The Precambrian Shield and the Lower Paleozoic Shelf: The Unstable Provenance of the Lower Paleozoic Flysch Sandstones and Conglomerates of the Appalachians between Beaumont and Bic, Quebec

1974 ◽  
Vol 11 (7) ◽  
pp. 951-963 ◽  
Author(s):  
Jean Lajoie ◽  
Yvon Héroux ◽  
Bernard Mathey
Keyword(s):  
Flow Direction ◽  
Source Area ◽  
Mean Flow ◽  
Lower Paleozoic ◽  
Original Source ◽  
Early Ordovician ◽  
Late Cambrian ◽  
Lower Ordovician ◽  
Shelf Sediments ◽  
A Minor

Three sections of lower Paleozoic flysch in the Quebec Appalachians were sampled at Beaumont, Bic, and Trois Pistoles in order to determine the position, composition, and relief of the source area. At Beaumont, the mean flow direction of sediment transport is east-southeasterly; at Trois Pistoles and Bic it is south-southeasterly. Locally there is strong dispersion of the data but no northerly directions have been observed.Albite is the common plagioclase in all Cambrian sandstones; grains generally show polysynthetic twins, but in a few beds only untwinned albite is present. Oligoclase and andesine are the dominant plagioclases in Lower Ordovician rocks. The accessory suite has few diagnostic species; pink garnet is present in all sections, but absent in the basal unit at Bic. Diopside, sphalerite, and barite are found only in the Lower Ordovician rocks at Beaumont. At the three localities, the feldspar content, grain size, and sand/shale ratio vary up-section.The original source area for the sandstones and conglomerates consisted of an early Paleozoic shelf and a Precambrian land-mass. The oldest sands were derived from Precambrian metasediments, Paleozoic shelf sediments, Precambrian sodic plutons, and to a minor degree from gneisses. In Late Cambrian time the major contributors were sedimentary rocks of the shelf, sodic plutons, and gneisses. By Early Ordovician time most of the sands were derived from Grenvillian gneisses and shelf sedimentary rocks.The relief of the Grenvillian Orogenic Belt was high and denudation rapid from Early Cambrian to Late Cambrian, suggesting continuous, but irregular uplift. Uplift of the shelf began early in Cambrian, with major movements occurring in Late Cambrian when the Grenvillian source was rejuvenated. The source area was stabilized by Early Ordovician time.

New Monoplacophora (Mollusca) from Late Cambrian and Early Ordovician of Missouri

1986 ◽  
Vol 60 (3) ◽  
pp. 606-626 ◽  
Author(s):  
Bruce L. Stinchcomb
Keyword(s):  
New Species ◽  
New Genus ◽  
New Genera ◽  
New Genus And Species ◽  
Upper Cambrian ◽  
Early Ordovician ◽  
New Family ◽  
Late Cambrian ◽  
Lower Ordovician ◽  
A New Species

Fourteen new species and six new genera of the molluscan class Monoplacophora are described from the Upper Cambrian Potosi and Eminence formations and the Lower Ordovician Gasconade Formation of the Ozark Uplift of Missouri and some new biostratigraphic horizons are introduced. A new superfamily, the Hypseloconellacea nom. trans. Knight, 1956, and a new family, the Shelbyoceridae, are named. The genus Proplina is represented by five new species: P. inflatus, P. suttoni from the Cambrian Potosi Formation, P. arcua from the Cambrian Eminence Formation and P. meramecensis and P. sibeliusi from the Lower Ordovician Gasconade Formation. A new genus and species in the subfamily Proplininae, Ozarkplina meramecensis, is described from the Upper Cambrian Eminence Formation. Four new monoplacophoran genera in the superfamily Hypseloconellacea and their species are described, including: Cambrioconus expansus, Orthoconus striatus, Cornuella parva from the Eminence Formation, and Gasconadeoconus ponderosa, G. waynesvillensis, G. expansus from the Gasconade Formation. A new genus in the new family Shelbyoceridae, Archeoconus missourensis, is described from the Eminence Formation and a new species of Shelbyoceras, S. bigpineyensis, is described from the Gasconade Formation.

scholarly journals A missing link in the peri-Gondwanan terrane collage: the Precambrian basement of the Moroccan Meseta and its lower Paleozoic cover

