GeolCarp_Vol52_No6_349

GEOLOGICA CARPATHICA, 52, 6, BRATISLAVA, DECEMBER 2001

349 — 360

THE CENOMANIAN (LATE CRETACEOUS) RADIOLARIANS

FROM THE TOMALAR FORMATION, CENTRAL PONTIDES,

NORTHERN TURKEY

NIKITA BRAGIN

, LUBOV BRAGINA

, CEMAL TUNOGLU

and UGUR KAGAN TEKIN

Geological Institute of Russian Academy of Sciences, Pyzhevsky 7, 109017 Moscow, Russia; bragin@ginran.msk.su

Geological Department, Hacettepe University, Beytepe-Ankara, Turkey; tunay@hacettepe.edu.tr

General Directorate of Mineral Research and Exploration (MTA), Geological Research Department,

06520 Balgat-Ankara, Turkey; kagan@mta.gov.tr

(Manuscript received December 13, 2000; accepted in revised form October 4, 2001)

Abstract: The lower part of the Late Cretaceous Tomalar Formation (Devrekani Basin, Central Pontides, northern Tur-
key) is characterized by the presence of light-green ribbon cherts and cherty mudstones (approximately 10 m thick) with
abundant well-preserved Radiolaria. The presence and coexistence of such taxa as Acaeniotyle macrospina,
Archaeospongoprunum salumi, Becus horridus, Cavaspongia euganea, Dactyliodiscus longispinus, Halesium sexangulum,
Hexapyramis pantanellii, Pessagnobrachia irregularis, Pyramispongia glascockensis, Savaryella quadra, Vitorfus
brustolensis, Novixitus dengoi, N. weyli, Phalangites telum and others clearly indicate the Cenomanian age. The Tomalar
Formation covers the whole Upper Cretaceous due to the presence of Maastrichtian planktonic Foraminifera from the
upper part of this formation. The radiolarian assemblage of the Tomalar Formation correlates well with the coeval fauna
of the Western Mediterranean.

Key words: Cenomanian, Turkey, Central Pontides, Devrekani Basin, Tomalar Formation, cherts, Radiolaria.

Introduction

Chert, chert-micritic, and volcanogenous-chert units are com-
monly present in various regions of Turkey. They are usually
supposed to be formed in the paleo-oceans or seas with deep-
water  conditions.  The  age  of  these  units  are  of  great  impor-
tance for understanding the geological history of the Mediter-
ranean mobile belt, as well as for the comprehensive analysis
of the development of oceanic basins and related ophiolite su-
ture zones. Therefore, the age data of these deposits have to be
applied  for  studies  of  regional  tectonics.  Cherts  are  poorly
characterized by macrofossils, foraminifers and other paleon-
tological remains that have prime importance for biostratigra-
phy.  For  this  reason,  many  such  units  in  various  regions  of
Turkey (for example, in the Pontide Orogenic Belt and in the
Izmir—Ankara—Erzincan  suture  zone)  still  have  no  precise
dates.  Only  radiolarians  are  very  common  and  diverse  in
cherts and cherty mudstones, and they can be utilized for solv-
ing stratigraphical problems.

The pioneering studies of the Mesozoic Radiolaria of Tur-

key  (De  Wever  et  al.  1979;  Pessagno  &  Poisson  1981;  De
Wever 1981a,b,c, 1982a,b), as well as the recent works (Bra-
gin  &  Tekin  1996,  1999;  Tekin  1999;  Mekik  et  al.  1999;
Mekik 2000), reflected these problems and presented valuable
data for the geology of the studied areas and for further devel-
opment  of  the  radiolarian  biostratigraphy.  The  cited  works
covered two large stratigraphic intervals: the Middle Triassic—
Early Jurassic, and the Late Jurassic—Early Cretaceous.

This article is concerned with the first finding of the diverse

and correlative Late Cretaceous (Cenomanian) radiolarian as-

semblage  from  the  Devrekani  Basin,  Central  Pontide  region
(northern Turkey). It should be noted that the presence of radi-
olarites and radiolarians in the Upper Cretaceous of this region
has been mentioned several times (Tunoglu 1991a, 1993, 1994),
but detailed study of siliceous microfosils has not yet been re-
alized. The Late Cretaceous Radiolaria from Turkey are inter-
esting for two reasons: firstly they provide new biostratigraph-
ic  data  for  regional  lithostratigraphic  units,  and  secondly  the
occurrence of numerous radiolarian taxa in Turkey allows the
further  progress  of  paleobiogeography  of  this  planktonic
group. In this study, the first preliminary data that need to be
discussed and analysed in further studies are submitted.

