Lower Ordovician Trilobites Research Articles

Lower Ordovician Trilobites from SE Sardinia (Italy): A new record of the “Taihungshania bioprovince”

A systematic description of the so far unique trilobite fauna and the associated biota from the Arenarie di San Vito Formation, in the outcrops close to the abandoned Tacconis mine (allochthonous nappe zone, Sarrabus, SE Sardinia, Italy), proves the occurrence of Taihungshania shui landayranensis, Ampyx priscus, Asaphellus sp., Merlinia sp., Niobe fourneti?, Geragnostus sp. and Symphysurus sp., accompanied by several taxa of graptolites, ichnofossils and less common bivalves, gastropods, cephalopods and hyolithids. The taphonomical signature, sedimentary structures and “Raphiophorid biofacies” clearly argue for an early Floian age and a median platform (i.e., offshore to shoreface) depositional environment. The occurrence of T. shui landayranensis in Sardinia allows us to determine the age of the Arenarie di San Vito Formation (just below the Sarrabese unconformity) and to discuss the palaeobiogeographical affinities highlighting the value of the “Taihungshania bioprovince”. The Tacconis trilobite fauna displays close affinities with Montagne Noire in France, Taurides in Turkey, Alborz in Iran, and south China, placing the SE Sardinia allochthonous area in a global Ordovician palaeogeographic sketch. A brief discussion on relationships and palaeobiogeographical affinities between the Sardinian nappe zone and the autochthonous “foreland” Sulcis-Iglesiente, which are adjacent today, strongly suggests a separation during the Ordovician, although both areas pertain to the Gondwana margin.

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

McCobb, L.M.E., Boyce, W.D., Knight, I. & Stouge, S., 2014. Lower Ordovician trilobites from the Septembersø formation, North-East Greenland. Alcheringa 38, 575–598. ISSN 0311-5518.The informally named Septembersø formation is a 76 m thick succession of microbial and peritidal shelf carbonates deposited on the North-East Greenland shelf of Laurentia. The formation, assigned to the lower part of the Cape Weber Formation in all previous studies, lies disconformably upon the Skullrockian Antiklinalbugt Formation (revised) and conformably below the Tulean to Blackhillsian Cape Weber Formation (revised) in the Fimbulfjeld Group. With the exception of Randaynia, the modest trilobite fauna recovered from the Septembersø formation consists exclusively of bathyurids, and all represent new species. Both Chapmanopyge knudseni sp. nov. and Punka adamsi sp. nov. are represented by sufficient material to merit specific names. The remaining taxa, belonging to Bolbocephalus, Peltabellia, Randaynia and Chapmanopyge are left in open nomenclature. The trilobite genera present suggest that the Septembersø formation is referable to the Tulean Stage of the Ibexian Series, latest Tremadocian/earliest Floian in Global Standard terms.Lucy M. E. McCobb [lucy.mccobb@museumwales.ac.uk], Department of Natural Sciences, National Museum of Wales, Cathays Park, Cardiff CF10 3NP, UK; W. Douglas Boyce [dougboyce@gov.nl.ca] and Ian Knight [ianknight@gov.nl.ca], Geological Survey, Newfoundland and Labrador Department of Natural Resources, PO Box 8700, St. John’s, NL, Canada A1B 4J6; Svend Stouge [svends@snm.ku.dk], Natural History Museum of Denmark (Geological Museum), Øster Voldgade 5–7, DK-1350 Copenhagen K, Denmark.

