South America’s earliest (Ordovician, Floian) crinoids

2015 ◽  
Vol 89 (4) ◽  
pp. 622-630 ◽  
Author(s):  
Thomas E. Guensburg ◽  
Beatriz G. Waisfeld
Keyword(s):  
Late Ordovician ◽  
Middle Ordovician ◽  
Early Ordovician ◽  
Northwest Argentina ◽  
Anal Sac

AbstractTwo new Early Ordovician crinoids have been discovered in Gondwanan rocks of northwest Argentina.Ramseyocrinus argentinusn. sp., among the most complete for the genus, aids in reconstructing key morphology.Ramseyocrinusis unorthodox with just four radials forming the entire cup, these articulating to five arms above and a tetrameric stem below. Evidence is presented radials comprise A, B, D, and E ray elements (C absent) with B and D radials adjoining to form a compound facet for the C arm. Thus the cup entirely lacks posterior plating; an elongate anal sac projects from the CD tegmen region alongside the C arm. Cup synapomorphies closely linkRamseyocrinusand the Middle OrdovicianTetragonocrinus; inclusion of this clade within disparids is tenuous.Quechuacrinus ticsan. gen. and sp., increases the paleogeographic range of reteocrinid camerates, previously documented only from Laurentia. This taxon expresses synapomorphies characterizing the Late OrdovicianReteocrinus, demonstrating the antiquity of this morphotype.

scholarly journals Late Ordovician Palynomorphs

1985 ◽  
Vol 4 (1) ◽  
pp. 11-26 ◽  
Author(s):  
S. G. Molyneux ◽  
F. Paris
Keyword(s):  
New Species ◽  
North America ◽  
Late Ordovician ◽  
Middle Ordovician ◽  
Early Ordovician ◽  
Core Samples ◽  
Type Section ◽  
A New Species

Abstract. ACRITARCHSOrdovician acritarchs have been recorded in five core samples collected between 2520 ft. and 3000 ft. in Well E1-81, and ten cutting samples taken between 12150 ft. and 13240 ft. in Well J1-81A. All the assemblages recovered are of Late Ordovician age; no Early Ordovician or Middle Ordovician assemblages have been identified.Investigations have so far concentrated on the acritarch assemblages from Well El-81. The highest three Ordovician samples from depths of 2520 to 2550 ft., 2552 to 2557 ft., and 2562 to 2567 ft., yielded similar assemblages which include Veryhachium irroratum, V. cf. lairdii, V. oklahomense?, V. subglobosum, V. trispinosum, Villosacapsula setosapellicula and a new species, Striatotheca sp. A. Navifusa similis? is represented by one specimen in the sample from 2552 to 2557 ft. Another specimen from the same sample is tentatively referred to Aremoricanium syringosagis. Specimens of Baltisphaeridium, Peteinosphaeridium, Leiofusa and Eupoikilofusa occur throughout the interval 2520 to 2567 ft. but are rare. Commonly occurring species include V. irroratum and V. setosapellicula. V. irroratum has been recorded from the Middle Ordovician of North America (Loeblich & Tappan, 1969) and the Caradoc of England (Turner, 1984) but Cramer & Diez (1979) maintain that it has its acme in the Ashgill. V. setosapellicula is common in the Sylvan Shale of Oklahoma (Loeblich, 1970) which is generally understood to be of Ashgill age, but is rare in the Eden Shale (Caradoc) of Indiana (Colbath, 1979) and in the type section of the Caradoc Series in Shropshire, England (Turner, 1984). . . .

The “earliest tabulate corals” are not tabulates

Geology ◽  
2020 ◽  
Author(s):  
Robert J. Elias ◽  
Dong-Jin Lee ◽  
Brian R. Pratt
Keyword(s):  
Evolutionary History ◽  
Late Ordovician ◽  
Time Span ◽  
Cambrian Explosion ◽  
Middle Ordovician ◽  
Early Ordovician ◽  
Calcareous Alga ◽  
History Of ◽  
Geological Factors ◽  
Tabulate Corals

