Ordovician Graptolite Research Articles

Ordovician graptolite-bearing strata in southern Jiangxi with a special reference to the Kwangsian Orogeny

The Ordovician graptolite sequence of the Yongxin-Chongyi area in southern Jiangxi was suggested as a standard for the correlation of Ordovician in the Zhujiang region of South China. Based on a restudy of the Upper Ordovician graptolites, the Shikou and Huamianlong formations are recognized herein as a part of the Hanjiang Formation, corresponding only to the Diplacanthograptus caudatus-Diplacanthograptus spiniferus Zone. Two graptolite zones in the Longxi Formation of Yongxin and Chongyi, the Nemagraptus gracilis Zone and Climacograptus bicornis Zone, are redefined here. A rapid replacement of facies from the typical deep-water graptolitic black shale of Longxi Formation to the rapidly-accumulated, shallow-water clastic deposits of Hanjiang Formation indicates the tectonic initiation of the Kwangsian Orogeny. The thick clastic deposits of the Hanjiang Formation are proposed to come from a nearby source area that rose during the Kwangsian Orogeny. The D. caudatus-D. spiniferus graptolite Zone of the Hanjiang Formation indicates the initiation time of this tectonic event.

Darriwilian (Middle Ordovician) graptolite faunas of the Sandia Region, southern Peru

AbstractOrdovician graptolite faunas of Peru are restricted to a short interval in the Middle to basal Upper Ordovician, found in three regions of the country. All Peruvian graptolite faunas are strongly dominated by shallow water elements of the Atlantic Faunal Realm, represented largely by Didymograptus s. str. and Aulograptus, but a number of faunal elements of the pandemic isograptid biofacies have recently been discovered in the Sandia Region of SE Peru. Peruvian graptolite faunas are reviewed and the new records from the Sandia Region are discussed in detail. The faunas from the Purumpata and Iparo members of the San José Formation range in age approximately from the Undulograptus austrodentatus Biozone to the Holmograptus lentus Biozone (early to middle Darriwilian). The faunas provide a better understanding of faunal composition and diversity in this region and help to correlate shallow water and deeper water graptolite faunas from this time interval. Biserial graptolites are rare in most samples and usually indeterminable, but a single identifiable specimen of Undulograptus austrodentatus was found, indicating a level close to the base of the Darriwilian. A number of specimens of the genera Isograptus and Arienigraptus from the Sandia Region represent pandemic graptolite faunas of the isograptid biofacies, described for the first time from this region. Copyright © 2009 John Wiley & Sons, Ltd.

Upper Ordovician (Sandbian–Katian) graptolite and conodont zonation in the Yangtze region, China

ABSTRACTThe graptolite and conodont biostratigraphy of the latest Darriwilian, Sandbian and early and middle Katian succession on the Yangtze Platform is reassessed based on numerous new fossil collections and previously published data. At least at some localities, the lowermost Miaopo Formation is of pre-Nemagraptus gracilis Zone age (uppermost Pygodus serra and lowermost P. anserinus conodont zones). The rest of this formation (except for the uppermost part, which lacks diagnostic graptolites) has a diverse graptolite fauna of the N. gracilis Zone. The uppermost part of the Miaopo Formation contains few biostratigraphically diagnostic graptolites but the occurrence of conodonts of the Baltoniodus alobatus Subzone of the Amorphognathus tvaerensis Zone suggests equivalence with part of the Climacograptus bicornis graptolite Zone. The conodont succession of the Datianba Formation is virtually identical with that of the Miaopo Formation, confirming that these units are coeval. The lowermost part of the overlying non-graptolitic Pagoda Formation represents the upper A. tvaerensis Zone, and its upper part represents the A. superbus Zone. The occurrence of Dicellograptus elegans in the overlying Chientsaokou Formation (equivalent to the Linhsiang Formation in Yangtze Gorges region) suggests equivalence with the Pleurograptus linearis Zone in Scotland, which is consistent with the relatively non-diagnostic conodont fauna in these Chinese units. The biostratigraphic data are in good agreement with the δ13C chemostratigraphy and permit the establishment of precise correlations with the Baltoscandic and North American successions.

