Abstract The Ordovician was a key period in the biological and geological history of the Earth. ‘A Global Synthesis of the Ordovician System’ is presented in two volumes of The Geological Society, Special Publications series. The first volume (SP532) covers general aspects of the Ordovician and also includes the syntheses of the Ordovician successions of Europe. To provide a comprehensive global overview, this second volume (SP533) represents a journey through the Ordovician System around the world. Reviews of the Ordovician of North America include syntheses of Alaska, Greenland, Canada, the USA and Mexico, whereas the South American Ordovician is summarized in a specific chapter related to Argentina and neighbouring countries. The Ordovician System of Africa is presented in chapters covering the north and the south of the continent where significant Ordovician successions occur. Australia and New Zealand, as well as Antarctica, are visited in separate chapters. Asia provides the most complex Ordovician successions that are reviewed in chapters covering Turkey and the Levant region, the Middle East, Central Asia, Kazakhstan, India, SE Asia, China, Korea, and Japan. Our journey covers a great number of locations but, with many successions still to be fully described, our knowledge of the Ordovician of the world remains incomplete.

Abstract Ordovician strata in Greenland are extensively exposed in North Greenland and northern East Greenland; additional small traces (loose blocks) are recorded from the craton of West Greenland. The western North Greenland succession is nearly identical to that of the Franklinian Basin exposed on Ellesmere Island, Arctic Canada; the eastern North Greenland represents the (present) northeastern corner of Laurentia and provides the connection to the East Greenland Caledonian platform. The northern East Greenland succession is the natural northern extension of the Caledonian platform of northern Europe and the Appalachian platform of eastern North America. During the Ordovician Greenland occupied a palaeogeographical subtropical to tropical position with a faunal assemblage typical of Laurentia. A prominent faunal peak of diversification occurred in the Late Ordovician. The stratigraphical succession of Greenland is summarized and age relationships are discussed with reference to the fossil faunas and breaks in the successions and correlation between the locations and regions are provided.

Abstract The Ordovician was a key period in the biological and geological history of the planet. ‘A Global Synthesis of the Ordovician System’ is presented in two volumes of The Geological Society, Special Publications . This first volume (SP532) charts the history of the Ordovician System and explores significant advances in our understanding of the period's biostratigraphy, including more precise calibration of its timescale with tephra chronology and regional alignments using astrochronology and cyclostratigraphy. Changes in the world's oceans, their shifting currents and sea levels, the biogeography of their biotas and the ambient climate are described and discussed against a background of changing palaeogeography. This first volume also includes syntheses of Ordovician geology of most European countries, including historical key areas, such as the British Isles, Baltoscandia and Bohemia.

Abstract The Ordovician System was introduced by Charles Lapworth as a solution to the overlapping unit stratotypes loosely defined by Adam Sedgwick, for the Cambrian, and Roderick Murchison, for the Silurian. The Ordovician has emerged as one of the longest and most significant of the geological periods. Following an interval of intensive research of all the key regions of the globe, unit stratotypes in the type areas of England and Wales have been replaced by seven global stages and three series based on Global Stratotype Sections and Points (GSSPs), enhancing the definition of these chronostratigraphic units and facilitating global correlation. As a consequence, the biological and geological events during the period can be recognized and the magnitude and significance of biotic originations and extinctions understood with some confidence.

Abstract Owing to the increasing availability of data for many fossil groups and a generally accepted palaeogeographical configuration, palaeontologists have been able to develop progressively more robust palaeobiogeographical scenarios for the spatial distributions of Ordovician marine faunas. However, most research in Early Paleozoic palaeobiogeography centres on data derived from extensively studied localities in North America and Europe. Thus, clear patterns are emerging of regional biogeography for these areas. However, the fragmentary nature of data from other regions hinders the development of a detailed understanding of palaeogeographical schemes of many clades at the global level. Provincial patterns are now available for several fossil groups, but the global coverage remains generally fragmentary. Palaeobiogeographical investigations were traditionally focused on better understanding of palaeogeographical scenarios and often employed quantitative analyses of faunal similarity. More recently palaeobiogeographical analyses have expanded to investigate questions such as the location and pace of speciation and macroevolution together with macroecological change. For example, studies on the evolution of speciation levels in the frame of the taxonomic radiation of the Great Ordovician Biodiversification are now available. Future investigations, including modelling, will provide more integrative, global patterns of provincialism, including the location of Ordovician biodiversity hotspots and the recognition of latitudinal diversity gradients.

