Abstract The Ordovician successions of France and neighbouring areas of Belgium and Germany are reviewed and correlated based on international chronostratigraphic and regional biostratigraphic charts. The same three megasequences related to the rift, drift and docking of Avalonia with Baltica can be tracked in Belgium and neighbouring areas (Brabant Massif and Ardenne inliers), western (Rhenish Massif) and northeastern Germany (Rügen). The remaining investigated areas were part of Gondwana in the Ordovician. The Armorican Massif shares with the Iberian Peninsula a Furongian–Early Ordovician gap (Toledanian or Norman gap), and a continuous Mid–Late Ordovician shelf sedimentation. The Occitan Domain (Montagne Noire and Mouthoumet massifs), eastern Pyrenees and northwestern Corsica share with southwestern Sardinia continuous shelf sedimentation in the Early Ordovician, and a Mid Ordovician ‘Sardic gap’. In the Ordovician, the Maures Massif probably belonged to the same Sardo-Occitan domain. The Vosges and Schwarzwald massifs display comparable, poorly preserved Ordovician successions, suggesting affinities with the Teplá-Barrandian and/or Moldanubian zones of Central Europe.

Abstract The Ordovician outcrops of central Europe belong to various areas with, in general, a very complex tectonic evolution. In this chapter, we review the localities that were attributed to peri-Gondwanan terranes. We do not therefore include a detailed description of areas attributed to the Baltica palaeocontinent (Denmark, southern Sweden, Baltic States, northeastern Poland). Whereas the northwestern part of Central Europe belonged, during the Ordovician, to the eastern part of the microcontinent of Avalonia (Belgium, western and northern Germany, possibly northwestern Poland), the outcrop areas of the Rhenohercynian, Saxothuringian and Moldanubian zones have mostly been assigned to Gondwana-derived terranes (such as, in palaeogeogra-phical terms, Armorica or the Armorican Terrane Assemblage (ATA) and Perunica) or to sedimentary basins in the vicinity of the Gondwanan supercontinent. Our review includes the Avalo-nian sequences of Belgium in the northwestern part of the investigated area of Central Europe, continues into western, northern and eastern Germany and extends into northwestern and southern Poland. The review of the Ordovician of the Saxothuringian and the Moldanubian zones includes the outcrop areas of southeastern Germany, the Czech Republic and southwestern Poland. The Ordovician from the pre-Variscan parts of the Alpine mountain chains of Switzerland, Austria and northern Italy are also briefly discussed. In terms of stratigraphy, the British Ordovician series and stages were generally used as a standard in most parts of western and central Europe. However, in the last two decades, significant progress has been made in Ordovician series and stage boundary definitions on a global scale. A tripartite division of

Abstract In an overview of the Silurian of Central Europe, it is important to realize that during this period the study area was spread more widely over the globe than nowadays because at least two oceans were present in the area which have since disappeared. Several palaeocontinents such as Baltica or Gondwana, smaller palaeo-plates such as Avalonia and Far Eastern Avalonia, and Peri-Gondwana terranes such as Perunica, were separated by the Tornquist Sea and the Rheic Ocean. These palaeocontinents were brought together in the present-day configuration by closing of the oceans and the subsequent orogenic collisions, respectively termed the Caledonian and Variscan orogenies. Plate movements before and during the Alpine orogeny also brought pieces of northern Gondwana into the study area. These Proto-Alps are now included in the basement of the Alps and are observable in several tectonic windows (e.g. Carnic Alps).

Abstract Tectonically disturbed Ordovician rocks penetrated by deep drillholes in Pomerania, NW Poland (Koszalin-Chojnice Zone) belong to the Heligoland-Pomerania Deformation Belt. Earlier data demonstrate that the Avalonia-Baltica collision occurred in Late Ordovician times, but in Pomerania, the timing of convergence has not been ascertained, and it is uncertain if the rocks underneath the Koszalin-Chojnice Zone belong to Avalonia or Baltica. Data from chitinozoans, organic-walled Palaeozoic microfossils with applications in biostratigraphy and palaeobiogeography, were assessed from ten boreholes (Brda 2; Brda 3; Chojnice 5; Karsina 1; Kościernica 1; Nowa Wieś 1; Okunino 1; Sarbinowo 1; Skibno 1; Wyszebórz 1) to address these problems. The results improve the biostratigraphy of the cores and demonstrate that the youngest Ordovician rocks are of a Burrellian (early mid Caradoc) to Cheneyan (late mid Caradoc) age. Because these rocks are interpreted as forming part of the deformation belt, the obtained ages put a lower age limit on the initiation of foreland basin sedimentation on the foreland of the orogeny, i.e. the Baltic platform. Quantitative comparison of chitinozoan assemblages demonstrates a high level of similarity between Pomerania and Avalonia. Together, Pomerania and Avalonia show greater similarity to Baltoscandia than to North Gondwana, supporting the idea that the Tornquist Ocean had narrowed significantly in early Caradoc times.

ABSTRACT Biostratigraphic investigations have been carried out on Ordovician chitinozoans mostly from the Quwarah, Ra’an, Kahfah and Hanadir members of the Qasim Formation in central Saudi Arabia. Among the 96 core samples processed from seven wells, about half of them (from wells Berri-84, Shedgum-239, Ain Dar-196 and Ain Dar-277) provided workable specimens, whereas the other wells, namely Ain Dar-281, Haradh-51 and Abu Jifan-25 were barren. Some chitinozoan species of Baltic affinities (e.g. Laufeldochitina striata ) or of Laurentian affinities (e.g. Lagenochitina cf. pirum ) are present, but most of the recovered chitinozoan species are of northern Gondwana affinities. These chitinozoans allow accurate correlation with the local chitinozoan biozones already established for northern Saudi Arabia. Precise correlation with some of the Ordovician chitinozoan biozones for the northern Gondwana regions can also be proposed (e.g. lower part of the pissotensis biozone). The available samples are not, however, sufficiently closely spaced for characterizing all the Ordovician chitinozoan biozones. It is not yet possible, therefore, to document eventual hiatuses in the Ordovician sedimentary succession of central Saudi Arabia. The investigated samples from the Quwarah, Ra’an, Kahfah and Hanadir members of the Qasim Formation are respectively dated as Ashgill, late Caradoc/earliest Ashgill, Caradoc and Llanvirn. Strata referred to the Sarah Formation are probably of topmost Ashgill age but may range into earliest Llandovery. Several new species have been observed. They are presently kept in open nomenclature until better preserved material is available for proposing well-documented diagnosis.