones,
Fig. 4.1) with microfossils (Cadosina parvula, Stomiosphaera
moluccana,  Cadosina  semiradiata  semiradiata,  Colo-
misphaera  pulla,  and  Carpistomiosphaera  tithonica)  docu-
menting  Early  Tithonian  Pulla  and  Tithonica  Zones.  The
last,  thickest  and  most  micritic  layer  (L58,  Fig. 4.2)  repre-
sents  the  highstand  conditions  close  to  the  end  of  the  M22
normal  paleomagnetic  Chron  distinguished  by  Houša  et  al.
(1996, 1999).

2. The second cycle is composed of thin-bedded nodular

to brecciated pale greenish limestones (wackestone to pack-
stone)  with  red  cherts  and  marly  interlaminae  (L59  to  L67
beds). The thicker L68 layer forms the highstand part of the
cycle.  In  microfacies,  Saccocoma  Agassiz  and  Globochaete
alpina  Lombard  predominate  over  crinoid  ossicles,  bivalve
and  aptychi  fragments,  ostracod  shells,  foraminiferal  tests,
calcified radiolarians, and dinoflagellates (Cadosina semira-
diata semiradiata, Cadosina semiradiata fusca and Parasto-
miosphaera  malmica).  The  last  mentioned  dinocysts
represent an index association of the Early Tithonian Malmi-
ca Zone.

The calcareous nannofossil assemblage from the interval

L52 to L68 (Fig. 5) is dominated by Conusphaera mexicana
mexicana, Conusphaera mexicana minor, Cyclagelosphaera
margerelii,  Cyclagelosphaera  deflandrei,  Watznaueria  bar-
nesae, and Watznaueria manivitae. The absence of the nan-
nolith  Polycostella  beckmannii  in  the  association  permits
parallelization of this part of the sequence with the Early Ti-
thonian  Hexapodorhabdus  cuvillieri  (NJ  20-A)  Subzone  of
the Conusphaera mexicana mexicana Zone (Roth et al. 1983;
emended by Bralower et al. 1989).

3. Pale rose-grey marly nodular to brecciated limestones

with red-brown cherts and red marly intercalations form the
higher, third cycle (beds L69—L89).

3a. The lower part (beds L69—L74), which is correlatable

with the upper part of the M21 normal  Magnetozone,
consists  of  radiolarian-globochaetid  wackestone  and
packstone.  The  radiolarian  tests  are  mostly  calcified.
Saccocomas occur frequently, and are accompanied by
fragments  of  bivalve  molluscs  and  aptychi,  foramini-
feral  and  ostracod  tests.  Acme  accumulation  of
obliquipithonellid  cadosinid  thick-walled  forms  like
Cadosina semiradiata semiradiata (L69, Fig. 4.3) and
Cadosina semiradiata fusca (indicating the Semiradia-
ta  Acme  Zone  sensu  Reháková  2000b)  accompanied
by abundant Conusphaera could be a proxy of increas-
ing sea surface temperature conditions.

3b. The middle part (beds L75—L79) is formed by rose-

grey biomicrite of the radiolarian-Saccocoma-Globo-
chaete microfacies (packstone, wackestone). The

223

THE BRODNO SECTION – A POTENTIAL REGIONAL STRATOTYPE (WESTERN CARPATHIANS)

micrite matrix contains numerous calcified radiolarians,
saccocomas  and globochaetes.  Bivalve  fragments,  ju-
venile  ammonites  and  foraminifers  (Lenticulina  sp.)
occur  less  frequently.  Calcareous  dinoflagellate  cysts
(Parastomiosphaera

malmica,

Schizosphaerella

minutissima,  Colomisphaera  carpathica,  Cadosina
semiradiata semiradiata, Cadosina semiradiata fusca)
and early calpionellid forms with microgranular lorica
(Longicollaria dobeni, Borziella slovenica and Daciel-
la danubica) indicate the Dobeni Subzone of the Mid-
dle  Tithonian  Chitinoidella  Zone,  which  was
distinguished  in  the  Brodno  section  for  the  first  time
here. These strata are equivalent to the lowermost part
of the M20 reversed Magnetozone (Houša et al. 1996,
1999).

3c. The upper part of the interval (L80—L89) consists of

marly nodular to brecciated limestones with marly in-
terlaminae.  The  calcareous  content  increases  upwards
up  to  thin  bedded  pale  limestones  with  an  indistinct
nodular texture in the uppermost part. The rock micro-
facies and microfossil content is similar to that of the
underlying beds. Calcareous  dinoflagellates  are  repre-
sented by Schizosphaerella minutissima,  Colomisphaera
carpathica, Colomisphaera nagyi, Colomisphaera tenuis,
and  Cadosina  semiradiata  semiradiata.  The  occurrence
of  Chitinoidella  boneti,  Borziella  slovenica,  Dobeniella
tithonica,  Dobeniella  cubensis,  and  Dobeniella  bermu-
dezi characterizes the Boneti Subzone of the Chitinoidella
Zone.

