THE MEDITERRANEAN LOWER CRETACEOUS

In the Lorn Depression the Lower Cretaceous is presented in its full volume from
the Berriasian to the Albian included. In this region Lower Cretaceous sediments
are connected with a transition both with the underlying (Tithonian) and with the
overlying (Cenomanian) sediments. The upper part of the Lower Cretaceous is absent
only in Vidin District (Vidin and the villages Gomotarci, KoSava, Milcina
Lâka, Simeonovo), and Cenomanian marls overlie directly Valanginian limestones
beds or Simeonovo Formations (at borehole R-l Simeonovo).
In Vidin District the Lower Cretaceous is represented by the Berriasian and
Valanginian, which are not differentiated. They are connected with various limestones
and with the dolomitized limestones of the type of the Kaspican Formation.
Its upper part is denuded everywhere, being covered by Cenomanian clayey-calcareous
(mainly marl) sediments.
The thickness of the Berriasian-Valanginian sediments in this region is 495-622 m.
In the region of the villages Dàlgodelci, Gorna Gnojnica, Komostica, Kovacica
and Medkovec, Lorn area, the Lower Cretaceous is found in its full volume. At
its base is the Berriasian which is represented by dense and partly intraclastic
limestones of the Glozene Formation. The presence of the Berriasian in this region
has been proved for the first time by Jovceva and Trifonova (Йовчева,
Трифонова, 1964). In borehole R-6 Dàlgodelci (depth 3364-3422 m)
they have found: Berriasella sp., Calpionella elliptica Cad., Tintinnopsella carpathica
(M u r g., F i.) and Calpionellopsis oblonga (C a d.), as well as many foraminifera.
The thickness of the Berriasian in this region is 58 -70 m.
The sediments of the Valanginian, which is connected with the Salas Formation,
lie higher up with gradual transitions. The characteristic Upper Valanginian ammonite
Busnardoicles subcampyloto.xus N i k. was found in borehole R-l Hajredin
2880.80 m). From borehole R-6 Dàlgodelci Jovceva and Trifonova (Йовчева,
Трифонова, 1964) report Calpionelliles darderi (С о 1.) — a characteristic
Valanginian species.
The thickness of the Valanginian in this region is 75-125 m.
The Hauterivian is represented by clayey limestones with intercalations of marls
(Salas Formation) and by micrograined, in some places slightly clayey and slightly
aleuritic limestones from the peripheral part of the Salas Formation.
Characteristic ammonites were found in boreholes R-2 Komostica, R-l and
R-6 Dàlgodelci and R-l Hajredin: Lyticoceras sp., Crioceratites rodighieri D i m.,
C. duvali L é v., C. quenstedti (О о s t.), etc. The thickness of the Hauterivian sediments
in this region is 142-280 m.
The Barremian is represented by micrograined slightly clayey limestones, Among
them Barremites difficilis (d'O r b.) andB. subdifficilis (К a r.) were found in borehole
R-6 Dàlgodelci at 3145 m. The thickness of the Barremian sediments is 105-
126 m.
The sediments of the Aptian are connected through gradual transitions with
the Barremian sediments. The lower and middle parts of the Aptian sections are built
of clayey limestones, whereas the upper part is formed of marls to slightly aleuritic
clayey limestones (Tràmbes Formation).
Characteristic Upper Aptian bivalvs: Aucellina caucasica (B u с h.) and A.
pompechii P a v 1., were found in borehole R-6 at 2823.50 to 2825.20 m.
Rich foraminifera associations are also found among the Aptian sediments
in this region. The thickness of the Aptian is 123-309 m.
The Albian is represented by marls which are connected with a gradual transition
with the Aptian marls. They are covered by Cenomanian marls with a fast lithological
transition.
Characteristic Albian macrofossils were found in a number of intervals in
borehole R-l Kovacica at 1839-1840 m : Idiohamites favrinus (P i с t.), Idiohamites
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