THE MEDITERRANEAN LOWER CRETACEOUS

already defined stages and led to the appearance of many new names which are
synonyms or homonyms of well-known stage terms.
Stratigraphie practice has substantiated the global development of the aboveindicated
stages, which correspond to the main phases in the development of the
ammonite successions in the Lower Cretaceous. These stages were later divided into
substages, and after 1890 the respective ammonite zones were defined in them. The
1890-1913 period is characterized precisely as the time when the foundations were
laid for the ammonite zonal differentiation of the Lower Cretaceous in the type region
of its stages.
In stratigraphie research we should be free from the hypnosis of the stratotypes,
but nevertheless we should bear in mind their significance for the stability
of the nomenclature. The revisionist spirit of every new generation is well known,
but the strife for constant innovations threatens stability in stratigraphy. This is
why, the existence of "reference standards", such as the stratotypes, is an essential
prerequisite for the development of stratigraphy.
2. GENERAL CHARACTERISTIC OF THE STAGES
2.1. Berriasian
The stage term Berriasian was created by С oquand (1871) to define the deep-sea
sediments at the base of the Cretaceous System in Southeastern France, previously
designated as "couches de Berrias à Terebratula diphyoides" or "couches à ciment".
The stratotype of the Berriasian is found to the north of Berrias village, Ardèche
(Southeastern France), from where P i с t e t (1867) described the classical
fauna in text and figures. Pictet's opinion was clearly formulated and he definitely
emphasized that the fauna in the Berrias area belongs to the base of the Cretaceous
System.
Before defining the Berriasian Stage, Coquand repeatedly used expressions
such as "couches de Berrias", "faune de Berrias", etc., finally stating his opinion
as follows: "ammonite-bearing limestones from Berrias and from Gange are
in relation with the Valanginian beds with Natica leviathan, whose base they form"
(Coquand, 1869, p. 102).
The status of the Berriasian has been the object of long and arduous discussions
which last to this day. In 1965 the main problems related to this status
were discussed (Nikolov, 1965b), therefore only some basic aspects will be
given here.
Opinions concerning the place of the Berriasian Stage may be united in four
groups :
1. The Berriasian belongs to the Cretaceous, and it is a substage of the Valanginian.
This is the original view of Pictet and Coquand who differentiated the
Berriasian.
2. The Berriasian and the Valanginian are independent stages at the base of
the Cretaceous System. This view is founded on the specific ammonite characteristics
of the two units, which, although manifesting some common elements,
possess clearly differentiable associations.
3. The Berriasian is independent of the Valanginian, but it is transversed by
the Jurassic-Cretaceous boundary and its lower part belongs to the Jurassic System.
This view is often expressed by the concept "transient stage" or "transient
beds", but it is not based on serious scientific arguments.
4. Recently some authors have suggested that the Berriasian should be attributed
to the Jurassic System as the upper part of the Tithonian Stage, on the ground
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