Calcareous nannofossils obtained from L69 up to L96 were

assigned  to  the  Polycostella  beckmannii  Subzone  (NJ  20-B;
Roth et al. 1983; emended by Bralower et al. 1989) within the
range of the Middle Tithonian; Magnetochron M21n to M20n
(after Bralower et al. 1989). The assemblages of the lower part
of  this  interval  are  typified  by  the  predominance  of  Conu-
sphaera  mexicana  mexicana,  accompanied  by  Conusphaera
mexicana  minor,  Watznaueria  barnesae,  and  Watznaueria
manivitae. The nannolitic form of Polycostella beckmannii re-
veals a high degree of abundance in the interval L77 to L83.
Discorhabdus  ignotus  and  Zeugrhabdotus  erectus  occur  in  a
lower degree of abundance through this subzone.

4. The fourth cycle (L90—L98) is represented by a complex

of  pale  bedded  indistinctly  nodular  biomicrite  limestones.
Wackestones of radiolarian-Saccocoma-Globochaete, and lo-
cally  silicified  Saccocoma-radiolarian  biomicrites  (Fig. 4.4)
contain  mainly  radiolarians,  globochaetes,  and  saccocomids.
Bivalve  shell  and  aptychi  fragments,  ostracods,  foraminifers,
Colomisphaera tenuis, Schizosphaerella minutissima, and Co-
lomisphaera carpathica are less frequent. Calpionellids Chiti-
noidella  boneti,  Dobeniella  tithonica,  Dobeniella  bermudezi
and transitional early hyaline forms of Praetintinnopsella an-
drusovi characterize the uppermost part of the Boneti Subzone
(Chitinoidella Zone) and the passage into the Praetintinnop-
sella Zone.

5. The fifth cycle (Fig. 7) starts with the L99 layer, where

the reverse paleomagnetic Kysuca Subzone has been distin-
guished by Houša et al. (1996) below a complex of well-bed-
ded pale rose-grey “Maiolica” limestones of the Pieniny
Limestone Formation (C1—C13). Limestone layers (4 to

20 cm  thick)  are  separated  by  thin  (2  to  40 mm)  marly  in-
terlaminae.  If  the  sedimentary  rate  is  assumed  to  attain
2.9 mm/kyr  (as  deduced  from  the  biostratigraphy),  each  a
bed  represents  a time  interval  of  up  to  40 kyr.  Cycles  are
then  interpreted  as  climatically  driven  obliquity  ones.  A
quantitative  microfacies  analysis  indicates  the  presence  of
cyclical units (60 to 232 cm in thickness), which could rep-
resent eccentricity cycles. Biomicrite wackestone with Cras-
sicollaria-Globochaete-radiolarian

microfacies

(Fig. 4.5)

contains  Crassicollaria  intermedia,  which  predominate  over
Crassicollaria  massutiniana,  Crassicollaria  parvula,  Calpi-
onella alpina,  Calpionella  grandalpina  (Fig. 7.8),  Tintinnop-
sella remanei, and Tintinnopsella carpathica. The association
of calcareous dinoflagellates is composed of Schizosphaerel-
la minutissima, Colomisphaera carpathica, Cadosina semir-
adiata  semiradiata,  Cadosina  semiradiata  fusca,  and
Stomiosphaerina  proxima  (an  Early  Berriasian  age  was  at-
tributed to the last mentioned cyst by Řehánek 1992, only).
The  calpionellid  index  association  indicates  the  Remanei
Subzone of the Crassicollaria Zone.

Samples L98 to C26 were attributed to the Microstaurus

chiastius Zone NJK (Fig. 11) (sensu Bralower et al. 1989). In
this work, the FO of Helenea chiastia and Hexalithus noeliae
indicates  the  Late  Tithonian  Hexalithus  noeliae  Subzone
(NJK-A). Coccoliths of the Watznaueriaceae group (Watznaue-
ria barnesae, Watznaueria manivitae) fluctuate in a range from
25  to  80 %.  The  abundance  of  Cyclagelosphaera  margerelii
fluctuates  in  a  range  from  3—20 %  in  the  whole  succession.
Discorhabdus  ignotus  and  Zeugrhabdotus  erectus  occur  in  a
higher degree of abundance (up to 10 %) in the C1B bed. The
LO  of  Polycostella  beckmannii  observed  in  the  C4A  sample
indicates a Late Tithonian age.

6. The sixth cycle (C14—C16) is built up of well bedded

pale Maiolica limestones with thin (up to 2 cm) marly inter-
beds.  Crassicollaria-Globochaete  and  radiolarian-Crassicol-
laria  microfacies  in  biomicrite  wackstone  is  dominated  by
globochaetes and calpionellids. A general decrease in calcare-
ous  plankton  abundance  is  correlated  with  increase  of  radi-
olarians.  Calpionellids  are  dominated  by  small  forms  of
Crassicollaria  brevis.  Calpionella  grandalpina,  Calpionella
alpina, Crassicollaria parvula and Tintinnopsella carpathica,
saccocomas,

radiolarians,

aptychi,

bivalve

fragments

and foraminifers (Lenticulina sp., Spirillina sp.) are rare. The
association of calcareous dinoflagellates consists of
Schizosphaerella minutissima, Colomisphaera carpathica,
and Stomiosphaerina proxima. The interval was attributed to
the Brevis Subzone of the Late Tithonian Crassicollaria Zone.

