scholarly journals Darriwilian (Middle Ordovician) conodonts and graptolites from the Cerro La Chilca Section, Central Precordillera, Argentina

2020 ◽  
Vol 47 (1) ◽  
pp. 125 ◽  
Author(s):  
Fernanda Serra ◽  
Nicolás A. Feltes ◽  
Matías Mango ◽  
Miles A. Henderson ◽  
Guillermo L. Albanesi ◽  
...  
Keyword(s):  
Taxonomic Composition ◽  
Black Shales ◽  
San Juan ◽  
Present Contribution ◽  
Stratigraphic Sequence ◽  
Middle Ordovician ◽  
The North ◽  
Calcareous Shale ◽  
Generic Composition ◽  
Conodont Fauna

The Ordovician System is extensively represented in the Precordillera of San Juan Province, Argentina. At the Cerro La Chilca in the Jáchal area, the limestone of the San Juan Formation is paraconformably overlain by interbedded limestone and shale of the Gualcamayo Formation. The present contribution reports new data on the conodont fauna and biostratigraphy of these darriwilian units, revising local and regional chronostratigraphic relationships. New information on the composition of conodont and graptolite associations through the stratigraphic sequence is presented. The presence of Paroistodus horridus horridus, Yangtzeplacognathus crassus, and Histiodella sinuosa constrain the uppermost strata of the San Juan Formation to the lower part of the Y. crassus Zone, according to the Baltoscandian scheme, and to the H. sinuosa Subzone of the Periodon macrodentatus Zone of the North American scheme. In the overlying Gualcamayo Formation the co-occurrence of Y. crassus with Histiodella holodentata enable the recognition of the Y. crassus Zone and the H. holodentata Subzone of the P. macrodentatus Zone. The identification of these zones allows for precise global and regional correlation. A graptolite assemblage that belongs to the epipelagic and deep-water biotopes with some components restricted to low paleolatitudes is recognized. This diverse assemblage is characteristic of the pelagic biofacies. The important diversity of graptolites in this section suggests a favorable environment for their development. Local changes in the taxonomic composition are recognized through the Gualcamayo Formation. When comparing this fauna with that of different study localities from the Central Precordillera (Cerro Potrerillo, Oculta Creek, Cerro Viejo de Huaco and Las Aguaditas Creek) slight differences in the generic composition are observed. Taxonomic differences support the preference of certain associations for particular environments; though, graptolites are more diverse in black shales facies, which represent deeper environments (the Los Azules Formation), in relation to the calcareous-shale facies of the Gualcamayo Formation from Cerro La Chilca and correlative unit at Las Aguaditas Creek.

Subspeciation within a punctuated equilibrium evolutionary event: Phylogenetic history of the Lower-Middle Ordovician Paroistodus originalis—P. horridus complex (Conodonta)

2000 ◽  
Vol 74 (3) ◽  
pp. 492-502
Author(s):  
Guillermo L. Albanesi ◽  
Christopher R. Barnes
Keyword(s):  
Carbonate Platform ◽  
Black Shales ◽  
San Juan ◽  
Carbonate Production ◽  
Middle Ordovician ◽  
Lower Member ◽  
Speciation Event ◽  
Restricted Environment ◽  
Evolutionary Event ◽  
Middle Member

A microevolutionary event involving the conodont Paroistodus lineage is documented in the Gualcamayo Formation (Middle Ordovician), Argentine Precordillera. A detailed sampling of limestones throughout the upper part of the San Juan Formation and the lower member of the Gualcamayo Formation yielded over 14,000 well-preserved conodont elements. Paroistodus originalis (Sergeeva, 1963) was recorded through the upper 230 m of the San Juan Formation and the lower member (10 m thick) of the Gualcamayo Formation. The derived species Paroistodus horridus (Barnes and Poplawski, 1973) was recorded throughout the middle member of the Gualcamayo Formation (65 m thick). The intermediate linking forms between both species are identified as two new taxa: Paroistodus horridus primus Albanesi, 1998b, and P. h. secundus Albanesi, 1998b. They were recorded in the uppermost 70 cm of the lower member. Apparently, the speciation event occurred under stressed environmental conditions with the drowning of the carbonate platform, i.e., the San Juan Formation, and the beginning of a deeper and restricted environment represented by the Gualcamayo black shales. The demise of the carbonate production was caused by a sea level rise and a significant influx of volcanic ashes. The punctuated speciation event occurred within an allopatric setting while the Precordillera occupied an isolated (Iapetus) oceanic position in its overall drift from Laurentia to Gondwana.

