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 rocks, found in northern, east-central, interior and southern Alaska, formed in a variety of depositional and palaeogeographic settings. Shallow- and deep-water strata deposited along the northwestern Laurentian margin occur in east-central Alaska (Yukon River area) and probably correlative rocks crop out to the north in the Porcupine River area. Ordovician strata elsewhere in Alaska are parts of continental or island arc fragments that, as indicated by faunal and detrital zircon data, have been variously displaced. In northern Alaska, Ordovician rocks are included in the Arctic Alaska–Chukotka Microplate (AACM), a composite tectonic entity with a complex history. Some Ordovician strata in the AACM (parts of the North Slope subterrane) represent displaced fragments of the northern Laurentian margin. Coeval strata in southwestern parts of the AACM (York and Seward terranes, Hammond subterrane) share distinctive lithologic and biotic features with Ordovician rocks in interior Alaska (Farewell and related terranes). Ordovician strata in southeastern Alaska (Alexander terrane) also likely compose a composite crustal fragment that accumulated in a complex arc system. Shared features between many of these units suggest similar origins as part of one or more crustal fragments situated in the palaeo-Arctic between Laurentia, Baltica and Siberia during early Paleozoic time.

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 Ordovician rocks extensively border and cover Laurentia or the North American Craton in Canada. These rocks represent diverse and significant successions spread across a variety of depositional and palaeogeographic settings in the Canadian Arctic Islands, Eastern Canada, Western Canada and the Canadian Interior. During much of the Ordovician, Laurentia straddled the palaeoequator and was flooded by extensive epicontinental seas, experiencing high temperatures and high faunal diversity. The central and western parts of the Laurentian Craton remained relatively stable during the Ordovician, but there was substantial tectonic activity with the Taconic Orogeny affecting the Appalachian area and the Pearya composite terrane affecting the Franklinian Margin along its eastern and northern margins, respectively. The large Hudson Bay and Williston basins and smaller satellite basins cover the cratonic interior in Canada. These shallow intracratonic basins, dominated by marine carbonates with some evaporites, are the erosional remnant of a more extensive sea episodically connected with the adjacent platformal areas during the Ordovician. The Global Boundary Stratotype Section and Point (GSSP) for the base of the Ordovician System is exposed in Green Point, western Newfoundland while the Ordovician–Silurian boundary interval is well exposed on Anticosti Island, Québec but is also present in Ontario, Manitoba, Yukon and Arctic Canada.

Abstract The Ordovician rocks of the conterminous United States (US) have a complex history, spanning multiple ancient basins, shifting palaeoclimate and evolving tectonic regimes. The US portion of the palaeocontinent of Laurentia occupied a relatively stable and isolated position around the southern tropics during the Ordovician. In general, Lower Ordovician rocks form a vast autochthonous blanket of fine-grained (tropical) carbonates that covered much of Laurentia, named the ‘Great American Carbonate Bank’. Outboard, ribbon carbonates and graptolitic shales are found in allochthonous fragments of the ancient continental margin. Middle Ordovician strata are more lithologically diverse, including the addition of several regionally distributed sandstones of the inner detrital belt, mostly overlying the Sauk–Tippecanoe unconformity. Upper Ordovician strata show the greatest lithologic and faunal diversity, reflecting steepening topography resulting from regional compression along the south Laurentian (Appalachian) margin. Recent advances in the interpretation of the US Ordovician come primarily from studies of carbon and oxygen stable isotopes, sequence stratigraphy, palaeoecology, tephrochronology, redox geochemistry, strontium isotopes and geochronology.