The FO of Nannoconus infans (C13) and the FO Nannoco-

nus wintereri (C17) has been recorded in the interval with
dominance of small crassicollarians. Both forms (according
to Tavera et al. 1994) indicate the Late Tithonian NJK-b to
NJK-c subzones. According to Tremolada et al. (2006), both
these forms flourished under warmer and possibly more nu-
trient-depleted surface waters.

7. The seventh cycle – bedded pale grey limestone with

thin  (up  to  2 cm)  interbeds  of  marl  (C17—C22)  consists  of
biomicrite  wackestone  to  packstone  of  crassicollarian-globo-
chaete  and  radiolarian-globochaete-crassicollarian  microfa-
cies.  Globochaete  occurs  commonly;  Crassicollaria  parvula

224

MICHALÍK, REHÁKOVÁ, HALÁSOVÁ and LINTNEROVÁ

and Calpionella grandalpina predominate over Crassicollaria
colomi.  Calpionella  alpina,  Tintinnopsella  carpathica,  and
Tintinnopsella  doliphormis  are  frequent.  The  association  of
calcareous  dinoflagellates  contains  Schizosphaerella  minutis-
sima,  Colomisphaera  carpathica,  Colomisphaera  fortis,  and
Stomiosphaerina proxima. The presence of Crassicollaria co-
lomi indicates the Colomi Subzone of the Crassicollaria Zone.
Sole Cruciellipsis cuvillieri was found in C20, close to the FO
of  Nannoconus  wintereri.  Bralower  et  al.  (1989)  correlated
this datum with the base of the Calpionella alpina Zone coin-
ciding with the top of the ammonite Durangites Zone.

8. The eighth cycle – well bedded pale grey biomicritic

wackestone  with  thin  (up  to  1 cm)  marly  insertions  (C23A—
C25A). The calpionellid-globochaete microfacies is dominat-
ed  by  small  sphaerical  forms  of  the  Calpionella  alpina.
Crassicollarians (Crassicollaria parvula, Crassicollaria colo-
mi)  along  with  Calpionella  grandalpina  and Tintinnopsella
carpathica are less frequent. The base of the Alpina Subzone
of the Calpionella Standard Zone was identified in the C24A
Bed.  The  Brodno  Magneto-Subchron  was  located  in  layer
C24B.

9. The nineth cycle – well bedded pale biomicritic wack-

estones with Calpionella-Globochaete and Calpionella-radi-
olarians microfacies (C25B—C27E). As a rule, the degree of
abundance of radiolarians is inversely related to that of calpi-
onellids (Fig. 7; Reháková & Michalík 1994; Pszczółkowski
et  al.  2005).  Limestones  also  contain  frequent  Globochaete
alpina;  foraminiferal  fragments,  radiolarians,  ostracods,  ap-
tychi, ophiuroids, bivalves, juvenile ammonites, Crassicollaria
parvula,  Tintinnopsella  carpathica,  Cadosina  semiradiata
fusca, Cadosina semiradiata semiradiata are very rare. The
microbreccia  layers  contain  small  limestone  clasts  with  Ti-
thonian microfossils.

10. The tenth cycle – a complex with anomalously thick

(20—48 cm)  layers  of  biomicritic  Calpionella  wackestone
(C28A—C29A).  Its  upper  part  shows  submarine  slumping
features.  Small  sphaerical  forms  of  Calpionella  alpina  still
dominate  the  calpionellid  association.  The  FO  of  Nannoco-
nus steinmanni minor, the increase in abundance and diversi-
ty  of  nannoconids  in  C28  enabled  drawing  the  base  of  the
NJK-D  Nannoconus  steinmanni  subsp.  minor  Subzone,
which is correlated with the lowermost Berriasian. The asso-
ciation of calcareous nannofossils in this part of the succes-
sion  is  characteristic  of  the  start  of  the  nannoconid  bloom
and  the  FO  of  Nannoconus  steinmanni  minor,  Nannoconus
globulus  minor,  and  Nannoconus  kamptneri  minor.  These
forms  are  accompanied  by  Conusphaera  mexicana  mexicana,
Cyclagelosphaera  deflandrei,  Cyclagelosphaera  margerelii,
Diazomatholithus lehmannii, Discorhabdus ignotus, Watznaue-
ria barnesae, Watznaueria britannica, Watznaueria manivitae,
and Zeugrhabdotus embergeri.

11. The eleventh cycle – thick-bedded cherty limestones

with  radiolarian-Calpionella  microfacies  (C29B—C38).
Abundant  radiolarians  are  dispersed  in  the  wackestone,  but
also concentrated in six 4—6 cm thick radiolarite layers. The
first  occurrence  of  Remaniella  ferasini  (Catalano)  in  the
overlying  thick-bedded  cherty  “Maiolica”  limestones  indi-
cates the base of the Ferasini Subzone of the standard Calpi-
onella Zone (Reháková & Michalík 1997a).

