The Black Sea region is favorable for understanding the role of  fluids in structure formation.
The large Kerchen-Taman mud-volcano  province has long been known onshore on its northeast.  The  numerous mud volcanoes there occur largely in regions where  thick Oligocene-Miocene Maykop clays are present.  Geological  and geophysical studies in the deep-water depression to the south  of the Crimea have disclosed gentle anticlines that do not have  roots in the Eocene sediments.  Faults are present at their crests,  and in places also sag grabens.  Sag grabens occur in various  other parts of the sea floor.  Seismic bright spots indicate  considerable gas saturation of the rocks. 

Among the indications of strong gas flows are cones of mud  volcanoes.
Ten such cones have been found in the central part  of the Black Sea, as well as several buried cones that are not  expressed in the sea-floor relief.  Most of the breccia of these  cones consists of Maykop rock.  Thickness of the Maykop is  particularly great in this part of the Black Sea basin.  Seven mud  volcanoes have been found in the Sorokin downwarp, which is  along the north-central margin of the Black Sea.  This also  coincides with an area of thick Maykop clays.  Above the crests  of the Andrusov (central Black Sea between West and East  Black Sea depressions) and Shatskiy (northeast Black Sea)  swells in the Neogene sediments are numerous faults  accompanied by seismic dynamic anomalies and sag craters  of small amplitude but rather large area up to several kilometers  wide.  These features are located everywhere above local highs  on the top of the Mesozoic.  This is due probably to flow of fluid  from Mesozoic rocks. 

The sedimentary section of the Black Sea is deformed over  large areas, and flow of fluids has played an important role in  this process, which is defined as fluidodynamic deformation.   Such deformation provides channels for vertical migration of  hydrocarbons from oil-gas-source rocks.  The main oil-source  rocks in the Black Sea basin are generally held to be upper  Eocene and Maykop clays.  It is proposed here that the main  oil has been generated not by all the Maykop clays but only a  comparatively narrow stratigraphic interval, 

The structural unity of the Oligocene-Neogene downwarps  including the West Kuban downwarp with its large oil-gas fields  is a basis for a high assessment of its deep-water analogs in  the Black Sea - the Sorokin and Tuapse downwarps.  The main  exploration targets on the Shatskiy and Andrusov swells are  anticlinal traps in Mesozoic rocks.  Upper Jurassic limestone  reefs are promising in some areas. 

     The gas hydrate deposits of the Black Sea are without doubt  related genetically to large deposits of free gas.

Taken from Maysner and Tugolesov, 2001; digested in Petroleum  Geology, vol. 36, no. 3, 2002, in preparation, one seismic section,  one structure map, and one cross section.

Copyright 2002 James Clarke.  You are encouraged to print out this  News Letter and to forward it to others.  Earlier News Letters are  available at our web page:       http://geocities.com/internetgeology/    This News Letter is distributed without charge in the interest of our  science. To be added to the mailing list please send your e-mail  address to:       jamesclarke@erols.com    For information on the journal Petroleum Geology please telephone  703 759-4487 or FAX 703 759-3754. There is a time for everything...a time to be silent and a time to  speak. Ecclesiastes 3:1,7.
 

VILNIUS TEN SUMMIT PRESAGES "BIG BANG" ENLARGEMENT OF NATO. Ten countries aspirant to NATO membership--the Vilnius Ten group of countries--held a summit meeting in Bucharest on March 25-26. As anticipated (see the Monitor, March 21), the event focused on the Black Sea direction of NATO's enlargement. With the Baltic states already on a firm track toward membership in the alliance, Romania and Bulgaria now look increasingly likely to also receive invitations this year to commence the NATO accession process.

The "Big Bang" enlargement scenario, encompassing the three Baltic states, Slovakia and Slovenia in Central Europe, and Romania and Bulgaria on the Black Sea--a scenario that looked unrealistic only a few months ago--has now become a distinct possibility, termed "robust enlargement" in recent statements by U.S. and some other allied officials.

The new focus on the Black Sea stems from four main factors. First, that region's strategic value to the U.S.-led current and planned antiterrorism operations. Second, a growing awareness that the Black Sea region is closely linked with the South Caucasus and the Caspian basin, the whole area being indivisible in terms of security. Third, vocal support by pivotal NATO ally Turkey--in an unusual tandem with Greece in this case--for Bulgaria's and Romania's inclusion in NATO, so as to close the gap between the alliance's Southeastern and Central European tiers. And, fourth, as a corollary, American leadership in all the processes--antiterrorism campaign, NATO enlargement, Caspian basin energy development--that have made the Black Sea region into a strategic prize.