Integrated chitinozoan, conodont, and graptolite biostratigraphy from the upper part of the Cape Cormorant Formation (Middle Ordovician), western Newfoundland

2001 ◽  
Vol 38 (3) ◽  
pp. 387-409 ◽  
Author(s):  
Roberto Albani ◽  
Gabriella Bagnoli ◽  
Jörg Maletz ◽  
Svend Stouge
Keyword(s):  
Early Stage ◽  
Foreland Basin ◽  
Black Shales ◽  
Head Group ◽  
Middle Ordovician ◽  
Head Groups ◽  
Taconic Orogeny ◽  
Low Diversity ◽  
Conodont Fauna ◽  
Abundance And Diversity

The Cape Cormorant Formation of the Table Head Group exposed on the Port au Port Peninsula, western Newfoundland, is composed of dark-brown to black shales with interbeds of thin calcareous silty and sandy distal turbidites. Distinctive carbonate conglomerates and breccias derived from the foundering shelf are occasionally found in the formation. The sediments accumulated in the foreland basin formed during the early stage of the Taconic orogeny. The faunas from the upper part of the Cape Cormorant Formation include graptolites, conodonts, and chitinozoans. The graptolites are well preserved, but are of low diversity and are referred to the Darriwil Pterograptus elegans Zone. Conodonts recorded from the distal turbidites are rare and fragmented. The faunas include taxa that are known from the St. George and Table Head groups. The conodont fauna is tentatively assigned to the Histiodella kristinae Phylozone and to the younger, unzoned interval. The chitinozoans are well preserved and the yield is high. The fauna is assigned to the Cyathochitina jenkinsi Zone and to an undefined interval. The abundance and diversity of the chitinozoan assemblages display a cyclic pattern, which is related to changes of the oceanic watermass in the foreland basin. The new chitinozoan species Belonechitina nevillensis n. sp., Belonechitina uniformipunctata n. sp., and Cyathochitina cormorani n. sp. are described.

scholarly journals Bioestratigrafía y provincialismo de conodontes del tramo medio-superior de la Formación San Juan en el cerro Viejo de Huaco, Precordillera, Argentina

2018 ◽  
Vol 45 (2) ◽  
pp. 274 ◽  
Author(s):  
Matías J. Mango ◽  
Guillermo L. Albanesi
Keyword(s):  
North Atlantic ◽  
Species Level ◽  
San Juan ◽  
Insufficient Information ◽  
Entire Interval ◽  
Middle Ordovician ◽  
The North ◽  
Atlantic Province ◽  
The North Atlantic ◽  
Color Alteration

The present study deals with the conodont biostratigraphy from the middle and upper parts of the San Juan Formation (Lower-Middle Ordovician) exposed at the Los Gatos creek section, west of the cerro Viejo de Huaco, Central Precordillera of San Juan Province. The numerous conodonts recovered, corresponding to 55 species, allow to recognize a series of biozones in the studied section. The biostratigraphic analysis carried out herein allows determining associations of conodonts assignable to the Oepikodus evae, Oepikodus intermedius, Baltoniodus triangularis-Tripodus laevis and Lenodus variabilis zones that correspond to the middle Floian to lower Darriwilian. The Baltoniodus navis and Microzarkodina parva zones were not identified due to insufficient information provided by this stratigraphic section. In general, the levels corresponding to the Baltoniodus triangularis-Tripodus laevis Zone contain more conodonts, than the records of other localities from Precordillera. These specimens are well preserved with a color alteration index (CAI) of 2-2.5, indicating overburden paleotemperatures ranging from 60° and 155° C. The large presence of fragmented conodonts, with recrystallized surfaces and crystal overgrowth, could indicate the effect of distinctive diagenetic fossil processes on the bearer limestone. The analysis of the diversity and abundance of genera and species of conodonts by chronostratigraphic intervals presents a great percentage of cosmopolitan taxa, 18% and 38% in common, at species level, only with the North-American Midcontinent Province (NAMP), and with a small percentage with the North-Atlantic Province (NAP) and the Precordillera, which allows to approximate a greater paleobiogeographic affinity of the conodonts recovered with those of the NAMP than those of the NAP for the entire interval studied. On the other hand, the Precordillera is verified as a province with its own characteristics as identified by several authors.