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

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 (Ibexian) trilobites from the Tribes Hill Formation, central Mohawk Valley, New York State

The Early Ordovician Tribes Hill Formation of east-central New York State is a sequence of peritidal to subtidal carbonates and minor shales that rests disconformably on Late Cambrian carbonates and is, in turn, succeeded disconformably by Middle Ordovician strata. More than 800 trilobites from 24 collections are assigned to six species: Bellefontia gyracantha (Raymond), Clelandia parabola (Cleland), Hystricurus ellipticus (Cleland), Hystricurus cf. Hystricurus oculilunatus Ross, Symphysurina convexa (Cleland), and Symphysurina cf. Symphysurina woosteri Ulrich. Two distinct biofacies are present: the Bellefontia Biofacies in subtidal shales with thin, storm-generated bioclastic interbeds, and the Gastropod–rostroconch Biofacies in shallow, carbonate bank lithofacies. The trilobites of the Tribes Hill Formation are assigned to a single, informal biostratigraphic unit, the Clelandia parabola Fauna, which is correlative with trilobite Zone B of the Garden City Formation of Utah and with the Bellefontia franklinense Subzone of the McKenzie Hill Formation of Oklahoma.

Generic longevity in Lower Ordovician trilobites: relation to environment

The longevity of genera living at the edge of the early Ordovician North American plate is related to their position on the former shelf, that is preserved in richly fossiliferous sections of Spitsbergen. Genera which endure for a long period (SO Myr or more) tend to be confined to shallow-water sites associated with algal mounds at the edge of the carbonate platform (illaenid-cheirurid community type) or deep-water sites with low oxygen concentration, and probably beneath the thermocline (olenid community type). The latter includes “conservative” forms that have survived from the Cambrian. The long ranges of the olenid community type are attributed to the adaptation of only a few genera to a highly specific, stressed environment. The endurance of the illaenid-cheirurid genera is due to the persistence of the tropical shelf-edge habitat, with high predictability of resources, to which the Ordovician forms became adapted early on. The nileid community type, which occurred between the platform edge and olenid-bearing environment, was the site of rapid generic turnover and may have been the source for subsequent recruitment into other environments. The inner shelf also had rapid generic replacement, dominated by a single family, the Bathyuridae. Rapidity of evolution in this site may be due to the spatial heterogeneity of the epeiric environment, as in the Devonian phacopids studied by Eldredge (1974).

Lower Ordovician trilobites of the Oxford Formation, eastern Ontario

The only Lower Ordovocian trilobites known to occur in Ontario are a small collection of generally poorly preserved asaphid, bathyurid, and pliomerid trilobites from the Oxford Formation in the area between Ottawa and Brockville. This fauna consists of Bolbocephalus convexus (Billings), Gignopeltis rarus (Billings), Goniotelina subrectus (Bradley), Strotactinus salteri (Billings), and Isoteloides sp. This fauna is late Canadian and early Arenigian in age. The trilobite, conodont, and mollusk faunas indicate correlations of the Oxford Formation with the Phillipsburg 'Series' of Quebec, Fort Cassin Formation of New York and Vermont, mid- to upper St. George Group of Newfoundland, and mid-Fillmore Formation of Utah. A neotype is chosen for Strotactinus salteri.

On the Relation between the Lower Ordovician Trilobites and Conodont Horizons in South Korea

On the Relation between the Lower Ordovician Trilobites and Conodont Horizons in South Korea

Lower Ordovician Trilobites from Western Utah and Eastern Nevada. Lehi F. Hintze

<i>Lower Ordovician Trilobites from Western Utah and Eastern Nevada</i>. Lehi F. Hintze

Upper Cambrian and Lower Ordovician Trilobita and Ostracoda from Vermont

INTRODUCTION AND ACKNOWLEDGMENTS During the last fifteen years, a renewed attack has been made upon the difficult problems presented by the complicated fold and thrust structures in the older Paleozoic strata of northwestern Vermont. The campaign led by Arthur Keith bids fair to resolve the difficulties which baffled such eminent and acute geologists as Sir William Logan, Elkanah Billings, James Hall, Jules Marcou, and Charles D. Walcott. Like Sir William, Keith realized that fossils might be the master key for opening the secrets of this chamber of mysteries, and at an early date induced Charles Schuchert to collaborate in the work. Schuchert has been kind enough to turn over for study such Upper Cambrian and Lower Ordovician trilobites as he and his associates have collected during visits to the area over a long period, and several years ago the writer described such fossils as had then been collected from what . . .