2018 ◽  
Vol 55 (1) ◽  
pp. 33-51 ◽  
Author(s):  
Dominik Letsch ◽  
Mohamed El Houicha ◽  
Albrecht von Quadt ◽  
Wilfried Winkler
Keyword(s):  
Carbonate Platform ◽  
Source Area ◽  
Source Rocks ◽  
Lower Paleozoic ◽  
Northern Margin ◽  
Precambrian Geology ◽  
The North ◽  
Late Cambrian ◽  
Paleozoic Rocks ◽  
Rifted Margin

This article provides stratigraphic and geochronological data from a central part of Gondwana’s northern margin — the Moroccan Meseta Domain. This region, located to the north of the Anti-Atlas area with extensive outcrops of Precambrian and lower Paleozoic rocks, has hitherto not received much attention with regard to its Precambrian geology. Detrital and volcanic zircon ages have been used to constrain sedimentary depositional ages and crustal affinities of sedimentary source rocks in stratigraphic key sections. Based on this, a four-step paleotectonic evolution of the Meseta Domain from the Ediacaran until the Early Ordovician is proposed. This evolution documents the transition from a terrestrial volcanic setting during the Ediacaran to a short-lived carbonate platform setting during the early Cambrian. The latter then evolved into a rifted margin with deposition of thick siliciclastic successions in graben structures during the middle to late Cambrian. The detritus in these basins was of local origin, and a contribution from a broader source area (encompassing parts of the West African Craton) can only be demonstrated for postrifting, i.e., laterally extensive sandstone bodies that seal the former graben. In a broader paleotectonic context, it is suggested that this Cambrian rifting is linked to the opening of the Rheic Ocean, and that several peri-Gondwanan terranes (Meguma and Cadomia–Iberia) may have been close to the Meseta Domain before drifting, albeit some of them seem to have been constituted by a distinctly different basement.

A revision of the stratigraphic nomenclature of the Cambrian–Ordovician strata of the Philipsburg tectonic slice, southern Quebec

2007 ◽  
Vol 44 (12) ◽  
pp. 1775-1790 ◽  
Author(s):  
O Salad Hersi ◽  
G S Nowlan ◽  
D Lavoie
Keyword(s):  
Middle Ordovician ◽  
Upper Cambrian ◽  
Early Ordovician ◽  
Late Cambrian ◽  
Lower Ordovician ◽  
Stratigraphic Position ◽  
Stratigraphic Nomenclature ◽  
Unconformable Contact ◽  
Tectonic Slice ◽  
Upper Boundary

The Philipsburg tectonic slice is bounded to the west by a northeast–southwest-trending thrust fault (Logan’s Line) and preserves 10 formations of Middle (?) to Late Cambrian (Milton, Rock River, and Strites Pond formations), Early Ordovician (Wallace Creek, Morgan Corner, Hastings Creek, and Naylor Ledge formations), and early Middle Ordovician (Luke Hill, Solomons Corner, and Corey formations) age. The strata were previously assigned to the Philipsburg Group. Early correlations between the Philipsburg succession and coeval strata of the St. Lawrence Platform were mainly based on sparse macrofauna and inferred stratigraphic position. Unconformities at the Cambrian–Ordovician and Early Ordovician – Middle Ordovician boundaries occurring in autochthonous St. Lawrence Platform and the allochthonous Philipsburg succession (Philipsburg tectonic slice) highlight new stratigraphic interpretations between the inner-shelf (St. Lawrence Platform) and the outer-shelf (Philipsburg) successions. The succession in the Philipsburg tectonic slice is divided into three new groups. The Middle (?) to Upper Cambrian Missisquoi Group (new) includes the Milton, Rock River, and Strites Pond formations. The upper boundary of the Missisquoi Group is defined by the upper unconformable contact between the Upper Cambrian Strites Pond Formation and overlying Lower Ordovician Wallace Creek Formation. The Missisquoi Group correlates with the Potsdam Group of the St. Lawrence Platform. The Lower Ordovician School House Hill Group (new) includes the Wallace Creek, Morgan Corner, Hastings Creek, and Naylor Ledge formations. The upper boundary of this group is marked by a regionally extensive unconformity at the top of the Naylor Ledge Formation and correlates with the younger Beekmantown-topping unconformity. The School House Hill Group is correlative with the lower to upper part of the Beekmantown Group (Theresa Formation and the Ogdensburg Member of the Beauharnois Formation) of the St. Lawrence Platform. The Middle Ordovician Fox Hill Group (new) consists of the Luke Hill, Solomons Corner, and Corey formations. This group correlates with the uppermost part of the Beekmantown Group (Huntingdon Member of the Beauharnois Formation and the Carillon Formation).

