GeolCarp_Vol66_No6_489

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, DECEMBER 2015, 66, 6, 489—498 doi: 10.1515/geoca-2015-0040

A review of magnetostratigraphic results from the

Tithonian—Berriasian of Nordvik (Siberia) and possible

biostratigraphic constraints

PETR SCHNABL

, PETR PRUNER

and WILLIAM A.P. WIMBLEDON

Institute of Geology of the Czech Academy of Sciences, v.v.i., Rozvojová 269, 165 02 Praha 6, Czech Republic;

schnabl@gli.cas.cz; pruner@gli.cas.cz

School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, United Kingdom;

mishenka1@yahoo.co.uk

(Manuscript received September 29, 2014; accepted in revised form October 8, 2015)

Abstract: In this contribution we examine and discuss recently published magnetostratigraphic data from the Nordvik
section (north Siberia) around the Tithonian—Berriasian (J/K) boundary, with a special emphasis on calibration with
biostratigraphy and the reliability of both the fossil and magnetic records, as well as sedimentation rates. Specifically,
we discuss original new interpretations by Bragin et al. (2013) and the commentary on that work by Guzhikov (2013).
We consider some limitations of the Nordvik section, and conclude that the base of M18r, because it is in a condensed
part of the sequence, makes a poor contender for precise long-range correlation. We discuss the lack of ammonites at
several magnetozone boundaries, and whether the bases of the local zones of Craspedites taimyrensis and Arctoteuthis
tehamaensis can be used to bracket the correlative horizon of Calpionella alpina, a widespread marker in the middle of
M19n.2n in Tethys.

Key words: review, magnetostratigraphy, magnetozones M20—M16, Tithonian—Berriasian boundary, biostratigraphy,
biotic markers, calibration, Cretaceous, Jurassic, boreal.

Introduction

The magnetostratigraphy of the Tithonian/Berriasian sequence
at Nordvik (NE Siberia) was first described by Houša et al.
(2007), the first paleomagnetic study of any marine arctic se-
quence. Bragin et al.’s (2013) revision of that study is very
interesting  and  it  presents  new  and  important  results  in  the
Tithonian—Berriasian  (M20—M16r)  interval,  including  new
interpretations of M17r. We would like to suggest some ad-
ditional interpretations of Bragin et al.’s (2013) results rela-
tive  to  the  account  of  Houša  et  al.  (2007).  We  also  make
observations  on  Guzhikov’s  (2013)  commentary,  which  con-
tains several significant remarks that merit discussion. These
three cited works and Dzyuba (2012) give all necessary data
on geography, location and the details of the local succession.

Thirty years ago, the name Tithonian was selected by the

International Jurassic Subcommission of the ISC as the glo-
bal term for the final stage of the Jurassic, and all other stage
names  (even  d’Orbigny’s  senior  name  of  Portlandian)  were
suppressed (Sarjeant & Wimbledon 2000). This decision was
implemented in all countries, and inside Russia (Zhamoida &
Prozorovskaya  1997)  the  name  “Volgian”  was  dropped.  In
terms  of  international  stage  nomenclature,  it  seems  that  the
“Volgian” spans two periods/systems and perhaps three stan-
dard  ages/stages:  the  topmost  Kimmeridgian  (Scherzinger  &
Mitta 2006; but see Rogov 2010), the Tithonian and the low-
est Berriasian. Here we only employ global standard age/stage
names and use local biozones in discussing the vital contribu-
tion that magnetostratigraphy makes at Nordvik.

Promotion of magnetostratigraphy in the J/K (Tithonian/

Berriasian) interval was first undertaken thirty years ago, and
today it is universally accepted that it is an essential tool when
integrated with biostratigraphic markers (e.g. Lowrie & Chan-
nell 1983; Ogg et al. 1984, 1991, 1994; Galbrun 1985; Ogg &
Lowrie 1986; Houša et al. 1999, 2004; Speranza et al. 2005;
Grabowski  &  Pszczółkowski  2006;  Channell  et  al.  2010;
Pruner et al. 2010; Wimbledon et al. 2011). Use of magneto-
stratigraphy at the J/K boundary without biostratigraphic con-
trol was advocated by Man (2008): however, this view has not
been  taken  up  by  other  workers  (Grabowski  et  al.  2010a,b,
2013; Pruner et al. 2010). As the sole Russian site in the Ti-
thonian/Berriasian interval with described magnetostratigra-
phy,  Nordvik  uniquely  fits  with  the  stratigraphic  pattern
determined  in  Tethys.  The  numerous  J/K  sections  studied  in
western Tethys afford a solid set of paleomagnetic data and a
powerful constraint on biostratigraphy; actually, in this, the in-
terval  has  a  much  larger  data  set  than  exists  for  most  strati-
graphic sequences and most previously selected GSSP levels.
Importantly,  also,  magnetostratigraphy  has  been  applied  to
both marine and non-marine J/K strata. But it is worth keeping
our  feet  on  the  ground,  remembering  that  magnetostrati-
graphic units are preserved in tangible rock intervals, subject
to condensation, erosion and non-sequence, and diagenetic af-
fects, just like the sediments themselves: this is a global ‘time
scale’ that still may have ‘minutes’ and ‘days’ missing, or the
clock reset. It is as important to try to examine the nature of
magnetization, and to consider the completeness of its record,
as it is for the biostratigraphic one. The definition of the mag-

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netozones that straddle the Tithonian/Berriasian interval and
their essential calibration with fossil markers (calpionellids,
calcareous nannofossils, ammonites, palynomorphs, radi-
olaria, belemnites, forams, buchiids etc.) is a task that many
colleagues, including the Berriasian WG, have valuably ad-
dressed in recent years (Wimbledon 2014).

One of the main stratigraphic problems in the Tithonian—

Berriasian interval is biotic endemism and limited biodiversity.
Guzhikov (2013) several times mentions the need to achieve a
correlation between Tethys and boreal areas (actually he refers
only  to  Siberia)  where  this  endemism  and  low  diversity  are
prominent. But this is too narrow a focus: we are faced with a
much bigger puzzle in the Tithonian—Berriasian, complicated
by  these  two  already  stated  biotic  limitations.  Defining  a
boundary for the base of the Berriasian involves consideration
of  correlations  within  the  biotic  core  area  of  western  Tethys
(Morocco, Tunisia, Iberia, France,   Italy, Central Europe, Tur-
key,  Bulgaria,  Ukraine,  Caucasus)  to  western  ‘Atlantic’
Tethys  (Cuba,  Mexico,  and  on  to  California),  to  eastern
Tethys (Iran, Tibet, Australasia, Russian Far East, Japan), but
also  to  Gondwana  (Iraq,  Yemen,  Madagascar,  Argentina,
Chile), to the non-marine areas (USA, UK, Poland, Mongolia,
China), and also to the boreal basins with their separate biozo-
nations,  including  Siberia.  The  task  with  which  we  are  con-
cerned involves all of this and is hampered by endemism, to a
greater  or  lesser  extent,  throughout.  Ammonite  problems  are
not confined to Siberia or the Russia platform: in Tethys it has
never proved possible to define one ammonite zonal scheme,
and  in  Gondwana  and  the  Pacific  mostly  endemic  faunas  re-
quire  separate  zonal  definition  (e.g.  Imlay  &  Jones  1970;
Jeletzky 1984; Howarth 1992; Howarth & Morris 1998; refer-
ences in Cantú-Chapa 2009; Zeiss & Leanza 2011; Vennari et
al.  2013).  All  of  this  is  the  reason  why  in  this  interval  fossil

groups other than ammonites are employed for correlation.
Paleomagnetic techniques are vital, most certainly, in combi-
nation with the fullest range of microfossil and macrofossil el-
ements, each calibrated against the other.