Early diversification of ordovician graptolites in Jiangnan Slope, South China

Early diversification of ordovician graptolites in Jiangnan Slope, South China

Facies preference predicts extinction risk in Ordovician graptolites

The most abundant and diverse graptolite assemblages are found in offshore, deep-water black shales—the classical “graptolite fades” (deep-water or isograptid biofacies). The mean duration of Ordovician graptolite species confined to the deep-water facies (here referred to as “group 1” species) is 2.19 Myr, significantly shorter than the mean duration of species in the deep-water facies that are also known in sediments of the shallow-water shelf or platform (“group 2” species) −4.42 Myr, indicating a significantly higher extinction probability (p= <0.001). These figures are based on the precise age ranges of species derived from the time-calibrated composite sequence of 1446 Ordovician to early Devonian graptolites, built by the constrained optimization procedure (CONOP) from 256 measured sections worldwide, and exclude the effects of the Hirnantian mass extinction. The difference between groups cuts across families, morphological types, and pandemic/endemic distributions. An environmental influence is strongly suggested, and although both groups were planktonic, they were unlikely to have shared the same habitat in the water column. The new duration measurements therefore are interpreted as favoring a depth-stratification of graptolite habitats in the water column.

The Upper Tremadocian (Ordovician) graptoliteBryograptus: taxonomy, biostratigraphy and biogeography

Abstract: The taxonomy, biostratigraphical and palaeogeographical distribution of the Lower Ordovician graptolite genus Bryograptus is evaluated. Bryograptus is recognized as a distinct triradiate anisograptid with a multiramous, pendent rhabdosome. The species of the genus Bryograptus can be interpreted as shallow water faunal elements with a strongly limited biogeographical distribution to the Atlantic Faunal Realm. Bryograptus is restricted to a narrow interval in the Upper Tremadocian, the Bryograptus Biozone of Scandinavia and South America (Argentina), making it a taxon with a high potential for precise biostratigraphical correlations. The proximal end development can be used to differentiate the genus Bryograptus from other pendent multiramous graptoloid genera with a homoplastic rhabdosome development. Characteristics of the proximal end development and structure easily differentiate these genera in relief specimens, but not in flattened material.

Darriwilian graptolites of the Shihtien Formation (Ordovician) in west Yunnan, China

West Yunnan in southwestern China formed an important part of the Sibumasu Terrane during the Ordovician. The Ordovician rocks of the region are exposed at many localities but have been strongly affected by several phases of tectonic activity, especially by the most recent Himalayan phase that commenced in the Paleogene. For these reasons, together with the difficult access to the localities, the Ordovician graptolites and biostratigraphy of this region are rather poorly known. Herein, we describe a Darriwilian graptolite fauna from the Shihtien Formation at Baoshan and Shidian, western Yunnan. The fauna comprises 11 genera and 15 species, including Didymograptus artus, D. murchisoni, D. spinulosus, Pterograptus sp., Hustedograptus vikarbyensis, H. teretiusculus, Archiclimacograptus angulatus, A. riddellensis, Haddingograptus oliveri, Proclimacograptus angustatus, and the dendroids Dictyonema, Palaeodictyota, Dendrograptus, Callograptus and Ptilograptus, indicating an age of middle to late Darriwilian. Two graptolite biozones are recognized: the Didymograptus artus and Didymograptus murchisoni biozones, in ascending order. The graptolite fauna is substantially similar to those of Baltica and South China.

Holmograptus spinosus and the Middle Ordovician (Darriwilian) graptolite biostratigraphy at Les Méchins (Quebec, Canada)

