Conodont Biostratigraphy of the Middle and Upper Ordovician of Europe and Eastern North America

Abstract

Detailed investigations of the stratigraphically remarkably complete Middle and Upper Ordovician succession inSweden have permitted recognition of a sequence of five main conodont zones and ten subzones, principally based on evolutionary changes in rapidly evolving stocks of multielement species. Zonal fossils include species of Amorphognathus, Eoplacognathus, Prioniodus, and Pygodus. The Pygodus serrus, the Pygodus anserinus, the Amorphognathus tvaerensis, and the lower part of the Amorphognathus superbus Zones are Middle Ordovician, the upper part of the Amorphognathus superbus and the Amorphognathus ordovicicus Zones are Upper Ordovician in age. The Pygodus serrus Zone is subdivided into five, the Pygodus anserinus Zone into two, and the Amorphognathus tvaerensis Zone into three subzones. The conodont zones and subzones established are recognizable not only in the Balto-Scandic area but also, to a large extent, in other parts of Europe and in eastern North America. Although the horizontal distribution of Ordovician conodonts in Europe and eastern North America is still incompletely known, it is evident that the lower Middle Ordovician deposits of this area contain elements of at least three major conodont faunal provinces, namely the American midcontinent province, the North Atlantic province, and the Australian province. Llanvirnian faunas of the Balto-Scandic area are unlike most contemporaneous conodont faunas from eastern North America, although a few common species permit some important correlations. Llandeilian and lower Caradocian faunas are similar in 83 on June 1, 2015 memoirs.gsapubs.org Downloaded from 84 SYMPOSIUM ON CONODONT BIOSTRATIGRAPHY the Balto-Scandic area and in the eastern part of the Appalachian Valley, due mainly to an invasion of Balto-Scandic species into the Appalachian Valley during the deposition of rocks corresponding to the Glyptograptus teretiusculus through lower Diplograptus multidens graptolite zones. Younger Ordovician faunas from eastern North America and Europe have, with some exceptions, little in common; the American faunas are of midcontinent type, whereas a Balto-Scandic type of fauna was distributed over much of Europe (

Conodont biostratigraphy and global correlation of the middle Darriwilian-lower Sandbian (Ordovician) Las Aguaditas Formation, Precordillera of San Juan, Argentina

“…The index species Pygodus anserinus was identified 4.5 m from the base, in sample LAgF1.5. The presence of the upper subzone of the P. anserinus Zone was confirmed by the identification of B. variabilis in LAgF2 which, according to Bergström (1971), indicates this interval. Moreover, a typical Sandbian graptolite association which consists of Leptograptus, Pseudoclimacograptus, Archiclimacograptus, Dicranograptus, Acrograptus and Dicellograptus, was recovered 10 m above the base of the middle member of the Las Aguaditas Formation .…”

“…This zone correlates with equivalent strata in Newfoundland , the Marathon basin, Texas (Bergström, 1978), strata in the Great Basin and Rocky Mountains (Harris et al, 1979), Poland (Dzik, 1994), Sweden (Bergström, 1971(Bergström, , 2007, northwestern China (Zhen et al, 2011a), Thailand (Agematsu et al, 2007), Kazakhstan , and New South Wales in Australia (Zhen et al, 2003).…”

Shorter contributions to paleontology and stratigraphy

“…D. delicatus is known to range into the very earliest Whiterockian. Its occurrence in the Newala, together with representatives of Cristodus loxoides and Glyptoconus quadraplicatus (table 1), species that are not known to range into the Whiterockian, indicates that the Extension of ranges below and above the stratigraphic levels of the Newala and the Lenoir Limestones sampled for this study are, for the Newala, from Shaw (1987) and, for the Lenoir, from Sweet and Bergstrom (1962), Bergstrom (1971), and Schmidt (1982). ( fig.…”

“…The rather complete exposure of Ordovician rocks in the vicinity of Pratt Ferry, Ala., has become a key section for biostratigraphic studies in the southernmost Appalachians, particularly for Middle Ordovician index fossil groups (brachiopods: Cooper, 1956;conodonts: Sweet and Bergstrom, 1962, Bergstrom, 1971, and Schmidt, 1982graptolites: Ruedemann, 1947, Decker, 1952, and Finney, 1977. In this report, we add to the paleontologic documentation of this section the distribution of conodonts in several meters of beds both below and above the Lithostratigraphy and Conodont Biostratigraphy at Pratt Ferry, Central Alabama C5 disconformity separating the Newala and Lenoir Limestones, an interval not covered by previous conodont studies.…”

A review of geological origins and relationships in the Ballantrae Complex, SW Scotland

“…The latter might have been coeval with the pillow lavas but might also have been a younger unconformable cover subsequently infolded with them. The lavas are commonly assumed to form the northern exposed extremity of the Ballantrae Complex, but the cherts have yielded conodonts (Lamont & Lindström 1957) that in modern terms can be assigned to the anserinus and/or serra conodont biozones (Bergström 1971) of Late Llanvirn to earliest Caradoc age. So, depending on the exact relationship of the cherts with the lavas, it is possible that the latter are younger than those of the Ballantrae Complex sensu stricto.…”