Discussion

Selecting a J/K boundary

The consensus amongst researchers for generations has

been  that  the  final  selection  of  a  GSSP  for  the  Berriasian
Stage  should  be  at  a  locality  in  Tethys  (Colloquia  1963,
1973; Zakharov et al. 1996; Wimbledon et al. 2011). Tethys
was the largest geographical unit in Tithonian and Berriasian
times,  with  the  clearest  consistency  in  its  biotas  (notably
those  listed  above),  and  it  has  the  largest  number  of  strati-
graphically  useful  marker  taxa  in  the  boundary  interval
(Fig. 1).  So  the  hunt  has  been  on  for  the  last  few  years  to
identify and fix the better markers and then the best site for a
GSSP. Another task also exists, to derive better correlations
with  the  more  problematic  and,  biotically,  sometimes  more
impoverished  regions.  Nordvik,  described  by  Bragin  et  al.
(2013)  and  discussed  by  Guzhikov  (2013),  sits  in  one  of
these,  in  the  Siberian  boreal  embayment.  Guzhikov  (2013)
refers to a “Boreal Realm”, when he, in fact, only discusses
Siberia  (or,  at  the  most,  Siberia  plus  the  Russian  Platform
embayment),  a  part  of  the  boreal  far  removed  from  Tethys
where most J/K boundary studies have been focussed. Sibe-
ria has its own ammonite scale around the Tithonian/Berria-
sian boundary level, one different to the other boreal regions,
for  instance,  Greenland,  UK  or  Canada,  though  some  indi-
vidual ammonite species have wider distributions.

Fig. 1. Jurassic/Cretaceous (Tithonian/Berriasian) correlative framework. Argentina column after Vennari et al. (2014).

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In Siberia, and elsewhere, magnetostratigraphy must cer-

tainly play a key role, as it takes no note of biotic provincial-
ism,  paleoclimate,  geography,  or  facies.  And  it  can  help
constrain correlations afforded by provincial and endemic bio-
tas. However, Guzhikov (2013), in enthusiastically promoting
the  virtues  of  magnetostratigraphy,  states  several  times  that
biostratigraphic boundaries are diachronous. This truism is, of
course,  a  constant  preoccupation  for  practising  biostratigra-
phers  and  we  agree  with  the  International  Commission  on
Stratigraphy  (ICS)  that  “…the  boundaries  of  the  material
stratigraphic  occurrence  of  species,  are  diachronous...”  but
also that “This fact has, however, been overstated. …In rap-
idly evolving lineages this may be less than one million years,
so that most biostratigraphic datings attain a higher degree of
resolution than the use of radioisotopes” (Remane et al. 1996).

One correlative method with potential is that using stable

isotope stratigraphy. The stable isotope record at Nordvik
shows an irregular decrease in

O values towards the

Tithonian/Berriasian  boundary,  which  is  interpreted  as  the
result of gradual warming (Žák et al. 2011). However, corre-
lation over wider areas using this method is complicated by
differing  facies  and  lithologies  between  boreal  and  tethyan
areas, as well as the limited abundance of belemnites, noted
in  parts  of  the  Nordvik  sequence  (Žák  et  al.  2011:  see  the
more recent work of Dzyuba et al. 2013). Sadly, chemostrati-
graphic  evidence  is  not  very  helpful  in  marking  or  bracket-
ing  a  J/K  boundary.  Published  accounts  show  that  lower
carbon isotope values characterize the latest Jurassic and the
Berriasian, with no significant positive carbon isotope values
seen until well into the Valanginian.

Guzhikov has recently discussed several alternative, wholly

paleomagnetic, ‘definitions’ of a Tithonian/Berriasian bound-
ary: at the base of M18r, even at the base of M17r (Bagaeva et
al.  2011;  Guzhikov  et  al.  2012;  Guzhikov  2013).  But  not  at
levels which are constrained accurately by biostratigraphy. He
also  mentions  the  Occitanica  Zone  as  a  contender  level,
though this (in ?M17r) has not been seriously considered in re-
cent years as a J/K boundary: the Occitanica Zone per se is, in
any case, not recognizable in any part of the boreal or any Pa-
cific/austral  region  (nor  most  of  Tethys).  In  answer  to  these
proposals of so many apparent alternatives, it needs to be re-
membered that, in fixing a boundary, we do not have a clean
sheet in front of us – far from it: we are constrained by the
history of research, usage, consensus and conventions, and by
the  decisions  made  in  the  last  five  years  by  the  Berriasian
Working  Group  of  the  ISCS.  Even  if  we  were  to  suggest  a
magnetostratigraphic primary marker for the Tithonian/Berri-
asian boundary, it would need to be tightly ‘sandwiched’ be-
tween  consistent  and  widespread  fossil  markers.  Numerous
widely  used  biostratigraphic  datums  cannot  be  ignored,  and
there is no merit in choosing a magnetozone boundary that is
far removed from traditional levels and which has inadequate
or no biostratigraphic calibration.

