scholarly journals Characteristics, distribution and diagenetic stages of chert in the La Silla Formation (Lower Ordovician), Argentine Precordillera

2009 ◽  
Vol 81 (4) ◽  
pp. 781-792 ◽  
Author(s):  
Mariana M. Raviolo ◽  
José A. Barbosa ◽  
Virgínio H. Neumann
Keyword(s):  
San Juan ◽  
Late Cambrian ◽  
Lower Ordovician ◽  
Argentine Precordillera ◽  
Diagenetic Evolution ◽  
Porous Sediments ◽  
Shallow Platform

The late Cambrian - late Tremadocian La Silla Formation is a carbonate unit of the eastern Precordillera in Argentina whose facies indicate a shallow platform environment. Until this moment, there were no studies that referred to the diagenetic evolution of these rocks. The present study involves the characteristics and distribution of the silicification that affects this unit and determines its different diagenetic stages through petrographic (with cathodoluminescence support) and stratigraphic analyses. An early diagenetic chert, in a stage previous to the compactation, was observed. This chert is related to silica-rich seawater in contact with permeable and porous sediments. A later pulse of chert, associated with fracturing, also occurs. The knowledge provided by the characteristics and distribution of chert in these carbonates is significant, especially when considering that the La Silla Formation in San Juan province is the most quarried unit for the elaboration of lime.

A new Late Cambrian pentastomid and a review of the relationships of this parasitic group

2005 ◽  
Vol 96 (2) ◽  
pp. 163-176 ◽  
Author(s):  
Dieter Waloszek ◽  
John E. Repetski ◽  
Andreas Maas
Keyword(s):  
Systematic Position ◽  
Host Group ◽  
Upper Cambrian ◽  
Late Cambrian ◽  
Lower Ordovician ◽  
Stem Lineage ◽  
New Form ◽  
Available Information ◽  
High Degree ◽  
Derivatives Of

ABSTRACTPentastomida, tongue worms, are a taxon of about 130 species of parasites, living exclusively in the respiratory tracts of vertebrates. Three-dimensionally preserved Upper Cambrian larvae already demonstrate a high degree of adaptation to parasitism, striking morphological conservatism, and a high diversification by the Late Cambrian, thereby suggesting a likewise diversified host group. Not least due to their highly modified morphology, the systematic affinities of pentastomids remain controversial. The two major alternatives place the group as either close to branchiuran crustaceans or as stem-lineage derivatives of the Euarthropoda. To this set of Cambrian fossil representatives of the pentastomids we can add a new form from Lower Ordovician boundary beds from Sweden, most likely reworked from Upper Cambrian horizons. Based on this new species, named Aengapentastomum andresi gen. et sp. nov., and the available information about fossil and Recent pentastomids, we review the diverging ideas on the systematic position of this fully parasitic taxon.

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.

Amsassia (calcareous alga) from the Lower Ordovician (Tremadocian) of western Newfoundland, and the biologic affinity and geologic history of the genus

2021 ◽  
pp. 1-18
Author(s):  
Dong-Jin Lee ◽  
Robert J. Elias ◽  
Brian R. Pratt
Keyword(s):  
South China ◽  
Geologic History ◽  
Shallow Marine ◽  
Middle Ordovician ◽  
Calcareous Alga ◽  
Tarim Block ◽  
Lower Ordovician ◽  
History Of ◽  
Argentine Precordillera ◽  
Extinct Group

Abstract Modular coral-like fossils from Lower Ordovician (Tremadocian) thrombolitic mounds in the St. George Group of western Newfoundland were initially identified as Lichenaria and thought to include the earliest tabulate corals. They are here assigned to Amsassia terranovensis n. sp. and Amsassia? sp. A from the Watts Bight Formation, and A. diversa n. sp. and Amsassia? sp. B from the overlying Boat Harbour Formation. Amsassia terranovensis n. sp. and A. argentina from the Argentine Precordillera are the earliest representatives of the genus. Amsassia is considered to be a calcareous alga, possibly representing an extinct group of green algae. The genus originated and began to disperse in the Tremadocian, during the onset of the Great Ordovician Biodiversification Event, on the southern margin of Laurentia and the Cuyania Terrane. It inhabited small, shallow-marine reefal mounds constructed in association with microbes. The paleogeographic range of Amsassia expanded in the Middle Ordovician (Darriwilian) to include the Sino-Korean Block, as well as Laurentia, and its environmental range expanded to include non-reefal, open- and restricted-marine settings. Amsassia attained its greatest diversity and paleogeographic extent in the Late Ordovician (Sandbian–Katian), during the culmination of the Great Ordovician Biodiversification Event. Its range included the South China Block, Tarim Block, Kazakhstan, and Siberia, as well as the Sino-Korean Block and Laurentia, and its affinity for small microbial mounds continued during that time. In the latest Ordovician (Hirnantian), the diversity of Amsassia was reduced, its distribution was restricted to non-reefal environments in South China, and it finally disappeared during the end-Ordovician mass extinction. UUID: http://zoobank.org/ef0abb69-10a6-46de-8c78-d6ec7de185fe