It was U.S. President George W. Bush who broadened NATO's enlargement agenda to include the Black Sea direction in his June 2001 address in Warsaw. On that occasion, Bush chose to underline historic considerations and common values as the basis for enlarging the alliance "from the Baltic to the Black Sea." Soon afterward, September 11 provided the strategic impetus behind Black Sea enlargement. The post-September dynamics have underscored the value of the Black Sea region to U.S. and NATO strategies in a vast area from the Balkans to the Caspian and beyond.

Representing the United States at the Bucharest meeting, U.S. Deputy Secretary of State Richard Armitage called for a "robust enlargement," "the fullest, widest possible enlargement" of the alliance, when it holds its summit in Prague this coming November. Armitage also announced that he would travel from Bucharest directly to NATO headquarters in Brussels in order to brief the European allies, "to make sure that there is no mistake in Brussels about the position of the United States regarding the widest possible NATO membership."

The high level of U.S. representation contrasted starkly with the level of West European representation at the Vilnius Ten summit. The West European prime ministers and foreign affairs ministers did not honor the invitations to attend. Western Europe as a whole shone through its absence at the meeting. It was left to the defense minister of Luxembourg to hold mightily aloft the banner of Europe in front of the NATO aspirant countries.

Poland's President Aleksander Kwasniewski addressed the summit on behalf of a new member country of NATO. Kwasniewski underscored the vital importance of Ukraine to the international order now taking shape in East-Central Europe and the Black Sea basin. He urged NATO member and candidate countries to develop close and friendly cooperation with Ukraine, to consider the possibility of Ukrainian membership in NATO in the future, to recognize the strong potential of Ukraine's military industry for participation in joint projects, and to support Ukraine's military reforms with a view to developing modern units capable of interoperable cooperation with NATO allied units.

Georgia is also situated in the immediate eastern neighborhood of the soon-to-enlarge NATO. President Eduard Shevardnadze is underscoring the significance of Georgia's location as an extension of southeastern Europe geographically, economically and strategically. On a visit to Germany (Berliner Morgen Post am Sonntag, March 24), overlapping with the Vilnius-Ten meeting, Shevardnadze reaffirmed Georgia's goal of "knocking at NATO's door" by 2005. (PAP, BNS, BTA, March 25-27; NATO Enlargement Daily Brief, March 18, 25-26; see the Monitor, March 15, 21; Fortnight in  Review, March 21).

     The Black Sea deep-water depression is a sedimentary basin  filled by thick Cenozoic deposits.  Present there in addition to  structural swells and downwarps are such interesting features as  clay diapirs, mud volcanoes, and large deltaic deposits.  The  geology indicates high favorability for oil and gas and also special forms of hydrocarbons as gas hydrates. 

     The structure of the sedimentary fill of this deep-water basin  has become known only since 1978 when "Yuzhmorgeologiya"  began a systematic common depth point seismic survey.  Before  that time there was no clear understanding as to the stratigraphy  or structure. 

     The stratigraphic subdivision of the sediments of the basin is  based on recognition and correlation of seismic marker reflecting  horizons.  This 12-kilometer pile of sediment cannot with accuracy  be subdivided and correlated with onshore sections.  Among the  numerous reflecting interfaces are recognized five marker horizons.  In addition to the top of the pre-Mesozoic rocks there is the top of the Eocene, top of the Maykop Series, an horizon close to the  base of the Meotis, and an horizon at the base of the Quaternary.   Even though the age boundaries are only approximate, they are  traced without interruption on the seismic profiles. 

     Syn-sedimentary subsidence of the basin is accepted as well  as deep-water conditions beginning with the Paleogene,  Two  depressions isolated from one another existed in the Paleogene:  West Black Sea and East Black Sea.  They subsequently merged  to form the single Black Sea depression.  Individual sectors along  the margin continued to be involved in the overall subsidence as the  depression broadened.  This process continues at the present time. 

     An enormous flexure is present along the entire border of the  Black Sea depression.  Thickness of the Cenozoic sediments is  several times greater on the subsided limb of this flexure than on the  uplifted limb.  On the connecting segment, that is, on the border of  the depression, each bed thins to pinchout. 

