Download THE BLACK SEA BASIN CRETACEOUS VOLCANIC BELTS: NEW

PROCEEDINGS OF THE IV INTERNATIONAL SCIENTIFIC AND TECHNICAL CONFERENCE
"GEOLOGY AND HYDROCARBON POTENTIAL OF THE BALKAN-BLACK SEA REGION"
11 - 15 SEPTEMBER 2013, VARNA, BULGARIA
THE BLACK SEA BASIN CRETACEOUS VOLCANIC BELTS: NEW DISCOVERIES BASED ON RESULTS
OF “GEOLOGY WITHOUT LIMITS” INTERNATIONAL 2D SEISMIC PROJECT
Anatoly Nikishin1, Aral Okay2, Okan Tüysüz2, Ali Demirer3, Nikolay Amelin4, Evgeny Petrov4
1 Moscow
State University, Russia
Technical University, Turkey
3 TPAO, Turkey
4 Geology Without Limits, Russia
2 Istanbul
Abstract: Interpretation of new 2D seismic data of “Geology Without Limits” project for the Black Sea Basin led to new
understanding of Black Sea Basin structure and history. One of the main news is discovery of Albian and Late
Cretaceous (Campanian-?) belts of buried volcanic structures. Albian chain of volcanos is located along Shatsky Ridge.
Late Cretaceous chain of volcanos was documented to the north of Pontides volcanic belt.
Introduction
Geological structure of the Black Sea has been under investigation since the publications of regional
seismic lines for the entire area in the 1980’s [1, 2, 3]. More recent seismic lines were shot for regional parts of
the sea and were published by many authors.
Formation history and dynamics of the Black Sea basins were discussed in many publications.
Starting from several classical works [2, 4, 5, 6], it is considered that that the Western Black Sea Basin and the
Eastern Black Sea Basin were formed as back-arc basins behind the Pontide volcanic arc.
This work is based upon results of interpretation of the new regional seismic lines acquired in 2011
within the international project Geology Without Limits in whose realization specialists from Russia, Turkey,
Ukraine, Romania and Bulgaria took part (Fig. 1).
Some results
We have discovered a lot of new structures in the Black Sea. Main results will be published [7]. We will
focus on discoveries of Cretaceous volcanic belts in the Black Sea Basin (Fig. 2).
On some lines (e.g. BS-110, 120, 140, 160, 170, 220, 222, Fig. 3), singled out are probably isometric
highs 500-2500 msec high and 10-15 km in diameter, of conical shape and without eroded down tops.
Geographically, these highs are located closer to Turkey. At least some of them show positive seismic velocity
anomalies (Fig. 3). It is probable that most of these highs (if not all) are submarine volcanoes. Their bases lie
approximately at the stratigraphic level of Cretaceous or Upper Cretaceous deposits. Dimensions of the
supposed volcanoes are commensurable with dimensions of arc volcanoes in Kamchatka, the Kurils, and
Indonesia. In Turkey the Cretaceous volcanic arc of Pontides stretches parallel to the coast (Fig. 2). The
maximum of volcanism is in the Santonian-Campanian (or Campanian) age [8]. That is why we assume that
the age of these hypothetical volcanoes is Santonian-Campanian. Since these volcanoes do not have distinct
signs of erosion, it means that they formed underwater at sea depths of not less than 2 km. It follows from this
that by end of Cretaceous the Western and the Eastern Black Sea Basins were already deepwater basins.
On the Shatsky Ridge there are several structures looking like volcanoes (Line BS-200) (Fig. 4) for the
interval of Albian. Albian volcanics are known in the Adjaro-Trialeti Zone in Georgia and in the area of
Balaklava in the Crimea [7, 9, 10]. A hypothesis can be made that in Albian a volcanic belt was going from the
area of Balaklava, through the Shatsky and Andrusov Ridges and was docking into the Adjaro-Trialeti Zone.
The volcanic belt was above-subduction one as it is shown for the Adjaro-Trialeti Zone and for the Balaklava
area [7, 9, 10].
Thickness of the Albian volcanics and volcanoclastic sediments may reach several hundreds of
meters. The Albian volcanics and volcanoclastics are well known from the Karkinit Graben on the Odessa
Shelf [7, 9, 10].
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PROCEEDINGS OF THE IV INTERNATIONAL SCIENTIFIC AND TECHNICAL CONFERENCE
"GEOLOGY AND HYDROCARBON POTENTIAL OF THE BALKAN-BLACK SEA REGION"
11 - 15 SEPTEMBER 2013, VARNA, BULGARIA
Figure 1. Location of the seismic lines used in the paper. The seismic lines were done in a frame of “Geology
Without Limits” project in 2011.
Figure 2. Location of the Cretaceous and Eocene volcanic zones in the Black Sea area.
