RECORDS OF THE VOLCANIC ACTIVITY IN THE EASTERN PONTIDE 377
GEOLOGICA CARPATHICA, 54, 6, BRATISLAVA, DECEMBER 2003
SEDIMENTOLOGICAL, PALEONTOLOGICAL AND VOLCANIC
RECORDS OF THE EARLIEST VOLCANIC ACTIVITY
IN THE EASTERN PONTIDE CRETACEOUS VOLCANIC ARC
CEMIL YILMAZ, CÜNEYT ªEN and A. SIBEL ÖZGÜR
MMF Geological Engineering Department, Karadeniz Technical University, Trabzon, Turkey;
email@example.com; firstname.lastname@example.org; email@example.com
(Manuscript received December 10, 2002; accepted in revised form June 23, 2003)
Abstract: This study deals with the volcanic blocks occurring within the Upper Coniacian-Santonian red limestone
which crops out in the Maçka area (Trabzon, NE Turkey). The red limestones are thin to medium-bedded, and mostly
consist of wackestones, rich in planktonic foraminifers with subordinate radiolarians and inoceramid bivalve fragments.
In the upper part of the formation, volcanic blocks occur which consist of andesite to dacite and show microlitic-porphy-
ritic texture with plagioclase and pyroxene as phenocrysts. Chemical data indicate that these volcanic rocks are calc-
alkaline in character and show similar trace and rare earth element chemical signatures with those of arc related volcanics.
The limestones and the volcanic blocks are discoloured in proximity of the boundary. The contact relationships suggest
that the volcanic lava blocks were still hot when they fell on the unlithified pelagic limestone muds. These data empha-
size that the earliest Cretaceous volcanism started at the Late Coniacian-Santonian boundary in the Eastern Pontide
Key words: Cretaceous, Turkey, Pontide volcanic arc, volcanic rocks, pelagic limestone.
The Northern part of Turkey is geotectonically known as the
Pontide orogenic belt (Ketin 1966). Many studies carried out
in this region concluded that the eastern part of the Pontides
was a volcanic arc during Mesozoic and Cenozoic times
(Tokel 1972; Gedikoûlu et al. 1979; ýengör & Yôlmaz 1981;
Bektaþ 1984; Yalçônalp 1992; Robinson et al. 1995; Okay &
ýahintürk 1997; Yôlmaz et al. 1997). However, it remains a
matter of debate whether the Eastern Pontides were the north-
ern active continental margin of Gondwana (Dewey et
al.1973; Bektaþ et al. 1999) or the southern active continental
margin of Eurasia during the Cretaceous (ªengör et al. 1981;
Adamia et al. 1981). According to Bektaº et al. (1999), the Pa-
leotethys ocean floor began to be consumed by southward
subduction under the Pontides at the beginning of the Late
Cretaceous and the subduction related calc-alkaline volcanic
and associated pyroclastic rocks represent the northern edge of
the Eastern Pontide magmatic arc. The volcanic activity was
not continuous and it allowed sediment accumulations during
the non-eruptive phases (Taslô et al. 1994; Yôlmaz & Karslô
1997). Because the volcanic rocks have covered these sedi-
mentary formations, smaller and discontinuous outcrops of
sedimentary rocks are seen in the region. The lack of volcano-
stratigraphic, paleontological, sedimentological and petrologi-
cal data have led to the volcanic rock often being ignored in
many field studies conducted in the region. The data presented
in this study will help to understand the age of the volcanic ac-
tivity, and the evolution of the Eastern Pontide magmatic arc.
The Eastern Pontides can be divided into three lithologic as-
semblages corresponding to the northern, southern and axial
zones (Bektaº et al. 1995, 1999). The northern zone consists
of Mesozoic-Cenozoic volcanic rocks (Pontide magmatic arc)
widespread along the Black Sea Coast. The southern zone in-
cludes the Hercynian granitic and metamorphic basement, Li-
assic rift related sediments, Middle Jurassic-Lower Cretaceous
platform carbonates, Upper Cretaceous slope to basin sedi-
ments and Tertiary volcano-siliciclastic rocks. The axial zone
or back-arc basin or Anatolids (Ketin 1966) consists of Al-
pine-type peridotites and metamorphic massifs.