Abstract In Mexico, Ordovician sedimentary rocks are exposed in the states of Baja California, Sonora, Chihuahua and Oaxaca, comprising approximately 30 stratigraphic successions ranging from Lower to Upper Ordovician. The ages of the sequences have been established primarily by utilizing conodonts and graptolites, which have also allowed us to differentiate between platform and oceanic basin environments. The State of Sonora has the most complete Ordovician stratigraphic sequences, ranging from Tremadocian to Hirnantian. The deposits in Baja California are Floian in age, while the sequences of Chihuahua range from Sandbian to Katian, and the deposits in Oaxaca are Tremadocian. The Ordovician deposits of northern Mexico (Baja California, Sonora, and Chihuahua) present a palaeogeographic relationship to the North American craton, mainly owing to faunal interspecific affinities, while the southern deposits (Oaxaca) are controversial owing to the high degree of endemism of the faunas; however, they show affinity with Gondwana, Baltica and Avalonia, with a possible insular origin. The biotic assemblages of the Ordovician of Mexico include a variety of taxa, including algae, poriferans, corals, bryozoans, brachiopods, molluscs, trilobites, echinoderms, graptolites and conodonts as predominant elements. Despite many years of field studies in Mexican Ordovician localities, biostratigraphic correlations are as yet insufficient and incomplete or are based on limited interpretations. Thus, the Ordovician biostratigraphic data from Mexico compiled in the present paper have great potential and significant value. The advancement in the knowledge of the Ordovician biostratigraphy of Mexico will contribute to a major understanding of the relationships with the Ordovician System to a continental scale. Future advances will come mainly through increasing the amount and quality of data as well as improving biocorrelations among the Ordovician sequences of Mexico.

Abstract Early Paleozoic rocks are widespread, superbly exposed, and reach several thousand metres thick in southern South America. A largely quadripartite geotectonic subdivision of this huge area encompasses: (1) intracratonic basins forming the sedimentary cover of the Amazonian craton (Brazilian collage); (2) a clastic platform surrounding the Amazonian craton and the Pampia Terrane (Sierras Subandinas and Cordillera Oriental); (3) subduction-related parautochthonous volcanic arcs and associated volcano-sedimentary basins (Puna–Famatina arc); and (4) crustal fragments accreted to the proto-Andean margin of Gondwana (e.g. Cuyania Terrane). In this context, disparity in the geodynamic histories, preserved record and geological knowledge are remarkable. Biostratigraphical frameworks allow the recognition of global chronostratigraphical Ordovician subdivisions with fairly good resolution in the Early and Middle Ordovician of the Precordillera and the Early Ordovician of the Cordillera Oriental of Argentina. In Sierras Subandinas and Cordillera Oriental of Bolivia the Ordovician statigraphy is almost complete, although these extensive regions are still poorly known. In addition, trilobite-rich assemblages from the Cordillera Oriental and brachiopod-rich ones from Precordillera and Famatina offer a remarkable template for dissecting regionally different scenarios underlying Ordovician diversifications. Overall, a more complete knowledge of this key area of Gondwana will certainly enhance our understanding of the global dynamics during the Ordovician.

Abstract Outcrops of the Ordovician System in South Africa are extensive; they cover significant portions of the Northern, Western and Eastern Cape provinces as part of the Cape Fold Belt as well as the KwaZulu-Natal Province as supracrustal cover overlying the Natal sector of the Paleoproterozoic Namaqua-Natal metamorphic province. Within the Cape Fold Belt, Ordovician rocks of the Table Mountain Group (Piekenierskloof, Graafwater, Peninsula, Pakhuis and Cedarberg formations as well as the enigmatic Sardinia Bay Formation) outcrop extensively whilst pre-Cape rocks of the Kansa Group (Vaartwell, Uitvlug, Gezwinds Kraal and Schoongezigt formations) and Schoemanspoort Formation are present within the Kango Inlier encapsulated by the fold belt. The Natal Group (Durban and Mariannhill formations) is entirely located within KwaZulu-Natal. For the most part, these metasiliciclastic rocks are markedly unfossiliferous except for the world class fossil deposits of the Cedarberg Formation and important trace fossil sites in the Graafwater, Peninsula and Pakhuis formations. The lack of palaeontological material and other accurate geochronological proxies in these successions (as well as those of the Kansa and Natal groups and Schoemanspoort Formation) makes estimations of relative age constraints tenuous at best and difficult to correlate with global Ordovician chronostratigraphic frameworks. Regardless of the challenges faced in correlating these rocks within global frameworks, these rocks provide a unique low latitude glimpse into Earth surface processes and the feedback loops that ensued within the biological realm along the southern margin of Gondwana.

