DRAGASTAN, OVIDIU, The University of Bucharest, Bucharest, Romainia; RADU MUTIU, Oil Geological Institute, Bucharest, Romania; CONSTANTIN SISMAN, Petromar Co., Constanta, Romania; and STEFAN POPESCU, Oil Geological Institute, Bucharest, Romania

ABSTRACT: Moesian Cretaceous Carbonate Platforms (The Eastern Romanian Sector and Data about the Adjacent Black Sea Offshore)

The Moesian Platform or Moesian Block is an independent unit placed between the Carpathian and the Balkanian Orogen-belts. This unit has functioned as a platform built, in time from several paleozoic and mesozoic "superposed platforms." An increased differentiation of the facies and formations occurs beginning with the Upper Jurassic and then in the Cretaceous.

An individualization of two basins takes place during the Cretaceous: a western basin with pelagic, deep-water sedimentation containing Ammonites and Calpionellids, and an eastern basin with a continental-brackish facies and a neritic, shelf shallow carbonate facies, coral reefs (barriers and patch-reefs), algae, foraminifers and biostromites with Nerinea.

Towards east, in the Black Sea offshore, the facies contain sandstones, siltites, clays, argillaceous shales, evaporites; the calcareous deposits are less represented.

As parts of the Cretaceous sequence, there have been identified the following lithostratigraphic units:

(1) The polycolore marls and clays Formation with dolomite limestone and rarely, gypsum interlayers: Upper Purbeckian (= Lower Berriasian);

(2) The Cernavoda Formation, calcareous, formed by two members: the lower, Hinog Member (Middle Berriasian), calcareous with clay interlayers, and the upper, Aliman Member (upper Berriasian-Valanginian), calcareous, with algae, foraminifers and reefs (Sponges, Hydrozoans and Hexacorals);

(3) The Dumbraveni Formation, dolomitic with micritic limestone interlayers and Favreina salevensis (upper Berriasian-Valanginian);

(4) The Ostrov-Girlita Formation formed by limestones with Miliolids, Salpingoporella dinarica, Orbitolinids and Pachyodonts (Barremian-lower Aptian);

(5) The Vadu Formation in the offshore contains laminite-algal limestones, salt, anhydrites, anhydrite cemented breccia, and in the upper part grey-greenish clays (Purbeckian).

In the offshore of the Northern Black Sea Basin two cycles of sedimentation have been identified: (1 ) a lower transgressive cycle corresponding to the compression stage composed by flysh deposits (Neocomian-Barremian-lower Aptian) from the North Dobrogea-Crimea-Caucasus Orogen belt, an intracratonic rift which starts in the Triassic, and; (2) an upper cycle beginning by a global, transgressive event in Albian and continued until the Senonian with detrital-limestone-chalks deposits from shelf and shelf-margin systems.

In the Moesian Platform, like in the Black Sea Basin, the upper cycle corresponds to a generalized transgression and is interrupted by regional unconformities: Aptian/Albian; Cenomanian/Turonian; Santorian/Campanian and Maastrichtian/Danian.

In the eastern sector of the Moesian Platform, oil and gas are exploited in the following fields: Urziceni-Jugureanu-Golelia having limestones and reef limestones from the Cernavoda and Ostrov-Girlita Formations as reservoir rocks; Vultureanca-Draghineasa with reservoir rocks from Cernavoda Formation and; in the Moesian Platform as in the Black Sea offshore, the reservoir rocks being the glauconite sandstones and the calcareous sandstones from the Albian-Cenomanian; in the Lebada oil field; and, probably, in the Senonian chalks.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.