The study area is located in the Northeastern Pontides,
30 km south of the city of Trabzon, around the town of Maçka
(Figs. 1 and 2). Because of the destruction of the Cretaceous
to Tertiary aged volcanic rocks (the Maçka volcanics), a single
stratigraphic succession from bottom to top does not occur in
the Maçka-Zigana area. Therefore, a composite section is pre-
sented which is based on some short sections (Fig. 3).
The stratigraphic succession in the study area ranges from
Jurassic to Cenozoic. The Lower Jurassic Bürnük Formation
at the base of the succession consists of thin to medium bed-
ded tuffs intercalated with spilitic basalts. The Bürnük Forma-
tion is overlain by the ùnaltô Formation (Ketin & Gümüþ
1963), which is mainly represented by thick-bedded grey-co-
loured limestones interbedded with dolomites and dolomitic-
limestones. On the basis of a scarce benthic foraminiferal as-
semblage the formation is referred to Middle JurassicLower
378 YILMAZ, ªEN and ÖZGÜR
Cretaceous (Taslô 1984; Yalçônalp 1992). The Berdiga For-
mation horizontally and vertically passes into the Çaûlayan
Formation (Ketin & Gümüþ 1963), which consists of mega-
breccias, calciturbidites, siltstones and marl-limestone depos-
ited as a sedimentary prism on fault slopes derived from the
Early Cenomanian tectonic deformation of the ùnaltô Forma-
tion. In the upper part of the formation, marly limestones grade
into thin to medium-bedded red coloured limestones, known as
the Kapanboazô Formation (Ketin & Gümüþ 1963). The Up-
per Cretaceous-Cenozoic Maçka volcanics known as the Pon-
tide arc volcanics (Yôlmaz & Karslô 1997) consist of dacite,
andesite and basalt and related pyroclastic rocks.
of the Kapanbo
The Kapanboûazô Formation, about 20 to 45 m thick, mainly
consists of thin to medium-bedded, red coloured limestones in-
cluding at the top volcanic blocks with andesitic to dacitic in
composition (Figs. 3 and 4). The red limestones are mostly
wackestones, rich in usually well-preserved planktonic fora-
minifers (Fig. 3/3), with subordinate radiolarian and inoceram-
id bivalve fragments (Fig. 4D). The planktonic foraminifers in-
clude various species of Globotruncanidae and Heterohelicidae,
such as Marginotruncana coronata Bolli, Marginotruncana
pseudolinneiana Pessagno, Hedbergella flandrini Porthault,
Dicarinella concavata (Brotzen), Dicarinella primitiva (Dalbiez),
Calcisphaerula innominata Bonet, Stomiosphaera sphaerica
(Kaufmann), Maginotruncana sp., Heterohelix sp., Schackoi-
na sp., Globigerinelloides sp., Dicarinella sp., Hedbergella
sp., Radiolaria sp., Globigerinidae, indicating a late Coniacian
to Santonian age.
Fig. 1. Main tectonic features, tectonic zones of the eastern Pontides (Bektaº et al. 1999) and location of the study area. F1 Niksar-
ùspir fault; F2 Suºehri-Maden fault; F3 Espiye-Maden fault; F4 Suºehri-Gümüºhane fault; F5 Kôrôklô-Rize fault; F6 Pulur
fault; F7 Suºehri-Espiye fault. 1 Paleozoic granites; 2 Paleozoic metamorphic basement; 3 serpentinite; 4 Cretaceous
ophiolitic melange; 5 Mesozoic sedimentary rocks; 6 Cretaceous and Eocene arc volcanics; 7 undifferentiated Mesozoic and
Cenozoic; 8 caldera or dome; 9 fault; 10 thrust fault; 11 orthogonal drape and drage folds. NAF North Anatolian Fault;
NEAF North East Anatolian Fault.
Fig. 2. Geographical location and geological map of the study
area. 1 Çaûlayan Formation, 2 Kapanboûazô Formation, 3
Maçka Formation, 4 Stratigraphic sections.
