At several outcrops, poor planktonic graptolites
and trilobites of the Cyclopygid Biofacies occur in this association.
Palaeogeographically, the Lower Ordovician graptolites
of the studied area are similar to other scattered records occurring in South-Polar Peri-Gondwanan terranes, where the scarcity of Rhabdinopora and other anisograptid graptolites
is linked with the extensive development of shallow-water facies dominated by sandstones and green micaceous shales.
Hirnantian (latest Ordovician) graptolites
from the upper Yangtze region, China.
Hirnantian mudstones are abruptly but conformably overlain by anoxic black shales with abundant graptolites
of the basal Silurian Akidograptus ascensus Biozone (Storch 2006).
However, intercalations of dark grey calcareous mudstone with graptolites
are lacking in these marlstones and therefore the sections have an intermediate position between the Riga and Jaani formations.
In Proceedings of the Sixth International Graptolite
Conference of the GWG (IPA) and the SW Iberia Field Meeting 1998 of the International Subcommission on Silurian Stratigraphy (ICS-IUGS), Madrid, 1998 (Gutierres-Marco, J.
The upper Wenlock is a dynamic time slice of the Silurian Period, marked by substantial environmental and biotic changes, with especially profound graptolite
and conodont extinctions.
The definitions of the series and stages of the Silurian System and their correlation are traditionally based on relatively well developed graptolite
were not found from the Viki core either, but the single occurrence of R.
The presence of early Ordovician (late Tremadocian to early Arenigian) graptolites
in the underlying Bright Eye Brook Formation of the Woodstock Group (see above) and Late Ordovician (early Caradocian) graptolites
in the overlying Belle Lake Formation of the Meductic Group (see below) restricts the depositional range of the volcanic components (Porten Road, Eel River, and Oak Mountain formations) of the Meductic Group to between early Arenigian and Llanvirnian time.
System Series Stage Age Regional Beds Period Epoch stage SILURIAN PRIDOLI JURA MINIJA Varniai Silale LUDLOW LUDFORDIAN PAGEGIAI DUBYSA GORSTIAN System Series Biozones Period Epoch Graptolites
Conodonts SILURIAN PRIDOLI N.
A stepwise extinction during the Mulde Event in the Homerian (Wenlock, Silurian) has been suggested for hemipelagic fauna such as graptolites
and conodonts (Jaeger 1991; Jeppsson 1993; Kaljo et al.