On the non-existence of a Cadomian basement in southern France (Pyrenees, Montagne Noire): implications for the significance of the pre-Variscan (pre-Upper Ordovician) series

2004 ◽  
Vol 175 (6) ◽  
pp. 643-655 ◽  
Author(s):  
Bernard Laumonier ◽  
Albert Autran ◽  
Pierre Barbey ◽  
Alain Cheilletz ◽  
Thierry Baudin ◽  
...  
Keyword(s):  
Lower Cambrian ◽  
Classical Model ◽  
Black Shales ◽  
High Grade ◽  
Upper Ordovician ◽  
Lower Paleozoic ◽  
Early Ordovician ◽  
Lower Ordovician ◽  
Montagne Noire ◽  
Back Arc

Abstract The deepest Hercynian metamorphic terrains in the Pyrenees and in the nearby Montagne Noire are made up of medium-grade orthogneisses and micaschists, and of high-grade, often granulitic, paragneisses. The existence of a granitic-metamorphic Cadomian basement and of its sedimentary Lower Paleozoic cover was advocated from the following main arguments: (i) a supposed unconformity of the Lower Cambrian Canaveilles Group (the lower part of the Paleozoic series) upon both granitic and metamorphic complexes; (ii) a ca. 580 Ma U-Pb age for the metagranitic Canigou gneisses. A SE to NW transgression of the Cambrian cover and huge Variscan recumbent (“penninic”) folds completed this classical model. However, recent U-Pb dating provided a ca. 474 Ma, early Ordovician (Arenigian) age for the me-tagranites, whereas the Vendian age (581 ± 10 Ma) of the base of the Canaveilles Group was confirmed [Cocherie et al., 2005]. In fact, these granites are laccoliths intruded at different levels of the Vendian-Lower Cambrian series. So the Cadomian granitic basement model must be discarded. In a new model, developed in the Pyrenees and which applies to the Montagne Noire where the orthogneisses appear to be Lower Ordovician intrusives too, there are neither transgression of the Paleozoic nor very large Hercynian recumbent folds. The pre-Variscan (pre-Upper Ordovician) series must be divided in two groups: (i) at the top, the Jujols Group, mainly early to late Cambrian, that belongs to a Cambrian-Ordovician sedimentary and magmatic cycle ; the early Ordovician granites pertain to this cycle; (ii) at the base, the Canaveilles Group of the Pyrenees and the la Salvetat-St-Pons series of the Montagne Noire, Vendian (to earliest Cambrian?), are similar to the Upper Alcudian series of Central Iberia. The Canaveilles Group is a shale-greywacke series with rhyodacitic volcanics, thick carbonates, black shales, etc. The newly defined olistostromic and carbonated, up to 150 m thick Tregurà Formation forms the base of the Jujols Group, which rests more or less conformably on the Canaveilles Group. The high-grade paragneisses which in some massifs underlie the Canaveilles and Jujols low- to medium grade metasediments are now considered to be an equivalent of the Canaveilles Group with a higher Variscan metamorphic grade; they are not derived from metamorphic Precambrian rocks. So, there is no visible Cadomian metamorphic (or even sedimentary) basement in the Pyrenees. However, because of its age, the Canaveilles Group belongs to the end of the Cadomian cycle and was deposited in a subsident basin, probably a back-arc basin which developed in the Cadomian, active-transform N-Gondwanian margin of this time. The presence of Cadomian-Panafrican (ca. 600 Ma) zircon cores in early Ordovician granites and Vendian volcanics implies the anatexis of a thick (> 15 km?) syn-Cadomian series, to be compared to the very thick Lower Alcudian series of Central Iberia, which underlies the Upper Alcudian series. Nd isotopic compositions of Neoproterozoic and Cambrian-Ordovician sediments and magmatites, as elsewhere in Europe, yield Paleoproterozoic (ca. 2 Ga) model-ages. From the very rare occurrences of rocks of this age in W-Europe, it can be envisionned that the thick Pyrenean Cadomian series lies on a Paleoproterozoic metamorphic basement. But, if such a basement does exist, it must be “hidden”, as well as the lower part of the Neoproterozoic series, in the Variscan restitic granulites of the present (Variscan) lower crust. So a large part of the pre-Variscan crust was made of volcano-sedimentary Cadomian series, explaining the “fertile” characteristics of this crust which has been able to produce the voluminous Lower Ordovician and, later, Upper Carboniferous granitoids.