Biostratigraphy integrated with magnetostratigraphy

Guzhikov (2013) states, echoing Zakharov (2011), that

ammonite markers should take priority over other fossils in
identifying the Tithonian/Berriasian boundary, “instead of

calpionellids and nannoconids, as recently suggested by Wim-
bledon et al. (2011)”. This does not accurately represent what
has  been  suggested  or  published:  Wimbledon  et  al.  (2011)
discussed possibilities for defining the J/K boundary using all
useful  fossil  markers  (including  ammonites)  and  magneto-
stratigraphy.  Any  suggestion  that  ammonites  alone  can  be
used overlooks the limitations of the fossil record and is un-
tenable: in some regions ammonite distributions are disjunct,
or ammonites are endemic, or there are few or no ammonites.
It is clear why for decades a multiplicity of complementary or
alternative fossils have been used: calpionellids, nannofossils,
palynomorphs,  belemnites,  radiolaria,  forams,  bivalves  etc.
Thus  numerous  workers  have  in  recent  years  tried  to  use
such a wider range of J/K fossil groups in an integrated fash-
ion.  We  can  again  quote  Remane  et  al.  (1996):  “The  use  of
fossils for calibrating chronostratigraphic units does not only
involve tracing of biostratigraphic boundaries. It is indeed less
a matter of correlation than of determining relative ages within
a biochronological standard of reference. Biochronology is the
reconstruction of the succession of species in time through the
synthesis  of  local  and  regional  biostratigraphic  data  ...  The
chronostratigraphic  reliability  of  biostratigraphic  bound-
aries  can  thus  be  tested  by  comparing  data  from  different
species.” – our italics. This is the approach of the ICS. And
in  Tethys  we  are  fortunate  that  there  was  very  considerable
biodiversity and a sizable range of fossil markers is available
to help bracket any Tithonian—Berriasian boundary.

For several generations, apart from occasional aberrations,

definitions of a J/K boundary have focused on one interval,
between the base and top of one ammonite subzone (that of
Berriasella  jacobi),  and,  in  the  last  thirty  years,  more  and
more,  on  the  widespread  and  more  consistently  recognized
turnover  from  Crassicollaria  assemblages  to  small  Calpio-
nella (e.g. Remane 1963, 1986; Pop 1976; Houša et al. 1999,
2004; Altiner & Özkan 1991; Lakova 1993; Benzaggagh &
Atrops  1997;  Pszczółkowski  et  al.  2005;  Boughdiri  et  al.
2006;  Michalík  et  al.  2009;  Michalík  &  Reháková  2011;
Benzaggagh et al. 2012; López-Martínez et al. 2013a,b). Lat-
terly this has been widely reinforced by the use of calcareous
nannofossil FADs (references in Casellato 2010). The deci-
sion of a new Berriasian WG, at its first meeting, to consider
the base of the Jacobi Subzone as a primary boundary con-
tender was strongly promoted by several distinguished work-
ers,  including  incidentally  Russian  colleagues  such  as  Drs
Sey, Kalacheva and Bogdanova. At its third workshop in Mi-
lan,  the  group  considered  the  potential  of  various  markers
and  levels  for  a  GSSP,  always  combined  with  magneto-
stratigraphy, and still broadly in the Jacobi Subzone. This in-
terval,  the  upward  sequence  of  M19n.2n,  M19n.1r  and
M19n.1n,  in  particular,  provides  several  paleomagnetic  and
biotic markers in close order (Wimbledon et al. 2011; fig. 1).

The suggestion (Guzhikov 2013) that the base of M18r is a

suitable  contender  for  the  J/K  boundary  has  not  been  sup-
ported  by  biostratigraphic  data.  The  essential  task  of  con-
straining  the  magnetozone  boundaries  with  calibrated  fossil
markers has not been addressed. The proposal of M18r goes
back to the work of Ogg & Lowrie (1986): then it was based
on the belief that the boundary lay “in the middle of various
biostratigraphic definitions” of the boundary in Tethys. The

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Berriasian  Working  Group  decided  to  study  approximately
the  same  levels,  in  the Berriasella  jacobi  Subzone,  and  po-
tential GSSP levels in key sections, in all regions, that would
make it possible to calibrate the key biological markers with
the magnetozones. More study has revealed that the bases of
the Alpina and Jacobi biozones are not coincident (as has of-
ten been stated in the past), and neither of them is seen to lie
close  to  the  base  of  M18r  (e.g.  Wimbledon  et  al.  2013):  in
addition,  study  has  revealed  problems  with  definition/de-
marcation of the Jacobi Subzone. Examining ammonites and
calpionellids, some cited by Ogg & Lowrie (1986), and nan-
nofossils, the particular focus has therefore shifted to levels
where there are more closely spaced biotic markers, that is,
within and at the base of M19n.2n.

Biostratigraphic calibration of magnetostratigraphy at
Nordvik

In discussing Bragin et al. (2013) and the calibration of Si-

berian and Tethyan ammonite zonations, Guzhikov (2013)
suggests caution. And caution is indeed necessary, for no
ammonite scheme in Tethys or any part of the boreal near the
J/K boundary can really be said to be “calibrated”: they can
be approximated, and then only by use of magnetostratigra-
phy. Therefore, in suggesting “a detailed zone-by-zone bio-
stratigraphic correlation” of Tithonian—Berriasian rocks from
the boreal to Tethys, workers really only follow some rather
doubtful conventions in equating ammonite biozones. There
is a practice amongst some workers of depicting correlation

Fig. 2. Sedimentation rates in the Tithonian—Berriasian at Nordvik. xxxxx – the level of the iridium anomaly of Houša et al. 2007.

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charts  with  geographically  distant  columns  of  parallel  bio-
zones, zonal box neatly equalling zonal box – no gaps and
no  question  marks:  a  method  deplored  by  some  senior  am-
monite  stratigraphers,  notably  John  Callomon.  Ammonite
biozones,  like  any  other,  are  based  on  a  variably  imperfect
fossil record. Matching of local upper Tithonian—lower Ber-
riasian ammonite zones in Siberia to zones in Tethys, when
there  is  not  a  single  ammonite  in  common,  is  of  course,  no
match at all. Correlation of the Siberian biozonal scheme to a
J/K boundary in Tethys has in the past been very imprecise,
straddling  as  much  as  2.5 Ma  and  three  local  ammonite
zones: base of Okensis Zone to Sibiricus Zone (Zakharov et
al.  1996,  1997;  Zakharov  2003;  Guzhikov  2013).  Bragin  et
al.’s (2013) results at Nordvik importantly shed light on Si-
berian  ammonite  zone  durations  and  completeness,  and
heighten  concerns  over  variable  sedimentation  rates  and
non-sequence (Fig. 2).

