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.

Flexible crinoids from the Upper Ordovician Maquoketa Formation of the northern midcontinent and the evolution of early flexible crinoids

2001 ◽  
Vol 75 (2) ◽  
pp. 370-382 ◽  
Author(s):  
James C. Brower
Keyword(s):  
New Species ◽  
North America ◽  
Late Ordovician ◽  
Upper Ordovician ◽  
Middle Ordovician

Three flexible crinoids occur in the Upper Ordovician Maquoketa Formation of Illinois, Iowa, and Minnesota:Protaxocrinus girvanensisRamsbottom, 1961,Clidochirus anebosnew species, andProanisocrinus oswegoensis(Miller and Gurley, 1894).Protaxocrinus girvanensisis also found in the Upper Ordovician of Scotland which indicates that the ocean was narrow enough to allow at least one crinoid species to cross the barrier. The Upper Ordovician of North America and Scotland also share many common crinoid genera. Both phenetic and cladistic methods result in similar phylogenies of flexible crinoids.Protaxocrinuswas derived from a cupulocrinid ancestor during the Middle Ordovician.Clidochirusevolved fromProtaxocrinusor its ancestral stock prior to the Richmondian of the Late Ordovician. The RichmondianProanisocrinusand later anisocrinids are most closely related toClidochirusor its immediate predecessor. Thus, three major lineages of flexible crinoids,Protaxocrinus(taxocrinid group),Clidochirus(icthyocrinid), andProanisocrinus(anisocrinids and homalocrinids), appeared during the Ordovician. Despite their rarity during the Ordovician, all three flexible lineages survived the Latest Ordovician extinction, whereas their more abundant and successful cupulocrinid ancestors were eliminated.

scholarly journals An unusual sponge – microbe – synsedimentary cement framework in a Late Ordovician reef, Southampton Island (Nunavut, Canada)

2016 ◽  
Vol 53 (8) ◽  
pp. 815-822 ◽  
Author(s):  
Ariane Castagner ◽  
André Desrochers ◽  
Denis Lavoie
Keyword(s):  
Spatial Relationship ◽  
Late Ordovician ◽  
Calcareous Algae ◽  
Upper Ordovician ◽  
Shallow Marine ◽  
Early Ordovician ◽  
Subaerial Exposure ◽  
Close Spatial Relationship ◽  
Diverse Community ◽  
Calcite Cement

A large, resistant buildup at the top of the Upper Ordovician (Hirnantian?) Red Head Rapids Formation on Southampton Island (Nunavut, Arctic Canada) is dominated by massive boundstone and cementstone facies. These massive facies have more in common with the sponge–microbial reefs that dominated worldwide in the Early Ordovician, including the following primary components: early calcified sponge material, microbial elements, and synsedimentary cement. A close spatial relationship between sponge and microbial framework elements suggests that a poorly preserved decaying sponge framework provided substrates for the attachment and development of microbes and that the microbes played essential roles as reef consolidators. Centimetre-scale colonial metazoans are present and locally intergrown with the sponge and microbial components. Other mound-dwelling invertebrates or calcareous algae are rare. Although altered now to calcite, cement fabrics suggest that aragonite was ubiquitous as seafloor precipitate. Prior to its subaerial exposure in the latest Ordovician, the Red Head Rapids Formation buildup developed on the margin of a shallow-marine evaporative epicratonic basin where a diverse community of reef-building metazoans was unable to flourish.

Biostratigraphy and paleobiogeography of Middle and Late Ordovician conodonts from the Langkawi Islands, northwestern peninsular Malaysia

2008 ◽  
Vol 82 (5) ◽  
pp. 957-973 ◽  
Author(s):  
Sachiko Agematsu ◽  
Katsuo Sashida ◽  
Amnan B. Ibrahim
Keyword(s):  
North Atlantic ◽  
Peninsular Malaysia ◽  
Late Ordovician ◽  
Upper Ordovician ◽  
Low Latitude ◽  
Cool Water ◽  
Middle Ordovician ◽  
Water Conditions ◽  
Unidentified Species ◽  
Assemblage Zone

The Middle and Upper Ordovician sequence of the Langkawi Islands, northwestern peninsular Malaysia, contains 20 species of conodonts belonging to 15 genera and four unidentified species, which are described and illustrated. The following four biostratigraphic zones are established for the study area: the Scolopodus striatus assemblage zone, the Periodon sp. A range zone, the Baltoniodus alobatus range zone, and the Hamarodus europaeus range zone, in ascending order. The Middle Ordovician fauna belongs to the low-latitude, warm-water Australian Province. Conodonts of the H. europaeus zone represent the HDS (Hamarodus europaeus-Dapsilodus mutatus-Scabbardella altipes) biofacies, which has been reported from the cool-water North Atlantic Faunal Region. The middle Arenigian limestones in the study area were deposited on a shallow-water shelf, whereas the late Arenigian to middle Darriwilian limestones formed in hemipelagic deeper-water conditions on an outer shelf or slope.

