Lower Ordovician trilobites from the Baumann Fiord Formation, Ellesmere Island, Arctic Canada

Abstract

Sections through member B of the Baumann Fiord Formation on the Bache Peninsula, Ellesmere Island, Arctic Canada, contain a range of lithofacies indicating deposition in shallow subtidal settings above storm wave base. Macrofossils are generally rare, but low-diversity trilobite-dominated faunas occur in a section near Sanddöla Creek. The only other fossils common in the collections are poorly preserved gastropods. All of the trilobite species are apparently new, and four are formally named: Licnocephala sanddoelaensis, "Peltabellia" baumannensis, Bolbocephalus ellesmerensis, and Ceratopeltis bachensis. The species Ceratopeltis forteyi is introduced for material previously described from North Greenland. Rare additional species of Licnocephala and Jeffersonia are reported in open nomenclature. The trilobites occur in three stratigraphically and lithologically distinct associations, with species diversity ranging from two to four. Closest comparisons of the trilobite species all indicate that member B should be assigned to the Tulean Stage of the Ibexian Series. Rananasus Cullison, 1944, is placed in synonymy of Bolbocephalus Whitfield, 1890.

Lower Ordovician trilobites from the Septembersø formation, North-East Greenland

“…2, B. ellesmerensis Adrain & Westrop (2005) appears to possess a poorly defined fifth axial ring, in addition to the four seen in other Bolbocephalus species. Bolbocephalus ellesmerensis also has an axis and pleural fields of similar moderate convexity, resulting in a flatter profile compared with more convex, vaulted Bolbocephalus species, and its axial ring furrows are similarly shallow and weakly expressed.…”

“…On this basis, Peltabellia potentially ranges down into the Stairsian Stage. However, Adrain & Westrop (2005) challenged the trilobite evidence for age of the Poulsen Cliff fauna, and a Tulean age appears more likely.…”

“…With the exception of a single specimen of the symphysurinid Randaynia, the trilobite taxa recovered are members of the Bathyuridae, and although very rare bathyurid occurrences have been recorded from Stairsian strata of the western USA (see Adrain & Westrop 2005) and western Newfoundland (see Boyce 1989 and below), they did not become common until the Tulean.…”

“…Loch (2007) identified all genera found in the Septembersø formation from the Kindblade Formation of Oklahoma (although Peltabellia is not listed by Loch, the authors feel it is likely represented among the species assigned to 'Strigigenalis'). The trilobite fauna also suggests links with: the Poulsen Cliff Formation, western North Greenland (Fortey & Peel 1990) and Wandel Valley Formation, eastern North Greenland (Fortey 1986), the Barbace Cove Member, Boat Harbour Formation (Boyce 1989, 1997, Boyce & Stouge 1997 and the Catoche Formation, western Newfoundland (Fortey 1979, Boyce 1989, Baumann Fiord Formation, Ellesmere Island (Adrain & Westrop 2005), Romaine Formation, Mingan Islands, Quebec, and Rich Fountain Formation, Missouri (Cullison 1944; = Jefferson City Formation of Thompson, 1991. See also Fortey & Bruton, 2013 for a detailed discussion of regional correlations in southern Laurentia).…”

“…Adrain & Westrop (2005) synonymized Rananasus Cullison, 1944 with Bolbocephalus-probably based on the lack of any described Rananasus librigenae at the time. Loch (2007) subsequently described and illustrated librigenae for R. brevicephalus Cullison, 1944 andR.…”