RECORDS OF THE VOLCANIC ACTIVITY IN THE EASTERN PONTIDE 379
The matrix appears to be red to light brown in reflected light
and mostly consists of micrite intimately mixed with fine fos-
sil debris and some finely crystalline microspars. The volcanic
rocks show microlitic-porphyritic texture with commonly al-
terated andesine (An
) and pyroxene phenocrysts. Macro-
scopically the green coloured matrix is made of microlithic
plagioclase and some Fe-Ti oxides besides alteration products.
The limestone and the volcanic blocks are discoloured to yel-
low in proximity of the boundary. In fact, the limestone-volca-
nic block contacts are burnt (Fig. 4BC), because the lime-
stone changes colour from red to dark brown up to almost
black, while the andesite block boundaries are discoloured and
they show a smaller size of the crystals. Furthermore, the con-
tacts are also characterized by the occurrence of a microscopic
Fig. 3. General columnar section of the Maçka area and Çatak, Ortaköy and Kôzôlcôk measured stratigraphic sections.
380 YILMAZ, ªEN and ÖZGÜR
Fig. 4. Red pelagic limestone including andesitic blocks in the study area. A Red pelagic limestone in the Çatak area. BC Volcanic
rock fragments in the red pelagic matrix (scale bar is 2 cm in the B). D Microscopic view of the samples B. VRF volcanic rock frag-
ment; g Globotruncana sp. The arrows are marking cooked contact of the pelagic matrix and volcanic rock blocks (scale bar is 500
Fig. 5. Geochemical characteristics of the volcanic blocks (descriptions of the figures are given in the text).
RECORDS OF THE VOLCANIC ACTIVITY IN THE EASTERN PONTIDE 381
darkened matrix with burnt pelagic microfossils and with py-
rite crystals, which emphasize the destruction of the primary
Geochemistry of the volcanic blocks
in the Kapanboûazô Formation
Representative chemical analyses of the volcanic blocks are
given in Table 1. All samples were analysed by ICP-MS at the
ACME Chemical Laboratories, Vancouver British Columbia,
Canada. The investigated fragments consist of medium to
high-K calc-alkaline andesite and dacite normalized to 100 %
on a water free basis (Fig. 5A,B; Irving & Baragar 1971; Pec-
cerillo & Taylor 1976; Cox et al. 1979). Whole rock composi-
tions range from 56.7 to 62.4 wt. % SiO
, from 0.6 to
1.1 wt. % MgO, and from 1.8 to 2.3 wt. % K
O (Table 1).
concentrations are relatively constant near 14 wt. %
over the entire investigated samples. Whole rock LOI con-
tents vary from 3.7 to 7.7 wt. % and decrease with increasing
Table 1: Major (wt. %) and trace element (ppm) contents of volcanic rock inclusions in Kapanboûazô Formation.
size of the fragment (the sizes of investigated fragments are
less than 20 cm with the exception of samples C9 and C10,
their sizes are more than 75 cm). Incompatible element pat-
terns normalized to n-MORB composition show typical arc
characteristics (Fig. 5C normalization values from Sun & Mc-
Donough 1989). Fractionated trace element patterns show en-
richment in LIL elements relative to the n-MORB and display
slightly negative Nb and Ti anomalies. Chondrite normalized
REE patterns are fractionated (Fig. 5D normalization values
from McDonough et al. 1991). Step patterns have (La/Lu)
13 without pronounceable Eu anomaly.
Slighly different chemical compositions of fragments of the
Kapanboûazô Formation show that Late Coniacian-Santonian
submarine volcanic system has developed relatively large,
shallow reservoirs that were capable of developing a composi-
tional diversity. These chemical characteristics are in agree-
ment with geotectonic models proposed by previous studies
(i.e., Bektaº et al. 1999). However, both the age and chemistry
of the earliest arc volcanics in the Eastern Pontides are pre-
sented in this study for the first time.
382 YILMAZ, ªEN and ÖZGÜR
Fig. 6. Geodynamic evolution of the study area.