(1) Basin with oceanic ore highly rifted continental crust. (2) Zone of Cretaceous volcanic belt documented. (3) Zone of
proposed Cretaceous volcanic belt on continental slope and deeply buried block. (4) Zone of Eocene volcanism. (5)
Albian volcanos documented on land and proposed based on seismic data in the sea (partly using our new seismic
data). (6) Proposed Late Cretaceous (Campanian-?) volcano discovered using new seismic data (Geology Without
Limits project). (7) Contour of proposed Albian volcanic belt.
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PROCEEDINGS OF THE IV INTERNATIONAL SCIENTIFIC AND TECHNICAL CONFERENCE
"GEOLOGY AND HYDROCARBON POTENTIAL OF THE BALKAN-BLACK SEA REGION"
11 - 15 SEPTEMBER 2013, VARNA, BULGARIA
Figure 3. Geological interpretation of seismic line BS-222 (above) and seismic velocities along the same line
(below). A big mountain-like feature can be recognized at bottom of layered sedimentary sequence. This
structure has a positive seismic velocity anomaly. It means this structure is compiled by dense rocks. An
interpretation of this structure is Cretaceous volcano. The volcano was not eroded. Its height is up to 2.5
seconds. It means that late Cretaceous water depth was more that 2-3 km. The volcano was buried by
sediments only during Eocene times.
Figure 4. A fragment of seismic line BS-200 across Shatsky Ridge. One of structures is characterized by
hummocky seismic facies. Height of some hummocks is up to 0.2-0.4 sec. A regional stratigraphic level of
hummocky facia is nearly Albian. We propose that this is volcanic constructions of Albian age.
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PROCEEDINGS OF THE IV INTERNATIONAL SCIENTIFIC AND TECHNICAL CONFERENCE
"GEOLOGY AND HYDROCARBON POTENTIAL OF THE BALKAN-BLACK SEA REGION"
11 - 15 SEPTEMBER 2013, VARNA, BULGARIA
Figure 5. A cartoon of the formation of the Black Sea basin and the evolution of the Cretaceous volcanic belts.
Reconstructions of the Albian, Cenomanian, and Campanian are presented.
(1) volcanic belts; (2) deep basins with oceanic or continental (highly thinned by rifting) crust; (3) sedimentary
basins; (4) axes of the oceanic crust rifting or spreading; (5) normal faults; (6) strike–slips; (7) individual
volcanoes. In the map for the Albian, the Sudak, West Caucasian and East Caucasian deep troughs, which
formed in the Callovian–Late Jurassic, are shown.
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PROCEEDINGS OF THE IV INTERNATIONAL SCIENTIFIC AND TECHNICAL CONFERENCE
"GEOLOGY AND HYDROCARBON POTENTIAL OF THE BALKAN-BLACK SEA REGION"
11 - 15 SEPTEMBER 2013, VARNA, BULGARIA
Restoration of volcanic arcs in the tectonic history of the Black Sea Basin
In Albian, a volcanic arc was being formed. In the Transcaucasia, Albian volcanites are known in the
area of the Adjaro-Trialeti Zone [7, 9, 10]. In the southwest of the Crimea, in Balaklava, Albian tuffs with
volcanic bombs and lapilli are known [10, 11]. Albian volcanites are perhaps also present on the continental
margin west of Sevalstopol in Crimea [12]. The interpretation of our seismic lines has shown that Albian
volcanoes are possible on the Shatsky Ridge and the Andrusov Ridge. That is why we suppose that in Albian
a volcanic arc existed from the area of the Southwestern Crimea and stretched to the Transcaucasia [7, 9, 10].
We suggest calling it as the Balaklava-Trialeti volcanic arc.
The Campanian is the main epoch in formation of the Pontides volcanic belt that stretched in the west
into Bulgaria. The subduction zone was located south of this belt [8, 13, 14]. We believe that processes of
rifting and oceanic crust spreading had ended before the beginning of Campanian. But in the south of the
Black Sea a belt of submarine volcanoes up to 1-2 km high was being formed north of the recent Pontides.
Interpretation of the seismic lines shows that at the end of Late Cretaceous the Andrusov and Shatsky Rises
were being covered with a blanket of sediments and experienced general thermal subsidence the same as the
deepwater Eastern Black Sea and the Western Black Sea basins.
Our model of the Cretaceous Black Sea Basin history is shown on Fig. 5.
Conclusions
A chain of number buried submarine volcanoes of late Cretaceous (Campanian-?) age was
recognized in the Black Sea parallel to Late Cretaceous Pontides volcanic arc in northern Turkey. Possible
early Cretaceous (Albian-?) volcanic arc was proposed along Shatsky Ridge using seismic data.
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PROCEEDINGS OF THE IV INTERNATIONAL SCIENTIFIC AND TECHNICAL CONFERENCE
"GEOLOGY AND HYDROCARBON POTENTIAL OF THE BALKAN-BLACK SEA REGION"
11 - 15 SEPTEMBER 2013, VARNA, BULGARIA
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