Nordvik ammonite record

At Nordvik, ammonite biozones (Zakharov & Rogov 2008)

have  been  recognized,  sometimes  on  the  basis  of  a  few  spe-
cies,  and  even  sometimes  with  no  ammonites  (Fig. 3  –  co-
loured intervals): the majority of the 14.7 m sequence (Bragin
et al. 2013) between the base of M20n.1n and the top of (in-
complete)  M16r  has  none.  At  sites  in  Tethys  the  Tithonian/
Berriasian  (J/K)  boundary  has  been  identified  in  M19n
(Fig. 1):  at  Nordvik  M19  is  placed  within  the  Craspedites
taimyrensis  Zone  (Fig. 3  –  Houša  et  al.  2007;  Bragin  et  al.
2013). The zone has been recognized there, though the index
species is absent, and (confusingly) its lowest part only con-
tains the index for the biozone beneath, Craspedites okensis.
The  overlying  Chetae  Zone  has  yielded  one  ammonite  only,
assigned to Chetaites cf. chetae. Igolnikov (2010) noted a sim-
ilar  absence  of  ammonites  through  the  majority  of  the  Kochi
Zone.  No  doubt  more  finds  will  certainly  be  made,  but  cur-
rently at Nordvik the bases of the magnetozones which have
been identified – M19r, M19n, M18r, M17r and M16r – all
fall (Bragin et al. 2013) in intervals with no ammonites. This
suggests  the  need  to  find  accurate  and  repeatable  bio-
stratigraphic markers here and perhaps at alternative Siberian
sites,  sites  that  might  then  be  considered  for  sampling  for
paleomagnetism.  New  work  on  belemnites  has  improved  the
situation (Dzyuba 2012), affording wider correlations and ex-
citing  possibilities.  Importantly,  the  first  appearance  of  the
Californian  species  Arctoteuthis  tehamaensis  in  Siberia  pro-
vides  a  proxy  for  the  base  of  the  Calpionella  alpina  Zone
(Fig. 1  and  Fig. 3),  and  the  short-ranging  Lagonibelus  gus-
tomesovi marks the top of M19r. Further, Zanin et al.’s (2012)
recent listing of calcareous nannofossils from western Siberia,
including taxa found in Tethys, indicates one new line of re-
search. Arctoteuthis tehamaensis in Siberia does not occur in
beds  that  yield  Craspedites  okensis  (Oksana  Dzyuba,  pers.
comm.), and the first occurrence of  Arctoteuthis tehamaensis
at Nordvik is above the middle of M19.2n (Fig. 3). It cannot
be ruled out, therefore, that the Okensis Zone extends upwards
well into M19n.2n.

The scarcity of ammonites at critical levels thus leave us

with some outstanding questions. If the bottom of 19n.2n

falls at the base of the Taimyrensis Zone in Siberia (Houša et
al. 2007; Bragin et al. 2013), then, on the evidence of mag-
netostratigraphy  alone,  there  is  an  improved  approximation
to  the  base  of  the  Jacobi  Subzone  in  Tethys.  But  if  the
Taimyrensis/Okensis zonal boundary is higher relative to the
base  of  M19n.2n,  closer  to  horizons  with  the  first  A.  teha-
maensis, then there could instead be an approximation to the
base of the Alpina Subzone.

Sedimentation rates at Nordvik

There is some misunderstanding in the Guzhikov com-

mentary  (2013,  p. 350)  relative  to  the  conclusions  of
Grabowski on sedimentation rates (2011, p. 124). Grabowski,
using the Nordvik data of Houša et al. (2007), notes the rate
of  sedimentation  to  be  quite  uniform  in  M20n.ln  and  M19r
(ca.  11—12 m/Ma),  M18n  (ca.  9 m/Ma)  and  at  least  8 m/Ma
in M20n.2n. In magnetozones M19n and M18r, the sedimen-
tation rate seems to fall dramatically, to 1.5—2.0 m/Ma, simi-
lar  to  the  rate  in  condensed  rosso  ammonitico  sections
(Fig. 3). In the lithological log of Houša et al. (2007, fig. 2),
there is no sedimentation change which could indicate such
condensation;  however,  changes  in  sedimentation  rate  were
mentioned by Man (2011). It cannot be excluded that some
of the changes in condensation and sedimentation rate might
be related to the Mjølnir impact in the Barents Sea, which is
thought to have occurred close to the start of the late Berria-
sian (Zakharov et al. 1993; Smelror et al. 2001; Dypvik et al.
2006; Grabowski 2011; Wierzbowski et al. 2011; Wierzbowski
& Grabowski 2013).

Rock-magnetic results applied to magnetostratigraphy

As to technical issues, Chadima et al. (2006) and Houša et

al. (2007) used anisotropy of magnetic susceptibility (AMS)
as  a  main  rock-magnetic  method  to  discriminate  oblate  and
prolate magnetic fabrics. AMS in the group of oblate-fabric
samples is predominantly controlled by the preferred orien-
tation  of  iron-bearing  chlorites  or  micas,  and,  to  a  minor
extent,  by  the  ferromagnetic  fraction.  The  oblate,  bedding-
controlled,  magnetic  fabric,  and  the  low  remanent  magneti-
zation (RM) suggest that these samples may provide a good
record  of  the  ancient  field.  On  the  contrary,  in  the  samples
with  prolate  (rod  like)  AMS  structure  the  dominant  para-
magnetic  mineral  is  siderite,  which  was  formed  during
diagenesis.  During  siderite  formation  the  original  magnetic
signal is changed in the rock around the newly formed min-
erals,  and  new  magnetite  is  derived  from  weathering  of  the
siderite.

It is worth comparing Houša et al.’s (2007) fig. 2 and

fig. 9 with Bragin et al.’s (2013) fig. 2. Bragin et al. (2013)
have  identified  a  new  reversed  magnetozone,  defined  by  5
samples,  which  they  have  referred  to  M17r  (between  the
Chetae and Sibiricus ammonite zones). However, the lowest
of their samples has an anomalous Q-ratio, very low magnetic
susceptibility and low coercivity of remanence. Conversely,
the  next  sample  above  has  high  coercivity  of  remanence,
which is seen from the B

and S-ratio. This means that both

samples should be omitted from any evaluation.

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The Houša et al. (2007) interpretation of normal polarity

zone in the interval from 10 cm below and 30 cm above the
Nordvik  iridium  anomaly  is  based  on  results  from  10  sam-
ples.  The  two  reversed  samples  shown  by  Bragin  et  al.
(2013) show anomalous rock magnetic properties, similar to
the samples of Houša et al. (2007) in this part of the section.
One  could  be  partially  demagnetized  and  the  second  one
probably contains siderite, which has destroyed the original
magnetization.  The  last-mentioned  authors  could  not  obtain
samples  between  31 cm  and  54 cm  above  the  iridium
anomaly.  The  sample  55 cm  above  the  anomaly  contained

no primary magnetic component due to mineralogical alter-
ation. This means that equivalents of the three reversely po-
larized  samples  found  by  Bragin  et  al.  (2013)  were  not
sampled  by  Houša  et  al.  (2007).  Combining  the  paleomag-
netic data from the 2007 and 2013 publications, the reverse
polarity  zone  “M17r”  lies  in  the  interval  from  31 cm  to
~

50 cm above the iridium anomaly (Figs. 2, 4). Even so, the

anomalous samples suggest that there have been changes in
magnetic mineralogy, and the samples mentioned should be
omitted from further evaluation – we show them in the de-
tailed Fig. 4.

Fig. 3.

Comparison

the

magnetostratigraphic

schemes

Houša

al.

(2007)

and

Bragin

al.

(2013).

Belemnite

ranges

and

biozones

are

af-

ter

Dzyuba

(2012).