Isotope geochemistry, chemostratigraphy

The C and O isotope ratios could have been influenced by

burial history of sediment due to recrystallization of primary
carbonate minerals, to cementation and temperature increase
with burial depth, and to other processes. Fine-grained lime-
stone  composed  mainly  of  calcitic  micro-  and  nannoplank-
ton tests could retain its primary character. The fossils could
have  been  broken  and  disturbed,  partially  dissolved  and  re-
crystallized  in  micro-scale,  but  the  carbonate  composition
still  indicates  low  diagenetic  overprint  and  its  composition
can  be  regarded  as  more-or-less  primary.  Carbon  isotope
curves from bulk carbonate samples of the J/K boundary se-
quences  worldwide  show  smooth  trends  resulting  from
equilibrated  rates  of  bio-productivity  and  organic  matter
burial  (Weissert  &  Mohr  1986;  Weissert  &  Channel  1989;
Weissert & Lini 1991; Gröcke et al. 2003; Tremolada et al.
2006).  In  the  Brodno  sequence,  the  average  value  of

(L90—C27: 1.45 ‰) ranges between 1.3 and 1.5 ‰ (PDB)
(Fig. 10).

The lowermost cycle (up to L58) as a part of the Czorsztyn

Limestone Formation (the Ammonitico Rosso facies) con-
tains slightly a rised

C values (1.46—1.73 ‰). In the sec-

ond, third and fourth cycles,

C values gradually decrease

to the lowest value in L98 (1.28 ‰). The only small positive
excursion occurs in the L79 (1.51 ‰) sample, corresponding
to the Polycostella peak. Rhythmic fluctuations during grad-
ual rise of the average

C values in the 4

to 6

cycle (start

of  the  Maiolica  facies  at  the  base  of  the  Pieniny  Limestone
Formation)  probable  reflect  the  rhythmic  character  of  the
rock  sequence  due  to  sea-level  oscillations  (Figs. 7,10).  A
much  wider  range  of

C values (1.55—1.33) is recorded

from the 7

cycle (immediately below the J/K boundary

level) with a decrease in their average. The

C values in-

crease again in the cycles above the J/K boundary.

The authentic character of the

C record of our samples

is underlined by relatively high and conservative

O values

(—2.29  to  —0.88).  The  fractionation  of  oxygen  isotopes  is
more  sensitive  to  temperature  and  salinity  variations  in  the
marine  water.  The

O values in carbonate rock could re-

flect these environmental proxies recorded by micro- and
nannofossils (Price et al. 1998; Gröcke et al. 2003; Hay et al.
2006; Tremolada et al. 2006).

The mathematic average of the

O value in the Brodno

section attains —1.62 ‰.

O values less than the average

(from —1.85 to —2.29 ‰) in the 2

cycle could reflect a rela-

tively warmer episode during the Early Tithonian with tem-
perature  changes  in  the  range  of  2—3 °C  (Fig. 6).  Positive
excursions  in  cycles  3  and  4  (approximately  —1.5 ‰)  indi-
cate a progressive fall of temperature (nearly 2—3 °C), which
is  more  or  less  correlatable  with  the  Polycostella  flowering
(Fig. 9).  A  higher  positive

O excursion (C3 bed) poten-

tially indicates a change other than a temperature fall only.
This positive

O event was accompanied not only by earli-

er  diminishing  of  Polycostella,  but  also  by  drift  of  abun-
dance  of  Watznaueria  and  Cyclagelosphaera  which  could
indicate changes of water composition, for example of salin-
ity or eutrophication. Around the  J/K boundary (cycles 6, 7
and 8), the more negative

O values (—1.5 to —2.6 ‰) indi-

226

MICHALÍK, REHÁKOVÁ, HALÁSOVÁ and LINTNEROVÁ

cated a temperature increase. This is also indicated by rich
Nannoconus occurrence that pleads in favour of the end of
the cold period. Stable isotope analyses also proved a modest
cooling of the earliest Berriasian surface waters.

Organic matter contents in the Lower Tithonian 1

to 5

cycles (0.15 to 0.25 %) are gradually decreasing upwards in
each cycle. This fluctuation could be related to changing hu-
midity, which is also supported by rapid lithofacies fluctua-
tions (Fig. 7). The most impressive peak was observed at the
beginning  of  cycle 4  (L93;  Fig. 6).  The  lowest  values  were
attained just below the  J/K boundary, in the upper parts of
the cycles 5 to 8 (on the base of the Pieniny Limestone For-
mation). On the other hand, the calcium carbonate content is
gradually increasing (from 85 to 97 %) with small minimum
in  cycle  6  at  the  base  of  the  Pieniny  Limestone  Formation
(Fig. 6). The carbonate content increase fits well with the on-
set of nannoconids.

Discussion

As in many other Tethyan areas, the Late Jurassic sedi-

mentation  rate  in  the  Pieniny  Klippen  Basin  was  low.  The
condensed red nodular limestones of the “Ammonitico Ros-
so Facies” (the Czorsztyn Limestone Formation), which rep-
resent  the  Kimmeridgian  and  Tithonian  part  of  the  Kysuca
Succession, received only a limited terrigenous clastic input.
In an analysis of the periodicity of the Milankovitch frequen-
cy bands in the Spanish Rio Argos section, Hoedemaeker &
Lereveld (1995) situated sequence boundaries at the base of
marly interbeds. Similarly, according to Schlager (2005), si-
liciclastics  may  be  found  in  all  system  tracts,  as  they  are  a
common  constituent  of  basinal  lowstand  fans  (“reciprocal
sedimentation”).  To  the  contrary,  Michalík  (2007)  argued
that  the  character  of  lowstand  deposits  strongly  depends  on
the lithological composition of the shore area that emerged.
As  the  Lower  Cretaceous  lowstand  sequences  in  the  West
Carpathian  area  were  mostly  supplied  by  carbonate  plat-
form-derived calcidetritus, they were formed by fine-detrital
(the  grain  size  depends  on  the  proximity/distality  trends)
limestone beds.

