UTRECHT MICROPALEONTOLOGICAL BUllETINS

11.2.4.18. The Drepanoistodus forceps Assemblage Zone
Diagnosis: A conodont assemblage zone defined by part of the long range of
Drepanoistodus forceps, after the last occurrence of Stolodus stola and
before the first appearance of Microzarkodina flabellum (charts II, III and
IV, fig. 15).
Description: In the rock-sequence of N.W. Oland there is an interval which
may be characterized by Drepanoistodus forceps, one of the common long
ranging species, in between the level of disappearance of Stolodus stola and
the start of Microzarkodina flabellum. Prioniodus navis appeared to be rare
or absent in this interval. Frequent species in this zone are: Scolopodus
pese lephan tis, S.rex, Drepanodus arcuatus, Protopanderodus longibasis,
P.rectus, Drepanoistodus forceps, Periodon flabellum and Oistodus lanceolatus.
Oistodus papiliosus was sporadically found in this zone.
Type-locality: Locality 1 (fig. 5) near Horns Udde.
Type-strata: Some 35 em. of limestone beds at 1.60 to 1.95 m. above the
base of the Bruddesta Formation in section 14, sample 18 and 19 chart IV.
Remarks: Drepanoistodus conulatus and Paroistodus parallelus were not
actually found in this zone, but they might be present according to their
regional ranges.
As stated earlier, the lower boundary is not sharp. The upper boundary
equally lacks a pronounced character, because Microzarkodina flabellum is
often rare in the basal portion of the overlying Microzarkodina flabellum
Assemblage Zone.
11.2.4.19. The Microzarkodina flabellum Assemblage Zone
Diagnosis: A conodont assemblage zone based on the range of Microzarkodina
flabellum, before the first appearance of Triangulodus brevibasis (charts
II, III and IV, fig. 15).
Description: Scolopodus peselephantis, Protopanderodus rectus and Drepanoistodus
forceps were found throughout this zone. Microzarkodina flabellum,
Paroistodus parallelus, Drepanoistodus conulatus, Scolopodus rex,
Drepanodus arcuatus, Protopanderodus longibasis, Prioniodus navis and
Periodon flabellum are discontinuously present in this zone. Oistodus
papiliosus has its highest stratigraphic occurrence in the lower portion of the
Microzarkodina flabellum Zone. In all sections this highest occurrence of
Oistodus papiliosus is associated with "the Flowery Sheet".
Type-locality: The coastal cliff between Aleklinta and Djupvik, section 6.
Type-strata: The rock-interval from a level at about 1.65 m. up to about
4.35 m. above the base of the Bruddesta Formation in section 6.