Tectonic-sedimentary evolution of the frontal part of the Ukrainian Carpathian nappe structure

2021 ◽  
Vol 1-2 (183-184) ◽  
pp. 45-59
Author(s):  
Oleh Hnylko ◽  
Svitlana Hnylko ◽  
Maria Kulyanda ◽  
Romana Marchenko
Keyword(s):  
Deep Water ◽  
Taxonomic Composition ◽  
Black Shales ◽  
Carpathian Basin ◽  
Foraminiferal Assemblage ◽  
The North ◽  
Sedimentary Evolution ◽  
North Eastern ◽  
Compensation Depth ◽  
Latest Eocene

For the first time in the Ukrainian Carpathians, the depths and tectono-sedimentation processes in the north-eastern part of the Outer Carpathian Basin (Skyba and Boryslav-Pokuttya units) have been restored on the base of sedimentological and microfaunistic studies. It was established that in the Cretaceous-Eocene time, the deep-water (near Calcite Compensation Depth) turbidite and similar sedimentation (turbidites with Bouma textures, grainites, debris-flow deposits), which periodically alternated with (hemi)pelagic sedimentation (red, green and black shales) was dominant here. Sedimentation took place on the continental margin of the the Carpathian branch of the Tethys, where deep-water fans were formed. Cretaceous-Eocene background red and green shales are enriched in buried in situ benthic foraminifera which are similar in taxonomic composition and morphological features to the microfauna of the Carpathian-Alpine and Atlantic regions (deep-water agglutinated foraminifera), which indicate lower bathyal – abyssal depths of flysch sedimentation. Latest Eocene Globigerina Marl horizon contains the foraminiferal assemblage with plankton dominance, which indicates a general shallowing of the Outer Carpathian Basin (middle-upper bathyal conditions above a calcite compensation depth). Oligocene – lowermost Miocene Menilite-Krosno and Polyanytsia formations were accumulated in the Skyba and Boryslav-Pokuttya sub-basins. In the Miocene, shallow-water molasses were accumulated here. Probably, the tectonic uproot of flysch deposits from its substrate and their synsedymentary thrusting towards the platform caused a significant shallowing of the Skyba and Boryslav-Pokuttya sub-basins starting from the latest Eocene. These processes reflected the growth of the Carpathian frontal nappes at the final orogen formation stage.

Conodont biostratigraphy of Upper Silurian formations from the Rabat-Tiflet area (northwestern Meseta, Morocco)

2003 ◽  
Vol 174 (4) ◽  
pp. 337-342 ◽  
Author(s):  
El Mostafa Benfrika ◽  
Mohamed Raji
Keyword(s):  
North America ◽  
Lower Boundary ◽  
Black Shales ◽  
Present Contribution ◽  
Carnic Alps ◽  
The North ◽  
Index Species ◽  
Conodont Zonation ◽  
First Occurrence ◽  
Devonian Age

Abstract Silurian sections from the Rabat-Tiflet area (northwestern Moroccan Meseta) have been systematically sampled for conodonts. The conodont faunas are characterized by two index species of the European Silurian zonation (Ozarkodina sagitta sagitta and Ozarkodina remsceidensis eosteinhornensis) and two other index species of the north American zonation (Kockelella stauros and Kockelella variabilis). Recognition of the sagitta/stauros through lower variabilis zones in the lower part of the Silurian limestone and shale succession from the Rabat-Tiflet area, proves for the first time the presence of Wenlock below Ludlow-Pridoli, in the Silurian sequences of this area. Most of the Silurian from the northwestern Moroccan Meseta is represented by black graptolitic shales with intercalations of limestone (beds or lenses) in its upper part. The Silurian biostratigraphy of Morocco is generally based on graptolites [Willefert in Destombes et al., 1985]. In the present contribution the age of some Silurian sections (fig. 3) from the Rabat-Tiflet area is re-assessed by using conodonts. The stratigraphically important taxa have been described in Benfrika [1999]. Section Oued Grou I (G I) Situated near the barrage Mohamed Ben Abdellah, this section shows 30 m of alternating black shales and limestones. The lower part of this unit (I) provided : Ozarkodina sagitta sagitta, Kockelella absidata, Kockelella stauros, Ozarkodina bohemica, Ozarkodina excavata, Dapsilodus obliquicostatus, Panderodus unicostatus, Pseudooneotodus bicornis. The first appearance of Oz. sagitta sagitta and the K. stauros indicates the lower boundary of sagitta Zone established by Walliser [1964] in the Carnic Alps and also the lower boundary of stauros Zone proposed by Barrick et Klapper [1976] for North America (fig. 2). These species are of Wenlock age. Section Oued Grou II (G II): This section is located at approximately a hundred meters north of the preceding section. It is subdivided into 2 units : Unit IIA : 12 m of greyish to black limestones interbedded with green shales ; Unit IIB : 65 m of shales interbedded with some limestones. The conodonts identified in unit A are : Ozarkodina bohemica, Kockelella absidata and Kockelella stauros. This fauna is of Wenlock age. The first occurrence of Kockelella variabilis in sample indicates the lower variablis zone (lower part of Ludlow). Section Al Khaloua Iron Mines (AK) The limestones interbedded with shales of the lower part of the Al Khaloua section yield Polygnathoides emarginatus and Kockelella variabilis. This association is of Ludlow age. The conodonts from the upper part of this section (Caudicriodus sp. and Belodella devonica) indicate a Lower Devonian age. Section Oued Tiflet syncline (T) Two units are recognized : Unit A : 18 m of alternating black shales and greyish black limestones providing : Kockelella absidata, Ozarkodina bohemica, Decoriconus fragilis, Dapsilodus obliquicostatus, Ozarkodina excavata. This fauna is of Upper Wenlock to Lower Ludlow age ; Unit B : 34 m of black shales with some limestone intercalations, is probably of Ludlow-Pridoli age. Conclusion The Silurian conodont succession recognized in the Rabat-Tiflet area (northwestern Moroccan Meseta) allows to attribute the lower part of alternating limestones and shales to the Wenlock and the upper part to the Ludlow-Pridoli. The presence of the Wenlock in the Rabat-Tiflet area and also in the Oued Cherrat (under investigation) is demonstrated by conodonts. This suggests that the Silurian transgression has reached this area of the Moroccan Meseta during the Wenlock and not the Ludlow, as generally admitted. Furthermore, the conodont faunas allow to recognize affinities with those from North America and Central Europe. Two index species of the conodont zonation established by Walliser [1964] for the Carnic Alps have been recognized in Morocco, two other index species of the conodont zonation proposed by Barrick and Klapper [1976] for North America have been also identified in Morocco.