During the Berriasian age, subsiding West Carpathian ba-

sins were characterized by a great acceleration in the “plank-
tonic rain” of organic matter and calcareous microskeletons.
This  change,  which  was  detectable  in  the  majority  of  West
Carpathian  successions  also  produced  pelagic  sediments  of
the “Maiolica” type (the Pieniny Limestone Formation). This
sedimentary  pattern  persisted  until  the  Early  Aptian  in  the
Pieniny Klippen Belt (Michalík et al. 2008).

The J/K boundary line: a historical review

The J/K boundary has represented a source of controversy

for several decades. The problem consists mainly in the dif-
ference of local facies in different regions of the world, the
lack of ammonites with more than provincial distribution,
and reliable index fossils (Borza 1984; Remane 1991; Ogg et
al. 1991; Adatte et al. 1994). Four variants of the J/K bound-
ary have been drawn until the present: 1) the base of the Du-

rangites Zone, 2) the base of the Jacobi Zone, 3) the base of
the Occitanica Zone, and 4) the base of the Beriasella
privasensis Zone.

1. Houša et al. (1996) discussed identification of the J/K

boundary with the base of the Durangites Zone, which
should be identical with the marked calpionellid event – FO
of Calpionella grandalpina Nagy (base of the Remanei Sub-
zone inside the Crassicollaria Zone), which is approximately
at the beginning of the M19r Magnetochron. This opinion
has now been practically abandoned.

2. Long discussions about the placing of the J/K boundary

(Flandrin et al. 1975; Remane et al. 1986) have been terminat-
ed by the recommendation (Hoedemaeker et al. 1993) to draw
this line at the base of the Jacobi Zone. This datum line should
be  situated  at  the  base  of  the  Alpina  Zone  of  calpionellids.
Channel & Grandesso (1987) correlated the magnetostratigra-
phy of the Jurassic/Cretaceous boundary with micropaleonto-
logical  proxies.  They  put  the  boundary  between  the
Crassicollaria/Calpionella  Zones,  inside  the  M19n  Magneto-
chron. Bralower et al. (1989) parallelized the FO’s of Cruciel-
lipsis cuvillieri and Nannoconus wintereri with the uppermost
part  of  the  Crassicollaria  Zone  ( = uppermost  Durangites
Zone).  However,  Olóriz  &  Tavera  (1990),  Tavera  et  al.
(1994), and Olóriz et al. (1995) placed the base of the Jacobi
Zone  within  the  Crassicollaria  Zone  (in  the  Jurassic/Creta-
ceous Ammonitico Rosso sequence of the Puerto Espa

o sec-

tion) close to the A2/A3 boundary. They proposed a division
of the NJK Zone (Fig. 11) based on the FO’s of Nannoconus
infans,  Nannoconus  wintereri  and  Nannoconus  steinmanni
minor with the designations NJK-b to NJK-d. Gradstein et al.
(1995)  dated  this  time  level  as  144.2± 2.6 Ma.  According  to
Houša  et  al.  (1999),  the  base  of  the  standard  Crassicollaria
Zone in the Brodno section lies approximately in the middle
of the M20n Magnetozone. The base of the standard Calpio-
nella  Zone,  namely  the  Jurassic/Cretaceous  boundary  lies  in
the  middle  part  of  the  M19n  Magnetochron  (his  solution  2),
between C15A and C15B beds. These authors correlated their
Brodno  section  data  with  sections  in  northern  Italy  (Foza),
central  Italy  (Val  Bosso),  and  Spain  (Rio  Argos).
Pszczółkowski  et  al.  (2005)  identified  the  NJK-c  Subzone
with  the  Late  Tithonian  Nannoconus  wintereri  Subzone.
Grabowski & Pszczółkowski (2006) located the Jurassic/Cre-
taceous boundary (between the A and B calpionellid biozones
of Remane 1971; Remane et al. 1986) within the M19n Mag-
netochron, below the Brodno (M19n-1r) Subchron.

3. Ogg & Lowrie (1986) put the J/K boundary at the base

of the Grandis/Occitanica Zone (~ top of the Jacobi Zone =
the base of the Tirnovella subalpina Zone, correlated with
the base of the M18r Magnetochron.

4. The interval immediately above the base of the Beriasel-

la privasensis Zone (= M18n/M17r; Lowrie & Channel 1983;
Márton  1986)  is  typical  of  a  drowning  event  (Gawlick  &
Schlagintweit  2006),  with  synsedimentary  slumpings  (Hoe-
demaeker  &  Leereveld  1995),  kaolinite-  (Schyder  et  al.
2005),  phosphate-  (Houša  et  al.  2006b),  or  iridium  enrich-
ment (Zakharov et al. 1996), or even with the Mj  lnir- (Dyp-
vik  et  al.  2006),  Shatsky  Rise-  and  Morokweng  impact
craters (Koberl et al. 1997; Mahoney et al. 2005; Tremolada
et al. 2006).