Putative tabulate-like corals dating to the Cambrian Explosion are not true tabulates. Early Ordovician fossils identified as Lichenaria and previously accepted as the earliest tabulate corals actually belong to Amsassia, which may be a calcareous alga. The earliest definite tabulates appeared in the latest Middle Ordovician as part of the Great Ordovician Biodiversification Event, prior to the earliest confirmed occurrence of tabulate species that do belong to Lichenaria in the Late Ordovician. With Cambrian (Epoch 2) tabulate-like fossils being separated from the appearance of true tabulates by a time span of ~50 m.y., a direct phylogenetic connection is unlikely. Thus, the prevailing understanding of the origin and evolutionary history of tabulate corals needs to be reconsidered. The appearance of both major groups of Paleozoic corals, tabulates and rugosans, at the same time on separate paleocontinents must be taken into account in determining biological and geological factors involved in the Great Ordovician Biodiversification Event.

Ordovician deformations in the Pyrenees: new insights into the significance of pre-Variscan (‘sardic’) tectonics

2010 ◽  
Vol 147 (5) ◽  
pp. 674-689 ◽  
Author(s):  
J. M. CASAS
Keyword(s):  
Large Volume ◽  
Volcanic Activity ◽  
Late Ordovician ◽  
Normal Faults ◽  
Upper Ordovician ◽  
Middle Ordovician ◽  
Early Ordovician ◽  
Gondwana Margin ◽  
Magmatic Event ◽  
European Variscides

AbstractTwo deformational events which developed prior to the Variscan structures can be characterized in the Palaeozoic rocks of the Pyrenees: a Middle (?) Ordovician folding event and a Late Ordovician fracture episode. The Middle (?) Ordovician folding event gives rise to NW–SE- to N–S-oriented, metric- to hectometric-sized folds, without cleavage formation or related metamorphism. These folds can account for the deformation and uplift of the pre-Upper Ordovician (Cambro-Ordovician) sequence and for the formation of the Upper Ordovician unconformity. Ordovician folds control the orientation of the Variscan main-folding-phase minor structures, fold axes and intersection lineation in the Cambro-Ordovician sediments. The Late Ordovician fracture episode gave rise to normal faults affecting the lower part of the Upper Ordovician series, the basal unconformity and the underlying Cambro-Ordovician metasediments. Displacement of some of these faults diminishes progressively upwards of the series and tapers off in the upper part of the Upper Ordovician rocks, indicating that the faults became inactive during Late Ordovician times before deposition of the Ashgillian metasediments. Normal faults can be linked to the Upper Ordovician volcanic activity, which has been extensively described in the Pyrenees. The aforementioned deformation episodes took place after the Early Ordovician magmatic event, which gave rise to a large volume of plutonic rocks in the Pyrenees as in other segments of the European Variscides. This Middle Ordovician contractional event separated two extensional events in the Pyrenees from Early Ordovician to Silurian times. This event prevents us from assuming the existence of a continuous extensional regime through Ordovician and Silurian times, and suggests a more complex evolution of this segment of the northern Gondwana margin during the Ordovician.

Biogeography of Ordovician sponges

1999 ◽  
Vol 73 (1) ◽  
pp. 26-37 ◽  
Author(s):  
Marcelo G. Carrera ◽  
J. Keith Rigby
Keyword(s):  
North American ◽  
New South ◽  
New South Wales ◽  
Late Ordovician ◽  
Published Data ◽  
Middle Ordovician ◽  
Biogeographic Patterns ◽  
Early Ordovician ◽  
South Wales ◽  
Argentine Precordillera

Sponges have an unrealized potential importance in biogeographic analysis. Biogeographic patterns determined from our analysis of all published data on distribution of Ordovician genera indicate Early Ordovician sponge faunas have relatively low diversity and are completely dominated by demosponges. Early Ordovician (Ibexian) faunas are characterized by the widespread co-occurrence ofArchaeoscyphiaand the problematicCalathium.This association is commonly found in biohermal structures. Middle Ordovician faunas show an increase in diversity, and two broad associations are differentiated: Appalachian faunas (including Southern China and the Argentine Precordillera) and Great Basin faunas.Late Ordovician faunas show important changes in diversity and provincialism. Hexactinellid and calcareous sponges became important and new demosponge families appeared. Four Mohawkian-Cincinnatian associations are recognized here, including: 1) Midcontinent faunas; 2) Baltic faunas; 3) New South Wales faunas; and 4) Western North American (California and Alaska) faunas. However, two separate biogeographic associations are differentiated based on faunal differences. These are a Pacific association (western North American and New South Wales) and an Atlantic association (Midcontinent Laurentia and Baltica).Distribution of sponge genera and migration patterns are utilized to consider paleogeographic dispositions of the different continental plates, climatic features, and oceanic currents. Such an analysis points to close paleogeographic affinities between the Argentine Precordillera and Laurentian Appalachian faunas. However, significant endemicity and the occurrence of extra-Laurentian genera suggest a relative isolation of the Precordillera terrane during the Late Ibexian-Whiterockian. The study also shows a faunal migration from the Appalachian region to South China during the Middle Ordovician and the migration of faunas from Baltica to Laurentia in the Late Ordovician. The occurrence of Laurentian migrants in New South Wales during the Late Ordovician could be related to inferred oceanic current circulation between these two areas, although other paleogeographic features may be involved.