The Les Méchins region in Quebec provides a unique opportunity to understand the Darriwilian graptolite succession in eastern North America. The graptolite faunas of the upper member of the Anse au Crapaud Formation include the Arienigraptus gracilis , Oncograptus upsilon , Undulograptus austrodentatus , and Holmograptus spinosus biozone faunas and, thus, complement the well known Darriwilian faunas of the Cow Head, Table Head, and Goose Tickle groups of western Newfoundland. In particular, the Holmograptus spinosus Biozone interval of calcarenitic limestones bears a rare combination of benthic (shelly) and planktic (graptolitic) faunas with conodonts, brachiopods, ostracods, sponge spicules, and algal remains associated with common graptolites that allow an inter-continental correlation. The Holmograptus spinosus Biozone is introduced for the interval based on a diverse and characteristic graptolite fauna. The fauna includes among others, Atopograptus woodwardi , recognized for the first time in North America. The Holmograptus spinosus Biozone fauna can be found worldwide and is easily correlated into the conodont biofacies using species of the genus Histiodella . Ties between graptolite and conodont biozonations are discussed for the Darriwilian. Silicified ostracods are illustrated for the first time from the interval. Hustedograptus quebecensis is described as new.

Late Tremadocian Graptolites from the Mungok Formation of the Namaeri and Baeiljae Sections at Yeongwol, Korea

The early Ordovician graptolites from the upper part (Tumok Member) of the Mungok Formation of the Namaeri and Baeiljae sections at Yeongwol consist of five species belonging to five genera. They are Adelograptus cf. tenellus, Callograptus sp., Dendrograptus suni, Dictyonema sp., and Psigraptus jacksoni. Of these 5 species, Psigraptus is the most excellent index fossil for international correlation with the early Ordovician strata. Adelograptus cf. tenellus from the Mungok Formation of the Namaeri and Baeiljae sections is also recognized with especially short stipe relative to Adelograptus tenellus. Three graptolite zones (such as Adelograptus, Psigraptus, and Dendroid type zones) are correlated with those of Canada, Australia, and China, respectively. The upper part of the Mungok Formation is assigned to the late Tremadocian.

Advances in the Ordovician graptolite biostratigraphy of the St Petersburg area, Russia

The Ordovician shallow-water shelf deposits rich in benthic fauna are exposed along the Russian part of the Baltic- Ladoga Klint. Graptolites occur only at some stratigraphic levels, being comparatively numerous in marls and clays and very rare in carbonate layers. Since the 19th century graptolites have been collected from exposures of the Pakerort, Hunneberg, Billingen, and Volkhov regional stages (Tremadocian-Dapingian), while in the Uhaku-Idavere stratigraphic interval (Darriwilian-lower Sandbian) rare graptolites have been found in boreholes. Up to now, only some collections have been systematically studied. On the basis of new graptolite finds, recently the Pterograptus elegans Biozone was established in the upper Aseri Stage and the Nemagraptus gracilis Biozone in the lower Kukruse Stage. Detailed sampling of the Shundorovo Formation (upper Idavere Stage) resulted in the discovery of numerous diplograptids at five stratigraphic levels, in association with various dendroids. These diplograptids were provisionally assigned to ?Archiclimacograptus antiquus lineatus Elles & Wood. A systematic description of the late Darriwilian and early Sandbian diplograptids is under preparation.

Diversity history of Ordovician graptolites and its relationship with environmental change

Statistical analysis based on global data indicated that the planktonic graptolites presented a distinguished pattern from that of benthic communities during the great Ordovician biodiversification. The graptolites started to diversify from the beginning of Ordovician and reached an acme in the early Middle Ordovician, but subsequently underwent a steady decline to the end of Ordovician. During the Ordovician, many clades of the graptolites made their originations, flourishing and replacements. However, in different regions and distinct environments across the world, graptolites may presumably display distinct patterns of radiation and evolution, a hypothesis to be tested. Herein a study of the graptolite diversity in the Early to Middle Ordovician in the Upper Yangtze Region (Platform) and Jiangnan Region (Slope), South China, is conducted. The results indicate that graptolites underwent a remarkable increase in both regions, but with distinct magnitude, scope, process and patterns. The diversification of graptolites in the Upper Yangtze Region, though less prominent, is divided into four stages and includes two peaks. In the Jiangnan Region, the graptolite diversification is far more prominent and includes three stages and one peak. Based on the distinct diversity histories and composition of graptolites in the two representative regions, a ‘deep-water origin and shallow-water dispersal’ model is proposed for the Ordovician graptolite faunas. According to the model, the major graptolite faunas of Ordovician originated in the deep-water region on the continental slope, the source of the graptolite novelties, and subsequently spread into shallow-water region on the shelf. Besides, we also conduct a comparison study of the Ordovician graptolite diversity in South China and other major regions. The results display that the graptolites diversified globally in the Early and Middle Ordovician. At the beginning of Ordovician, graptolites underwent a significant ecological innovation of graptolites: planktonic forms were derived from their benthic ancestors. This derivation resulted in the great guild expansion of graptolites. In late Early Ordovician (Floian), the global expansion of graptolites commenced. From the Floian to the end of Middle Ordovician, the graptolites diversity increased remarkably and displayed three peaks for all the regions. However, the peaks are somewhat distinct in magnitude and timing among regions. The Darriwilian peak is prominent in both South China and Baltic region, but inconspicuous in Australasia. No close relationship between the graptolite diversification and the palaeolatitudes are supported herein. Instead, the graptolite diversification seems to coincide with the global sea-level rises, suggesting a possible intrinsic relationship between them.

