The sequence and correlation of Early Ordovician (Arenig) graptolite faunas in the Richardson Trough and Misty Creek Embayment, Yukon Territory and District of Mackenzie, Canada

Abstract

Four graptolite biozones are recorded from the Arenig portion of the Road River Group in the Richardson and Mackenzie mountains in the Yukon and Northwest Territories. In ascending order, these zones are Tetragraptus approximatus, Pendeograptus fruticosus, Didymograptus bifidus, and Parisograptus caduceus australis (new). The Castlemainian stage may be represented by nongraptolitic massive bedded chert. The Arenig-Llanvirn boundary is drawn below the first occurrence of Undulograptus austrodentatus. Fifty-four graptolite taxa are present, and 16 of these species and subspecies are recorded for the first time in this deep-water biotope, Résumé : Quatre biozones de graptolites sont enregistrées dans la portion arénigienne du Groupe de Road River et des monts Mackenzie au Yukon et dans les Territoires du Nord-Ouest. En ordre ascendant, ces zones sont : Tetragraptus approximatus, Pendeograptus fruticosus, Didymograptus bifidus et Parisograptus caduceus australis (nouvelle zone). L'étage du Castlemainien peut être représenté par un chert massif lité ne comportant pas de graptolites. La limite Arénigien-Llanvirn est placée sous la première occurrence de Undulograptus austrodentatus. Cinquante-quatre taxons de graptolites sont présents et seize de ces espèces et sous-espèces sont relevés pour la première fois dans ce biotope d'eau profonde,

Xiphograptus and the evolution of virgella‐bearing graptoloids

“…It is still difficult to identify these forms in poorly preserved material and misidentifications, and uncertainties are unavoidable. In well‐preserved specimens, however, the proximal development and geometry can show the true identity of this material, as is demonstrated by Jackson and Lenz (2006) who were able to differentiate two species of pendent didymograptids in their material from the Upper Floian of the Road River Group in the Richardson and Mackenzie Mountains of Yukon and the Northwest Territories.…”

“…E, GSC 133423, SPI63/08, mature specimen with cortical overgrowth in the proximal end, masking the sicula. G, GSC 129438 (Jackson and Lenz 2006, fig. 8q), specimen showing impression of virgella.…”

“…8q), specimen showing impression of virgella. H, GSC 129436 (Jackson and Lenz 2006, fig. 8o), specimen showing shape of sicula.…”

Taxonomy, Zonation and Correlation of the Graptolite Fauna across the Lower/Middle Ordovician Boundary Interval in the Yangtze Gorges Area, South China

“…The D. bifidus Zone of this paper corresponds approximately to the D. bifidus Zone of North America (Jackson and Lenz, 2006), the upper part of the D. varicosus Zone to D. (s.I.)…”

The Ordovician graptolite subfamily Kinnegraptinae in Victoria, Australia

“…F166 on the Mornington Peninsula. All Victorian specimens are of the same age: early Floian, La3, Paratetragraptus approximatus Biozone, but in the Yukon Territory, Canada, Jackson and Lenz (2006) have recorded it from both the P. approximatus and the succeeding T. fruticosus Biozones. Paradelograptus mosseboensis is from Hunneberg in southern Sweden, of La3 age (Erdtmann et al 1987).…”