Methods

In this study, a chert sample from the study area was pro-

cessed using techniques suggested by Pessagno & Newport
(1972), using diluted (5—10 %) hydrofluoric acid. The extract-
ed radiolarians have been studied under the light microscope
LOMO-MBS-9. The SEM microscope Cambridge Stereoscan
600 has been utilized for more precise determinations and pho-
tographic works. All these works were realized in the Geologi-
cal Institute of Russian Academy of Sciences, Moscow.

Geological setting

The study area is located in the northern part of the Turkey

(north-northeast of Kastamonu City and north of Devrekani

350 BRAGIN et al.

Town) (Fig. 1). This region belongs to the “Pontide Orogenic
Belt” (Ketin 1966), or to the “Rhodope-Pontide Fragment” ac-
cording to Sengör (1984). The Pontide area is characterized by
the presence of several basins with transgressive to regressive
Jurassic, Cretaceous and Tertiary successions. One of them is
the Devrekani Basin, which represents a depression with east-
northeast trending long axis, filled by the Late Mesozoic and
Cenozoic marine sediments, covering a metamorphic base-
ment of supposed Precambrian age in the south, and Jurassic
clastics and carbonates in the north (Fig. 1). Devrekani and the
other similar basins were entirely related to the Tethyan Fau-
nal Realm. This area has been studied by numerous investiga-
tors on the terms of regional geology, biostratigraphy, litholo-
gy and tectonics (Ketin 1962, 1966; Yilmaz 1979; Aydin et al.
1986; Tunoglu 1991a,b, 1992a,b, 1993, 1994; Sagular et al.
1991; Tunoglu & Batman 1995; Tunoglu & Temel 1996).

The Late Mesozoic of the southern part of the Devrekani

Basin is represented by the following lithostratigraphic units:

The Tomalar Formation first named and defined by Tunoglu

(1991b) is represented by Late Cretaceous cherts, marls and
micritic limestones, sometimes with beds of sandstones, with
total thickness ranging from 10 to 175 meters. Synonyms of
this formation in the other region of the Central Pontides are as
follows: Unaz Formation (Akyol et al. 1994), Kirensöküsü
Formation (Yilmaz 1979), Kapanbogazi Formation (Gedik &
Korkmaz 1984) and Nasibey Limestone Member (Terlemez &
Yilmaz 1980).

The Davutlar Formation, again first named and defined by

Tunoglu (1991b), is Latest Maastrichtian—Middle Paleocene in
age. The Cretaceous part is represented by basal conglomer-
ates, sandy limestones and sandy marls with total thickness
approximately 10—20 m (Fig. 2) (Tunoglu 1991b, 1992b).

The lowermost part of the Tomalar Formation is character-

ized by radiolarian cherts and mudstones, while the middle
and upper parts of this formation comprise two main lithologi-
cal types of limestone: wackestone/biomicrite and packstone/
intramicrite (Tunoglu 1992b). Both Tomalar and Davutlar For-
mations have erosional basal boundaries. The Tomalar Forma-
tion unconformably overlies the metamorphic basement (Gür-
leyik Gneiss of supposed Precambrian age). The Davutlar
Formation also lies on the Tomalar Formation with unconfor-
mity. In some places the Tomalar Formation is absent due to
complete erosion before the Late Maastrichtian transgression
(Fig. 1), and in such cases the Davutlar Formation lies directly
on the metamorphic basement.

According to the previous investigations, the upper part of

the Tomalar Formation in the type area, near Tomalar Village
(Fig. 1) is characterized by the presence of the Middle—Upper
Maastrichtian foraminifers such as Globotruncana folsosutu-
arti (Sigal), G. arca (Cushman), G. ventricosa (White), G. lin-
neiana (White), G. rosetta (Carsey), G. aegyptiaca (Nakkady),
Globotruncanita stuarti (De Lapparent) (determined by Vedia
Toker, Ankara University, Ankara) and nannofossils Arkhan-
gelskiella cymbiformis Vekshina, Eiffellithus gorkae Rein-

Fig. 1. Simplified geological map of the Devrekani Basin, compiled from Tunoglu (1994). 1 – Precambrian metamorphics, 2 – Jurassic
clastics and limestones, 3 – Upper Cretaceous Incigez and Tomalar Formations, 4 – Uppermost Maastrichtian to Paleogene Davutlar
Formation, 5 – Paleogene Gürleyikdere and Gurmalar Formations, 6 – Quaternary deposits, 7 – Locality of the Ürküt Section.