Nucularcidae: a new family of palaeotaxodont Ordovician pelecypods (Mollusca) from North America and Australia

2007 ◽  
Vol 44 (10) ◽  
pp. 1479-1501 ◽  
Author(s):  
John Pojeta Jr. ◽  
Christopher A Stott
Keyword(s):  
New Species ◽  
Type Species ◽  
New Genus ◽  
Late Ordovician ◽  
Eastern Canada ◽  
Middle Ordovician ◽  
New Family ◽  
Central Australia ◽  
Northeastern Usa ◽  
Subjective Synonym

The new Ordovician palaeotaxodont family Nucularcidae and the new genus Nucularca are described. Included in Nucularca are four previously described species that have taxodont dentition: N. cingulata (Ulrich) (the type species), N. pectunculoides (Hall), N. lorrainensis (Foerste), and N. gorensis (Foerste). All four species are of Late Ordovician (Cincinnatian Katian) age and occur in eastern Canada and the northeastern USA. Ctenodonta borealis Foerste is regarded as a subjective synonym of Nucularca lorrainensis. No new species names are proposed. The Nucularcidae includes the genera Nucularca and Sthenodonta Pojeta and Gilbert-Tomlinson (1977). Sthenodonta occurs in central Australia in rocks of Middle Ordovician (Darriwilian) age. The 12 family group names previously proposed for Ordovician palaeotaxodonts having taxodont dentition are reviewed and evaluated in the Appendix.

New echinoderms from the Early Ordovician of west Texas

1994 ◽  
Vol 68 (2) ◽  
pp. 324-338 ◽  
Author(s):  
James Sprinkle ◽  
Gregory P. Wahlman
Keyword(s):  
North America ◽  
El Paso ◽  
Middle Ordovician ◽  
Early Ordovician ◽  
West Texas ◽  
Lower Ordovician ◽  
Single Well ◽  
Thecal Plate ◽  
Stem Segments

Four specimens of blastozoan and crinozoan echinoderms are described from the Lower Ordovician El Paso Group in the southern Franklin Mountains just north of El Paso, west Texas.Cuniculocystis flowerin. gen. and sp., based on two partial specimens, appears to be a typical rhombiferan in most of its morphologic features except that it lacks pectinirhombs and instead has covered epispires (otherwise known only from Middle Ordovician eocrinoids) opening on most of the thecal plate sutures. The covered epispires inCuniculocystisindicate that some early rhombiferans had alternate respiratory structures and had not yet standardized on pectinirhombs, a feature previously used as diagnostic for the class Rhombifera.Bockia?elpasoensisn. sp. is a new eocrinoid based on one poorly preserved specimen that has a small ellipsoidal theca and unbranched brachioles attached to a flat-topped spoutlike summit. It is the earliest known questionable representative of this genus and the only one that has been described from North America.Elpasocrinus radiatusn. gen. and sp. is an early cladid inadunate crinoid based on a single well-preserved calyx. It fits into a lineage of early cladids leading to the dendrocrinids and toCarabocrinus.Several additional separate plates, stem segments, and a holdfast of these and other echinoderms are also described.

scholarly journals The Wandel Valley Formation (Early - Middle Ordovician) of North Greenland and its correlatives

1988 ◽  
Vol 137 ◽  
pp. 61-92
Author(s):  
J.S Peel ◽  
M.P Smith
Keyword(s):  
Canadian Arctic ◽  
East Greenland ◽  
Middle Ordovician ◽  
Early Ordovician ◽  
Lowermost Part ◽  
North Greenland

