Dicellograptus Complanatus Research Articles

Discovery of Anticostia uniformis from the Xiazhen Formation at Zhuzhai, South China and its stratigraphic implication

The Xiazhen Formation is an Upper Ordovician lithostratigraphic unit in the Jiangshan-Changshan-Yushan (JCY) area, which contains series of Late Ordovician reef successions. The reef successions of the Xiazhen Formation at Zhuzhai are critical for evaluation of the Late Ordovician marine diversity and palaeoecology. However, their age has long been uncertain and generally is regarded as of upper Katian, based on the occurrences of shelly fossils and correlation with the stratigraphic equivalent Changwu Formation. The newly discovered graptolite species Anticostia uniformis, in the Xiazhen Formation, together with the combined evidence of brachiopods and sedimentology, indicates an age range for the graptolite locality from the Dicellograptus complanatus Biozone to the Diceratograptus mirus Subzone of late Katian, but the graptolites do not rule out the possibility that it is Hirnantian.

Changes in marine productivity and redox conditions during the Late Ordovician Hirnantian glaciation

Changes in marine productivity and redox conditions during the end-Ordovician (Hirnantian) glaciation and Ordovician–Silurian transition were investigated through Mo-isotope and major- and trace-element analyses of the Wangjiawan (Hubei Province) and Nanbazi (Guizhou Province) sections from the Yangtze Platform of South China. Katian shales of the Wufeng Formation, which yield the graptolites Dicellograptus complanatus, Dicellograptus complexus, and Paraorthograptus pacificus, were deposited under euxinic conditions at both localities, as shown by high MoEF, UEF, and δ98Mo values. A major sea-level regression during the Hirnantian glaciation resulted in shallowing and a shift toward better-oxygenated conditions within the Yangtze Sea, as well as deposition of thin-bedded siliceous sediments, calcirudite debris flows, and limestone turbidites of the Kuanyinchiao Formation, the base of which correlates with the first phase of the end-Ordovician mass extinction. The termination of the Hirnantian glaciation at the top of the Kuanyinchiao Formation was associated with a major sea-level transgression, a rapid expansion of euxinia in the Yangtze Sea (as documented by a return of high MoEF, UEF, and δ98Mo values), and the second phase of the mass extinction, during which the cool-adapted Hirnantian Fauna went extinct.The long-term cooling trend of the Middle and Late Ordovician, which culminated in the Hirnantian glaciation, was driven by enhanced burial of organic carbon, as documented by δ13Ccarb, δ13Corg, and δ34Spy records. Increased organic carbon burial was linked to high rates of marine productivity, as shown by high TOC and biogenic Ba concentrations especially at the deeper, less-restricted Wangjiawan locale, producing the HICE (Hirnantian Isotopic Curve Excursion) δ13Ccarb excursion. The locus of organic carbon burial during the Hirnantian crisis shifted to deeper-water environments that were located outside the study region. The relatively rapid onset and termination of the Hirnantian glaciation were probably due to crossing of tipping points in the Late Ordovician climatic–oceanic system.

Late Ordovician (Katian) spores in Sweden: oldest land plant remains from Baltica

A palynological study of the Ordovician–Silurian boundary (Katian–Rhuddanian) succession in the Röstånga-1 drillcore, southern Sweden, has been performed. The lithology is dominated by mudstone and graptolitic shale, with subordinate limestone, formed in the deeper marine halo of southern Baltica. The palynological assemblages are dominated by marine microfossils, mainly chitinozoans and acritarchs. Sparse but well-preserved cryptospores, including Tetrahedraletes medinensis, Tetrahedraletes grayii and Pseudodyadospora sp., were encountered in the Lindegård Formation (late Katian–early Hirnantian), with the oldest record just above the first appearance of the graptolite species Dicellograptus complanatus. This represents the earliest record of early land plant spores from Sweden and possibly also from Baltica and implies that land plants had migrated to the palaeocontinent Baltica by at least the Late Ordovician.