THE CENOMANIAN RADIOLARIANS FROM CENTRAL PONTIDES, TURKEY 351

hardt, E. parallelus Perch-Nielsen, Lithraphidites corniolensis
serratus Shumenko, L. praequadratus Roth, L. quadratus
Bramlette et Martini, Predicosphaera cretacea Gartner, P.
grandis Perch-Nielsen, P. spinosa Gartner, Rucinolithus? mag-
nus Bukry, Staurolithes laffitei Caratini, and Thoracosphaera
thoracata Keupp (determined by Enis Kemal Sagular, Süley-
man Demirel University, Isparta) (Tunoglu 1991b, 1992b).

Fig. 2. Generalized columnar section for studied area. 1 – Calc-
silicatic gneiss, 2 – Marble, dolomitic marble, 3 – Granite, dior-
ite and diorite-porphyre, 4 – Chert, 5 – Micritic limestone, 6 –
Clay, 7 – Conglomerate, 8 – Sandy limestone, 9 – Massive cor-
al limestone, 10 – Unconformity, 11 – Location of radiolarian-
bearing sample (compiled from Tunoglu 1993).

Abundant macrofossils such as bivalves, echinoids, corals

have been obtained from the lowermost part of the Davutlar
Formation. The age of the formation is Late Maastrichtian to
Early  Paleocene  (?)  due  to  foraminiferal  fauna  such  as  Glo-
botruncana  aegyptiaca  Nakkady,  G.  arca  (Cushman),  Glo-
botruncanita  stuarti  (De  Lapparent),  Rosita  consuta  (Cush-
man),

fornicata (Plummer), Globigerina fringa

(Subbotina), G. triloculinoides (Plummer) (determined by Ve-
dia Toker, Ankara University, Ankara) (Tunoglu 1991b,
1992b). The Cretaceous-Tertiary boundary is tentatively
placed in the lower part of this formation.

Lithological description of Ürküt Section

The lower part of the Tomalar Formation is represented by

radiolarian  cherts  intercalated  with  cherty  mudstones  and
cherty marls. These lithologies are characterized by the pres-
ence of abundant radiolarians (Tunoglu 1991a, 1993, 1994). In
this study, sample 326 (radiolarian chert) from the Ürküt Sec-
tion  of  the  Tomalar  Formation  was  analysed  (coll.  Cemal
Tunoglu, Hacettepe University, Ankara). The Ürküt Section is
located  in  the  southern  part  of  Devrekani  Basin,  between
Ürküt and Ahmetoglu villages (Fig. 1). The Tomalar Forma-
tion is relatively thin (approximately 10 m) and only the lower
part  of  the  Tomalar  Formation  is  present  in  the  studied  sec-
tion.

The description of the Ürküt Section is given here in as-

cending order (Fig. 3):

1. (?) Precambrian calc-silicatic gneiss, intruded by dykes

of diorite-porphyre.

2. The Tomalar Formation. The lower part of this formation

is represented by light greenish-grey ribbon cherts (beds 5—10
cm thick) intercalated with yellowish-grey to light olive-co-
loured cherty mudstones and siltstones (beds 7—15 cm thick).
In the upper part of the unit, light-grey wackestone beds are
present. Sample 326 was collected from the lowermost ex-
posed bed of this formation. The approximate observed thick-
ness of this formation is 10 meters in the study area.

3. The Davutlar Formation. Polygenetic conglomerates with

well-rounded pebbles of granite, diorite, and gneiss are
present at the base and it gradually changes to coarse to mid-
dle-grained yellowish-grey sandstones and sandy limestones
towards the upper part.

The remarkable feature of this section is the chert deposi-

tion above the unconformity surface separating the Tomalar
Formation from the basement rock units. This fact needs addi-
tional discussion and explanation. Probably, this chert deposi-
tion was preceded by an episode of non-deposition or by a pe-
riod during which the previously formed sediments were
eroded (partly or completely). Some examples could be given
for this phenomenon.

1. The Upper Cretaceous sedimentary cover of the Troodos

Ophiolite Massif (Cyprus) starts with the unit of volcaniclas-
tic breccias and sandstones with strongly variable thickness
depending on the surface relief of underlying volcanics (Rob-
ertson & Hudson 1974; Simonian & Gass 1978; Osozawa &
Okamura 1993). The overlying Turonian-Campanian Perape-
dhi Formation consists of deep-water metalliferous sediments

352 BRAGIN et al.

(umbers) and radiolarian cherts (Mantis 1970; Robertson &
Woodcock 1979; Blome & Irwin 1985; Urquhart & Banner
1995; Bragina & Bragin 1996). In some areas (for example, in
the southern flank of the Limassol Forest Massif, central Cy-
prus) the unit of volcaniclastic breccias is not present and the
Turonian radiolarian cherts directly lie on the eroded surface
of the upper pillow lavas of the ophiolite complex (Blome &
Irwin 1985).

