This paper is a revision of the standard chronostratigraphy of the Ordovician of the historical type area in England and Wales. The revision is a response to the need for more precise definitions of series and stages, especially for practical international correlation. In some cases this has entailed moving horizons for Series bases away from those in the classical sections. The scheme will be used as the standard for a forthcoming revision of the Correlation Chart of the British Ordovician System. The Ordovician is divided into five series: Tremadoc, Arenig, Llanvirn, Caradoc and Ashgill. The Llanvirn is extended to include part of the classical Llandeilo Series, which is included within it as a stage. Where stage subdivisions of standard series have not yet been defined, as in the Tremadoc, they are proposed in this paper. However, Bancroft’s fine stadial divisions of the Caradoc, which have been criticized for their brevity and local utility, are combined into four new stages, which will have wider application. The former Caradoc subdivisions are retained as substages for the purposes of regional correlation.

A revision of Ordovician series and stages from the historical type area

Recent revisions to the biostratigraphic and chronostratigraphic assignment of strata from the type area of the Niagaran Provincial Series (a regional chronostratigraphic unit) have demonstrated the need to revise the chronostratigraphic correlation of the Silurian System of North America. Recently, the working group to restudy the base of the Wenlock Series has developed an extremely high-resolution global chronostratigraphy for the Telychian and Sheinwoodian stages by integrating graptolite and conodont biostratigraphy with carbonate carbon isotope (delta 13C(carb)) chemostratigraphy. This improved global chronostratigraphy has required such significant chronostratigraphic revisions to the North American succession that much of the Silurian System in North America is currently in a state of flux and needs further refinement. This report serves as an update of the progress on recalibrating the global chronostratigraphic correlation of North American Provincial Series and Stage boundaries in their type area. The revised North American classification is correlated with global series and stages as well as regional classifications used in the United Kingdom, the East Baltic, Australia, China, the Barrandian, and Altaj. Twenty-four potential stage slices, based primarily on graptolite and conodont zones and correlated to the global series and stages, are illustrated alongside a new composite delta 13C(carb) curve for the Silurian. Conodont, graptolite, isotope, New York, Ontario, series, Silurian, stage. (Less)

Revised correlation of Silurian Provincial Series of North America with global and regional chronostratigraphic units and delta 13C(carb) chemostratigraphy

Early Palaeozoic palaeobiogeography of the Variscan regions

Correlation of the Silurian and Devonian rocks in New York State

Chapter 22 – The Devonian Period

This report presents details of the development of the Silurian-Devonian boundary in the Barrandian area in Central Bohemia. It begins with a summary of previous investigations, followed by a survey of the general facies development of the region. The most important stratigraphic sections in which the boundary occurs are described and illustrated. Details of biostratigraphy concentrate primarily on the occurrence of index fossils. The second part of the paper is concerned with a discussion of individual faunal groups and their importance in delineating the boundary, their dependence on facies, and their value in correlation. Finally, the general development of the Silurian-Devonian boundary in the Barrandian is discussed, the stage and zonal subdivisions of the boundary beds are revised, and stratotypes are defined or specified in greater detail. Principal conclusions may be summarized as follows: 1. The Silurian-Devonian boundary is defined at the base of the Monograptus uniformis Zone which is coincident with the Pridolian-Lochkovian boundary. 2. Although unaccompanied by facies change, the boundary is well defined bio-stratigraphically on the basis of graptolites and other faunas. 3. Recent investigations confirm that there is no demonstrable stratigraphic hiatus or facies change at the boundary, which can be defined confidently only through biostratigraphy. In the vicinity of the boundary, however, mainly in the Lower Lochkovian, sedimentation was locally condensed and a relatively long time-interval may be represented by a small thickness of sediments. 4. The base of the Devonian is marked by the sudden appearance of Monograptus uniformis. Two subspecies, M. uniformis uniformis and M. uniformis angustidens, appear simultaneously or separated only by a very short interval. 5. The first occurrence of the trilobite Warburgella rugulosa rugosa is a suitable auxiliary indicator of the boundary, and is a prominent marker horizon in the Lower Lochkovian. It appears essentially simultaneously with M. uniformis. Because of its wider facies tolerance, the species is used for correlating between platy limestones and shales and the purely carbonate development. 6. The boundary can also be identified by using faunas that occur in the upper part of the Pridolian. These include: abundant Monograptus transgrediens, Dayia bohemica (particularly in the carbonate facies), Spathognathodus steinhornensis eosteinhornensis, and Boucia ornatissima (in the shale-rich development). The trilobite Prantlia (Tetinia) minuta is a significant horizon marker at the Pridolian-Lochkovian boundary in the carbonate facies. In addition to graptolites, trilobites, and conodonts (especially Icriodus woschmidti), the sudden increase of an ostracod association including Acanthoscapha bohemica serves to identify the lowest Lochkovian in the platy-limestone facies. The latter association, however, may begin in the latest Pridolian. 7. Accumulations of Scyphocrinites remains occur at various stratigraphic horizons within the Pridolian and Lower Lochkovian. They reach a maximum in the platy-limestone and shale facies in the southeast limb of the Barrandian in the basal Lochkovian, where they are referred to as the "Scyphocrinites Horizon." The occurrence of the genus cannot, therefore, be used to delineate the Silurian-Devonian boundary or to define the stratigraphic units: Budnanian, Pridolian, or Lochkovian. End_Page 104------------------------ 8. Recent work has shown that almost all faunal groups in the boundary beds are facies-controlled. The fauna of the platy limestones and shales differs markedly from that of the pure carbonate facies. 9. The following chronostratigraphic division may be recognized: the Budnanian (equals Upper Silurian) Series is divided into the Ludlovian and Pridolian stages; the Lochkovian is the earliest Devonian stage. 10. The Pridolian-Lochkovian or Budnanian-Lochkovian boundary is redefined on the basis of graptolites, and stratotypes are revised accordingly.