scholarly journals Conodont biostratigraphy and global correlation of the middle Darriwilian-lower Sandbian (Ordovician) Las Aguaditas Formation, Precordillera of San Juan, Argentina

2016 ◽  
Vol 43 (1) ◽  
pp. 60 ◽  
Author(s):  
Nicolás A. Feltes ◽  
Guillermo L. Albanesi ◽  
Stig M. Bergström
Keyword(s):  
North American ◽  
Recovery Phase ◽  
San Juan ◽  
Conodont Biostratigraphy ◽  
Middle Ordovician ◽  
Study Section ◽  
The North ◽  
Global Correlation ◽  
Low Diversity ◽  
Argentine Precordillera

Middle Darriwilian to lower Sandbian conodonts were recorded from the Las Aguaditas Formation at its type section in the Argentine Precordillera. A total of 9,974 conodont specimens were recovered from 46 carbonate samples, which represent 68 species of 38 genera. A biostratigraphic study verified a middle Darriwilian age for the interval spanning the contact between the San Juan and the Las Aguaditas formations. The following zones are determined in the study section: the Lenodus variabilis Zone, with the Periodon gladysae and Paroistodus horridus subzones following the Precordilleran scheme; the L. variabilis, Yangtzeplacognathus crassus, and the Eoplacognathus pseudoplanus zones with the Microzarkodina hagetiana and M. ozarkodella subzones, and the Pygodus anserinus Zone, according to the Scandinavian scheme; the Periodon macrodentatus Zone, with the Histiodella sinuosa, H. holodentata and H. cf. holodentata subzones, and the P. zgierzensis Zone with the H. kristinae Subzone that correlates the North American scheme. A stratigraphic gap was recognized between the lower and middle members of the Las Aguaditas Formation. It comprises the Eoplacognathus suecicus and Pygodus serra zones, and the lower subzone of the Pygodus anserinus Zone. The variation of conodont diversity through the study section conforms to shallowing and deepening patterns, which accompanies the changes of the provenance lithology. Three conodont assemblages were quantitatively recognized: a) Diverse conodont association, b) Low diversity conodont association and c) Recovery phase association. We propose to use the North American biozonal scheme of conodonts for the Central Precordillera because of the affinity of documented index taxa, which provides a more accurate intercontinental correlation for the global Middle Ordovician Series.