A new aglaspidid euarthropod with a six-segmented trunk from the Lower Ordovician Fezouata Konservat-Lagerstätte, Morocco

2015 ◽  
Vol 153 (3) ◽  
pp. 524-536 ◽  
Author(s):  
JAVIER ORTEGA-HERNÁNDEZ ◽  
PETER VAN ROY ◽  
RUDY LEROSEY-AUBRIL
Keyword(s):  
Phylogenetic Relationship ◽  
New Genus ◽  
Taxonomic Revision ◽  
Morphological Disparity ◽  
Early Ordovician ◽  
Late Cambrian ◽  
Lower Ordovician ◽  
Group A

AbstractA new euarthropod with an uncommon morphology, Brachyaglaspis singularis gen. et sp. nov., is described from the Early Ordovician (middle Floian) Fezouata biota of Morocco. The presence of a pair of postventral plates, widely attached to each other and located under the posterior-most trunk tergite and the base of the tailspine, indicates a phylogenetic relationship with the enigmatic group Aglaspidida. The overall morphology of Brachyaglaspis most closely resembles that of the ‘Ordovician-type’ aglaspidids, more specifically the late Cambrian – Early Ordovician genus Tremaglaspis. However, the presence of a prominent cephalon and only six trunk tergites in the new genus deviates from the organization of all other known aglaspidid species, notably extending the known range of morphological disparity of the group. A taxonomic revision of this euarthropod group indicates that the most accurate name and authorship combination correspond to Aglaspidida Walcott, 1912.

scholarly journals A miniature Ordovician hurdiid from Wales demonstrates the adaptability of Radiodonta

2020 ◽  
Vol 7 (6) ◽  
pp. 200459 ◽  
Author(s):  
Stephen Pates ◽  
Joseph P. Botting ◽  
Lucy M. E. McCobb ◽  
Lucy A. Muir
Keyword(s):  
Diverse Group ◽  
Apex Predators ◽  
Total Group ◽  
Early Ordovician ◽  
Late Cambrian ◽  
Stem Group ◽  
Lower Ordovician ◽  
Filter Feeders ◽  
The Uk

Originally considered as large, solely Cambrian apex predators, Radiodonta—a clade of stem-group euarthropods including Anomalocaris— now comprises a diverse group of predators, sediment sifters and filter feeders. These animals are only known from deposits preserving non-biomineralized material, with radiodonts often the first and/or only taxa known from such deposits. Despite the widespread and diverse nature of the group, only a handful of radiodonts are known from post-Cambrian deposits, and all originate from deposits or localities rich in other total-group euarthropods. In this contribution, we describe the first radiodont from the UK, an isolated hurdiid frontal appendage from the Tremadocian (Lower Ordovician) Dol-cyn-Afon Formation, Wales, UK. This finding is unusual in two major aspects: firstly, the appendage (1.8 mm in size) is less than half the size of the next smallest radiodont frontal appendage known, and probably belonged to an animal between 6 and 15 mm in length; secondly, it was discovered in the sponge-dominated Afon Gam Biota, one of only a handful of non-biomineralized total-group euarthropods known from this deposit. This Welsh hurdiid breaks new ground for Radiodonta in terms of both its small size and sponge-dominated habitat. This occurrence demonstrates the adaptability of the group in response to the partitioning of ecosystems and environments in the late Cambrian and Early Ordovician world.