2. The Jurassic Episkopi Formation (southwestern Cyprus)

overlies the Upper Triassic Vlambouros Formation (Swarbrick
& Robertson 1980). Uppermost part of the Vlambouros For-
mation is represented by Upper Norian to Rhaetian sand-
stones, siltstones and occasional micritic limestones (Bragin &
Krylov 1996). The lowermost part of the Episkopi Formation
includes Middle Jurassic radiolarian cherts. The lower contact
of the Episkopi Formation is clearly erosional and exhibits lat-
eral undulation (Bragin & Krylov 1996). Therefore, the depo-
sition of Middle Jurassic radiolarian cherts was preceded by a
period of erosion or non-deposition, and a large stratigraphic
gap (including the whole Lower Jurassic) appeared.

Radiolarian assemblage – discussion and

biostratigraphic interpretation

The radiolarian assemblage from sample 326 is character-

ized by the presence of the following taxa: Hexapyramis pan-
tanellii  Squinabol,  Hexapyramis  sp.  ex  gr.  H.  pantanellii
Squinabol, Acastea sp. cf. A. diaphorogona (Foreman), Acae-
niotyle  macrospina  (Squinabol),  Archaeocenosphaera?  mel-
lifera O’Dogherty, Staurosphaeretta wisniovskii (Squinabol),
S. micropora (Squinabol), Protoxiphotractus sp. cf. P. vento-
sus O’Dogherty, P. sp., Paronaella solanoensis Pessagno, P.
sp., Halesium sp. cf. H. diacanthum (Squinabol), H. quadra-
tum Pessagno 1971, H. sexangulum Pessagno, Patulibracchi-
um  woodlandensis  Pessagno,  Pessagnobrachia  irregularis
(Squinabol), Crucella aster (Lipman), C. irwini Pessagno, C.
messinae Pessagno, Savaryella quadra  (Foreman), S. sp. aff.

S. spinosa O’Dogherty, S. sp., Mesosaturnalis hueyi (Pessag-
no), Acanthocircus impolitus O’Dogherty, Vitorfus brustolen-
sis  (Squinabol),  Cavaspongia  californiaensis  Pessagno,  C.
euganea (Squinabol), Pyramispongia glascockensis Pessagno,
Alievium sp., Becus horridus (Squinabol), Pseudoaulophacus
sp. aff. P. sculptus (Squinabol), P. sp., Patellula sp. aff. P. he-
lios (Squinabol), Dactyliodiscus longispinus (Squinabol), Go-
dia sp. aff. G. concava (Li et Wu), G. lenticulata Jud, G. sp. cf.
G. lenticulata Jud, Dactyliosphaera sp. ex gr. D. maxima (Pes-
sagno), Archaeospongoprunum salumi Pessagno, Archaeodic-
tyomitra sliteri Pessagno, A. sp. ex gr. A. sliteri Pessagno, A.
sp. cf. A. squinaboli Pessagno, Obelisciotes sp. aff. O. turris
(Squinabol),  Xitus  antelopensis  Pessagno,  Novixitus  dengoi
Schmidt-Effing, N. weyli Schmidt-Effing, Amphipyndax stocki
(Campbell  et  Clark), Stichomitra  sp.  ex.  gr.  S.  alamedaensis

Fig. 3. Ürküt Section from the Tomalar Formation. 1 – (?) Precambrian metamorphic basement, 2 – Dyke of diorite-porphyre, 3 –
Cherts and cherty mudstones of the Tomalar Formation, 4 – Sandy limestones and marls of the Davutlar Formation, 5 – Basal con-
glomerate of the Davutlar Formation, 6 – Quaternary slope deposits, 7 – Sample locations, 8 – Unconformity.