227

THE BRODNO SECTION – A POTENTIAL REGIONAL STRATOTYPE (WESTERN CARPATHIANS)

Drawing the J/K boundary line in the Brodno sequence

As the West Carpathian J/K boundary sections are either

condensed  (Kutek  &  Wierzbowski  1966;  Wierzbowski  &
Remane 1992), or extremely poor in ammonites, their bios-
tratigraphy  (Borza  &  Michalík  1986;  Reháková  1995;  Re-
háková & Michalík 1997a) was based mostly on calcareous
microfossil  (calpionellids  and  dinoflagellates)  distribution.
The standard Chitinoidella Zone is correlatable with the Poly-
costella  beckmannii  Subzone  of  the  Conusphaera  mexicana
mexicana Zone. The Early/Middle Tithonian boundary in the
Brodno succession could be situated at the FO of the nannolith
Polycostella  beckmannii.  The  Middle/Late  Tithonian  bound-
ary  was  determined  by  the  calpionellid  standard  Praetintin-
nopsella  Zone  which  correlates  with  the  FO  of  Helenea
chiastia (in the Microstaurus chiastius Zone). The base of the
Late Tithonian interval considering the standard Crassicollaria
Zone  was  traced  by  the  FO’s  of  Litraphidites  carniolensis,
Nannoconus  infans,  Nannoconus  wintereri  and  Cruciellipsis
cuvillieri within the Microstaurus chiastius Zone.

The onset of the Alpina Subzone of standard Calpionella

Zone which was identified with the J/K boundary by Borza

& Michalík (1986), Remane et al. (1986), Reháková (1995),
Reháková  &  Michalík  (1997a),  Lakova  (1994)  etc.,  occurs
within  this  interval  (Figs. 8,  9).  Its  base  corresponds  to  the
morphological  change  in  Calpionella  alpina  loricas  with  a
“relative  explosion”  of  medium-sized  sphaerical  forms,  as
well as a sudden rapid decrease in their abundance (Remane
et  al.  1986).  Several  authors  discussed  complete  disappear-
ance  or  even  extinction  of  crassicollarians  (Tárdi-Filácz
1986;  Reháková  2000a).  The  interval  between  the  FO  of
Nannoconus wintereri co-occurring with small nannoconids,
and the FO of Nannoconus steinmanni minor, interpreted as
the  Tithonian/Berriasian  boundary  interval  (Bralower  et  al.
1989), was also recognized in the section studied (Fig. 9).

The detailed distribution of calcareous nannofossils, calpi-

onellids  and  dinoflagellates  has  been  correlated  with  the
magnetostratigraphic  polarity  chrons,  recognized  in  the
Brodno section by Houša et al. (1996a and b). Two distinct
fossil  nannobioevents  were  recognized  during  the  interval
correlated  with  M20r  to  M20n  Magnetozones:  the  domi-
nance of nannoliths of Polycostella beckmannii (~ calpionel-
lid Chitinoidella Zone) and the appearance of the calcareous
nannofossil association with Helenea chiastia (~ calpionellid

Fig. 11. Correlation scheme of the Jurassic/Cretaceous ammonite-, calcareous dinoflagellate-, calpionellid- and calcareous nannofossil bio-
stratigraphic zonation.

228

MICHALÍK, REHÁKOVÁ, HALÁSOVÁ and LINTNEROVÁ

Crassicollaria Zone). According to Houša et al. (1996a), the
base of the standard Crassicollaria Zone in the Brodno sec-
tion lies approximately in the middle of the M20n Magneto-
zone.  According  to  our  results,  this  limit  should  be  traced
higher;  it  aproximately  coincides  with  the  reverse  Kysuca
Subzone. Houša et al. (1999) correlated the base of the stan-
dard  Calpionella  Zone,  namely  the  Jurassic/Cretaceous
boundary  with  the  middle  part  of  the  M19n  Magnetochron
(solution 2),  between  the  C15A  and  C15B  beds.  Calpionel-
lids studied in this work allowed us to correlate this bound-
ary  interval  with  levels  close  to  the  Brodno  Subchron,
namely the C24A—C25A beds (Figs. 7—9).

Paleoecology

As the most abundant taxa in the poorly diversified nanno-

fossil association from the Brodno section are represented by
dissolution-resistant forms, their fluctuation is only partially
related to the original composition of the nannoplankton as-
semblage and it cannot be interpreted without taking into
consideration the taphonomical and diagenetic changes.

The maxima of the nannofossil abundance are supplied by

Watznaueria barnesae placoliths. Kessels

et al. (2003) inter-

preted  the  Watznaueriaceae  distribution  pattern  as  an  index
of a low productive, oligotrophic setting with abundant K-se-
lected  cosmopolitan  species.  On  the  other  hand,  Lees  et  al.
(2004),  and  Thomsen  (1989)  interpreted  the  bloom  of  this
taxon as an indicator of a eutrophic environment with an op-
portunistic  life  strategy.  Tremolada  et  al.  (2006)  supposed
that  Watznaueria  manivitae  represents  an  oligotrophic  tem-
perature-related taxon, while Watznaueria britannica was re-
garded as a mesotrophic or eutrophic taxon. The peak of the
Watznaueria spp. in the Brodno sequence fits well the Late
Tithonian cooling curve.