Abstract Rock successions in Britain and Ireland, and more especially those in Wales, were instrumental in the founding and naming of the Ordovician System, and the Anglo-Welsh series established both initially and subsequently were used widely as a standard for Ordovician chronostratigraphy. Although now largely superseded in the global scheme of series and stages, they retain their local and regional importance. The Ordovician System in Britain and Ireland documents the history of a segment of the Earth's crust that incorporated opposing peri-Gondwanan and peri-Laurentian/Laurentian margins of the Iapetus Ocean during its closure, and is accordingly complex. The complexity arises from the volcanic and tectonic processes that accompanied oceanic closure coupled with the effects of eustatic sea-level changes, including the far-field effects of the Late Ordovician glaciation. For the past three decades, Ordovician successions in Britain and Ireland have been discussed in terms of terranes. Here we review Ordovician successions in each terrane, incorporating the results of recent research and correlating those successions via biostratigraphical schemes and radiometric dates to the global Ordovician series and stages.

Abstract Palaeogeographers, geographers and structural geologists use different well-defined terms to designate continental and tectonic units, whereas biogeographers, palaeobiogeographers and palaeontologists use a wide range of subjective terminologies to describe biogeographical and palaeobiogeographical units. The absence of clear definitions and of rules or guidelines for palaeobiogeographical nomenclature has resulted in frequent misunderstandings and general confusion, in particular when applied to ancient time periods, such as the Palaeozoic. Palaeogeographical and palaeobiogeographical terminology used in Palaeozoic geology and palaeontology is reviewed, and recent attempts to standardize palaeobiogeographical nomenclature summarized. We make a number of proposals for future use of terms to avoid confusion and misunderstandings.

Abstract The phylogeographical evolution and the consequent changing distribution and diversity of rhynchonelliform brachiopods through the Ordovician are linked to the dynamic palaeogeography of the period. The Early Ordovician (Tremadocian and Floian) is characterized by globally low-diversity faunas with local biodiversity epicentres, notably on the South China Palaeoplate; low-latitude porambonitoid-dominated faunas with early plectambonitoid and clitambonitoid representatives, as well as high-latitude assemblages mostly dominated by orthoids, can be recognized, but many taxa are rooted in Late Cambrian stocks. The Early Ordovician displays a steady increase in rhynchonelliformean biodiversity, which was mostly driven by the increasing success of the Porambonitoidea and Orthoidea, but the billingsellids and early plectambonitoids also contributed to this expansion. During the Early to Mid Ordovician (Dapingian–Darriwilian), marine life experienced an unprecedented hike in diversity at the species, genus and family levels that firmly installed the suspension-feeding benthos as the main component of the Palaeozoic fauna. However, this may have occurred in response to an early Darriwilian annihilation of existing clades, some of which had been most successful during the Early Ordovician. New clades rapidly expanded. The continents were widely dispersed together with a large number of microcontinents and volcanic arcs related to intense magmatic and tectonic activity. Climates were warm and sea-levels were high. Pivotal to the entire diversification is the role of gamma (inter-provincial) diversity and by implication the spread of the continents and frequency of island arcs and microcontinents. The phylogeographical analysis demonstrates that this new palaeogeographical configuration was particularly well explored and utilized by the strophomenides, especially the Plectambonitoidea, which radiated rapidly during this interval. The porambonitoids, on the other hand, were still in recovery following the early Darriwilian extinctions. Orthides remained dominant, particularly at high latitudes. Biodiversity epicentres were located on most of the larger palaeoplates, as well as within the Iapetus Ocean. Provincial patterns were disrupted during the Sandbian and early Katian with the migration of many elements of the benthos into deeper-water regimes, enjoying a more cosmopolitan distribution. Later Katian faunas exhibit a partition between carbonate and clastic environments. During the latest Katian, biogeographical patterns were disrupted by polewards migrations of warm-water taxa in response to the changing climate; possibly as a consequence of low-latitude cradles being developed in, for instance, carbonate reef settings. Many clades were well established with especially the strophomenides beginning to outnumber the previously successful orthides, although this process had already begun, regionally, in the mid to late Darriwilian. At the same time, atrypoid and pentameroid clades also began to radiate in low-latitude faunas, anticipating their dominance in Silurian faunas. The Hirnantian was marked by severe extinctions particularly across orthide-strophomenide clades within the context of few, but well-defined, climatically controlled provincial belts. Supplementary material: The individual localities and a reference list for the data sources are provided at: http://www.geolsoc.org.uk/SUP18667

Abstract The northeastern margin of Laurentia formed an important part of the Iapetus Ocean and includes the development of the Franklinian Basin in North Greenland and Arctic Canada. The uninterrupted continental margin bordering the North American craton is represented by well-exposed successions in Northeast and eastern North Greenland, together with Svalbard and Bjørnøya. Physiographically, the northeastern margin of Laurentia during the early Paleozoic history of Greenland was a northward extension of the passive rifted continental margin of the Caledonian continental edge of Laurentia. It was a transform-rifted margin and represents the part of the Laurentian margin that borders the Arctic part of the North Atlantic Ocean. Geologically, the northwestern segment of the continental margin has a somewhat different setting and development from farther south in the Northeast Greenland–Svalbard segment but both regions overlie a thick and extensive package of Neoproterozoic rocks and were affected by the Caledonian orogeny.