Early orthoceratoid cephalopods from the Argentine Precordillera (Lower-Middle Ordovician)

2007 ◽  
Vol 81 (6) ◽  
pp. 1266-1283 ◽  
Author(s):  
Björn Kröger ◽  
Matilde S. Beresi ◽  
Ed Landing
Keyword(s):  
New Species ◽  
Southern Hemisphere ◽  
North China ◽  
North China Block ◽  
Middle Ordovician ◽  
Strong Affinity ◽  
Middle Latitudes ◽  
The North ◽  
Lower Ordovician ◽  
Argentine Precordillera

The Early and Middle Ordovician Orthocerida and Lituitida of Precordilleran Argentina are described, and their systematics and paleogeographic significance are revised. These cephalopods show a strong affinity to coeval faunas of North China, suggesting a location of the Precordillera at middle latitudes in the Southern Hemisphere east of the North China block and relatively close to the Gondwanan margin during the early Middle Ordovician. The descriptive terminology of characters of the septal necks, the position and shape of the siphuncule, and the shape of the connecting ring is improved. The distribution of these characters support an emendation of the Baltoceratidae, Sactorthoceratidae, and Proteoceratidae. Braulioceras n. gen. (Sactorthoceratidae) and Palorthoceras n. gen. (Orthoceratidae) are erected. The new species Braulioceras sanjuanense, Eosomichelinoceras baldisii, Gangshanoceras villicumense, and Rhynchorthoceras minor are proposed. Palorthoceras n. gen. from the Lower Ordovician Oepikodus evae Zone represents the earliest known orthocerid.

Ordovician cheirurid trilobites from the Argentine Precordillera

1999 ◽  
Vol 73 (6) ◽  
pp. 1155-1175 ◽  
Author(s):  
Gregory D. Edgecombe ◽  
Brian D. E. Chatterton ◽  
Norberto E. Vaccari ◽  
Beatriz G. Waisfeld
Keyword(s):  
New Species ◽  
San Juan ◽  
Argentine Precordillera

New cheirurid trilobite species from the Las Aguaditas Formation in San Juan Province include the Llanvirn Macrogrammus rafi, and the Early Caradoc Ceraurinella zhoui, Nieszkowskia jakei, and N. yongyii. Precordilleran species, such as the Llanvirn Macrogrammus pengi new species from the Gualcamayo Formation, reinforce sinoparapilekiinid affinities for the poorly known Macrogrammus Whittard, 1966, although the monophyly of Sinoparapilekiini requires corroboration. The ontogeny of Ceraurinella zhoui confirms the presence of early protaspid stages for this genus (and Cheirurinae in general). Rare cheirurids include species of Heliomeroides, Pateraspis, and an additional acanthoparyphinid.

Systematics and paleoecology of Late Cambrian echinoderms from the western United States

1997 ◽  
Vol 71 (6) ◽  
pp. 1091-1109 ◽  
Author(s):  
Colin D. Sumrall ◽  
James Sprinkle ◽  
Thomas E. Guensburg
Keyword(s):  
United States ◽  
Great Basin ◽  
Rocky Mountains ◽  
New Genus ◽  
Western United States ◽  
New Genus And Species ◽  
Late Cambrian ◽  
Lower Ordovician ◽  
Single Piece ◽  
Low Diversity