Abstract The Ordovician of North and West Africa comprises three main transgressive–regressive sequences understood as ‘second-order’ cycles of 10–15 myr duration. Tide- to wave-dominated shallow-marine clastic successions, preserving incidental bryozoan carbonates to the north, include fluvial deposits over the most proximal southern stretches of the platform. The boundary with Cambrian strata remains unclear but the latter are progressively less represented to the south in the undifferentiated ‘Cambro-Ordovician’. To the north, graptolites, brachiopods and trilobites combined with palynomorphs provide a robust biostratigraphic frame. Maximum flooding intervals occurred in the early to middle Tremadocian, middle Darriwilian and middle to late Katian. Two events interfered with an overall long-term transgressive trend. The ‘intra-Arenig’ (late Floian?) tectonic event highlighted palaeohighs coinciding with Paleoproterozoic basements. Gondwanan drainage basins were reorganized, which had an impact on sediment sourcing and distribution of detrital material (e.g. zircons) feeding the pre-Variscan Europe. The second event is the end-Ordovician glaciation. The domain supported the greatest part of the Hirnantian glaciers and may also have preserved pre-Hirnantian glacial archives. It is not until the very latest Ordovician that offshore conditions developed far inland; it is however suspected that this inundation benefited from a transient postglacial isostatic flexure.

Abstract This contribution addresses the current state of knowledge of the mainly siliciclastic Ordovician rocks in Jordan, Syria and southern Turkey, including advances in palaeontology, stratigraphy, depositional facies analysis and supra-regional correlation. The extensive and excellent exposures of the sedimentary succession in southern Jordan represent the regional reference for the Ordovician System in the southern Levant. We discuss the sedimentological and faunal characteristics as well as the stratigraphy and correlation of the succession. For the northern Levant (especially southeastern Turkey) and the western and eastern Taurides, the Ordovician succession and an updated sedimentary architecture is explained, and a comprehensive correlation for the region is presented. Increased knowledge on the fossil content from these regions enables correlation across the southern parts of the Arabian Plate to southern Turkey, and with the greater Gondwanan regions, far field as southwestern Europe and northern Africa. The depositional environments in the southern and northern Levant and southern Turkey encompass non-marine to shallow-marine areas in the lower part of the Ordovician that are followed upsection by shelf deposits of variable proximity up to the glacial episode in the Late Ordovician that is traceable in each of the areas. Characteristic signals in the Ordovician succession are represented by the trans-regional early Darriwilian unconformity and by the base of the Hirnantian glacial-related deposits followed by lower Silurian strata, visible across the entire region. New data from zircon-based provenance analysis clearly implicate the Arabian Shield as the main source of a huge amount of the clastic detritus within the Ordovician succession. In the course of the entire Cambrian–Ordovician interval, progressive deeper erosion of the Arabian Shield occurred. Sediment sources from regions farther away indicate long time of exposure and resedimentation, and some long-distance transportation, but their sedimentary influence was only of minor extent. The excellent outcrops mainly in southern Jordan, in southeastern Turkey and in the Taurides represent potential regions for further research.

Abstract Ordovician studies in Iran have shown significant progress since the beginning of the century. A number of individual faunas have been documented and a biostratigraphical framework based on conodonts, chitinozoans, acritarchs and trilobites developed. Correlation of Ordovician successions with the International Chronostratigraphic Chart has been significantly improved, and the position of the series and stage boundaries can be recognized with greater precision. While geographical proximity to temperate latitude Gondwana is apparent for most Iranian terranes, biogeographical links of Alborz and Kopet-Dagh with South China prevailed through the Early–Middle Ordovician. In Pakistan, Ordovician deposits have a restricted distribution in the Karakorum block (Chitral). Here they are represented by the Yarkhun and Vidiakot formations with Floian–Darriwilian acritarchs, chitinozoans and early Darriwilian conodonts. In Peshawar District of the North-West Frontier Province, an Early–Middle Ordovician age is likely for the Misri Banda Quartzite with Cruziana rugosa trace fossils. It is overlain conformably by carbonates of the Panjpir Formation, which has an inferred Middle Ordovician–Silurian age. Presently available information on the Ordovician of Afghanistan is mostly based on reconnaissance studies performed almost half a century ago, and a few monographed Early and Late Ordovician faunas.