A regional tectonic event of Katian (Late Ordovician) age across three major blocks of China

The present paper deals with a tectonic event of Late Ordovician age affecting three blocks of China, i.e. South China, North China and Tarim. In the North China and the Tarim platforms, as well as their marginal belts, there was a regional uplift during the early Katian Stage of the Ordovician. The uplift was indicated by the unconformities between the Ordovician successions and overlying late Paleozoic strata. New biostratigraphic studies of conodonts and graptolites from many sections at Longxian and Yaoxian, North China shows that the youngest Ordovician strata are of the early Katian age corresponding to graptolite Diplacanthograptus spiniferus Biozone. The same level has been recognized to represent the uppermost Ordovician in the platform area of Tarim, whereas in the marginal belt the top boundary of the Ordovician is slightly younger, corresponding to the graptolite Dicellograptus complanatus Biozone. Thus, the regional uplift in North China and Tarim is shown by the disconformity between the early Katian strata and Late Paleozoic strata, the onset coinciding with that of the Kwangsian Orogeny in South China. The designation Kwangsian Orogeny later fell into disuse and was replaced by the term Caledonian Orogeny. However, in terms of geographic location, tectonic nature, and the timing of activity, the Caledonian Orogeny differs significantly from the orogenic event in South China, and the continued use of this term in South China is inappropriate and misleading.

Gastropods and tergomyans from the Upper Ordovician (Viru–Harju) of the Fågelsång area, Scania, southern Sweden

A diverse tergomyan and gastropod assemblage is described from the Global Boundary Stratotype Section and Point (GSSP) section of the Sandbian Stage, Upper Ordovician, in the Fågelsång area, Scania, southern Sweden. Deep water graptolitic mudstone and shale comprise the succession, and previously only one gastropod species was known. The new material spans the Sularp Formation through the Lindegård Mudstone (Nemagraptus gracilis–Dicellograptus complanatus biozones). Fourteen species are described: two tergomyan, five bellerophontoid gastropods, and seven anisostrophically coiled gastropods. Three species are new: Peelerophon hodites, Tetranota scanica and Lophospira sandbiana. Three taxa (Tritonophon subtrilobatus, Tetranota scanica and Holopea mobergi) are found high in the Lindegård Mudstone (Vormsi–Pirgu stages). Cyrtodiscus, Peelerophon and Tritonophon are recorded for the first time in Baltoscandia. Some taxa may have been transported from shallower water settings, whereas species of Peelerophon, Joleaudella, Mestoronema and Sinuites may have been part of the local benthos. Except for Bucania erratica, no species are shared with the fauna of the coeval Dalby Limestone in Sweden. Deaechospira elliptica, common in the Dalby Limestone, is not recorded at Fågelsång, although two closely related species are found (Deaechospira rotunda and Deaechospira? sp.). The Fågelsång assemblage has more in common with the older to coeval fauna of the Elnes and Arnestad formations in the Oslo Region, Norway (e.g. sharing Joleaudella, Sinuites, Mestoronema and Pararaphistoma). The Sandbian fauna of Fågelsång includes peri-Gondwanan taxa, e.g. Cyrtodiscus, Peelerophon and Deaechospira. Nevertheless, cluster analysis reveals that the faunas of Baltica and Laurentia were most similar, whereas faunas from Perunica and Baltica remained distinct and separated during the Darriwilian–Sandbian. The few similarities may result from spread of a temperate fauna supplementing rather than replacing taxa in deep water assemblages. The main Fågelsång assemblage coincides both with the Baltoscandian Middle Caradoc Faunal Turnover and the Gutenberg Carbon Isotope Excursion. http://zoobank.org/urn:lsid:zoobank.org:pub:093F6504-B3FA-42A4-94C2-FF460D549F18

Upper Ordovician graptolites and biostratigraphy of the Röstånga 1 core,Scania, S. Sweden

A core drilling at Röstånga in 1997, referred to as Röstånga 1, penetrated a significant portion of the Upper Ordovician-Lower Silurian succession in this classical Lower Palaeozoic outcrop area in W central Scania. In descending order the Upper Ordovician of the core embraces the following units (stratigraphic thickness in parenthesis): Lindegård Mudstone (27.8 m), Fjäcka Shale (13.6 m), Mossen Formation (0.6 m), Skagen Formation (0.8 m), and Sularp Formation (19.9 m+). Graptolites are described from the Lindegård Mudstone, the Fjäcka Shale, and the Mossen Formation. The graptolites are classified into 12 taxa, among which 9 are identified to species. Graptolites are very rare in the Mossen Formation, which has yielded only two specimens of Pseudoclimacograptus scharenbergi.The Fjäcka Shale yielded a fairly diverse graptolite fauna, indicative of the Pleurograptus linearis Zone.This zone is succeeded by the Dicellograptus complanatus Zone, with the zonal index appearing in the lower part of the Lindegård Mudstone immediately above graptolites indicative of the P. linearisZone. No graptolites were recovered from the Skagen Formation and the Sularp Formation.