Another Late Tithonian peak of abundance (up to 20 %) in

the Brodno succession refers to Cyclagelosphaera margere-
lii Pittet & Mattioli (2002) and Oliver et al. (2004) assumed
that  this  taxon  occupied  an  intermediate  position  in  the
trophic preference continuum between the more oligotrophic
Watznaueria  manivitae  and  the  small-sized  more  eutrophic
Watznaueria  britannica.  Cyclagelosphaera  margerelii  has
been  interpreted  as  an  element  of  extremely  abundant  low-
diversified  neritic  nannofloral  assemblage  from  a  lagoonal
environment  with  marked  salinity  variations  (Tremolada  et
al. 2006). Salinity variations should also have been responsi-
ble of thinning of the crassicollarian loricas around the  J/K
boundary (Reháková 2000a).

The most striking changes in the Brodno section concern

the  composition  and  abundance  of  three  genera  (Conu-
sphaera,  Polycostella,  and  Nannoconus).  Conusphaera  pre-
dominates  in  the  late  Lower  Tithonian  nannofossil
association. The acme peak of Polycostella starts immediately
later, at the beginning of the Middle Tithonian. The Nannoco-
nus expansion is observed during the latest Tithonian (Fig. 5).
Nannoconids  were  probably  the  most  successfull  group  that
adapted  better  to  warmer  and  more stratified  water  masses.
Erba (1994) supposed that the Nannoconus was a deep- (lower
photic)  dweller  that  flourished  with  a deep  nutricline  and
marked  oligotrophic  surface  waters.  According  to  stable  iso-

tope data (Gröcke et al. 2003) this form flourished in warmer
and  possibly  less  nutrient-supplied  surface  waters  than  Poly-
costella, which proliferated in a relatively colder environment.
The  offset  in  abundance  between  Nannoconus  spp.,  Conus-
phaera spp., and Polycostella spp. could result from biologi-
cal  competition  in  the  same  ecological  niche  (Bornemann  et
al.  2003)  through  significant  changes  in  the  temperature
and nutrient availability during the  J/K boundary. The gradu-
al increase in thick calcifying nannoliths since the Middle Ti-
thonian  corresponds  to the  general  enhancement  of  CaCO

and with the carbonate accumulation rates in western Tethys
and middle Atlantic areas. Increased calcification of the nan-
noplankton was favoured by drier climate, atmospheric pCO

drop and more dynamic exchange of oligotrophic or alkaline
surface oceanic waters (Bornemann, l. c.).

Occurrence of the first hyaline calpionellids (L94) can also

be considered as a paleoenvironmental indicator. The Middle
Tithonian microgranullar calpionellids were replaced by hya-
line ones due to both the increase of the nutrient content (nan-
noplankton)  and  the  high  calcium  carbonate  saturation  of
sea-water  (Reháková  &  Michalík  1997b).  Two  distinct  mor-
phological changes of hyaline calpionellids can be recognized
during the Late Tithonian and Early Berriasian. The first one
is characterized by the replacement of diversified crassicollari-
ans association of the Remanei Subzone by the association in
which small Crassicollaria brevis dominates. The second one
was  observed  at  the  beginning  of  the Alpina  Subzone  where
crassicollarians  rapidly  decreased  in  abundance  and  were
completely  replaced  by  small  sphaerical  Calpionella  alpina.
The  abundance  distribution  of  small  calpionellids  coincides
with the intervals of higher abundances of nannoconids. Con-
sider  the  Nannoconus  as  a deep-  (lower  photic)  dweller,  that
flourished  with  a deep  nutricline  and  marked  oligotrophy  of
surface waters (Erba 1994), we can conclude that both micro-
organism groups inhabited similar environmental niches.

The stratigraphic and paleoecological potential of calcare-

ous  dinoflagellates  has  been  discussed  by  Reháková
(2000a,b). In the Brodno section, Lower Tithonian cysts show
distinct change in abundance and composition. Orthopithonel-
lids dominated in the Malmica Zone, but they were replaced
by  obliquipithonellids  dominated  by  Cadosina  semiradiata
semiradiata in the Semiradiata Zone. Coinciding acme peaks
of  Cadosina  semiradiata  semiradiata  and  Conusphaera  spp.
represent probable indicators of warmer surface waters.

The data obtained indicate a sea water temperature in the

range between 15.5—21.3 °C, when we used

—1.0 ‰

V-SMOW,  deemed  appropriate  for  the  ice-free  world  of
post-Jurassic times (Gröcke et al. 2003). These values fit the
Kimmeridgian—Tithonian  14—21 °C  temperature  interval  cal-
culated  by  Gröcke  et  al.  (l.c.),  Price  et  al.  (1997,  2000)  for
northern Tethys. However, this relative large (5—6 °C)  tem-
perature fluctuation seems to be unrealistic. A part of this ap-
parent  temperature  fall  could  be  attributed  to  the  effect  of
surface-water  salinity  decrease  (see  also  Tremolada  et  al.
2006, etc). The

O indicates that the uppermost Tithonian

deposits  were  formed  during  a  relatively  cold  period
(18.5 °C  in  average)  temporally  interrupted  by  warm  epi-
sodes but overall arid rather than humid (Fig. 6). This is also
documented  by  the  monotonous

C content and low con-

229

THE BRODNO SECTION – A POTENTIAL REGIONAL STRATOTYPE (WESTERN CARPATHIANS)

tents of organic carbon. Short term fluctuation of

O val-

ues indicated temperature-, salinity changes and invasion of
warm water (or stagnancy of cold water input) into the basin
around the J/K boundary interval: this is documented by
blooms and definitive expansion of nannoconids, accompa-
nied by depletion of the calpionellid association.