Fig.  4.  Scanning  electron  micrographs  of  the  radiolarians  from
the  Devrekani  region.  1  –  Hexapyramis  pantanellii  Squinabol;
Scale bar = 100 µm. 2  –  Hexapyramis sp. ex. gr. H. pantanellii
Squinabol; Scale bar = 200 µm. 3 – Acastea sp. cf. A. diaphorog-
ona (Foreman); Scale bar = 100 µm. 4 – Acaeniotyle macrospina
(Squinabol);  Scale  bar  =  100  µm.  5—6  –  Archaeocenosphaera?
mellifera  O’Dogherty;  Scale  bar  for  all  figures  =  100  µm.  7  –
Staurosphaeretta wisniovskii (Squinabol); Scale bar = 200 µm. 8—
9  –  Staurosphaeretta  microporus  (Squinabol);  Scale  bar  for  all
figures  =  200  µm.  10  –  Protoxiphotractus  sp.  cf.  P.  ventosus
O’Dogherty;  Scale  bar  =  100  µm.  11  –  Protoxiphotractus  sp.;
Scale bar = 100 µm. 12—13 – Paronaella solanoensis Pessagno;
Scale  bar  respectively  =  100,  200  µm.  14  –  Paronaella    sp.,
Scale  bar  =  100  µm.  15  –  Halesium  sp.  cf.  H.  diacanthum
(Squinabol); Scale bar = 100 µm. 16 – Halesium quadratum Pes-
sagno; Scale bar = 155 µm. 17 – Halesium sexangulum  Pessag-
no; Scale bar = 100 µm. 18—19 – Patulibracchium woodlanden-
sis  Pessagno;  Scale  bar  respectively  =  200,  100  µm.  20  –
Pessagnobrachia  irregularis  (Squinabol);  Scale  bar  =  100  µm.
21—22 – Crucella aster (Lipman); Scale bar for all figures = 100
µm.  23  –  Crucella  messinae  Pessagno;  Scale  bar  =  100  µm.  24
– Crucella irwini Pessagno; Scale bar = 100 µm.

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THE CENOMANIAN RADIOLARIANS FROM CENTRAL PONTIDES, TURKEY 355

(Campbell  et  Clark),  Stichomitra  communis  Squinabol,  and
Phalangites  telum  O’Dogherty  (Figs.  4—6).  Some  planktonic
foraminifers were also derived from the same sample, but they
are  non-determinable  due  to  poor  preservation.  Elements  of
Porifera  (macroscleres  and  microscleres)  were  not  indicated,
as well as other remains of benthic fossils.

A radiolarian assemblage was derived only from one sam-

ple, and we cannot study now the vertical distribution of radi-
olarian taxa in the section. Therefore, we can present here only
initial data on these fossils. Anyway, the recovered assem-
blage is characterized by good preservation, abundance and
taxonomic diversity. It allows us to present general informa-
tion about this assemblage, to compare and to correlate it with
previously described coeval associations, and to use these data
for new biostratigraphic interpretations.

All listed radiolarian species have good preservation and

were probably not affected by any redeposition, sorting or par-
tial dissolution. This conclusion is based on the fact that very
thin  and  delicate  shells  or  their  parts  (long  thin  spines,  thin
rings of Saturnalidae) are well preserved. Some large network-
like radiolarian shells were also obtained. These data may re-
flect  very  calm  depositional  conditions  of  cherts  that  were
probably  formed  by  slow  background  planktonogenic  sedi-
mentation in the relatively deep-water environment. Absence
of benthic remains (Porifera elements) also supports these con-
clusions.

The major part of the taxonomic composition of the studied

assemblage  (38  species,  including  those  determined  in  open
nomenclature) is represented by spumellarians. Only 11 nas-
sellarian species were obtained. One might suppose that this
taxonomic  domination  of  Spumellaria  could  be  interpreted
here  as  a  feature  of  a  relatively  shallow-water  environment.
On the contrary, some previously described Cenomanian radi-
olarian  assemblages  also  exhibit  taxonomic  domination  by
Spumellaria.  For  example,  the  Cenomanian  associations  re-
covered  from  relatively  deep-water  lithologies  of  Northern
Apennines (O’Dogherty 1994) have 113 spumellarian and 91
nassellarian species. Therefore, such a feature as the taxonom-