Ammonite

ranges

shown

the

right

are

after

Za-

kharov

Rogov

(2008)

–

asterisk

(*)

marks

ammonite

species

cited

those

authors,

but

not

collected

them.

xxxxx

–

iridium

anomaly.

blocks

indicate

barren

intervals,

with

record

ammonites.

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Speculation about the M16n.1r subzone

Guzhikov (2013, fig. 1, p. 351), interpreting Bragin et al.’s

(2013)  results,  labels  a  subzone  as  M16n.1r.  This  thin  sub-
zone is rare: Tominaga & Sager (2010) found it in one third
of  their  profiles.  The  Guzhikov  interpretation  is  not  at  all
compelling,  as  in  the  Nordvik  section  the  supposed
“M16n.1r” (called the “Feodosiya” by Guzhikov, after a re-
versal  identified  in  southern  Ukraine)  is  isolated,  with  no
samples  below  or  above.  It  is  worth  examining  Bragin  et
al.’s  original  figure  (2013,  fig. 9)  and  the  discrepancy  in
Guzhikov’s  (2013,  fig. 1)  positioning  of  “M16n.1r”.  We
have  tried  to  clarify  the  problem  in  Fig. 4,  by  combining
Houša et al.’s (2007) and Bragin et al.’s (2013) sample data.
We cannot agree with Guzhikov’s interpretation, and the rea-
sons for our interpretation are described above.

Magnetostratigraphic niceties

We agree totally with Guzhikov’s statement that magneto-

stratigraphy done without statistical and field tests (e.g. rever-
sal  test,  fold  test,  conglomerate  test  etc.)  is  not  sufficiently
reliable. It is true, but there are not enough sections that ex-
hibit  folds  or  conglomerates.  Sections  showing  the  J/K
boundary  usually  do  not  contain  enough  reversed  polarity
samples to pass the reversal test. In many cases, there are not
enough normal and reversed polarity zones to enable a com-
parison  with  the  GPTS  using  the  method  proposed  by  Man
(2008),  even  though  the  sequence  of  the  magnetozones
around  the  J/K  boundary  is  quite  unique.  The  Kysuca  and
Brodno subzones in M20n and M19n, respectively, are often
found  in  Tethys,  and  they  were  found  also  at  Nordvik.  In
contradiction to Guzhikov (2013), we believe that these sub-
zones  should  be  common  in  boreal  areas  as  well,  and  this
could  to  be  investigated  in  other  sections  in  Siberia,  and
Russia in general, to prove that they are laterally consistent.

Limitations on long-range biostratigraphy imposed by en-
demic biotas

Guzhikov’s diffident quotation of Zakharov’s assertion

that an ammonite taxon can afford a global scale and provide
correlation  at  the  J/K  boundary  deserves  careful  examina-
tion. No ammonite species, or other alternative single fossil,
provides a marker that has anything remotely approaching a
global  distribution.  There  are  no  ammonites  in  Siberia  (or
other  boreal  areas  –  the  Russian  platform,  UK  or  Green-
land) that make possible a correlation with any section in any
part  of  the  lowest  Berriasian,  or  with  the  traditional  J/K
boundary interval in Tethys. Since study started, it is a corre-
lation that no-one has been able to make: over-concentration
on  ammonites  in  this  situation  has  not  been  the  solution  to
the correlative problem, but perhaps the cause. Our inability
to correlate these J/K intervals in Siberia (which uniquely in
the Russian boreal has magnetostratigraphy) with the rest of
the  world  prompted  correspondence  in  2010  between  the
ISCS  Berriasian  WG  and  the  Russian  Cretaceous  Commis-
sion, inviting collaboration and wider application of magne-
tostratigraphy  (as  at  Nordvik),  and  more  efforts  to  identify

Fig. 4.

Detailed

view

paleomagnetic

parametres

around

the

Jurassi

/Cretaceous

boundary.

Red

line

represents

the

iridium

anomaly

(as

Houša

al.

2007).

Samples

with

high

magnetic

sus-

ceptibility

and

high

content

siderite

are

not

plotted

the

diagram.

the

magnetostratigraphic

column,

black

denotes

norm

polarity,

white

reversed

polarity,

and

grey

mostly

normal.

This

the

authors’

interpretation.

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new biological markers that might improve correlations: that
is, non-ammonite taxa, and non-endemic taxa that extend
outside Siberia, or the Russian platform.

Conclusions

Berriasian belemnite records at Nordvik open new prospects

for  correlation,  for  instance  with  California,  and  thus  via
North America with Tethys. But there appears to be a need
for greater refinement of Nordvik ammonite records relative
to magnetozone boundaries. The exact stratigraphic position
of  the  base  of  the  Craspedites  taimyrensis  Zone  must  be
higher  than  previously  published,  and  perhaps  even  within
M19n.2n,  closer  to  a  putative  Tithonian/Berriasian  bound-
ary, and nearer the base of the Calpionella alpina Subzone.

The newly interpreted sedimentation rate is seen to be

much  lower  than  previously  assumed:  in  M17r  it  equals
0.16 m/Ma.  However,  the  rate  at  the  level  of  the  iridium
anomaly  might  have  been  even  lower,  though  a  figure  can
only be approximated. The evidence of Bragin et al. (2013)
that slower sedimentation/condensation commenced in M18r
tells against its proposal by Guzhikov (2013) as a marker for
the  J/K  boundary.  Though  several  Tethyan  sections  exist
with  uncondensed  M18r,  its  thinned  presence  at  Nordvik
(the only published Russian section with J/K magnetostrati-
graphy  to  date),  means  that  Guzhikov’s  (2013)  reasoning,
that this is a preferred global marker that can be identified in
Siberia,  is  undermined.  This,  in  particular,  leads  us  to  urge
that  additional  Tithonian/Berriasian  sections  suitable  for
paleomagnetic  and  biostratigraphic  calibration  be  sought  in
Siberia (and other Russian areas).

Acknowledgments: We would like to acknowledge insti-

tutional  support  from  the  Institute  of  Geology  of  the  CAS,
v.v.i,  No.  RVO6785831  and  Projects  GAP210/16/09979,
DEC-2011/03/B/ST10/05256 of the National Science Centre,
Poland. We would like to express appreciation to our student
Šimon  Kdýr  and  colleagues  Kristýna  Čížková  and  Jiří
Petráček  for  their  support.  We  extend  our  sincere  thanks  to
colleagues for their help with discussion and data on Siberian
sites,  especially  to  Oksana  Dzyuba  and  Martin  Koš•ák,  and
for  information  on  ammonite  finds  to  Alexander  Igolnikov,
Viktor Zakharov and Mikhail Rogov.