Abstract The region of Kyrgyzstan, Tajikistan and Uzbekistan includes five first-order tectonic units with an Early Paleozsoic sedimentary record, comprising North Tien Shan, Karatau Naryn, Turkestan–Alai, Zeravshan–Hissar and the Central Pamirs. Available palaeobiogeographical and palaeomagnetic data suggest that these were widely dispersed in the Ordovician. North Tien Shan, Karatau Naryn, Turkestan–Alai were separate microcontinents located in the low southern latitudes throughout the Ordovician in relative proximity to the western Gondwana margin. Zeravshan–Hissar and the Central Pamirs were also parts of the Gondwana supercontinent but were located in temperate latitudes. The geological literature on the Ordovician of the region is assessed to provide an updated palaeontological record, outline of lithostratigraphy and biostratigraphic correlation based on the International Chronostratigraphic Chart. The Ordovician biostratigraphy of Central Asia is mainly graptolite-based; however, that record is discontinuous, and the absence of detailed faunal logs and lack of monographic studies causes difficulty in precisely locating system and stage boundaries. Although an extensive faunal record has been documented, often it is based on preliminary taxonomical identifications which are not reliable for high-resolution biostratigraphy and tracing biodiversity patterns.

Abstract A comprehensive review of the current state of research on Kazakh Ordovician litho-, bio- and chronostratigraphy is presented. An Ordovician lithostratigraphic framework applied to eight Kazakh first-order tectonic units is outlined and its correlation with the International Chronostratigraphic Scale is given. Presently used criteria for definition of the Kazakh Ordovician regional stages are critically discussed and revaluated. The archipelago model is considered as the most appropriate for reconstruction of the relative position of inferred Kazakh volcanic island arcs and microcontinents in the Ordovician Period. A biogeographical assessment of Kazakh Ordovician benthic faunas suggests strongest affinity to the contemporaneous faunas of Tarim, South and North China and to a lesser degree to the Australian sector of Gondwana, while biogeographical connections with Siberia and Baltica are negligible. During the Sandbian to Katian, a loose cluster of Kazakh microcontinents and island arcs became a major biodiversity hotspot and species pump located at low latitudes on both sides of the equator. Radiolarian cherts from accretionary complexes preserved an almost complete record of biogenic sedimentation for at least 30 Ma from the Furongian to Darriwilian, providing a unique opportunity to study biotas and environments in Ordovician oceans.

Abstract Ordovician rocks of the Indian Tethyan Himalaya contain a conspicuous angular unconformity between mostly marine Cambrian and overlying terrestrial Ordovician strata, which is a record of the Kurgiakh Orogeny. This tectonic event is traceable across the Tethyan Himalaya from Pakistan to Bhutan. The Pin Formation in the Spiti Valley provides a high-resolution account of the marine depositional history, palaeontology and isotope geochemistry of Late Ordovician events. The middle (Takche) member is late Katian and the upper Mikkim Member is lower Silurian (Llandovery), based on an ozarkodinid conodont fauna. The Pin Formation records the Boda event, the last warming interval prior to Hirnantian glaciation. The δ 13 C carb chemostratigraphic data allow precise global correlation, and recognition of the Paroveja positive excursion, the last major excursion of the Katian. The Mikkim Member records a ‘lower HICE’ (Hirnantian isotopic carbon excursion) of the Katian–Hirnantian boundary interval. Palaeontological data indicate that there are no known fossils diagnostic of any Ordovician ages older than the Katian Stage in India. Evidence of Ordovician sedimentary rocks in the Lesser Himalaya is intriguing, but presently equivocal. The widespread absence of pre-Katian strata on the Indian subcontinent is due to erosion associated with the Kurghiak orogeny and delayed onlap onto topographically high areas.

Abstract China presently comprises several independent tectonic palaeoplates or terranes and parts of other blocks, which have been assembled over geological time. In the Ordovician, these blocks included South China, North China, Tarim, Qaidam, Junggar, Qiangtang-Qamdo, Lhasa and partially Himalaya, Sibumasu and Indochina, as well as the Altay-Xing'an and Songpan-Garze fold belts, which were discrete but near-adjacent. Twelve stratigraphic megaregions bounded by tectonic sutures or major fault zones can be recognized. Some of them are further differentiated into several regions according to the lithological and biotic facies or distinct stratigraphic sequences. Here, the palaeontologic features and biostratigraphic framework of these stratigraphic megaregions and regions are summarized. The unified biostratigraphic framework presented herein is supported by 33 graptolite biozones and 27 conodont biozones, together with supplementary biozones, communities or associations of brachiopods, trilobites, cephalopods, chitinozoans, acritarchs and radiolarians. With constraints of integrative chronostratigraphy, biostratigraphy, chemostratigraphy, cyclostratigraphy and magnetostratigraphy, along with some geochronologic data, our understanding of the temporal and spatial distribution of the Ordovician lithostratigraphic units on these major blocks has been significantly advanced. Vast amounts of new data accumulated in recent decades also constrain the major Ordovician geological and biotic events evident in China, such as marine anoxia, faunal turnovers and tectonic orogenies.