The Silurian-Devonian Boundary in the Barrandian

The 18 trilobite assemblages distinguished in the Silurian of central Bohemia sensitively reflect different palaeoenvironments influenced particularly by the submarine volcanic activity. Richly diversi­ fied shallow water assemblages occurring in carbonates at or in proximity of volcanic elevations grade seawards into less diversified deeper water assemblages found in different shale deposits. The trilobite faunas range in Benthic Assemblages 2 to 6 in BoucoT's ( 1 975) classification and show in composition and grouping many analogies with those of Devonian or other times. Introduction Trilobites constitute an important component of the Silurian fauna of the classical Barrandian area in central Bohemia. Due to their frequent occurrence and suitable preservation, they attracted attention since the first half of the 1 9th century and were systematically described in many monographs and papers, starting with those of BARRANDE ( 1 846, 1 852, 1 872) and HAWLE & CORDA ( 1 847) and continuing up to the recent works of SNAJDR ( 1 960, 1 980), PRIBYL & VANEK ( 1 973, 1 9 8 1 etc . ) a. o . Also the stratigraphic importance of Silurian trilobites has been evaluated particularly in the studies of HORNY ( 1 955, 1 962), who established several trilobite biohorizons within the carbonate development of the Upper Silurian, but ecostrati­ graphic trilobite studies have remained out of the principal interests . The presented review has been prepared in a similar way as that dealing with Devonian trilobites (CHLUrA.C 1 983) and is intended as one of Czechoslovak contributions to the IGCP Project Ecostratigraphy. In the text, the following abbreviations of authors names are used : BARR. = BARRANDE, BEYR. = BEYRICH, Bouc . = BOUCEK, C. = CORDA, CH. = CHLUrA.C, H. = HAWLE, PRo = PRIBYL, PT. = PRANTL, SN . = SNAJDR, V. = VANEK. In the classification of benthic assembla­ ges, BOUCOT'S ( 1 975) grouping and nomenclature are applied (abbr. B.Ass . ) . The author is deeply grateful to Dr . V. HAVLicEK, Dr . M. SNAJDR and Dr. P . STORCH for critically reading the manuscript and for valuable comments . \". Author's address : Dr. Ivo CHLUPAC, Ustredni ustav geologicky, Malostranske nam. 19 , 1 1 8 2 1 Praha 1, Czechoslovakia. 0078-042 1 /87/001 7-0169 $ 4.50 © 1987 Gebrlidcr Borntraeger, 01 000 Berlin ' 0-7000 Stuttgart (c) 2015 www.schweizerbart.com DOI:10.1127/nos/17/1987/169

Ivo Chlupáč

Papers

The Silurian-Devonian Boundary in the Barrandian

Ecostratigraphy of Silurian trilobite assemblages of the Barrandian area, Czechoslovakia

Pragian/Zlíchovian and Zlíchovian/Dalejan boundary sections in the Lower Devonian of the Barrandian area, Czech Republic

Series or Stages within Palaeozoic Systems