Fig.  5.  Scanning  electron  micrographs  of  the  radiolarians  from  the
Devrekani  region.  1  –  Savaryella  quadra  (Foreman);  Scale  bar  =
100 µm. 2 – Savaryella sp. aff. S. spinosa O’Dogherty; Scale bar =
100 µm. 3 – Savaryella sp.; Scale bar = 100 µm. 4—5 – Mesosatur-
nalis hueyi (Pessagno); Scale bar for all figures = 100 µm. 6 – Acan-
thocircus  impolitus  O’Dogherty;  Scale  bar  =  100  µm.  7  –  Vitorfus
brustolensis (Squinabol); Scale bar = 40 µm.  8—9 –  Pyramispongia
glascockensis Pessagno; Scale bar for all figures = 100 µm. 10—11 –
Cavaspongia  euganea  (Squinabol);  Scale  bar  for  all  figures  =  100
µm.  12  –  Becus  horridus  (Squinabol);  Scale  bar  =  100  µm.  13  –
Pseudoaulophacus  sp.  aff.  P.  sculptus  (Squinabol);  Scale  bar  =  100
µm. 14 – Pseudoaulophacus  sp.; Scale bar = 100 µm. 15 – Alievi-
um sp.; Scale bar = 100 µm. 16 – Patellula sp. aff. P. helios (Squin-
abol);  Scale  bar  =  100  µm.  17  –  Dactyliodicus  longispinus  (Squin-
abol); Scale bar = 100 µm. 18 – Godia concava (Li et Wu); Scale bar
=  200  µm.  19  – Godia  lenticulata  Jud;  Scale  bar  =  200  µm.  20  –
Godia  sp. cf. G. lenticulata Jud; Scale bar = 100 µm. 21  – Dactyl-
iosphaera ex. gr. maxima (Pessagno); Scale bar = 100 µm. 22 – Ar-
chaeospongoprunum salumi Pessagno; Scale bar = 100 µm.

ic Spumellaria/Nassellaria ratio needs additional studies and
cannot be used now for interpretations of Mid-Cretaceous pa-
leoenvironments.

Spumellaria have some quantitative domination over Nas-

sellaria, but we cannot make any speculations based on such
domination in only one sample. We marked clear quantitative
domination  of  several  species:  Archaeocenosphaera?  mel-
lifera,  Acaeniotyle  macrospina,  Savaryella  quadra,  Pyrami-
spongia  glascockensis,  and  Stichomitra  communis.  The  last
species  is  extremely  abundant  in  all  known  Cenomanian  as-
semblages  from  the  Mediterranean  region:  Northern  Italy
(O’Dogherty 1994), Central Italy (Salvini & Marcucci-Passe-
rini  1998),  Southern  Spain  (O’Dogherty  1994)  and  Crimea
(Bragina 1999, 2001).

Generally, this assemblage has very close affinity to several

previously  studied  Cenomanian  radiolarian  fauna  from  the
Western Mediterranean (O’Dogherty 1994; Salvini & Marcuc-
ci-Passerini 1998), Crimea (Bragina 1999, 2001) and Atlantic
Ocean (Erbacher 1994). All determined taxa are known from
these regions. Several species (Pyramispongia glascockensis,
Stichomitra  communis,  Xitus  antelopensis,  and  others)  are
known from North America (Pessagno 1976), and they seem
to have very wide (circumtropical) paleogeographical appear-
ance.  The  studied  assemblage  is  less  taxonomically  diverse
than  coeval  assemblages  from  Italy  (O’Dogherty  1994),  but
this  can  be  explained  by  our  insufficient  knowledge  of  radi-
olarians from the Ürküt Section that were studied in only one
sample. On the contrary, the assemblage from northern Turkey
is more diverse than the Upper Cenomanian assemblage from
Crimea that consists of only 20 species (Bragina 1999, 2001).

The presence of several well-studied coeval radiolarian as-

semblages correlated with other microfossils, especially with
planktonic  Foraminifera  (O’Dogherty  1994;  Erbacher  1994;
Bragina  2001)  provide  numerous  radiolarian  biostratigraphic
data that have to be used in this study. We utilized all well de-
termined  species  with  restricted  stratigraphic  range  for  our
biostratigraphic interpretation (Fig. 7), and these data allow us
to determine the age of the studied association. We did not use
taxa determined in open nomenclature, because they need de-
tailed study, description and revision that will be a subject of
further investigations.

The total number of 26 well-determined species were analy-

sed,  and  their  ranges  were  estimated  according  to  previous
publications  on  the  Cretaceous  Radiolaria  (Foreman  1975;
Pessagno  1976,  1977;  Holzer  1980;  Schmidt-Effing  1980;
Thurow  1988;  Erbacher  1994;  O’Dogherty  1994;  Bragina
1999, 2001). We had summarized the previous biostratigraphic
data  to  show  the  maximal  approximate  range  for  every  spe-
cies, and we gave more attention to the well-studied taxa. The
following results were obtained:

1. Large part of analysed taxa (11 species) have their first

appearance  in  the  Middle  Albian  (Acaeniotyle  macrospina,
Archaeocenosphaera?  mellifera,  Staurosphaeretta  wishnio-
vskii, Pessagnobrachia irregularis, Crucella messinae, C. ir-
wini, Savaryella quadra, Acanthocircus impolitus, Archaeod-
ictyomitra  sliteri,  Stichomitra  communis,  and  Phalangites
telum).  Therefore,  the  studied  assemblage  is  undoubtedly
younger than Early Albian.