Abstract The Ordovician succession of the Korean Peninsula is part of the Cambro-Ordovician Joseon Supergroup exposed in the Taebaeksan Basin of South Korea and the Pyeongnam Basin of North Korea. This review summarizes the advances made on these successions over the past two decades, focusing on the Taebaeksan Basin. The Ordovician succession in the Taebaeksan Basin comprises the Taebaek, Yeongwol, Yongtan, Pyeongchang and Mungyeong groups, of which the Taebaek and Yeongwol groups have been studied in detail. These strata are mixed carbonate–siliciclastic deposits formed in peritidal to deep-subtidal environments. Sedimentological and palaeontological studies show that the Korean Ordovician succession represents local variations of the Great Ordovician Biodiversification Event, exemplified by reef evolution, changes in sedimentary systems and changes in invertebrate fossil assemblages. Recent studies of the Yongtan, Pyeongchang and Mungyeong groups have demonstrated that these units are important for understanding the tectonic evolution of the Taebaeksan Basin. The Ordovician strata in the Taebaek Group are generally similar to those of the Pyeongnam Basin and North China; however, the Upper Ordovician–Devonian strata between the two Korean basins show palaeontological affinities to those of South China, perhaps recording the Permo-Triassic collision between the Sino-Korean (North China) and South China blocks.

Abstract Ordovician Japan formed a mature arc-trench system developed along the palaeo-Pacific (Panthalassa) margin of the Greater South China (GSC) continental block. GSC consists of South China, East China Sea, SW–NE Japan and the Khanka–Jiamusi–Bureya megablock in the Far East; Paleozoic GSC was thus, in total, twice as large as the South China components by themselves (Yangtze and Cathaysia). The Ordovician crust of Proto-Japan comprised coeval arc-related rocks, such as granitoids, supra-subduction zone ophiolites and fore-arc basin strata, although most of them were considerably fragmented. The Ordovician and middle–late Paleozoic fossils from Japan are highly limited but suggest that Proto-Japan was positioned in the low-latitude domains probably of the palaeo-Pacific Ocean in connection to Paleo-Tethys. GSC became separated from Rodinia in the Neoproterozoic, and its Proto-Japan segment evolved as a collision-free subduction margin for nearly 500 myr since the mid-Cambrian. The GSC framework provides critical constraints to the palaeogeographical reconstruction of circum-Pacific continental blocks. First, the Cambro-Ordovician GSC should have been isolated from Australia/India/East Antarctica that formed East Gondwana by a relatively wide ocean domain for keeping ‘subduction potential’. Second, the Cathaysian margin of GSC should have faced to an extensive ocean without major continents since the Cambrian. The palaeo-Pacific is the only possible candidate for this.

Abstract This paper describes the Ordovician stratigraphy of the Sibumasu Block, which formed part of equatorial peri-Gondwana during the early Paleozoic, and summarizes the palaeoenvironmental conditions that prevailed during that time. Upper Cambrian sequences are commonly dominated by coarse-grained clastic rocks of shallow-marine origin. The lithology of the Lower Ordovician varies from region to region, with fine-grained clastic rocks in the Shan Plateau, shallow-marine clastic rocks in northern to western Thailand and shallow-marine carbonate rocks in southern Thailand to northwestern Malaysia. Middle Ordovician strata consist entirely of shallow- to deeper-water carbonate rocks, with the exception of turbidites in midwestern Malaysia. Upper Ordovician rocks show an overall deeper environment, and the uppermost Ordovician consists of pelagic and deeper, fine-grained clastic rocks. On the basis of palaeobiogeographical data, the Sibumasu Block was adjacent to Western Australia throughout the early Paleozoic. Upper Cambrian rhyolitic rocks in the Shan Plateau and Lower–Middle Ordovician volcanics in midwestern Malaysia may have formed as a result of tectonomagmatism associated with the subduction of the Proto-Tethys Ocean plate into the northern Gondwanan margin. The close similarity of Late Ordovician fossil assemblages from Sibumasu and South China may be due to a sea-level rise during this time.