     The border of the depression is best expressed on the top of the  Mesozoic, where the amount of flexure ranges from 6 to 12 km,  At  the upper bend of the flexure thin Cenozoic sediments are practically  horizontal and are represented by all the recognized seismic units.   At the lower bend of the flexure the thick Cenozoic sediments are  almost horizontal but thin and bend upward on approach to the border.   On the connecting segment thinning of the beds creates the impression  that the seismic units have merged into a single unit. 

     According to morphology the border slope of the Black Sea  depression is an analog of the continental slopes of the oceans.                                 Continued 

Taken from Maysner and Tugolesov, 2001; digested in Petroleum  Geology, vol. 36, no. 3, 2002, in preparation, one seismic section,  one structure map, and one cross section.

Copyright 2002 James Clarke.  You are encouraged to print out this  News Letter and to forward it to others.  Earlier News Letters are  available at our web page:       http://geocities.com/internetgeology/    This News Letter is distributed without charge in the interest of our  science. To be added to the mailing list please send your e-mail  address to:       jamesclarke@erols.com    For information on the journal Petroleum Geology please telephone  703 759-4487 or FAX 703 759-3754. There is a time for everything...a time to be silent and a time to  speak. Ecclesiastes 3:1,7.

The syn-sedimentary nature of the downwarping of the Black Sea  basin during the Cenozoic is a basis for calculating rates of sedimen-  tation and downwarping.  Maps of thickness on scale of 1:500,000   were used to detertmine average rates of deposition. 

A sharp increase in rates of deposition has been found for the  Quaternery in comparison with those for the Paleogene and Neogene.  This is due in part to the Danube, which during the Cenozoic filled the  Cis-Carpathian downwarp and then in Quaternary time flowed into  the Black Sea.  The rate of Quaternary sedimentation in the  submarine Danube delta reached almost 1.5 mm/year, and for the  rest of the basin - 0.44 mm/year.  Average rates for the Paleogene  and Neogene were from 0.06 to 0.13 mm/year, reaching 0.17 to  0.24 mm/year in the most subsided part of the West Black Sea  depression.  Rate of deposition and rate of downwarping were  approximately equal in both the West and East Black Sea  depressions because in spite of thick sediment accumulation  the basins remained deep-water features. 

A significant role in formation of the thick sedimentary fill of the  Black Sea basin has been played by debris cones of rivers.  These  are particularly numerous in the Quaternary section, showing up  clearly on the sea floor.  These debris cones constitute more than  half of the modern slope of the depression.  They are grouped in  several sectors. 

The largest of these sectors is the Danube debris cone, which  formed during the course of the entire Quaternary.  Sediments of  its fore-delta add 2.5-3 km to the total thickness of the Quaternary  section.  They comprise a considerable part of the northwest shelf.   Below the lip of the shelf the broad, gentle slope consists of  numerous submarine debris cones, which are expressed in  varying degree in the relief of the sea floor. 

Alternation of thick lenses of lateral accumulation (debris cones)  with much thinner members of predominantly vertical accumulation  show up clearly on the seismic time sections.  It is quite clear that  both forms of sedimentation took place simultaneously. 
The Don-Kuban debris cone formed in a similar way; however,  its area is several times less than that of the Danube although its  thickness is about the same.  The debris cones of the Georgian  sector of the shelf are similar, although average thickness of the  Quaternary there is less.  Numerous submarine canyons cut  deeply into these debris cones.  They appaer to have formed at  the same time as the cones themselves. 

No large amounts of submarine deltaic sediments collected  before the Quaternary because in addition the the Danube  emptying into the Cis-Carpathian downwarp, the Don and Kuban  emptied into the Indolo-Kuban downwarp.

Continued next week Taken from Maysner and Tugolesov, 2001; digested in Petroleum  Geology, vol. 36, no. 3, 2002, in preparation, one seismic section,  one structure map, and one cross section. Copyright 2002 James Clarke.  You are encouraged to print out this  News Letter and to forward it to others.  Earlier News Letters are  available at our web page:  http://geocities.com/internetgeology/
This News Letter is distributed without charge in the interest of our  science. To be added to the mailing list please send your e-mail  address to:       jamesclarke@erols.com    For information on the journal Petroleum Geology please telephone  703 759-4487 or FAX 703 759-3754.
There is a time for everything...a time to be silent and a time to  speak. Ecclesiastes 3:1,7.