Integrated Upper Ordovician graptolite–chitinozoan biostratigraphy of the Cardigan and Whitland areas, southwest Wales

To help calibrate the emerging Upper Ordovician chitinozoan biozonation with the graptolite biozonation in the Anglo-Welsh, historical type basin, the graptolite-bearing Caradoc–Ashgill successions between Fishguard and Cardigan, and at Whitland, SW Wales, have been collected for chitinozoans. In the Cardigan district, finds of Armoricochitina reticulifera within strata referred to the clingani graptolite Biozone (morrisi Subzone), together with accessory species, indicate the Fungochitina spinifera chitinozoan Biozone, known from several Ordovician sections in northern England that span the base of the Ashgill Series. Tanuchitina ?bergstroemi, eponymous of the succeeding chitinozoan biozone, has tentatively been recovered from strata of Pleurograptus linearis graptolite Biozone age in the Cardigan area. The T. ?bergstroemi Biozone can also be correlated with the type Ashgill Series of northern England. Chitinozoans suggest that the widespread Welsh Basin anoxic–oxic transition at the base of the Nantmel Mudstones Formation in Wales, traditionally equated with the Caradoc–Ashgill boundary, is of Cautleyan (or younger Ashgill) age in the Cardigan area. In the broadly time-equivalent, graptolite-rich Whitland section, also in SW Wales, two Baltoscandian chitinozoan biozones and a subzone have been recognized (again using accessory species), namely the Spinachitina cervicornis Biozone?, the Fungochitina spinifera Biozone and the Armoricochitina reticulifera Subzone. The new chitinozoan data provide a more precise means of correlation between the Whitland and Cardigan successions and suggest that the Normalograptus proliferation interval of the Whitland section is at least partly attributable to the Dicellograptus morrisi Subzone of the Dicranograptus clingani Biozone, rather than equating with the overlying Pleurograptus linearis Biozone.

Graptolites from the Lower Ordovician (Tremadoc) Mungok Formation in Danyang area, Korea

Lower Ordovician (Upper Tremadoc) graptolites were found for the first time at the two sections of the Mungok Formation in Danyang area: the Seokgyori and Daejeonri sections. The graptolites from these sections comprise two species of two genera: Adelograptus brevibrachiatus and Psigraptus jacksoni. The graptolite faunas of the sections in the area show simple composition relative to Yeongwol area; they appear to be correlated to: (1) the Adelograptus cf tenellus Zone of Yeongwol area, (2) the Adelograptus cf. tenellus Zone of Yukon, Canada, (3) the Psigraptus Zone of Tasmania, Australia, and (4) the Psigraptus jacksoni Zone of Jilin, China. The age of graptolite beds of the Mungok Formation at Danyang appears to be early Upper Tremadoc of the Lower Ordovician.