Conclusions

The high-resolution quantitative analysis of calpionellids,

dinoflagellates and calcareous nannofossil assemblages indi-
cates  major  variations  in  their  abundance  and  composition.
Correlation of the calcareous microplankton distribution and
stable  isotope  analyses  was  used  in  the  characterization  of
the  J/K boundary interval as well as in the reconstruction of
the paleoceanography of this time.

The biostratigraphical study based on the distribution of

calpionellids  allowed  us  to  distinguish  the  Dobeni  Subzone
of the Chitinoidella Zone in the Brodno sequence for the first
time.  The    J/K  boundary  interval  can  be  characterized  by
several calpionellid events – the onset, diversification, and
extinction  of  chitinoidellids  (Middle  Tithonian);  the  onset,
burst  of  diversification,  and  extinction  of  crassicollarians
(Late Tithonian); and the onset of the monospecific Calpio-
nella alpina association close to the  J/K boundary.

The J/K boundary in the Brodno section is traced between

the Crassicollaria and Calpionella Zone. This limit is defined
by  the  morphological  change  of  Calpionella  alpina  tests.
The base of the Crassicollaria Zone is correlated with the re-
verse  Kysuca  Subzone,  and  the  base  of  the  standard  Calpi-
onella  Zone  is  located  just  below  the  reverse  Brodno
Subzone.

The abundance peak of obliquipithonellid cysts in the Semi-

radiata Zone isochronous with flourishing Conusphaera spp.
was used as the indicator of warmer surface waters.

For the first time, two nannozones: the Conusphaera mexi-

cana  mexicana  and  the  Microstaurus  chiastius  Zones  were
distinguished in the Western Carpathians. Calcareous nanno-
fossils from the lower half of the studied sequence are corre-
lated  with  the  Early  to  Middle  Tithonian  Conusphaera
mexicana  mexicana  Zone  (NJ-20).  This  zone  comprises  the
Polycostella beckmannii Subzone; the latter consisting of the
Hexalithus noeliae or NJK-A, NJK-b- and NJK-c Subzones.

Calcareous nannofossils show poorly diversified associa-

tions  at  the    J/K  boundary.  The  abundance  of  Watznaueria
spp.,  Cyclagelosphaera  spp.,  Conusphaera  spp.,  and  Poly-
costella  spp.  in  the  studied  section  is  relatively  high.  Other
nannofossils  are  rather  rare.  Conusphaera  predominates  in
the  Tithonian  nannofossil  assemblage  (showing  the  Middle
Tithonian peak). Polycostella increased in abundance during
the Boneti Subzone of the Chitinoidella Zone. On the basis
of the appearance of the Polycostella beckmannii nannoliths,
the  Early/Middle  Tithonian  boundary  was  located  in  the
Polycostella beckmannii Subzone.

The Middle/Late Tithonian boundary was determined by

the FO of the Helenea chiastia coccolith accompanied by the
first small nannoconids. Small nannoconids appeared during
the Late Tithonian and increased in abundance during the

Berriasian. Polycostella group diminished in abundance to-
wards the onset of the Crassicollaria Zone. The Late Titho-
nian interval was dated more precisely by the appearance of
Hexalithus noeliae and Litraphidites carniolensis within the
Microstaurus chiastius Zone.

From the point of view of nannofossil stratigraphy, the Ti-

thonian/Berriasian boundary interval should be limited con-
sidering the FO of Nannoconus wintereri together with small
nannoconids at the base, and the FO of Nannoconus stein-
manni minor at the top. Evolution of nannofossil, calpionellid
and dinoflagellate genera coincided with assumed paleoceano-
graphical changes across the J/K boundary interval.

Stable isotope (

C) analyses indicated a relatively

cold period occasionally disturbed by warm episodes during
the  uppermost  Tithonian.  This  is  also  documented  by  low
contents of organic carbon. Near the  J/K boundary the oxy-
gen isotope values indicated temperature and salinity chang-
es  probably  influenced  by  an  invasion  of  warm  water  (or
stagnancy  of  cold  water  input)  into  the  basin  resulting  in
nannoconid bloom episodes. Late Tithonian cooling was fol-
lowed by temperature increase during the very end of the Ti-
thonian and at the beginning of the Berriasian.

Acknowledgments: This is a contribution to the 506 IGCP
UNESCO Project, APVV-0248-07, APVV-0280-07, APVV-
0465-06, APVT 51-011305, and VEGA Grant Projects 6026,
2035 and 3178. We are grateful to Prof. Dr. Mabrouk
Boughdiri, Dr. Michal Krobicki and Dr. J. Soták for critical
reading of the text and for many inspiring comments.

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