Late Ordovician to earliest Silurian graptolite and brachiopod biozonation from the Yangtze region, South China, with a global correlation

Late Ordovician to earliest Silurian is an important geological period marked by large geological and biological events. However, the strata and fossils of this interval are not complete in many parts of the world. Based on studies of 43 sites in South China, in particular the continuous sections on the Yangtze platform, we recognize a complete succession including seven graptolite zones and two shelly faunas. In ascending order, the graptolite zones are the Dicellograptus complanatus, Dicellograptus complexus, Paraorthograptus pacificus (including Lower Subzone, Tangyagraptus typicus Subzone and Diceratograptus mirus Subzone), Normalograptus extraordinarius–Normalograptus ojsuensis, Normalograptus persculptus, Akidograptus ascensus and Parakidograptus acuminatus zones. The shelly faunas are the Foliomena–Nankinolithus and Hirnantia faunas, which may be correlated with D. complanatus Zone and N. extraordinarius–N. ojsuensis to part of N. persculptus zones respectively. The biozonation through this interval from the Yangtze region can be correlated with that of other parts of the world such as Dob's Linn in Scotland, Spain and Portugal, Thuringia–Saxonia–Bavaria, Bohemia, Poland, Kazakhstan, Kolyma, Malaya Peninsula, Yukon, Canadian Arctic Islands, Nevada, Argentina, Niger and Victoria, Australia. The Hirnantian Substage, which has been proposed by us recently, includes the N. extraordinarius–N. ojsuensis Zone, Hirnantia fauna and N. persculptus Zone. The base of the Hirnantian Substage is marked by the First Appearance Data (FADs) of N. extraordinarius and N. ojsuensis, which have been determined to be synchronous on a global scale.

Stratigraphy and graptolites of the Upper Ordovician Point Leamington Formation, central Newfoundland

The Point Leamington Formation, as redefined herein, comprises a thick sequence of siliciclastic turbidites containing occasional Upper Ordovician graptolites and lies with the Exploits Subzone of the Dunnage Zone in central Newfoundland. The base of the unit is marked by the first coarse- to medium-grained sandstone, at a level that varies from the Dicranograptus clingani Zone to the Pleurograptus linearis Zone. Several intervals of interbedded black shales and siltstones higher in the formation yield assemblages characteristic of the P. linearis, Dicellograptus complanatus and Dicellograptus anceps zones. Debris-flow breccias occur at several levels within the Point Leamington Formation—some contain graptolitic, black shale clasts derived from the underlying Lawrence Harbour Formation—and range in age from Nemagraptus gracilis Zone to D. clingani Zone. Both the graptolite assemblages and lithostratigraphic succession of the Point Leamington Formation are similar to those of coeval rocks in southern Scotland, confirming a strong relationship between the two areas during the Late Ordovician.

Age and correlation of the Honorat Group, southern Gaspé Peninsula

The Honorat Group of southern Gaspé consists of two formations: the Arsenault and the Garin. The Arsenault Formation, heretofore considered barren, has yielded a graptolite faunule indicative of a Llanvirn–Llandeilo age (early Middle Ordovician), suggesting a correlation with the lower Mictaw Group of Gaspé as revised by de Broucker. A hiatus of indeterminate magnitude, corresponding to the Taconic unconformity, probably separates the Arsenault Formation from the overlying Garin Formation. The Garin has yielded graptolites ranging from the upper Climacograptus spiniferus Zone to the Paraclimatograptus manitoulinensis Zone (late Middle to early Late Ordovician). The C. spiniferus Zone graptolites are identical to those of the upper γ sequence of the Cloridorme Formation of northern Gaspé and the Blind Brook Formation of the Munsungun Anticlinorium of Maine but differ somewhat from those from the upper Tetagouche Group of New Brunswick, which are closer to those from the Summerford and Exploits groups of north-central Newfoundland. The C. spiniferus zone has a wide distribution in eastern North America. It correlates with the Orthograptus amplexicaulis Zone of the southwestern United States and with the Climacograptus baragwathi Zone (Ea2) of the Pacific faunal province.The Matapédia Group, stratigraphically above the Honorat Group, has yielded both shelly fossils and a few graptolites. The ages of the graptolites now date it as Late Ordovician to late Early Silurian (Dicellograptus complanatus Zone – Monograptus sedgwickii Zone).