Although echinoderm debris is locally common, articulated specimens are rare in Late Cambrian rocks from the Great Basin and Rocky Mountains of the western United States and are mostly associated with hardgrounds. The fauna, including cornute stylophorans, trachelocrinid eocrinoids, solute homoiosteleans, and rare edrioasteroids, includes several members of the archaic Cambrian Evolutionary Fauna, which had already passed its maximum diversity for echinoderms. In addition to the low diversity, articulated specimen abundance is very low, averaging only about one-tenth that found in overlying Lower Ordovician units. The transition between the Cambrian and Paleozoic Evolutionary Faunas for echinoderms in North America apparently occurred rapidly very close to the Cambrian-Ordovician boundary, because no unequivocal examples of the Paleozoic fauna (such as crinoids, glyptocystitid rhombiferans, asteroids, or echinoids) were found in the Late Cambrian sections.New taxa include several cothurnocystid stylophorans assigned to Acuticarpus delticus, new genus and species, Acuticarpus? republicensis, new species, and Archaeocothurnus goshutensis, new genus and species; Scotiaecystis? species, a poorly preserved cornute stylophoran with lamellipores; Minervaecystis? species, a fragmentary solute homoiostelean based on several steles; Tatonkacystis codyensis, new genus and species, a well-preserved trachelocrinid eocrinoid with five unbranched arms bearing numerous brachioles; an unnamed, poorly preserved, epispire-bearing eocrinoid; an unnamed, poorly preserved, globular eocrinoid? lacking epispires; and an unnamed, heavily weathered, edrioasterid edrioasteroid. Nearly all holdfasts found in these Upper Cambrian units are single-piece blastozoan types, probably belonging to trachelocrinid and other eocrinoids. Distinctive columnals and thecal plates of several additional undescribed eocrinoids and other echinoderms were locally abundant and are also described.

Upper Ordovician (Sandbian) bryozoan fauna from Argentine Precordillera

2012 ◽  
Vol 86 (5) ◽  
pp. 721-752 ◽  
Author(s):  
Andrej Ernst ◽  
Marcelo Carrera
Keyword(s):  
North America ◽  
San Juan ◽  
Growth Forms ◽  
Upper Ordovician ◽  
Argentine Precordillera

A stenolaemate bryozoan fauna containing 20 species belonging to 18 genera is described from the Las Plantas and Las Aguaditas formations (Upper Ordovician, Sandbian) in San Juan Province, Precordillera of Western Argentina. One genus with one species is new: Argentinodictya lenticulata n. gen. n. sp. (Cryptostomata, Ptilodictyina). Four species are new: one trepostome Parvohallopora parvula n. sp., two cryptostomes Trigonodictya parvula n. sp. and Ptilodictya intermedia n. sp., and phyloporinine Chasmatopora rossae n. sp. The bryozoan assemblage of the Las Plantas Formation is more diverse than that of the Las Aguaditas Formation. Fourteen species are restricted to the Las Plantas Formation, five species occur in both formations, and one species is restricted to the Las Aguaditas Formation. Erect growth forms are dominant in the studied fauna. The majority of bryozoan taxa display palaeobiogeographic relations to Sandbian–Katian deposits of North America, with two species also known from the Katian of Europe.

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.

Stiptognathus new genus (Conodonta: Ibexian, Lower Ordovician), and the apparatus of Stiptognathus borealis (Repetski, 1982)

2000 ◽  
Vol 74 (1) ◽  
pp. 92-100 ◽  
Author(s):  
R. L. Ethington ◽  
Oliver Lehnert ◽  
J. E. Repetski
Keyword(s):  
United States ◽  
Western Australia ◽  
Type Species ◽  
New Genus ◽  
Western United States ◽  
Canning Basin ◽  
Extant Genus ◽  
Lower Ordovician ◽  
Argentine Precordillera ◽  
The Individual

Collections from upper Ibexian (Tulean Stage) rocks of western United States, from the Canning Basin in western Australia, and from the Argentine Precordillera contain a seximembrate apparatus of multidenticulate conodonts whose elements have been included by authors in species of Prioniodus Pander, 1986, and Reutterodus Serpagli, 1974. The individual elements as well as the complete apparatus are not consistent with assignment of the species to either of these genera or to any other extant genus. A new generic name, Stiptognathus Ethington, Lehnert, and Repetski, is proposed with Reutterodus borealis Repetski, 1982, as type species. The apparatus consists of Pa, Pb, Sa-c, and M elements; the genus represents either the Prioniodontidae or the Periodontidae.

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