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.

The brachiopod Ptychopleurella lapworthi (Davidson) from the Ordovician of Girvan, S.W. Scotland

1986 ◽  
Vol 60 (4) ◽  
pp. 845-850 ◽  
Author(s):  
D. A. T. Harper
Keyword(s):  
North America ◽  
Sedimentary Facies ◽  
Upper Ordovician ◽  
Middle Ordovician ◽  
Identity Recognition ◽  
Early Ordovician ◽  
Iapetus Ocean ◽  
Northwestern Margin

The small, distinctive, glyptorthinine brachiopod Ptychopleurella Schuchert and Cooper is widely distributed in rocks of early Ordovician to late Silurian age. Several species are known from the Barr and Ardmillan successions (middle-upper Ordovician) of the Girvan district, S.W. Scotland, one of which, ‘Orthis Lapworthi’ Davidson, has not been described in modern terms as there has been some confusion concerning its true identity. Recognition of this species of Ptychopleurella permits comparison with congeners elsewhere, strengthens the correlation of this part of the Girvan Succession with the middle Ordovician of North America, and provides a more complete record of this genus in the slope sedimentary facies of the northwestern margin of the Iapetus Ocean.

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.

scholarly journals Formation of the rear slope of the island arc of Chingiz Kaledonid ridge in eastern Kazakhstan

2019 ◽  
pp. 72-80
Author(s):  
S. G. Samygin
Keyword(s):  
Volcanic Activity ◽  
Volcanic Rocks ◽  
Island Arc ◽  
Middle Ordovician ◽  
Upper Cambrian ◽  
Early Ordovician ◽  
Landslide Processes ◽  
Mass Frontier ◽  
Eastern Kazakhstan

Process of formation of the island-arc rear slope is considered on the example of the Upper Cambrian–Middle Ordovician arc found in the Chingiz ridge in eastern Kazakhstan. Its occurrence is shown at the end of volcanic activity in the island-arc structure, beginning at the end of the early Arenig (from the end of the Flos century of the Early Ordovician) with tephroturbidites appearance. After the cessation of volcanism, two sedimentation cycles were distinguished in the sedimentary section of the slope in the middle Ordovician: (1) transgressive when the island arc submerged, (2) and regressive when the Chingiz arc began to build up at the beginning of the Llanwyrn (Darrivilian) century. The sedimentation was repeatedly accompanied by landslide processes, which ended in the middle of llanvirna (darrivilia) with the disruption of tectonic-gravity plate composed of Upper Cambrian volcanic rocks with limestone in the sole, resulting in the formation of coarsely fragmented mixtite at the allochthonous mass frontier, the further sedimentation on the rear slope stopped. Keywords: the island-arc; rear slope; sedimentation cycles; landslide processes

New recumbent echinoderm genera from the Bois d'Arc Formation: Lower Devonian (Lochkovian) of Coal County, Oklahoma

2007 ◽  
Vol 81 (6) ◽  
pp. 1486-1493 ◽  
Author(s):  
Ronald L. Parsley ◽  
Colin D. Sumrall
Keyword(s):  
Great Britain ◽  
West Virginia ◽  
North American ◽  
Lower Devonian ◽  
Late Ordovician ◽  
Upper Ordovician ◽  
Early Devonian ◽  
Middle Ordovician

An echinoderm fauna from the Lower Devonian (Lochkovian) Cravatt Member of the Bois d'Arc Formation near Clarita, Oklahoma, has yielded specimens of recumbent, essentially bilaterally symmetrical taxa which are similar to Ordovician genera but absent or sparsely represented in Silurian strata. Claritacarpus smithi n. gen. and sp., is a dendrocystitid homoiostele with morphology similar to the Late Ordovician Dendrocystoides Jaekel, 1918; the anomalocystitid stylophoran Victoriacystis aff. holmesorum Ruta and Jell, 1999 shows strong affinities to Victoriacystis holmesorum Ruta and Jell, 1999, Humevale Formation, of Victoria, Australia; and the pleurocystitid rhombiferan, Turgidacystis graffhami n. gen. and sp., has close affinities to the Middle Ordovician Coopericystis Parsley, 1970 of West Virginia and Henicocystis Jell, 1983 of Victoria, Australia. Claritacarpus and Turgidacystis are North American range extensions for homoiosteles and pleurocystitids, respectively, being previously unknown from rocks younger than Upper Ordovician. Globally, Silurian homoiosteles and pleurocystitids are unknown although both occur in the Lower Devonian of Germany and Australia; additionally, Early Devonian pleurocystitids are known from Great Britain and Bohemia. These genera illustrate a pseudoextinction pattern suggesting a significant unsampled Silurian “homalozoan” and pleurocystitid history.

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