Upper Ordovician graptolites from the D. complanatus Zone of the Moffat and Girvan districts and their significance for correlation

Synopsis At its type development at Dob's Linn, southern Scotland, the Dicellograptus complanatus Zone is represented by two thin black shale bands some 9 m above the base of the Upper Hartfell Shale Formation. Contrary to previous reports, the fauna is moderately diverse with an assemblage including Dicellograptus complanatus Lapworth, D. minor Toghill, Climacograptus miserabilis Elles and Wood, C. tubuliferus Lapworth, Orthograptus socialis (Lapworth), Orthoretiolites ? pulcherrimus (Keble and Harris) and Plegmatograptus ? sp. indet. At Girvan the D. complanatus Zone is contained within the Mill Formation of the Upper Whitehouse Group and the lower part of the Shalloch Formation. The basal Mill Formation yields a still more diverse low D. complanatus Zone fauna, with the addition of Dicellograptus alector Carter? (? = D. gravis Keble and Harris), D. cf. minor Toghill, Orthograptus cf. calcaratus (Lapworth) and Glyptograptus ? cf. occidentalis Ruedemann. The D. complanatus Zone correlates with the D gravis (Ea4) and C. uncinatus (Bol) zones of Australia, and probably with the C. pygmaeus and C. manitoulinensis zones of north-eastern North America.

Acritarch biostratigraphy of thedicellograptus complanatusgraptolite zone from the Vaureal formation (Ashgillian), Anticosti Island, Quebec, Canada

Abstract Forty‐two species of organic‐walled microphytoplankton (ac‐ritarchs) and a single specimen of a spore‐like microfossil are documented from the Dicellograptus complanatus graptolite Zone in the Vaureal Formation on Anticosti Island, Quebec. Our samples are from cored intervals in the New Associated Consolidated Paper #1 well. These cores contain biostratigraphically useful chitinozoans and graptolites which precisely correlate these intervals with lower to middle Ashgillian. Conodonts, ostracodes, and megafossils from outcrops of the Vaureal Formation on Anticosti Island support this lower to middle Ashgillian correlation for our sampled interval. The acritarch assemblages obtained from the sampled interval contain abundant well‐preserved specimens. Of these, some forms considered diagnostic of the Dicellograptus complanatus (graptolite) Zone are Multiplicisphaeridium bifurcatum, M. irregulare, Orthosphaeridium insculptum, Poikilofusa spinata, Sylvanidium paucibrachium, and Veryhachium hamii. Four...

The use of experimental palaeontology in reproducing the effects of diagenetic flattening on graptolites

The detailed effects of diagenetic flattening on the graptolitc rhabdosomc have been investigated experimentally. The initial procedure, to test the effects of flattening on cylinders constructed from a variety of semi-brittle to plastic materials when compressed in a plaster ‘matrix’, demonstrates that a degree of rigidity is necessary to prevent lateral spread on diagenetic compression, even when lateral confining pressures are present. A second experiment demonstrates conclusively that the effects of flattening on the thecal style of Dicellograptus complanatus proposed by Briggs & Williams (1981; Lethaia 14) can be simulated. A model of an aseptate diplograptid produced a median depression when compressed but no preservational ‘median septum’, which is considered to be produced in several diplograptid taxa. It is shown that some diplograptids spread laterally along a median line when flattened in scalariform orientation although this has not yet been achieved experimentally owing to the high degree of compression required. □Graptolithina, diagenesis, flattening,

Les chitinozoaires de la zone à Dicellograptus complanatus Formation de Vauréal, Ordovicien supérieur, Ile d'Anticosti, Québec

Borehole samples from the Vaureal Formation (Upper Ordovician), Anticosti Island, Quebec contain well preserved assemblages of chitinozoans; in this paper the specimens found in the Dicellograptus complanatus zone are described.In addition to the new forms recorded, Cyathochitina vaurealensis n. sp. and C. anticostiensis n. sp., the assemblages are characterised by Acanthochitina barbata and Lagenochitina baltica, species which enable a correlation to be made between the Upper Ordovician (Upper Caradocian – Lower Ashgillian) of Europe.