Members are formally described within the Wandel Valley Formation (Early - Middle Ordovician) of the Ryder Gletscher Group in central and eastem North Greenland. In Peary Land the names Pyramideplateau Member (the combined lower and middle informal members of previous usage) and Vestervig Elv Member (the upper member) are proposed. In Kronprins Christian Land, the Alexandrine Bjerge Member (new) overlies the previously named Danmarks Fjord and Amdrup Members. Conodont studies, supported by the macrofauna, indicate that the Pyramideplateau, Danmarks Fjord and Amdrup Members are of late Canadian (Early Ordovician) age. The Canadian-Whiterockian boundary lies within the lowermost part of the Vestervig Elv and Alexandrine Bjerge Members. The top of the former is of earliest Late Whiterockian age while the Alexandrine Bjerge Member only extends into the late Middle Whiterockian. The members of the Wandel Valley Formation are correlated with coeval successions in western North Greenland, East Greenland, the Canadian Arctic Islands and Svalbard.

scholarly journals Die Gattung Erratencrinurus Krueger, 1971 (Trilobita; Ordovizium) aus baltoskandischen Geschieben

Fossil Record ◽  
2004 ◽  
Vol 7 (1) ◽  
pp. 69-132
Author(s):  
H.-H. Krueger
Keyword(s):  
New Species ◽  
Hard Rock ◽  
Late Ordovician ◽  
Middle Ordovician ◽  
Different Types ◽  
Single Spine ◽  
Pore Canals ◽  
Different Parts

Aus der mittel- bis oberordovizischen Trilobitenfamilie Encrinuridae, die in Baltoskandia durch die Untergattungen <i>Erratencrinurus</i> und <i>Celtencrinurus</i> repräsentiert wird, werden achtzehn Arten beschrieben, darunter die vier neuen Arten <i>Erratencrinurus (E.) sellinensis, E. (E.) heinrichi, E. (E.) praecapricornu</i> und <i>E. (E.) rhebergeni</i>. Das überwiegende Material stammt aus dem schwer zu präparierenden Ostseekalk. Die Tripp'sche Tuberkelformel wurde der <i>Erratencrinurus</i>-Gruppe angepasst; innerhalb der <i>Erratencrinurus</i>-Gruppe können drei verschiedene Schilder-Typen des scutum rostrale nachgewiesen werden. Unterschiedliche Tuberkeltypen bis hin zu extremen Stacheln wurden beschrieben. Außerdem kann eine Reduzierung von drei Thoraxialstacheln im Mittelordovizium zu einem im oberen Oberordovizium festgestellt werden. Verschiedene Regionen des Panzers von <i>Erratencrinurus (E.) sellinensis</i>, die Porenkanäle besitzen, werden dargestellt. Ein neuer Häutungstyp kann an Panzerhemden von <i>Erratencrinurus (E.) seebachi</i> beschrieben werden. <br><br> In Baltoscandia the Middle to Late Ordovician trilobite family <i>Encrinurida</i> is represented by the two subgenera <i>Erratencrinurus</i> and <i>Celtencrinurus</i>. Out of these 18 species, four new species are described herein. Most of the material comes from the Ostseekalk which is an extremely hard rock and thus difficult to preparate. The tubercle formula after Tripp is applied to the <i>Erratencrinurus</i> group and led to the distinction of three different types of scutum rostrale shields. Various types of tubercles which may even pass into extreme spines are described. The number of thoracic spines becomes reduced from three spines in Middle Ordovician taxa to a single spine in youngest Ordovician species. Different parts of the carapace of <i>Erratencrinurus sellinensis</i> with pore canals are illustrated and a new moulting type of E. <i>seebachi</i> is introduced. New species are <i>E. sellinensis. E. heinrichi, E. praecapricornu and E. (E.) rhebergeni.</i> <br><br> doi:<a href="http://dx.doi.org/10.1002/mmng.20040070106" target="_blank">10.1002/mmng.20040070106</a>

Composition, structure and tectonic analysis of the Shangrimuce arc-continent collision zone on the northern margin of the Central Qilian, NW China