References

Altiner D. & Özkan S. 1991: Calpionellid zonation in north—west-

ern Anatolia (Turkey) and calibration of the stratigraphic ranges
of some benthic foraminifers at the Jurassic—Cretaceous
boundary. Geol. Romana 27, 215—235.

Bagaeva M.I., Arkadiev V.V., Baraboshkin E.Y., Gorbenko E.Y.,

Guzhikov  A.Y.,  Manikin  A.G.  &  Perminov  V.A.  2011:  New
data on bio- and magnetostratigraphy of the Berriasian—Valang-
inian boundary sediments in eastern Crimea. In: Shurygin B.N.,
Lebedeva  N.K.  &  Goryacheva  A.A.  (Eds.):  Palaeontology,
stratigraphy  and  palaeogeography  of  the  boreal  Mesozoic  and
Cenozoic.  Vol.  I.  Mesozoic.  INGG  SO  RAN,  Novosibirsk,
23—26.

Benzaggagh M. & Atrops F. 1997: Stratigraphie et associations de

faune d’ammonites des zones du Kimméridgien, Tithonien et
Berriasien basal dans le Prérif interne (Rif, Maroc). Newslett.
Stratigr. 35, 127—163.

Benzaggagh M., Cecca F., Schnyder J., Seyed-Emami K. & Reza

Majidifarde  M.  2012:  Calpionelles  et  microfaunes  pélagiques
du Jurassique supérieur—Crétacé inférieur dans les Formations
Shal  et  Kolur  (Montagnes  du  Talesh,  chaîne  de  l’Elbourz,
Nord-Ouest  Iran).  Répartition  stratigraphique,  espèces  nouv-
elles,  revision  systématique  et  comparaisons  regionals.  Ann.
Paléont. 98, 253—301.

Boughdiri M., Sallouhi H., Maalaoui K., Soussi M. & Cordey F.

2006: Calpionellid zonation of the Jurassic—Cretaceous transi-
tion in north Atlasic Tunisia. Updated Upper Jurassic strati-
graphy of the “Tunisian Trough” and regional correlations.
C.R. Geoscience 338, 1250—1259.

Bragin V.Y., Dzyuba O.S., Kazansky A.Y. & Shurygin B.N. 2013:

New data on the magnetostratigraphy of the Jurassic—Creta-
ceous boundary interval, Nordvik Peninsula (northern East Si-
beria). Russ. Geol. Geophys. 54, 335—348.

Cantú-Chapa A. 2009: Ammonites of the Cretaceous Taraises and

lower Tamaulipas formations in eastern Mexico. In: Bartolini
C. & Román Ramos J.R. (Eds.): Petroleum systems in the
southern Gulf of Mexico. AAPG Memoir 90, 191—216.

Casellato C.E. 2010: Calcareous nannofossil biostratigraphy of Up-

per Callovian—Lower Berriasian successions from Southern
Alps, North Italy. Riv. Ital. Paleont. Stratigr. 116, 357—404.

Chadima M., Pruner P., Šlechta S., Grygar T. & Hirt A.M. 2006:

Magnetic fabric variations in Mesozoic black shales, northern
Siberia, Russia: possible palaeomagnetic implications. Tec-
tonophysics 418, 145—162.

Channell J.E.T., Casellato C.E., Muttoni G. & Erba E. 2010: Magne-

tostratigraphy, nannofossil stratigraphy and apparent polar wan-
der for Adria-Africa in the Jurrasic—Cretaceous boundary
interval. Palaeogeogr. Palaeoclimatol. Palaeoecol. 293, 51—75.

Colloque sur la Crétacé inferieur (Lyon, 1963) 1965: Memoires du

Bureau de Recherches Geologiques et Minieres. No. 34. Bu-
reau de Recherches Géologiques et Minières, 1—840.

Colloque sur la limite Jurassique—Crétacé (Lyon—Neuchatel, 1973)

1975: Memoires du Bureau de Recherches Geologiques et
Minieres. No. 86. Bureau de Recherches Géologiques et
Minières, 1—393.

Dypvik H., Smelror M., Sandbakken P.T., Salvigsen O. & Kalleson

E. 2006: Traces of the marine Mjølnir impact event. Pal-
aeogeogr. Palaeoclimatol. Palaeoecol. 241, 621—636.

Dzyuba O.S. 2012: Belemnites and biostratigraphy of the Jurassic—

Cretaceous boundary deposits of northern east Siberia: new data
on the Nordvik Peninsula. Stratigr. Geol. Correl. 20, 53—72.

Dzyuba O.S., Izokh I.P. & Shurygin B. 2013: Carbon isotope excur-

sions in Boreal Jurassic—Cretaceous boundary sections and their
correlation potential. Palaeogeogr. Palaeoclimatol. Palaeoecol.
381—382, 33—46.

Galbrun B. 1985: Magnetostratigraphy of the Berriasian stratotype

section (Berrias, France). Earth Planet. Sci. Lett. 74, 130—136.

Grabowski J. 2011: Magnetostratigraphy of the Jurassic/Cretaceous

boundary interval in the Western Tethys and its correlations
with other regions: a review. Volumina Jurassica 9, 105—128.

Grabowski J. & Pszczółkowski A. 2006: Magneto- and biostrati-

graphy of the Tithonian—Berriasian pelagic sediments in the
Tatra Mountains (central western Carpathians, Poland): sedi-
mentary and rock magnetic changes at the Jurassic/Cretaceous
boundary. Cretaceous Research 27, 398—417.

Grabowski J., Haas J., Márton E. & Pszczółkowski A. 2010a: Mag-

neto- and biostratigraphy of the Jurassic/Cretaceous boundary
in the Lokút section (Transdanubian Range, Hungary). Stud.
Geophys. Geod. 54, 1—26.

497

TITHONIAN—BERRIASIAN MAGNETO- AND BIOSTRATIGRAPHY OF NORDVIK (SIBERIA, RUSSIA)

GEOL

EOL

EOLOGICA CARPA

OGICA CARPA

OGICA CARPATHICA

THICA

THICA, 2015, 66, 6, 489—498

Grabowski J., Michalík J., Pszczółkowski A. & Lintnerová O. 2010b:

Magneto-, and isotope stratigraphy around the Jurassic/Creta-
ceous boundary in the Vysoká Unit (Malé Karpaty Mountains,
Slovakia): correlations and tectonic implications. Geol. Car-
pathica 61, 309—326.

Grabowski J., Schnyder J., Sobien K., Koptikova L., Krzeminski L.,

Pszczółkowski A., Hejnar J. & Schnabl P. 2013: Magnetic
susceptibility and spectral gamma logs in the Tithonian—Berria-
sian pelagic carbonates in the Tatra Mts. (Western Carpathians,
Poland): Palaeoenvironmental changes at the Jurassic/Creta-
ceous boundary. Cretaceous Research 43, 1—17.