Diversification patterns of Early and Mid Ordovician graptolites in South China

AbstractDuring the Early and Mid Ordovician, graptoloids underwent a dramatic diversification. Many clades (e.g. anisograptids, dichograptids and biserials) originated and subsequently diversified during this interval, playing the most important roles in the evolution history of graptolites. In this study we conduct an analysis of the generic and species diversity history of Early to Mid Ordovician graptolites from the Yangtze Region (platform) and Jiangnan Region (slope) of South China, and provide evidence that the regionally distinct biodiversification patterns are related to the different representative environments of each region.Graptolite diversity measured across graptolite zones displays a remarkable increase in both regions during the Early to Mid Ordovician, but with distinct scales and patterns in each region. In the Upper Yangtze Region, the diversification is less rapid and can be divided into four phases. The second major diversification phase (early Arenig) is characterized by the rapid expansion of dichograptids, and the fourth diversification phase (mid‐late Darriwilian), which is preceded by a decline (third phase), is typified by the flourishing of biserial graptolites. The diversification of graptolites in the Jiangnan Region is more dramatic and shows a distinct pattern of rapid, progressive and sustained diversity rise from the early Arenig to the early Darriwilian. This rapid diversification is initially driven by the expansion of dichograptids and subsequently enhanced by the significant addition of glossograptids and diplograptids.A comparison of diversity patterns between the Upper Yangtze Region, the Jiangnan Region, Australasia, Baltoscandia and Avalonia indicates: (1) the global Arenig expansion of dichograptids is also recorded in South China, (2) the diversity pattern of the Upper Yangtze Region is largely comparable to that of Baltoscandia and Avalonia, but is considerably different from that of Australasia, and (3) the sustained rapid increase of graptolite diversity in the Jiangnan Region is not shared by any of the other regions. Copyright © 2007 John Wiley & Sons, Ltd.

The sequence and correlation of Early Ordovician (Arenig) graptolite faunas in the Richardson Trough and Misty Creek Embayment, Yukon Territory and District of Mackenzie, Canada

Four graptolite biozones are recorded from the Arenig portion of the Road River Group in the Richardson and Mackenzie mountains in the Yukon and Northwest Territories. In ascending order, these zones are Tetragraptus approximatus, Pendeograptus fruticosus, Didymograptus bifidus, and Parisograptus caduceus australis (new). The Castlemainian stage may be represented by nongraptolitic massive bedded chert. The Arenig–Llanvirn boundary is drawn below the first occurrence of Undulograptus austrodentatus. Fifty-four graptolite taxa are present, and 16 of these species and subspecies are recorded for the first time in this deep-water biotope, namely, Didymograptus? cf. adamantinus, D. asperus, D. dilatans, D. cf. kurcki, D. validus communis, Holmograptus aff. leptograptoides, H. sp. A, Isograptus? sp. nov. A, I. ? dilemma, Keblograptus geminus, Pseudisograptus manubriatus harrisi, Ps. m. koi, Ps. m. janus, Ps. cf. tau, Xiphograptus lofuensis, and Zygograptus cf. abnormis.

Ordovician graptolite evolutionary radiation: a review

AbstractBased on the global graptolite genera and higher rank taxa, we propose three radiation stages through the Ordovician. The isograptid type of development is present within anisograptids predominating in the Tremadocian. Thus, the evolutionary radiation of the Anisograptid fauna from Tremadocian is proposed as the beginning of the Ordovician graptolite radiation. The second graptolite radiation event is the radiation of the Dichograptid fauna, which began from the T. fruticosus Biozone. The third radiation event, the radiation of Diplograptid fauna began immediately after that of the dichograptids. This radiation includes the peak in total diversity of all the Ordovician graptoloids in the Nemagraptus gracilis Biozone. The radiation extended through the Sandbian and Katian and then was interrupted by a major extinction during the early Hirnantian. Thus, the Ordovician graptolite radiation events coincide with those of the three graptolite faunas proposed by Bulman. The distribution and expansion of the Ordovician graptolites in South China may exemplify the graptolite origination pattern, which begins from the slope belt and expanded into both the shelf and oceanic zones. Copyright © 2006 John Wiley & Sons, Ltd.

EARLY MIDDLE ORDOVICIAN GRAPTOLITE BIOSTRATIGRAPHY OF THE LOVISEFRED AND ALBJÄRA DRILL CORES (SCANIA, SOUTHERN SWEDEN)

Early Middle Ordovician graptolites from the Albjara and Lovisefred drill cores (Scania, southern Sweden) can be differentiated into the Isograptus victoriae, Isograptus sp. nov. 2 and Maeandrograptus schmalenseei, Arienigraptus dumosus type ⁄ Pseudisograptus manubriatus biozones of Castlemainian and Yapeenian age and the Arienigraptus zhejiangensis and Undulograptus sinicus biozones of early Darriwilian age, replacing the old, long-ranging Didymo- graptus hirundo Biozone. Faunas from the drill cores include a number of species not previously recognized in Scandinavia.

