THE MEDITERRANEAN LOWER CRETACEOUS

The Albian around the town of Svistov (Fig. 14) is represented by differentgrained
sandstones which arc intercalated in some places by aleuritic marls. Here
is the stratotype of the Svistov Formation which is also transected in the boreholes
of the Grivica, Pisarovo, Krusovica, Gorni Dâbnik and Dolni Dubnik areas. The
phosphorite-bearing and glauconite beds between the villages Sanadinovo, Novacene
and Dekov should be considered as peripheral facies of the Svistov Formation.
The thickness of the Albian sediments varies in the different areas: from 94 m
(Tïàstenik village) to 687 m (Bârdarski Geran village), depending mainly on the
completeness of the sections and on the influence of the post-Albian denudation.
The Lower Cretaceous has most extensive surface outcrops in the northeastern
part of the Moesian Platform. In this area it is also revealed by many boreholes.
Therefore, the Lower Cretaceous has been relatively best studied in Northeastern
Bulgaria. More recent studies to be mentioned in this connection
are those of D i m i t r о v а (Димитрова, 1967), D i m i t r о v a, Cem
b с г s к i and Kostadinov (Д и м п т р о в а, Чембсрски, Костал
и нов, 1965), D i m i t г о v а, С e s i t e v and Breskovski (Димитрова.
Ч с ш и T e в, Б p e с к о в с к и, 1972), Breskovski (Бреск
о в с к и, 1966; Breskovski, 1975), Kostadinov and Breskovski
(К о с т а д и п о в, Б р е с к о в с к и, 1967) and N i k о 1 о v (H и к о л о в,
1969а). These works contain the entire literature on the stratigraphy of the Lower
Cretaceous in the area. In the present book only the latest data on the Lower
Cretaceous stratigraphy in Northeastern Bulgaria will be reported.
Berriasian sediments are not exposed in the northeastern part of the Moesian
Platform. They are found in all deep drillings transversing the uninterrupted succession
of the Kaspican Formation. However, the accurate differentiation of the Berriasian
in the boreholes of this carbonate Formation is impossible, due to the
absence of distinct fossil remains of organisms. According to borehole data, the conditionally
differentiated Berriasian part of the Kaspican Formation is represented
by dolomites, dolomitized limestones and intercalations of limestones.
Tn borehole S-30 Kardam (Popovo area) P. J о v ce va (oral communication)
has identified foraminifera from several levels. In all probability, the Trocholina
(Coscinoconus) alpina L e u p. found at 356.70 m and at 389.40 m is in the Berriasian
part of the section, because a characteristic Valanginian association has been
found higher up (at 32 0 m).
The Valanginian is generally developed in Northeastern Bulgaria. In the northeastern
part of the Moesian Platform it is connected with the Kaspican Formation. The
stage is represented at its base by micrograined dolomites and dolomitized limestones
which are replaced upwards by crystalline and granular limestones.
In borehole S-30 Kardam (Popovo area), at a depth of 320 m, P. Jove ev
a has found a characteristic microfossil association: Trocholina (Coscinoconus)
alpina Leu p., T. (Coscinoconus) elongata L e u p., Hechtina praeantiqua Bart.,
В г., Animodiscus cretaceous R e u s s and Quinqueloculina infravalangiana Bart.
In borehole S-11 Kalugerica the Valanginian is proved by foraminifera associations
the most characteristic among which is from 167.30 m: Trocholina (C.)
alpina L e u p., T. (C.) elongata L e u p., Quinqueloculina infravalangiana Bart. Cardim
imbricatum Leu m. was found in the same borehole at 152-156 m, Nerinea favrina
P i с t., С a m p. and Trigonia omata d'O г b. — in the interval 138.70-146.00 m.
Analogous fossil associations are found to the east-northeast in a number of
boreholes (S-31 Esenica, S-32 Dolina, S-10 Cernookovo and R-l Tjulenovo).
The upper boundary of the Valanginian in this area is traced along the upper
part of the Kaspican Formation, with the exception of the region to the north of
Sumen, Novi Pazar, Devnja and Cernevo, where the upper part (probably up to
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