THE MEDITERRANEAN LOWER CRETACEOUS

The natural outcrops of the Hauterivian sediments are very rich in ammonite
associations (H и к о л о в, X р и с ч е в, 1965b; H и к о л о в, 1969а). Characteristic
Hauterivian ammonites have also been found in a number of boreholes from
this zone.
Fig. 12. Relationships between the lithostratigraphic units along the Junak — Devnja line
Characteristic Hauterivian fossils have been found in the outcrops of the Asparuhovo
region, and they permit accurate correlation with the borehole sections:
Lyticoceras spp., Crioceratites duvali Lev., Olcostephanus astierianus (d'Orb.),
O. guebhardi (K i 1.) and Duvalia dilatât a (B 1.).
The following Hauterivian ammonites have been found in the outcrops close
to R-2 Veselinovo : Lyticoceras sp., Crioceratites spp., Olcostephanus jeannoti (d'O г b.).
O. astierianus (d'O r b.), O. guebhardi (K i 1.), etc.
The upper boundary of the Hauterivian in the region is denuded — the Hauterivian
deposits are usually covered by Quaternary sediments. Only in the Veliko
Ti'rnovo area and in the southwestern part of the Provadija Plateau, as well as in
sorue peripheral parts of the Eastern Fore-Balkan, the Hauterivian is covered normally
by Barremian deposits, and in the easternmost parts — by Upper Cretaceous
sediments.
The thickness of the Hauterivian sediments in the Eastern Fore-Balkan is 1200-
1800 m. Smaller thicknesses are connected with later denudation or with the transition
towards the Gorna Orjahovica Formation to the north.
The Barremian is well developed in the Eastern Fore-Balkan. Specific mixed
(wacke-type) rocks of the Hànevci Formation are revealed in the southernmost
strip, being replaced to the north by marly sandstone sediments (Kamôija and Gorna
Orjahovica Formations), widely represented in the middle and northern strips
of the Eastern Fore-Balkan. Everywhere Barremian sediments overlie with transitions
the Hauterivian deposits.
In the valley of Jantra River and around Veliko Târnovo, Gorna Orjahovica
and Ljaskovec, the Barremian is represented by marls,aleuritic clayey marls and sandstones.
These sediments are also found in the southeast — to the south of Malàk
Ciflik village and to the west of Dragizevo village. In the area under investigation
the Barremian also comprises the lower part of the Urgonian complex.
In this strip of the Fore-Balkan Barremian sediments are transversed only by
the drillings in the Veliko Târnovo area, while the remaining boreholes to the east
usually start in older rocks.
In the outcrops Barremian sediments are known from the valley of Jantra river,
around Gorna Orjahovica and Ljaskovec, where marls, aleuritic clayey marls
and sandstones are developed. These deposits are revealed further east as well —
to the south of Malàk Ciflik and to the west of Dragizevo villages. In the Jantra
river valley they are covered by Urgonian limestones.
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