The Early to Middle Ordovician graptolite faunal succession of the Trail Creek region, central Idaho, U.S.A

The Middle Ordovician graptolite biostratigraphy of the Trail Creek region of Idaho is reviewed and revised. The oldest known fauna belongs to the Didymograptellus bifidus Biozone. The Isograptus victoriae lunatus, I. victoriae maximodivergens, Oncograptus, Undulograptus austrodentatus and Holmograptus lentus Biozones can be differentiated. Pseudophyllograptus archaios (Braithwaite) is found for the first time in the Trail Creek region. This species represents a conspicuous North American mid-continent faunal element and enables the correlation of the endemic P. archaios-C. flexilis Biozone of Utah with the D. bifidus Biozone of the Pacific faunal realm, thus, providing an important tool for the correlation of endemic mid-continent faunas with the pandemic deep water graptolite faunas.

Narooma Terrane: Implications for the construction of the outboard part of the Lachlan Orogen

In its type area around Narooma, the Narooma Terrane in the Lachlan Orogen comprises the Wagonga Group, which consists of the Narooma Chert overlain by the argillaceous Bogolo Formation. Conodonts indicate that the lower, largely massive (ribbon chert) part of the Narooma Chert ranges in age from mid-Late Cambrian to Darriwilian-Gisbornian (late Middle to early Late Ordovician). The upper Narooma Chert consists of shale, containing Eastonian (Late Ordovician) graptolites, interbedded with chert. Where not deformed by later faulting, the boundary between the Narooma Chert and Bogolo Formation is gradational. At map scale, the Narooma Terrane consists of a stack of imbricate thrust slices caught between two thrust faults that juxtaposed the terrane against the coeval Adaminaby Superterrane in Early Silurian time. These slices are best defined where Narooma Chert is thrust over Bogolo Formation. The soles of such slices contain multiply foliated chert. Late extensional shear bands indicate a strike-slip component to the faulting. The Narooma Terrane, with chert overlain by muddy ooze, is interpreted to be an oceanic terrane that accumulated remote from land for ∼50 million years. The upward increase in the terrigenous component at the top of the Wagonga Group (shale, argillite, siltstone and sandstone of the upper Narooma Chert and Bogolo Formation) records approach of the terrane to the Australian sector of the Gondwana margin. Blocks of chert, argillite and sandstone reflect extensional/strike-slip disruption of the terrane as it approached the transform trench along the Gondwana-proto-Pacific plate boundary. Blocks of basalt and basalt breccia represent detritus from a seamount that was also entering the trench. There is no evidence that the Narooma Terrane or the adjacent Adaminaby Group formed in an accretionary prism/ subduction complex.

Lower Ordovician graptolite biozonation and lithofacies of southern Bolivia: relevance for palaeogeographic interpretations

The interpretation of the lithofacies and basin evolution of the early Ordovician of southern Bolivia is based on a number of sections on an E–W transect. Lithostratigraphic units are extremely diachronous and only the available data on the graptolite biostratigraphy enabled an interpretation of the basin evolution. The newly proposed graptolite biozonation includes the biozones of Rhabdinopora flabelliformis, Adelograptus sp., Araneograptus murrayi, Hunnegraptus copiosus, Tetragraptus phyllograptoides, Expansograptus protobalticus, Expansograptus holmi, Baltograptus minutus, Azygograptus lapworthi and Isograptus victoriae. Isograptus victoriae is the first isograptid identified from Gondwanan South America. The early Ordovician succession of southern Bolivia is the most complete one documented from South America and can be used as a standard for this continent. The faunas are most easily correlated with the faunal succession of Scandinavia and without doubt belong to the Atlantic graptolite faunal province. They show distinct differences from coeval faunas of the Argentine Precordillera, referable to the Pacific faunal province.