UTRECHT MICROPALEONTOLOGICAL BUllETINS

The highly discontinuous character of the sedimentation in the area, as
clearly demonstrated by the enormous amount of disconformities in all
sections, strongly influenced our conodont assemblage zonation.
Chart V shows, that below the Protopanderodus rectus/Oepikodus evae
Zone none of the assemblage zones is present in all parts of the area, and
many of them are confined to only one of the studied sections. Moreover,
the assemblage zones under the Protopanderodus rectus/Oepikodus evae
Zone were usually based on the first appearances of more than one species
(charts II, III and IV, and fig. 15). This phenomenon may be caused by
barren intervals between the studied samples in some cases, but in many
instances it must be due to gaps in the rock-sequences, at disconformities
which corresponded to considerable periods of non-deposition and/or erosion.
One has to conclude that the conodont assemblage zonation, presented
now, is probably incomplete for the time-interval between the Protopanderodus
rectus/Oepikodus evae Zone and our lowermost zone. The boundaries
between some assemblage zones are uncertain due to the barren intervals,
whereas many others coincide with important periods of non-deposition
and/ or erosion.
The conodont assemblage zones might be considered in many instances as
concurrent range zones, as may be seen from the following enumeration.
II.2A.I. The Cordylodus angulatus/Cordylodus prion Assemblage Zone
Diagnosis: A conodont assemblage zone characterized by the occurrence of
Cordylodus angulatus together with Cordylodus prion before the first appearance
of Cordylodus rotundatus (fig. 15).
Description: Cordylodus angulatus and C.prion are the only species found in
this zone, which is based on a single sample of section 9 (see sample 1, chart
III).
Type-locality: The coastal cliff at about 2 km. S.W. of Djupvik (fig. 2,
section 9).
Type-stratum: The conglomerate at about the middle of member Da-d3 in
the type-section of the Djupvik Formation. The assemblage was not recognized
in this member at Kopingsklint.
Remarks: The boundaries of this zone are unknown, because of the barren