Ibexian-Whiterockian (Ordovician) conodont palaeontology of east and eastern north Greenland
Samples collected from mid-Ibexian (mid-Tremadoc) to late Whiterockian (Llandeilo) of East and eastern North Greenland have yielded a total of 9,725 identifiable conodont clements. The conodonts are referred to 54 multi-element genera and 115 species, new taxa include three genera (Macheticodus, Wandelia and Wcbcrina) and nine species (Eucharodus apion, Macheticodus lekiskus, Multioistodus? celox, Pteracontiodus armillatus, Scalpellodus? narvhalensis, Sibiriodus? kalalekus, Wandelia fuscina, Weberina candidisphaera and Weberina guyi). The faunas are coniform-dominated and generally similar to shallow water, Midcontinent Province faunas found in North America. Some degree of endemicity is indicated by the presence of species found only in the eastern Canadian Arctic Islands and Greenland. The conodonts are referred to ten biozones, of which three zones in the Ibexian are newly named (the Loxodus bransoni, Glyptoconus quadraplicatus and Oepikodus communis Zones) as are three Ibexian sub-zones (the Acodus deltatus,?Reutterodus andinus and Protoprioniodus aranda). These are all based on the previous, informal faunal divisions established in North America. In East Greenland, the oldest faunas recovered, from the base of the Cape Weber Formation on Ella Ø, are referred to the L.bransoni Zone (mid-Ibexian). Both upper and lower boundaries are, however, diachronous and on Albert Heim Bjerge, 150km to the north, the base of the formation contains conodonts of the younger G.quadraplicatus Zone. On Ella Ø, the lbexian-Whiterockian boundary occurs within the lower part of the Narwhale Sound Formation and the youngest conodonts recovered are referable to the Histiodella altifrons Zone (early Whiterockian). The youngest Ordovician conodonts recovered from East Greenland are from the Heim Bjerge Formation, directly underlying Devonian conglomerates, on C.H.Ostenfeld Nunatak; these faunas contain taxa of the Polyplacognathus sweeti Zone (late Whiterockian). In eastern North Greenland, the Wandel Valley Formation unconformably overlies Cambrian carbonates, and conodonts recovered from the base probably belong to the O.communis Zone (late lbexian). The Ibexian-Whiterockian boundary lies at or just above the lower boundary of the Upper Member and the top of the formation contains taxa referable to the Polyplacognathus friendsvillensis Zone (late Whiterockian). Contouring of the colour alteration indices (CAl) in North Greenland indicates that the isotherms are parallel to the margin of the Hazen Trough; to the east, in Kronprins Christian Land, they swing around to become parallel to the Caledonian front. Fused clusters recovered from the Cape Weber and Heim Bjerge Formations are amongst the oldest euconodont assemblages recorded. They are principally of coniform species and suggest a grasping function analogous to that of chaetognath spines.