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THE CENOMANIAN RADIOLARIANS FROM CENTRAL PONTIDES, TURKEY 357

2. Five species (Vitorfus brustolensis, Cavaspongia euga-

nea, Dactyliodiscus longispinus, Xitus antelopensis, and No-
vixitus dengoi) appear for the first time in the Upper Albian.
Therefore, the Middle Albian range can be excluded due to
this lower limit of these well-known taxa.

Fig.  6.  Scanning  electron  micrographs  of  the  radiolarians  from  the
Devrekani  region.  1  –  Archaeodictyomitra  sliteri  Pessagno;  Scale
bar = 100 µm. 2—5 – Archaeodictyomitra sp. ex. gr. A. sliteri Pessa-
gno; Scale bar for figure 2, 3 and 5 = 100 µm, figure 4 is detail of
apical part of the figure 3, Scale bar = 40 µm. 6 – Archaeodictyo-
mitra  sp.  cf.  A.  squinaboli  Pessagno;  Scale  bar  =  40  µm.  7—8  –
Obeliscoites  sp.  aff.  O.  turris  (Squinabol);  Scale  bar  for  figure  7  =
100 µm, figure 8 is detail of medial part of figure 7, Scale bar = 40
µm.  9  –  Xitus  antelopensis  Pessagno;  Scale  bar  =  100  µm.  10  –
Novixitus dengoi Schmidt-Effing; Scale bar = 57 µm. 11—12 – No-
vixitus weyli Schmidt-Effing; Scale bar for figure 11 = 100 µm, fig-
ure 12 is detail of the apical part of figure 11, Scale bar = 40 µm. 13
– Amphipyndax stocki (Campbell et Clark); Scale bar = 100 µm. 14
–  Stichomitra  sp.  ex.  gr.  S.  alamedaensis  (Campbell  et  Clark);
Scale  bar  =  77  µm.  15—17  –  Stichomitra  communis  Squinabol;
Scale  bar  for  all  figures  =  100  µm.  18  –  Phalangites  telum
O’Dogherty; Scale bar = 77 µm. 19—21 – Radiolaria incertae sedis;
Scale bar for all figures = 200 µm.

3. Some of the taxa obtained from the Tomalar Formation

such as Halesium quadratum, H. sexangulum, Archaeospon-
goprunum salumi, and Novixitus weyli appear for the first time
in the Early Cenomanian. So, we can consider that the age of
the assemblage is younger than the Late Albian.

4. The Lower to Middle Cenomanian boundary is marked

by coeval known appearance and extinction of some species. It
is the first appearance level of Patulibracchium woodlanden-
sis and Pyramispongia glascockensis. Another important level
is the boundary between the Middle and Upper Cenomanian.
It  represents  the  last  appearance  level  of  Acaeniotyle  mac-
rospina, Pessagnobrachia irregularis, Savaryella quadra, and
Becus horridus. The species Staurosphaeretta wisniovskii was
supposed to disappear after the Lower Cenomanian according
to  two  previous  studies  (Origlia-Devos  1983;  O’Dogherty
1994). Recently, this species was found in the Upper Cenoma-
nian  and  Lower  Turonian  strata  of  Crimea  (Bragina  1999,
2001),  therefore,  it  has  a  wider  stratigraphic  range  than  was
supposed before.

5. The Cenomanian-Turonian boundary is characterized by

the last appearance of Hexapyramis pantanellii, Xitus ante-
lopensis, Novixitus dengoi, and N. weyli. According to recent
study of O’Dogherty (1994), two species among analysed fau-
na (Paronaella solanoensis and Mesosaturnalis hueyi) have

Fig. 7. Stratigraphic ranges of the selected radiolarian species from sample 326. The supposed range of Paronaella solanoensis is shown by
dotted line. Grey area indicate the age of assemblage (Cenomanian).

▲▲▲▲▲

358 BRAGIN et al.

their first appearance level at this boundary. Therefore, we
have again the problem of discordant ranges that should be
discussed.