Guzhikov A.Y. 2013: Solving unsolvable problems in stratigraphy

(Comments on the paper “New data on the magnetostratigraphy
of the Jurassic—Cretaceous boundary interval, Nordvik Penin-
sula (northern east Siberia)” by Bragin et al.). Russ. Geol. Geo-
phys. 54, 349—354.

Guzhikov A.Y., Arkadiev V.V., Baraboshkin E.Y., Bagaeva M.I.,

Piskunov V.K., Rud’ko S.V., Perminov V.A. & Manikin A.G.
2012: New sedimentological, bio-, and magnetostratigraphic
data on the Jurassic—Cretaceous boundary interval of Eastern
Crimea (Feodosiya). Stratigr. Geol. Correl. 20, 261—294.

Houša V., Krs M., Krsová M., Man O., Pruner P. & Venhodová D.

1999: High-resolution magnetostratigraphy and micropalaeon-
tology across the J/K boundary strata at Brodno near Žilina,
western Slovakia: summary of results. Cretaceous Research
20, 699—717.

Houša V., Krs M., Man O., Pruner P., Venhodová D., Cecca F.,

Nard G. & Piscitello M. 2004: Combined magnetostratigraphic,
palaeomagnetic and calpionellid investigations across Jurassic/
Cretaceous boundary strata in the Bosso Valley, Umbria, Cen-
tral Italy. Cretaceous Research 25, 771—785.

Houša V., Pruner P., Zakharov V.A., Koš•ák M., Chadima M., Rogov

M.A., Šlechta S. & Mazuch M. 2007: Boreal—Tethyan correla-
tion of the Jurassic—Cretaceous boundary interval by magneto-
and biostratigraphy. Stratigr. Geol. Correl. 15, 297—309.

Howarth M.K. 1992: Tithonian and Berriasian ammonites from the

Chia Gara Formation in northern Iraq. Palaeontology 35,
597—655.

Howarth M.K. & Morris N.J. 1998: Jurassic and lower Cretaceous

of Wadi Hajar, southern Yemen. Bull. Nat. Hist. Mus. London
(Geol.) 54, 1—32.

Igolnikov A.E. 2010: New ammonite finds from the Berriasian of

the  Nordvik  Peninsula.  In:  Baraboshkin  E.Yu.  &  Blagove-
schensky  I.V.  (Eds.):  Cretaceous  system  of  Russia  and  adja-
cent  countries:  problems  of  stratigraphy  and  palaeontology.
UIGU, Ulyanovsk, 163—165.

Imlay R.W. & Jones D.L. 1970: Ammonites from the Buchia zones

in northwestern California and southwestern Oregon. USGS
Professional Pap., 647-B.

Jeletzky J.A. 1984: Jurassic—Cretaceous boundary beds of western

and Arctic Canada and the problem of the Tithonian—Berria-
sian stages in the Boreal realm. In: Westermann G.E.G. (Ed.):
Jurassic—Cretaceous biochronology and biogeography of North
America. Geol. Assoc. Canada, Spec. Pap. 27, 175—255.

Lakova I. 1993: Middle Tithonian to Berriasian praecalpionellid

and calpionellids zonation of the Western Balkanides, Bulgaria.
Geol. Balcanica 23, 3—24.

Lowrie W. & Channell J.E.T. 1983: Magnetostratigraphy of the Ju-

rassic—Cretaceous boundary in the Maiolica limestone (Um-
bria, Italy). Geology 12, 44—47.

López—Martínez R., Barragán R. & Reháková D. 2013a: Calpionel-

lid distribution and microfacies across the Jurassic/Cretaceous
boundary in western Cuba (Sierra Los Organos). Geol. Car-
pathica 64, 195—208.

López—Martínez R., Barragán R. & Reháková D. 2013b: The Juras-

sic/Cretaceous boundary in the Apulco area by means of calpio-

nellids and calcareous dinoflagellates: an alternative to the
classical Mazatepec section in eastern Mexico. J. South Amer.
Earth Sci. 47, 142—151.

Man O. 2008: On the identification of magnetostratigraphic polarity

zones. Stud. Geophys. Geod. 52, 173—186.

Man O. 2011: The maximum likelihood dating of magnetostrati-

graphic sections. Geophys. J. Int. 185, 133—143.

Michalík J. & Reháková D. 2011: Possible markers of the Jurassic/

Cretaceous boundary in the Mediterranean Tethys – A review
and state of art. Geosci. Frontiers 2, 475—490.

Michalík J., Reháková D., Halásová E. & Lintnerová O. 2009: The

Brodno section – a potential regional stratotype of the Juras-
sic/Cretaceous boundary (Western Carpathians). Geol. Car-
pathica 60, 213—232.

Ogg J.G. & Lowrie W. 1986: Magnetostratigraphy of the Jurassic/

Cretaceous boundary. Geology 14, 547—550.

Ogg J.G., Hasenyager R.W. & Wimbledon W.A. 1994: Jurassic/

Cretaceous boundary: Portland-Purbeck magnetostratigraphy
and possible correlation to the Tethyan faunal realm. Geobios
17, 519—527.

Ogg J.G., Steiner M.B., Oloriz F. & Tavera J.M. 1984: Jurassic mag-

netostratigraphy. 1. Kimmeridgian—Tithonian of Sierra Gorda
and Carcabuey, southern Spain. Earth Planet. Sci. Lett. 71,
147—162.

Ogg J.G., Hasenyager R.W., Wimbledon W.A.P., Channell J.E.T.

& Bralower T.J. 1991: Magnetostratigraphy of the Jurassic/
Cretaceous boundary interval – Tethyan and English faunal
realms. Cretaceous Research 12, 455—482.

Pop G. 1976: Tithonian—Valanginian calpionellid zones from Cuba.

D.S. Sedint., Inst. Geol. Geofiz. 62, 237—266.

Pruner P., Houša V., Olóriz F., Koš•ák M., Man O., Schnabl P.,

Venhodová D., Tavera J.M. & Mazuch M. 2010: High-resolu-
tion magnetostratigraphy and biostratigraphic zonation of the
Jurassic/Cretaceous boundary strata in the Puerto Escaño sec-
tion (southern Spain). Cretaceous Research 31, 192—206.

Pszczółkowski A.,

Garcia-Delgado D. & Gil González S. 2005:

Calpionellid and nannoconid stratigraphy and microfacies of
limestones at the Tithonian—Berriasian boundary in the Sierra
Inferno (western Cuba). Ann. Soc. Geol. Pol. 75, 1—16.

Remane J. 1963: Les Calpionelles dans les couches de passage ju-

rassiques—crétacé de la fosse vocontienne. Trav. Lab. Géol.
Fac. Sci. Grenoble 39, 25—82.

Remane J. 1986: Calpionellids and the Jurassic—Cretaceous bound-

ary. Acta Geol. Hung. 2, 15—26.

