THE MEDITERRANEAN LOWER CRETACEOUS

Tn the northwestern part of the Kubrat region (boreholes R-l Ceresovo and
R-3 Pisanec), in R-2 Preslavci, as well as in the Tervel-Severci and Dulovo regions,
the Hauterivian is connected with different limestones belonging to the Ruse Formation.
The boundary between the Hauterivian and Valanginian in this region is
connected with the lithological boundary between the Ruse and Kaspican
tions.Forma­
The Lower Hauterivian age of the uppermost part of the Kaspican limestones
in the region of Hitrino village, Kaspican and Novi Pazar, Vetrino village—the
town of Devnja, has been proved by the following ammonites (Димитрова, 1967;
Николов, 1969a) : Acanthodiscus radiatus (Bru g.), A. twanensis В u s п..
G u i 11., A. waceki (N e u m., U h 1.), A. karakaschi (U h 1.), Leopoldia biassalensis
(К a г.), L. prenocostata (F e 1 i x), Leopoldia sp. and Lyticoceras sp.
Many characteristic Lower Hauterivian ammonites have been found in the marls
above the Kaspican Limestones. The thickness of the Hauterivian in this strip is
104-373 m.
In the northeasternmost (littoral) part of the area (Spasovo, Kardam and Balcik
regions, and the Zlatni Pjasâci) the Hauterivian sediments are developed in a
coastal type.
The sediments of the Hauterivian in this region overlie with a sharp boundary
the denuded surface of the Kaspican Formation. They arc represented by terrigenous
and clayey-calcareous deposits.
The Hauterivian is represented in the Spasovo region by variegated claystones,
in some places with carbonized plant detritus. The claystones are intercalated, with
limestones: clayey, dense, micrograined and porcelain-like. Intercalations of fineto
smallgrained sandstones also occur.
In the Balcik region the Hauterivian is represented by clayey-aleuritic limestones
with a little glauconite.
In the Zlatni Pjasâci area (boreholes R-l\ R-2* and R-3 X
Zlatni Pjasâci) the
Hauterivian is built of irregular alternation of sandy marls, sandy and aleuritic
limestones, and small-grained, predominantly quartz sandstones.
The Hauterivian sediments in this region are dated by microfauna. The thickness
of the Hauterivian sediments in the littoral part is between 0 and 658 m.
The Barremian is very well represented in Northeastern Bulgaria. The facial
environment of this stage is very similar along general lines with the Hauterivian.
In the southern part of the Moesian Platform clayey marls with rare intercalations
of sandstones (Gorna Orjahovica Formation) and of clayey-calcareous sediments
(Razgrad Formation) are developed, being replaced in the north by carbonate
rocks, extensively developed in the northernpart of the area (Ruse Formation).
In the strip between the villages Resen — Capaevo — Vasil Drumevo the Barremian
is connected with the Gorna Orjahovica Formation. It is represented by
marls with intercalations of fine-grained sandstones. In some places there are also
thin intercalations of clayey-calcareous siltstones.
Characteristic Barremian ammonites were found in borehole S-22 (Resen area):
at 58.10-63.40 m — Hemihoplites spp., Anahamulina cf. subcylindrica (d'O г b.)
and Barremites spp.; at 243.00-245.70 m — Barremites cf. subdifficilis (К a г.),
Pulchellia sp. and "Leptoceras" sp. ; at 384.60-394.40 m — "Leptoceras" sp. and
Barremites cf. difficilis (d'O г b.); at 404.00-416.50 m — Crioceratites (E.) emerici
L é v., Acrioccras tabarelli (A s t.), Spitidiscus sp. indet. and Barremites cf.
hemiptychus (K i 1.).
In borehole S-l Ljubenci, where the Barremian is represented by sediments
which are transitional, but probably closer to the Kamôija Formation, Barremian
ammonites have been found in two intervals: at 90.00 m — Holcodiscus sp. indet.;
at 479.00-484.50 m — Anahamulina subcylindrica (d'O г b.) and Holcodiscus spp.
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