Fe- and Mn-Enrichment in Middle Ordovician Hematitic Argillites Preceding Black Shale and Flysch Deposition: The Shoal Arm Formation, North-Central Newfoundland

1994 ◽  
Vol 102 (2) ◽  
pp. 197-214 ◽  
Author(s):  
Volker Brüchert ◽  
John W. Delano ◽  
William S. F. Kidd
Keyword(s):  
Black Shale ◽  
North Central ◽  
Middle Ordovician ◽  
Fe And Mn

The hexactinellid sponge Cyathophycus from the Lower-Middle Ordovician Vinini Formation of central Nevada

1995 ◽  
Vol 69 (3) ◽  
pp. 409-416 ◽  
Author(s):  
J. Keith Rigby
Keyword(s):  
New Species ◽  
Black Shale ◽  
North Central ◽  
Middle Ordovician ◽  
The North ◽  
Hexactinellid Sponge ◽  
North Fork

The new species Cyathophycus pseudoreticulatus and a fragment of Cyathophycus reticulatus? Walcott, 1879, are described and reported from the lower part of the Upper Member of the Vinini Formation from black shale of late Whiterockian age. The sponges were collected from the north fork of Vinini Creek, in the north-central part of the Roberts Mountains, Eureka County, Nevada.

Middle Ordovician Echinoderms from Northern Illinois and Southern Wisconsin

1975 ◽  
Vol 49 (S7) ◽  
pp. 1-74 ◽  
Author(s):  
Dennis R. Kolata
Keyword(s):  
New Species ◽  
New Genus ◽  
Carbonate Sediments ◽  
North Central ◽  
Middle Ordovician ◽  
South Central ◽  
The Family ◽  
Central Illinois ◽  
First Time ◽  
One New Species

Echinoderms of the Middle Ordovician Platteville and lower Galena Groups of north-central Illinois and south-central Wisconsin are represented by at least seven classes including the Homoiostelea, Cystoidea, Crinoidea, Stelleroidea, Edrioasteroidea, Cyclocystoidea, Echinoidea, and possibly Holothuroidea. The most abundant and diverse echinoderms are monocyclic and dicyclic inadunate and camerate crinoids, of which the cupulocrinids and glyptocrinids are best represented. Thirteen new species and one new genus of crinoids are described:Cremacrinus guttenbergensis, Anulocrinus forrestonensis, Isotomocrinus minutus, Carabocrinus oogyi, Dendrocrinus? springeri, Merocrinus britonensis, Cupulocrinus plattevillensis, C. molanderi, Reteocrinus rocktonensis, R. spinosus, Traskocrinus mahlburgi(n. gen. et sp.),Rhaphanocrinus buckleyi, Glyptocrinus charltoni, andG. pustulosis.One new species of rhombiferan cystoid,Coronocystis durandensis, is also described. Echinoids of the family Bothriocidaridae (Bothriocidaris solemin. sp. andNeobothriocidaris templetonin. sp.) are reported for the first time from North America and appear to be the earliest recorded occurrence. Remains of a third bothriocidarid characterized by coalesced podial pores have also been discovered. Light and scanning electron microscopy of well preserved cyclocystoid specimens reveal a number of previously undescribed morphologic features of the central disc and submarginal ring that may shed some light on their functional morphology.Cupulocrinus gracilisRamsbottom from the Upper Drummuck Group Starfish Bed at Thraive Glen near Girvan, Scotland, is here reassigned toC. drummuckensisn. sp.Echinoderms are associated with an abundant and diverse fauna consisting largely of suspension feeders, primarily strophomenid and orthid brachiopods and trepostome and cryptostome bryozoans. Other common groups include corals, trilobites, sponges, and mollusks. Filamentous brown, foliose red and siphonaceous green algae are associated with the fauna at some localities.Carbonate rocks of both the limestone and dolostone facies of the Platteville (Briton, Walgreen and Forreston Members) and lower Galene Groups in the study area consist primarily of abundant shelly invertebrates occurring as whole and broken, unabraded, commonly articulated remains “floating” in a calcisiltite matrix that is highly bioturbated. Carbonate sediments appear to have been deposited in a near-to below wave base, highly stable, open marine environment characterized by low depositional slopes, good circulation and low terrigenous influx.