Remane R., Bassett M.G., Cowie J.W., Klaus H., Gohrbandt K.H.,

Lane H.R., Michelsen O. & Wang N. 1996: Revised guidelines
for the establishment of global chronostratigraphic standards
by the International Commission on Stratigraphy (ICS). Epi-
sodes 19, 77—81.

Rogov M.A. 2010: A precise ammonite biostratigraphy through the

Kimmeridgian—Volgian boundary beds in the Gorodishche sec-
tion (Middle Volga area, Russia) and the base of the Volgian
Stage in its type area. Volumina Jurassica 8, 103—130.

Sarjeant W.A.S. & Wimbledon W.A.P. 2000: The terminal Jurassic

stage: history of a controversy in stratigraphy. Modern Geology
22, 1—34.

Scherzinger A. & Mitta V. 2006: New data on ammonites and

stratigraphy of the Upper Kimmeridgian and Lower Volgian
(Upper Jurassic) of the middle Volga Region (Russia). Neu.
Jb. Geol. Paläont., Abh. 241, 225—251.

Smelror M., Kelly S.R.A., Dypvik H., Mørk A., Nagy J. & Tsikalas

F. 2001: Mjølnir (Barents Sea) meteorite impact ejecta offers a
Volgian—Ryazanian boundary marker. Newslett. Stratigr. 38,
129—140.

Speranza F., Satolli S., Mattioli E. & Calamita F. 2005: Magnetic

stratigraphy of Kimmeridgian—Aptian sections from Umbria-

498

SCHNABL, PRUNER and WIMBLEDON

GEOL

EOL

EOLOGICA CARPA

OGICA CARPA

OGICA CARPATHICA

THICA

THICA, 2015, 66, 6, 489—498

Marche (Italy): New details on the M polarity sequence. J.
Geophys. Res. 110, B12109, 1—26.

Tominaga M. & Sager W.W. 2010: Revised Pacific M—anomaly

geomagnetic timescale. Geophys. J. Int. 182, 203—232.

Vennari V.V., Lescano M., Naipauer M., Aguirre-Urreta B.,

Concheyro A., Schaltegger U., Armstrong R., Pimentel M. &
Ramos V.A. 2014: New constraints in the Jurassic—Cretaceous
boundary in the High Andes using high-precision U-Pb data.
Gondwana Res. 26, 374—385.

Wierzbowski A. & Grabowski J. 2013: The meteorite Mjølnir crater

in the Barents Sea in stratigraphical interpretations. [Meteory-
towy krater Mjølnir na Morzu Barentsa w interpretacjach
stratygraficznych.] Przegl. Geol. 61, 516—522.

Wierzbowski A., Hryniewicz K., Hammer Ø., Nakrem H.A. & Little

C.T.S. 2011: Ammonites from hydrocarbon seep carbonate
bodies from the uppermost Jurassic—lowermost Cretaceous of
Spitsbergen and their biostratigraphical importance. Neu. Jb.
Geol. Paläont., Abh. 262, 267—288.

Wimbledon W.A.P. 2014: Warsaw remarks – Berriasian progress.

Volumina Jurassica 12, 107—112.

Wimbledon W.A.P., Casellato C.E., Reháková D., Bulot L.G., Erba

E., Gardin S., Verreussel R.M.C.H., Munsterman D.K. & Hunt
C.O. 2011: Fixing a basal Berriasian and Jurassic/Cretaceous
(J/K) boundary – is there perhaps some light at the end of the
tunnel? Riv. Ital. Paleont. Stratigr. 117, 295—307.

Wimbledon W.A.P., Reháková D., Pszczółkowski. A., Casellato

C.E., Halásová E., Frau C., Bulot L.G., Grabowski J., Sobień
K.,  Pruner  P.,  Schnabl  P.  &  Čížková  K.  2013:  A  preliminary
account  of  the  bio-  and  magnetostratigraphy  of  the  upper
Tithonian—lower  Berriasian  interval  at  Le  Chouet,  Drôme
(SE France). Geol. Carpathica 64, 437—460.

Zakharov V.A. 2003: In defence of the Volgian Stage. Stratigr.

Geol. Correl. 11, 585—593.

Zakharov V.A. 2011: Jurassic—Cretaceous boundary and Berriasian

GSSP: is there light at the end of the tunnel? Comments on

proposals on the J-K boundary by Berriasian Working Group.
News of palaeontology and stratigraphy 16—17, Supplements
to Russian Geology and Geophysics 52, 87—90.

Zakharov V.A. & Rogov M.A. 2008: The upper Volgian substage in

northeast Siberia (Nordvik Peninsula) and its panboreal correla-
tion based on ammonites. Stratigr. Geol. Correl. 16, 423—436.

Zakharov V.A., Lapukhov A.S. & Shenfil O.V. 1993: Iridium

anomaly at the Jurassic—Cretaceous boundary in Northern Si-
beria. Russ. J. Geol. Geophys. 34, 83—90.

Zakharov V.A., Bown P. & Rawson P.F. 1996: The Berriasian

Stage and the Jurassic—Cretaceous boundary. Bulletin van het
Koninklijk Belginstituut voor Natuurwetenschappen Supp. 66,
7—10.

Zakharov V.A., Bogomolov Y.I., ll’ina V.I., Konstantinov A.G.,

Kurushin N.I., Lebedeva N.K., Meledina S.V., Nikitenko B.L.,
Sobolev E.S. & Shurygin B.N. 1997: Boreal standard and bio-
stratigraphy of the Siberian Mesozoic. Russ. Geol. Geophys. 8,
965—993.

Zanin Y.N., Zamirailova A.G. & Eder V.K. 2012: Some calcareous

nannofossils from the Upper Jurassic—Lower Cretaceous Ba-
zhenov Formation of the West Siberian Marine Basin, Russia.
Open Geol. J. 6, 25—31.

Zeiss A. & Leanza H. 2011: Upper Jurassic (Tithonian) ammonites

from the lithographic limestones of the Zapala region, Neu-
quén Basin, Argentina. Beringeria 41, 1—52.

Zhamoida A.I. & Prozorovskaya E.L. 1997: Resolutions on the Ju-

rassic—Cretaceous boundary position in the Boreal Realm and
on the status of the Volgian Stage. Resolutions of the Interde-
partmental Stratigraphic Committee and its Permanent Com-
missions, St. Petersburg 29, 5—7.

Žák K., Koš•ák M., Man O., Zakharov V.A., Rogov M.A., Pruner

P., Rohovec J., Dzyuba O.S. & Mazuch M. 2011: Comparison
of carbonate C and O stable isotope records across the Juras-
sic/Cretaceous boundary in the Tethyan and Boreal Realms.
Palaeogeogr. Palaeoclimatol. Palaeoecol. 299, 83—96.