2021 ◽  
Author(s):  
Hongyuan Zhang ◽  
Zhibin Lei ◽  
Bo Yang ◽  
Qing Liu ◽  
Haijun Zhang ◽  
...  
Keyword(s):  
Shear Zones ◽  
Oceanic Lithosphere ◽  
Late Ordovician ◽  
Island Arc ◽  
Qilian Mountain ◽  
Northern Margin ◽  
Early Ordovician ◽  
Collision Zone ◽  
Two Stages ◽  
Back Arc

&lt;p&gt;A 1:50000 regional survey, covering an area of about 2000 km&lt;sup&gt;2&lt;/sup&gt;, was carried out in the Shangrimuce area of Qilian Mountain in Northwest China. The results show that during Caledonian, the northern margin of the Central Qilian block experienced collision with mature island arcs and subsequently northward expansion. In the Shangrimuce study area, five geological units have been identified; they are, form south to north, back-arc basin, early Ordovician island arc, inter arc basin, middle Late Ordovician island arc, and fore-arc and oceanic lithosphere amalgamation zone.&amp;#160;&lt;/p&gt;&lt;p&gt;(1) back-arc basin. In the Yangyuchi- Shule River- Cuorigang- Wawusi area, there may be a back-arc spreading basin, and there should be spreading basins in this area. It is speculated that there was a northward reverse subduction in the late Ordovician, accompanied by a syenite body, a broad spectrum dyke swarms and an accretionary wedge zone in the whole area.&lt;/p&gt;&lt;p&gt;(2) early Ordovician island arc. In the Shangrimuce-Dander area, the Proterozoic basement granitic gneiss, the early Ordovician island arc block and the high-pressure geological body all occur in the form of thrust horses, forming a double metamorphic belt, which reveals the existence of ocean subduction to south in the early Ordovician.&amp;#160;&lt;/p&gt;&lt;p&gt;(3) inter arc basin. On both banks of Tuolai River to the east of Yanglong Township, there are early Middle Ordovician inter-arc basins with oceanic crust.&amp;#160;&lt;/p&gt;&lt;p&gt;(4) middle Late Ordovician island arc. To the north of Tuolai River, there is a middle Late Ordovician island arc belt. Both sides of the island arc zone experienced strong ductile shear deformation, which recorded a complex arc-continent collision.&amp;#160;&lt;/p&gt;&lt;p&gt;(5) fore-arc and oceanic lithosphere amalgamation zone (Fig.1). The Yushigou area has developed a fore-arc and oceanic lithospheric amalgamation zone, with weakly deformed fore-arc flysch basin, strongly deformed siliceous rocks, pillow Basalt, diabase, gabbro, peridotite and other rock assemblages.&lt;/p&gt;&lt;p&gt;Combined with the characteristics of arc-continent collision zone in the Western Pacific, there are two stages of shear zone series (Fig.2). One is ductile shear zones formed by the South dipping gneissic belt, revealing the existence of oceanic subduction accretion wedge and emplacement of high-pressure rocks. Another superimposed one is north dipping. This indicates that the arc-continent collision caused by back-arc reverse subduction, which ultimately controls the overall geometric and kinematic characteristics of the shear zones in the region.&lt;/p&gt;&lt;p&gt;&lt;img src=&quot;https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.8219836ca50067454890161/sdaolpUECMynit/12UGE&amp;app=m&amp;a=0&amp;c=40b3389c641f2d0ca723e1527c32927e&amp;ct=x&amp;pn=gepj.elif&amp;d=1&quot; alt=&quot;&quot;&gt;&lt;/p&gt;&lt;p&gt;Figure 1 United sections showing a Caledonian trench-arc system in the Qilian Mountain, NW China.&lt;/p&gt;&lt;p&gt;&lt;img src=&quot;https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.8def566da50066084890161/sdaolpUECMynit/12UGE&amp;app=m&amp;a=0&amp;c=e82258ecc235c4e618abd6c035b58232&amp;ct=x&amp;pn=gepj.elif&amp;d=1&quot; alt=&quot;&quot;&gt;&lt;/p&gt;&lt;p&gt;Figure 2 Structural analysis at Hongyahuo, indicating two stages of deformation.&lt;/p&gt;&lt;p&gt;The research has been supported by projects from the Ministry of Land and Resources (No.201211024-04; 1212011121188) and the 2020 undergraduate class construction project from China University of Geosciences (Beijing) (No. HHSKE202003).&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

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