Paronaella solanoensis was considered by Erbacher (1994)

and  O’Dogherty  (1994)  as  restricted  stratigraphically  to  the
Alievium  superbum  Zone  (lower  Turonian).  Nevertheless,
Hull  (1997)  illustrated  as  Paronaella  sp.  aff.  P.  solanoensis
specimens from the Upper Jurassic (Tithonian). These forms
have very close affinity to the Late Cretaceous ones, and Hull
(1997) noted only minor differences. Kiessling (1999) also il-
lustrated similar forms from the Kimmeridgian to Valanginian
of various regions. Bragina (1999, 2001) reported this species
from the Upper Cenomanian of Crimea. Taking into account
the very wide stratigraphic ranges of some radiolarian species
in the Jurassic and Cretaceous (Acaeniotyle umbilicata = late
Oxfordian—early Aptian, Archaeodictyomitra apiarium = Mid-
dle Callovian—Early Aptian, Holocryptocanium barbui = Late
Tithonian—Cenomanian)  (Baumgartner  et  al.  1995),  we  sup-
pose that Paronaella solanoensis range is not restricted to the
Turonian.  It  should  also  be  noted  that  Alievium  superbum
(Squinabol),  the  zone  species  of  the  Lower  Turonian
(O’Dogherty 1994), is not present in the studied assemblage.

Mesosaturnalis hueyi (= Acanthocircus hueyi in O’Dogherty

1994) was also thought to appear at the Cenomanian-Turonian
boundary. Nevertheless, Foreman (1975) reported this species
from the Albian to Santonian. Forms in this study (Figs. 5.4
and 5.5) possess characteristic features of this species with
wide, massive, and strongly bladed ring. Therefore, Mesosat-
urnalis hueyi has a wider stratigraphic range than was sup-
posed by O’Dogherty (1994).

As a summary, 26 well-determined species are utilized for

biostratigraphic datation. It can be concluded that the age of
the studied assemblage is Cenomanian. The most probable re-
stricted range of assemblage is the middle Cenomanian due to
the fact that several species of our assemblage have presently
known first appearance levels at the early-middle Cenomanian
boundary, as well as some species which seem to be extinct at
the beginning of the late Cenomanian. All common and typi-
cal  Cenomanian  taxa  are  present  in  the  studied  assemblage.
The only exception is Pseudodictyomitra pseudomacrocepha-
la (Squinabol), characteristic species of the Albian—Turonian
interval, which is not present in studied assemblage. We ex-
pect to find this species during further studies. For example,
Pseudodictyomitra  pseudomacrocephala  is  very  rare  in  the
Upper  Cenomanian  of  Crimea  (Bragina  1999,  2001),  and  is
probably, rare in the studied assemblage too.

The assemblage from Ürküt Section can be correlated with

assemblages  of  Dactyliosphaera  silviae  Zone  (Radiolaria)  of
the  Cenomanian  from  Italy  and  Spain  (O’Dogherty  1994).
This radiolarian zone ranging from the middle part of Lower
Cenomanian to the lowermost part of Upper Cenomanian has
good correlation with ammonite and foraminiferal zonal suc-
cessions. The Dactyliosphaera silviae Zone is correlative with
ammonite zones Mantelliceras dixoni (upper part), Alternoa-
canthoceras rhotomagense, and A. jukesbrownei. It could also
be  correlated  with  foraminiferal  zones  Rhotalipora  brotzeni,
R. reicheli, and R. cushmani.

Conclusions

The radiolarian assemblage from the lower part of the

Tomalar  Formation  has  the  Cenomanian  (possibly  middle
Cenomanian) age. It has close affinity with coeval assemblag-
es of the Western Mediterranean and Atlantic Ocean and re-
flects  the  conditions  of  an  open  marine  basin.  This  affinity
provides  a  good  opportunity  to  apply  the  previously  defined
zonal  scales  of  the  Mid-Cretaceous  (Erbacher  1994;
O’Dogherty  1994)  in  the  Eastern  Mediterranean  area.  The
stratigraphic range of the Tomalar Formation probably covers
the interval from Cenomanian to Maastrichtian.

Further studies should be concerned with detailed sampling

of radiolarian-bearing lithologies from the Tomalar Formation,
taxonomic description of the Cenomanian Radiolaria and on
their biostratigraphic calibration by using other microfossils
(planktonic Foraminifera and nannofossils).

Acknowledgments: The authors greatly appreciate Prof. Dr.
C. Göncüoglu (Middle East Technical University, Ankara) for
his kind reviewing of the manuscript and Günül Atay (MTA,
Ankara) for technical support during preparation of work. Au-
thors express their thanks for Nina Gorkova (Geological Insti-
tute, Moscow) for studies on SEM. This work was partly sup-
ported by the Russian Foundation for Fundamental Studies
(Grants 00-05-64018 and 00-05-64298).

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