Research Article| November 01, 2013 Environmental changes in the Late Ordovician–early Silurian: Review and new insights from black shales nitrogen isotopes Michael J. Melchin; Melchin † 1Department of Earth Sciences, St. Francis Xavier University, Antigonish, Nova Scotia B2G 2W5, Canada †E-mail: mmelchin@stfx.ca Search for other works by this author on: GSW Google Scholar Charles E. Mitchell; Mitchell 2Department Geology, State University New York at Buffalo, 14260, USA Chris Holmden;...

Abstract Nearly 50 sections through the Llandovery and Wenlock black shales of Barrandian area (Bohemia) have been examined bed by bed. This has made possible compilation an improved well defined graptolite zonal scheme with much new biostratigraphic data included. A total 268 species subspecies found. Their stratigraphic distribution allows recognition 27 zones: ascensus–acuminatus, vesiculosus, cyphus, triangulatus–pectinatus, simulans, convolutus, sedgwickii, linnaei, turriculatus,...

Forty-three graptolite species belonging to fifteen genera are described from the upper Katian ornatus and pacificus biozones Hirnantian extraordinarius persculptus of Vinini Creek Martin Ridge reference sections north-central Nevada.Approximately half have not been previously recorded Nevada, six left in open nomenclature.Infraorder Neograptina Styracograptus gen.nov.are erected.The maximum diversity is organic-rich black shale lower part Biozone Formation.Species decreased abruptly at top...

Abstract Sedimentary sequences through the uppermost Ordovician (Hirnantian), Kosov Formation, are described. The Formation is a shale‐dominated formation with two thin horizons of sandy diamictites near base and ‘flysch’ units separated by shales forming main part formation, which overlain abruptly Silurian graptolitic shales. interpreted as glaciomarine origin, probably deposited from coastal winter ice. flysch have many beds hummocky cross‐stratification wave‐ripples indicating deposition...

Abstract The shale-dominated hemipelagic succession exposed in the southwestern part of Prague Synform preserves most complete Ludfordian graptolite record so far encountered from peri-Gondwanan Europe. Four biozones – Neocucullograptus inexpectatus , Nc. kozlowskii Pseudomonoclimacis latilobus–Slovinograptus balticus and Pristiograptus fragmentalis are recognized middle late Ludfordian, between Bohemograptus tenuis Biozone base Pridoli Series. Conodont occurrences restricted to scattered...

Mass extinctions disrupt ecological communities. Although climate changes produce stress in communities, few paleobiological studies have systematically addressed the impact of global on fine details community structure with a view to understanding how presage, or even cause, biodiversity decline during mass extinctions. Based novel Bayesian approach biotope assessment, we present study species abundance distribution patterns macroplanktonic graptolite faunas (∼447-444 Ma) leading into Late...

LethaiaVolume 29, Issue 1 p. 59-60 Free Access Generalized graptolite zonal sequence defining Silurian time intervals for global paleogeographic studies TATYANA N. KOREN, KORENSearch more papers by this authorALFRED C. LENZ, ALFRED LENZSearch authorDAVID K. LOYDELL, DAVID LOYDELLSearch authorMICHAEL J. MELCHIN, MICHAEL MELCHINSearch authorPETR STORCH, PETR STORCHSearch authorLECH TELLEK, LECH TELLEKSearch author First published: March 1996...

Abstract The Hirnantian and Llandovery sedimentary succession of the Barrandian area has been assigned to middle outer clastic‐shelf depositional settings, respectively. Deposition was influenced by remote Gondwanan glaciation subsequent, long‐persisting, post‐glacial anoxia triggered a current‐driven upwelling system. High‐resolution graptolite stratigraphy, based upon 19 formally defined biozones—largely interval zones—and five subzones, enabled detailed correlation between 42 surface...

ABSTRACT Following the melting of Gondwanan icecap and resulting postglacial sea-level rise, organic-rich shales were deposited in shelfal palaeo-depressions across North Africa Arabia during latest Ordovician to earliest Silurian. The unit is absent on palaeohighs that flooded only later when anoxic event had already ended. regional distribution Silurian black shale now well-known for subsurface central parts Murzuq Basin, Libya, where many exploration wells have been drilled represents...

Abstract Upper Ordovician – lower Silurian sequences of the Bohemian Massif (in Moldanubian Zone and Barrandian preserved in Prague Basin; Rožmitál area; metamorphic ‘islets’ mantle Central Pluton; Železné hory area), as well along northern margin Saxothuringian Lugian (= West Sudetian) zones, show evidence regressive–transgressive facies changes which can be related to glacio-eustatic sea-level fluctuations recognized elsewhere. Glacio-marine diamictites late (Hirnantian) age occur Basin...