Discussion and conclusion
The relationship between the pelagic red limestones and
volcanic blocks in the upper part of the Kapanboûazô Forma-
tion provide stratigraphic, paleontological and petrological in-
formation regarding the beginning of the volcanic activity in
the Eastern Pontides. The contact relationships between vol-
canic blocks and limestones suggest that the volcanic lava
blocks were still hot when they fell on the unlithified pelagic
limestone muds. Therefore, biostratigraphic data obtained
from pelagic limestones provide the age of the volcanic rocks.
The beginning of the volcanism in the Eastern Pontide volca-
nic arc may thus be referred to late ConiacianSantonian.
Many geotectonic models have been suggested to explain
the interesting geological features of the Eastern Pontides
(e.g. Bektaþ et al. 1995; Yôlmaz & Karslô 1997; Bektaþ et al.
1999; Yôlmaz & Korkmaz 1999; Yôlmaz & Karslô 2000). Al-
though the Jurassic to Early Cretaceous are clearly explained
RECORDS OF THE VOLCANIC ACTIVITY IN THE EASTERN PONTIDE 383
in these models, some Late Cretaceous tectono-stratigraphic
events are not well documented. On the basis of previous
studies (Yôlmaz & Korkmaz 1999; Yôlmaz & Karslô 2000)
and of the data presented in this paper, a new model for the
Maçka-Zigana area is proposed. Four distinct stages may be
distinguished in the geotectonic evolution of the study area
1 First Rifting Phase (Liassic): In this stage, under an ex-
tensional tectonic regime the Hercynian basement of the
whole Eastern Pontides was rifted into asymmetrical sedimen-
tary basins (Bektaþ et al. 1995; Yôlmaz 1997; Yôlmaz & Kork-
maz 1999). Volcaniclastic rocks accumulated in the grabens.
The red nodular limestone developed calcare ammonitico
rosso facies was deposited on the horsts and these condensed
sediments made-up the pelagic carbonate platform (Santonto-
2 Quiet Tectonic Period and Development of the Car-
bonate Platform (DoggerLower Cretaceous): After the ex-
tensional tectonic regime, a tectonically quiet regime pre-
vailed from the Dogger to the Lower Cretaceous. Platform
limestones (ùnaltô Formation), widespread and deposited in
shallow shelf conditions (Eastern Pontide Carbonate Platform,
Yôlmaz 2002) keep the geological records of the quiet period.
Continuing extensional activity process resulted in normal
faults causing crustal thinning and intense volcanism (Bürnük
3 Second Rifting Phase, Break-up of the Carbonate Plat-
form and accumulated Çaûlayan and Kapanboûazô Formation:
The quiet tectonic regime ended early in the Cenomanian and
a newly extensional tectonic regime again become active.
Those stresses broke up the carbonate platform and deepening
basins occurred as a result of normal faults. In the fault slopes
typical rift related sedimentary rocks (Çaûlayan Formation)
were deposited (Eberli 1987; Masse & Luperto-Sinni 1987;
Santantonio 1993; Enos & Stephens 1993; Miller & Heller
1994; Rosales et al. 1994; Yôlmaz 1997). At the same time in-
terval, pelagic foraminifers bearing limestones (Kapanboûazô
Formation) were deposited in the deep portion of the normal
fault related sedimentary basins.
4 Active Volcanic Period (Late ConiacianSantonian):
Volcanic inclusions present within the red pelagic limestones
of the Kapanboûazô Formation indicate the beginning of the
arc volcanism in the Eastern Pontides. That sub-marine volca-
nism continues to the end of the Tertiary. Geological records
of those volcanics are seen in large outcrops through the East-
ern Pontides and are known as the Pontide arc volcanics.
Acknowledgments: We thank D. Puglisi, J. Lexa and I.
Haydoutov for their critical reviews and MTA Paleontology
Service (Ankara) for the fossil determinations. We also thank
L. Martire who improved the English of the text. This study
was supported by funds from Karadeniz Technical University
(Trabzon, Turkey) Research Grants 98.118.002.1 awarded to
C. Yôlmaz and 98.112.005 awarded to C. ýen.
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