scholarly journals Cambrian–Silurian stratigraphy of Børglum Elv, Peary Land, eastern North Greenland

1977 ◽  
Vol 82 ◽  
pp. 1-48
Author(s):  
R.L Christie ◽  
J.S Peel
Keyword(s):  
Black Shale ◽  
Lower Cambrian ◽  
Late Ordovician ◽  
Dolomitic Limestone ◽  
Carbonate Mounds ◽  
Middle Ordovician ◽  
Clastic Rocks ◽  
Shale Formation ◽  
Lower Palaeozoic ◽  
North Greenland

A sequence of Lower Palaeozoic carbonate and clastic rocks is described from Børglum Elv, Peary Land, eastem North Greenland, and briefly compared to Lower Palaeozoic sections elsewhere in Greenland and in Spitsbergen. Lower Cambrian clastic rocks of the Buen Formation are followed by dolomite of the Lower Cambrian Brønlund Fjord Formation (125 m). Succeeding dolomite and dolomitic limestone of the Wandel Valley Formation (320 m) of Early to Middle Ordovician age are overlain by limestone of the Børglum River Formation (430 m) of Middle to Late Ordovician age. Un-narned Early Silurian dolomite and limestone formations (150 m and 320 m respectively) are followed by an un.narned Middle Silurian black shale formation (c. 100 m) and at least 800 m of a late Middle Silurian and younger un-named flysch formation. Carbonate mounds, originating in the highest beds of the un-named Silurian limestone formation, occupy stratigraphic levels through the overlying black shale formation and into the flysch formation.

Autochthonous and allochthonous rocks in the Pistolet Bay area in northernmost Newfoundland

1968 ◽  
Vol 5 (3) ◽  
pp. 501-513 ◽  
Author(s):  
M. F. Tuke
Keyword(s):  
Lower Cambrian ◽  
Volcanic Rocks ◽  
The Other ◽  
North Central ◽  
Middle Ordovician ◽  
Early Ordovician ◽  
Bay Area

Rocks outcropping in the northernmost part of the island of Newfoundland belong to two sequences, which are partly contemporaneous and very different in lithology. One sequence consists of Lower Cambrian sandstones and Lower and Middle Ordovician carbonates and shales. The other sequence consists of graywackes, volcanic rocks, and ultrabasic intrusions, which are, in part, early Ordovician. This latter sequence is interpreted as allochthonous because it is underlain by major low-angle faults and because of its strong facies contrast with the first sequence. The allochthonous rocks occur in three separate klippen.The trend of slickensides, attitude of folds, and deflection of beds at fault surfaces all indicate that movement along the low-angle faults that underlie the klippen was to the northwest. The klippen probably originated from an area 60 km to the southeast, which is on strike with similar rocks in north-central Newfoundland.It is suggested that the klippen moved by gravity sliding in late Middle Ordovician time.

Age and correlation of the Honorat Group, southern Gaspé Peninsula

1988 ◽  
Vol 25 (10) ◽  
pp. 1618-1628 ◽  
Author(s):  
John Riva ◽  
Michel Malo
Keyword(s):  
United States ◽  
North America ◽  
New Brunswick ◽  
Wide Distribution ◽  
Late Ordovician ◽  
Eastern North America ◽  
North Central ◽  
Middle Ordovician ◽  
The Pacific ◽  
Early Late

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).