Biostratigraphy of Graptolite-Bearing Beds of Upper Ordovician Maquoketa Formation of Northeastern Iowa: ABSTRACT

A graptolite fauna comprised of 3 species is present in the lower Elgin Member of the Maquoketa Formation. Although this fauna has been reported previously, revision and reevaluation of the taxonomy are proposed. The following taxa merit discussion and revision: Diplograptus peosta (Hall) belongs to the species group Orthograptus truncatus Lapworth. Its geographically and chronologically restricted occurrence dictates a subspecific designation. Climacograptus putillus (Hall) is a species which is very similar to C. mississippiensis Ruedemann. The 2 species differ with regard to the origin of the median septum; however, other strong affinities should be considered in a revision of both species. An unnamed subspecies of Orthograptus quadrimucronatus exhibits affinities wi h 2 subspecies from eastern North America. Its small size and restricted occurrence separate it as a distinct subspecies. The stratigraphic and geographic distribution of graptoloid species within the Maquoketa Formation suggests that 2 graptolite zones exist and the graptoloid species are provincial within both zones. Individually the graptoloid species of the Maquoketa Formation are similar to species reported to be late Caradocian, early Ashgillian, Edenian, Maysvillian, and Richmondian in age. Comparison of the Maquoketa graptolites with faunas of eastern and western North America suggests a discrepancy in previous correlations between the Richmond Stage and the Dicellograptus complanatus zone of western Texas. The graptolite fauna as a whole is correlated with the faunas of the Haymeadow Creek Member of northern Michigan as well as the upper Utica Formation of New York and Canada. End_of_Article - Last_Page 626------------

Palynology and Silurian-Lower Devonian (“Hunton”) Stratigraphy in the Subsurface of Oklahoma and the Texas Panhandle

Palynology is ideally suited to the solution of stratigraphic problems routinely encountered during petroleum exploration. An example of its suitability for such work is its successful application to the elucidation of subsurface “Hunton” stratigraphy in the Anadarko Basin of Oklahoma and the Texas panhandle. In this basin, spores, acritarchs, chitinozoans, and scolecodonts from cores and cuttings permit the dating and correlation of sedimentary rocks down to 21,000 ft. Palynology has revealed that over much of the Anadarko Basin “Hunton” beds rest upon Ordovician rocks no older than the worldwide Dicellograptus complanatus graptolite zone of Ashgill (Richmond) age, and suggests that in some parts of the basin uppermost Ordovician and basal “Hunton” strata form an unbroken depositional sequence. Palynology indicates that, contrary to many published views, “Hunton” beds of Devonian age are missing on the northern limb of the basin in the region of Custer and southern Dewey Counties, Oklahoma. It proves the existence of a thick sequence of Lower Devonian carbonate rocks on the southern limb of the basin in the subsurface of the Texas panhandle, thus providing the first record of dated Lower Devonian rocks in the panhandle or anywhere upon the southern limo of the Anadarko Basin beyond the immediate vicinity of the outcrops in south-central Oklahoma.

GENERAL OUTLINE OF THE ORDOVICIAN STRATIGRAPHY OF THE CHU-ILIYSKIYE MOUNTAINS

Great variety of lithic facies and abundance of varied faunas makes the Ordivician of this area ideal for study. Numerous detailed sections show that although many kinds of rock are exemplified the great majority are detrital in nature, with limestones constituting a lesser part. In order to conform to local stratigraphic circumstances, the Caradoc stage is redefined to include only the zones of Climacograptus wilsoni and Dicranograptus clingani. Similarly the Ashgill stage is redefined to include the zone of Pleurograptus linearis in addition to the zone of Dicellograptus complanatus. Throughout the section there are conflicts among the brachiopod, trilobite, cephalopod, and graptolite elements of the faunas concerning correct dating. In each case these have been resolved locally. Almost all the Ordovician series or formations overlap Precambrian rocks uncofformably at one place or another. This is particularly true of rocks below the Caradoc. The basal Akshal suite of limestones of questionable Tremadoc...