Abstract: The taxonomy and biostratigraphy of the Aeronian graptoloid graptolites Tanezzuft Formation (Murzuq Basin Al Qarqaf Arch area) is presented discussed with respect to their palaeoenvironmental setting palaeobiogeographical links. gregarius‐libycus , ‘ leptotheca ’, convolutus sedgwickii assemblage biozones tenuis Subzone are recognized correlated generalized zonal scheme successions in peri‐Gondwanan Europe. Rhuddanian/Aeronian boundary tentatively placed at base Biozone. Telychian...

Abstract Study of the lower Silurian black shale succession Prague Synform has enabled detailed insight into graptolite faunal dynamics and diversity trends from mid-Aeronian maximum through to late Aeronian crisis. Graptolite decreased 33 taxa in Lituigraptus convolutus Biozone 17 upper part Stimulograptus sedgwickii newly erected rastrum Biozone. The assemblages latter biozones exhibit low species richness along with high dominance. Many that became extinct early Zone were promptly...

The most ancient macroscopic plants fossils are Early Silurian cooksonioid sporophytes from the volcanic islands of peri-Gondwanan palaeoregion (the Barrandian area, Prague Basin, Czech Republic). However, available palynological, phylogenetic and geological evidence indicates that history plant terrestrialization is much longer it recently accepted land floras, producing different types spores, already were established in Ordovician Period. Here we attempt to correlate floral development...

Ten graptolite species have been recognized by a general revision of all the material (both historical and new) collected from Králův Dvůr Formation Prague Basin.One belongs to dicranograpid genus Dicellograptus remaining are biserial taxa assigned diplograptid genera Diplograptus Anticostia, lasiograptids Paraplegmatograptus Phormograptus, climacograptid Styracograptus, neodiplograptid Normalograptus Metabolograptus.Although specimens rare in these strata, there does appear be regular...

Eight Lower Silurian graptolite biozones ( triangulatus , convolutus linnaei turriculatus crispus griestoniensis tullbergi and spiralis ) three subzones runcinatus–gemmatus palmeus hispanicus have been recognized in the Sierra Menera, Nevera, Tremedal massifs Castilian Branch of Iberian Cordillera (Western Cordillera). Early Silurian, Rhuddanian low-diversity normalograptid faunas are also present these, together with rich Aeronian biozones, come from black, shaly intercalations within...

Seven species of graptoloid graptolites are described from Hirnantian and lower Rhuddanian formations the Austrian part Carnic western Karavanke Alps.The Plöcken Formation, latest Ordovician (Hirnantian) age, yields biozonal index graptolite Metabolograptus persculptus in Cellon Reference Section and, tentatively, Feistritzgraben Section.A distinctive assemblage indicating an earliest Silurian (early Rhuddanian) age comes Waterfall near Zollnersee Hütte.Along with presence Parakidograptus...

Abstract The late G orstian to early L udfordian hemipelagic succession of the south‐eastern part P rague S ynform preserves a rich fossil record dominated by 28 species planktic graptoloids associated with pelagic myodocopid ostracods, and nektobenthic orthocerid cephalopods, epibyssate bivalves, nektonic phyllocarids, rare dendroid graptolites, brachiopods, crinoids, trilobites, sponges macroalgae. Faunal dynamics have been studied particular reference graptolites. leintwardinensis...

The current Global Stratotype Section and Point (GSSP) for the Aeronian Stage (Llandovery Series, Silurian System), on Trefawr track in Llandovery area of Wales, is an inadequate marker precise, global, correlation. International Subcommission Stratigraphy has, therefore, undertaken selection a new GSSP this level. lowest occurrence graptolite Demirastrites triangulatus, 1.38 m above base black-shale succession Želkovice Formation at Hlásná Třebaň section Central Bohemia, proposed to mark...

The Všeradice section was trenched and continuously sampled for graptolites from the base of post-extinction upper Homerian strata to low in Ludlow. is divisible into three biozones, a lower parvus–nassa Biozone, middle praedeubeli–deubeli an ludensis–gerhardi last named being succeeded by lowest Ludlow nilssoni Biozone. graptolite diversity nine species part Biozone highest world. Five monograptid species, Pristiograptus parvus Ulst, 1974, P. dubius (Suess, 1851), Colonograptus deubeli...