Silurian (Llandovery) graptolites from the Bay of Exploits, north-central Newfoundland, and their geological significance

1991 ◽  
Vol 28 (10) ◽  
pp. 1534-1540 ◽  
Author(s):  
S. Henry Williams ◽  
Brian H. O'Brien
Keyword(s):  
United Kingdom ◽  
North America ◽  
Generic Level ◽  
North Central ◽  
Geological Significance ◽  
Middle Ordovician ◽  
The United Kingdom ◽  
Iapetus Ocean

Only one specimen of a Silurian graptolite has ever been recorded from Newfoundland, and it was not identifiable below generic level. The graptolite assemblage discussed and figured here, from a sequence of turbidites on Upper Black Island, north-central Newfoundland, includes the first positively identified Silurian taxa from the province, and provides the first unequivocal evidence of Silurian oceanic sedimentation in the Dunnage Zone. The graptolite taxa include Rastrites peregrinus (Barrande), Coronograptus? sp. cf. C. gregarius (Lapworth), Monograptus austerus sequens Hutt?, Orthograptus insectiformis (Nicholson), Monograptus spp. indet., "Climacograptus"? sp., and Glyptograptus? sp. This assemblage demonstrates that the strata, previously assigned to the Middle Ordovician Lawrence Harbour Formation, are actually Aeronian (middle Llandovery) in age and that the turbidites considerably postdate both the Lawrence Harbour and Point Leamington formations of the Exploits Subzone. Furthermore, the graptolite fauna is similar to that found in coeval sediments in the United Kingdom and Scandinavia but unlike any assemblages known from elsewhere in North America. This suggests the presence of open oceanic conditions, or deep marginal basins during the Llandovery hosting graptolites with European affinities, and raises the possibility that at least part of the Iapetus Ocean was still open in central Newfoundland during Early Silurian times.

A new Middle Ordovician reef assemblage from north-central China and its palaeobiogeographical implications

2014 ◽  
Vol 310 ◽  
pp. 30-40 ◽  
Author(s):  
Mirinae Lee ◽  
Ning Sun ◽  
Suk-Joo Choh ◽  
Dong-Jin Lee
Keyword(s):  
Central China ◽  
North Central ◽  
Middle Ordovician

scholarly journals Detrital Zircon Geochronology Across the Chopawamsic Fault, Western Piedmont of North-Central Virginia: Implications for the Main Iapetan Suture in the Southern Appalachian Orogen

2014 ◽  
Vol 41 (4) ◽  
pp. 503 ◽  
Author(s):  
K. Stephen Hughes ◽  
James P. Hibbard ◽  
Jeffrey C. Pollock ◽  
David J. Lewis ◽  
Brent V. Miller
Keyword(s):  
Detrital Zircon ◽  
Volcanic Rocks ◽  
Detrital Zircons ◽  
Fault System ◽  
North Central ◽  
Middle Ordovician ◽  
Metasedimentary Rocks ◽  
Southern Appalachian ◽  
Icp Ms ◽  
Appalachian Orogen