Upper Cambrian and Lower Ordovician conodont biostratigraphy and revised lithostratigraphy, Boothia Peninsula, Nunavut

2020 ◽  
Vol 57 (9) ◽  
pp. 1030-1047
Author(s):  
Shunxin Zhang
Keyword(s):  
Field Investigation ◽  
Limited Data ◽  
Upper Cambrian ◽  
Early Ordovician ◽  
Late Cambrian ◽  
Lower Ordovician ◽  
Conodont Zone ◽  
Stratigraphic Position ◽  
American Standard ◽  
A New Species

The strata exposed along Lord Lindsay River on southern Boothia Peninsula were previously named the Netsilik Formation, and then recognized as the Turner Cliffs Formation; the interpretation of the age and correlation was based on limited data. New detailed field investigation at 23 localities along the section resulted in the discovery of over 640 identifiable conodont specimens, with 35 species representing 16 genera, among which a new species, Rossodus? boothiaensis sp. nov., is recognized. Five North American standard conodont zone/subzone-equivalent faunas are documented from the section, namely the Hirsutodontus hirsutus Subzone-equivalent, Cordylodus angulatus, Rossodus manitouensis, Acodus deltatus/Oneotodus costatus and Oepikodus communis Zone-equivalent faunas. These faunas enable a new understanding of the age and stratigraphic position of the Netsilik and Turner Cliffs formations on southern Boothia Peninsula. The Netsilik Formation can be correlated with the lower member (except for the lowest part) and upper member of the Turner Cliffs Formation; the previously unmeasured upper part of the section can be associated with the lower Ship Point Formation. Based on the new conodont data, these three units are dated as early Age 10, late Cambrian to middle Tremadocian, Early Ordovician; late Tremadocian, Early Ordovician; and early Floian, Early Ordovician, respectively. This study fills a gap in upper Cambrian and Lower Ordovician biostratigraphy on Boothia Peninsula, and links the regional biostratigraphy to that of Laurentia.

scholarly journals The conodont genusTeridontus(Miller, 1980) from the Early Ordovician of Montagne Noire, France

2008 ◽  
Vol 82 (3) ◽  
pp. 612-620 ◽  
Author(s):  
Enrico Serpagli ◽  
Annalisa Ferretti ◽  
Robert S. Nicoll ◽  
Paolo Serventi
Keyword(s):  
Northeast China ◽  
Upper Cambrian ◽  
Early Ordovician ◽  
Late Cambrian ◽  
Lower Ordovician ◽  
The World ◽  
Montagne Noire

The conodont genus Teridontus was introduced in 1980 by Miller and was based on the Late Cambrian species Oneotodus nakamurai Nogami, 1967 from the Yencho Member of the Fengshan Fm. of northeast China. Teridontus was later reported from either the Upper Cambrian or Lower Ordovician (Landing et al., 1980; Miller, 1980; Landing and Barnes, 1981; Landing, 1983; An et al., 1983, 1985; Ni et al., 1983; Peng et al., 1983; Nowlan, 1985; Landing et al., 1986; Bagnoli et al., 1987; An, 1987; Buggisch and Repetski, 1987; Pohler and Orchard, 1990; An and Zheng, 1990; Seo and Ethington, 1993; Wang, 1993; Lehnen, 1994; Nicoll, 1994; Seo et al., 1994; Ji and Barnes, 1994; Taylor et al., 1996; Lehnert et al., 1997; Jia, 2000; Dubinina, 2000; Pyle and Barnes, 2002; Zeballo et al., 2005) sediments in numerous localities around the world, but a unanimous interpretation of the composition of the Teridontus apparatus organization was far from accepted.

Early Ordovician alkali-ultramafic Zhilandy complex (Central Kazakhstan): structure and age of formation

2019 ◽  
Vol 484 (1) ◽  
pp. 61-65
Author(s):  
R. M. Antonuk ◽  
A. A. Tretyakov ◽  
K. E. Degtyarev ◽  
A. B. Kotov
Keyword(s):  
Complex Formation ◽  
Central Asian Orogenic Belt ◽  
Early Cambrian ◽  
Early Ordovician ◽  
Late Cambrian ◽  
Central Asian ◽  
Geochronological Study ◽  
Three Stages ◽  
Late Neoproterozoic ◽  
Quartz Monzodiorites

U–Pb geochronological study of amphibole-bearing quartz monzodiorites of the alkali-ultramafic Zhilandy complex in Central Kazakhstan, whose formation is deduced at the Early Ordovician era (479 ± 3 Ma). The obtained data indicate three stages of intra-plate magmatism in the western part of the Central Asian Orogenic Belt: Late Neoproterozoic stage of alkali syenites of the Karsakpay complex intrusion, Early Cambrian stage of ultramafic-gabbroid plutons of the Ulutau complex formation, and Late Cambrian–Early Ordovician stage of formation of the Zhilandy complex and Krasnomay complex intrusions.

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