The Chopawamsic fault potentially represents the main Iapetan suture, previously unidentified in the southern extent of the Appalachian orogen.  The fault trends through the north-central portion of the western Piedmont of Virginia and separates the composite metaclastic Potomac terrane, commonly interpreted to be of Laurentian affinity, from the Chopawamsic terrane, the remains of a Middle Ordovician volcanic arc of uncertain crustal affinity.  To gain insight on the first-order orogenic significance of the Chopawamsic fault, we report the results of LA–ICP–MS U–Pb analyses of 1,289 detrital zircons from 13 metasedimentary rock samples collected from both sides of the fault.       The near exclusivity of Middle Ordovician zircon grains (ca. 470 – 460 Ma) in four sampled metasedimentary rocks of the Chopawamsic Formation likely represents the detrital recycling of syndepositional Chopawamsic volcanic rocks.  A subset of Cambrian and older grains hint at one or more additional, older sources.       Samples from the Potomac terrane include mostly Mesoproterozoic zircon grains and these results are consistent with previous interpretations that the metaclastic rocks are Laurentian-derived.  The youngest zircons (ca. 550 – 500 Ma) and the age of cross-cutting plutons indicate that at least some parts of the Potomac terrane are Late Cambrian – Early Ordovician.  The results imply temporally discrete and geographically isolated sedimentary systems during deposition of sedimentary rocks in the Chopawamsic and Potomac terranes.       Metasedimentary rocks near Storck, Virginia, previously identified as a successor basin, contain detrital zircon populations that indicate they are actually peri-Gondwanan derived metasedimentary rocks unrelated to a successor basin system; their geographic position between the Laurentian-derived Potomac terrane and the Chopawamsic terrane suggests a peri-Gondwanan affinity for the Chopawamsic arc and geographic separation of the Chopawamsic and Potomac terranes in the Middle Ordovician. Consequently, we tentatively support the hypothesis that the Chopawamsic fault system represents the main Iapetan suture in the southern Appalachian orogen.      Most detrital zircons from samples of the Arvonia successor basin crystallized in the Ordovician—Silurian or Mesoproterozoic.  These data suggest that the Arvonia basin was deposited in the latest Ordovician to Early Silurian only after the Late Ordovician accretion of the Chopawamsic arc to Laurentia.  SOMMAIRELa faille de Chopawamsic représente peut-être la principale suture japétienne, non-reconnue dans prolongement sud de l’orogène des Appalaches.  La faille traverse la portion nord du centre du piedmont ouest de Virginie et sépare le terrane métaclastique de Potomac, d’affinité laurentienne pensait-on, du terrane de Chopawamsic, vestige d’un arc volcanique de l’Ordovicien moyen d’affinité crustale incertain.  Afin de mettre en lumière la signification orogénique première de la faille de Chopawamsic, nous présentons les résultats d’analyses U-Pb par ICP–MS par AL sur 1 289 zircons détritiques provenant de 13 échantillons de roches métasédimentaires prélevés de chaque côté de la faille.     L’existence quasi-exclusive de grains de zircon de l’Ordovicien moyen (env. 470 – 460 Ma) dans quatre roches métasédimentaires de la Formation de Chopawamsic représente vraisemblablement le recyclage détritique des roches volcaniques synsédimentaires de Chopawamsic.  Un sous-ensemble de grains cambriens et plus anciens, évoque l’existence d’une ou plusieurs sources plus anciennes additionnelles.     Les échantillons du terrane de Potomac renferment principalement des grains de zircon du Mésoprotérozoïque, ce qui correspond avec les interprétations antérieures voulant que les roches métaclastiques soient d’origine laurentienne.  Les zircons les plus jeunes (env. 550 – 500 Ma) ainsi que l’âge des plutons qui recoupe l’encaissant indiquent qu’au moins certaines parties du terrane de Potomac sont de la fin du Cambrien ou du début de l’Ordovicien.  Les résultats impliquent l’existence de systèmes sédimentaires distincts au cours du temps, et isolés géographiquement durant le dépôt des roches sédimentaires dans les terranes de Chopawamsic et de Potomac.     Les roches métasédimentaires près de Storck en Virginie, jadis interprétées comme bassin successeur, renferment des populations de zircons détritiques qui indiquent qu’ils proviennent en fait de roches métasédimentaires péri-gondwaniennes sans rapport avec un système de bassin successeur; leur localisation géographique entre le terrane de Potomac issu des Laurentides et le terrane de Chopawamsic porte à penser que l’arc de Chopawamsic est d’affinité péri-gondwanienne, et que les terranes de Chopawamsic et de Potomac à l’Ordovicien moyen étaient séparés géographiquement.   En conséquence il nous semble justifié de proposer que le système de faille de Chopawamsic représente la principale suture japétienne dans le sud de l’orogène des Appalaches.     La plupart des zircons détritiques des échantillons du bassin successeur d’Arvonia ont cristallisés entre l’Ordovicien et le Silurien ou au Mésoprotérozoïque.  Ces données suggèrent que le bassin d’Arvonia s’est rempli de la fin entre l’Ordovicien et le début du Silurien, seulement après l’accrétion de l’arc de Chopawamsic à la Laurentie, à la fin de l’Ordovicien.

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