Katian (Late Ordovician) conodonts on the northwestern margin of the North China Craton

2021 ◽  
pp. 1-22
Author(s):  
Zhihua Yang ◽  
Xiuchun Jing ◽  
Hongrui Zhou ◽  
Xunlian Wang ◽  
Hui Ren ◽  
...  
Keyword(s):  
North China Craton ◽  
North China ◽  
Late Ordovician ◽  
Carbonate Platforms ◽  
Upper Ordovician ◽  
The North ◽  
Low Latitudes ◽  
Northwestern Margin ◽  
Conodont Fauna ◽  
Stratigraphic Range

Abstract Upper Ordovician strata exposed from the Baiyanhuashan section is the most representative Late Ordovician unit in the northwestern margin of the North China Craton (NCC). In total, 1,215 conodont specimens were obtained from 24 samples through the Wulanhudong and Baiyanhuashan formations at the Baiyanhuashan section. Thirty-six species belonging to 17 genera, including Tasmanognathus coronatus new species, are present. Based on this material, three conodont biozones—the Belodina confluens Biozone, the Yaoxianognathus neimengguensis Biozone, and the Yaoxianognathus yaoxianensis Biozone—have been documented, suggesting that the Baiyanhuashan conodont fauna has a stratigraphic range spanning the early to middle Katian. The Baiyanhuashan conodont fauna includes species both endemic to North China and widespread in tropical zones, allowing a reassessment of the previous correlations of the Katian conodont zonal successions proposed for North China with those established for shallow-water carbonate platforms at low latitudes. UUID: http://zoobank.org/7cedbd4a-4f7a-4be6-912f-a27fd041b586

scholarly journals Ecological-taxonomic analysis of the petrophyte flora of Ikhrek (Rutulsky district) surroundings of Republic of Dagestan

2016 ◽  
Vol 5 (4) ◽  
pp. 70-73
Author(s):  
Agarza Medzhidovich Khalidov
Keyword(s):  
Rocky Mountains ◽  
Genetic Relationships ◽  
Taxonomic Composition ◽  
Environmental Groups ◽  
North West ◽  
Taxonomic Analysis ◽  
The North ◽  
History Of ◽  
The Republic ◽  
Mountain Country

The study of petrophytes, as a peculiar group of plants, is important for understanding the history of the flora and nature in general. Their ecological characteristics, taxonomic composition, geographic and genetic relationships and other characteristics carry information about the stages of development of the mountain country and its flora. Rutulsky district is a part of Highland Dagestan and borders on the Republic of Azerbaijan in the South, Akhtynsky and Kurakhsky districts in the East, Tlyaratinsky and Charodinsky districts in the North-West, Kulinsky, Agulsky and Laksky districts of the Republic of Dagestan in the North. The relief of Highland Dagestan, which is the area of our research, is characterized by a large slope, stony and rocky mountains. The following paper contains taxonomic, biomorphic, ecological analyses of petrophyte complexes of the studied area and an analysis of endemism and relict flora of petrophytic complexes. Herbarium material has helped to find the dominant family, genera and species of petrophyte complexes of the area. Biomorphic and environmental groups of petrophyte complexes have been studied. Confinement of petrophytes to different environmental conditions has been established. Endemic, relict and protected species of petrophyte complexes have been identified.

scholarly journals Distribution of Microfossils in the Vendian Deposits of the Orsha Depression of the East European Platform, Belarus

2021 ◽  
Vol 29 (6) ◽  
pp. 627-640
Author(s):  
E. Yu. Golubkova ◽  
O. F. Kuzmenkova ◽  
E. A. Kushim ◽  
A. G. Laptsevich ◽  
S. S. Mankievič ◽  
...  
Keyword(s):  
East European Platform ◽  
Taxonomic Composition ◽  
Northwestern Part ◽  
East European ◽  
The Third ◽  
The North ◽  
Upper Vendian

Abstract— The complete sections of the Lower and Upper Vendian of the East European Platform were opened in the boreholes of Belarus. This allows us to consider this region as a stratotype area. In order to update the paleontological characteristics of the Vendian, organic-walled microfossils from the Bogushevsk-1, Bogushevsk-2 (Liozno), and Lepel-1 reference boreholes drilled in the north of the Orsha Depression were studied. The transitive assemblage I with Leiosphaeridia minutissima–Leiosphaeridia tenuissima was recognized in the Lower Vendian Liozno Formation of the Volyn Series and the Upper Vendian Kotlin Formation. The Redkino microfossil assemblages were identified at three stratigraphic levels in the Nizy, Selyava, and Chernitsa formations: assemblage II with Morania zinkovi, assemblage III with Morania zinkovi–Tynnia precambrica, and assemblage IV with Morania zinkovi–Tynnia precambrica–Striatella coriacea, respectively. The Kotlin assemblage V with Vendotaenia antiqua–Primoflagella speciosa was distinguished in the upper part of the Kotlin Formation (Bogushevsk-1 borehole). On the basis of the taxonomic composition, assemblages III and IV are correlated with the first Redkino biota of the Starorusskaya Formation; assemblage V is correlated with the third Kotlin biota of the Vasileostrovskaya Formation of the northwestern part of Russia. Our data show a high biostratigraphic potential of organic-walled microfossils, which should be used to substantiate regional stratigraphic units of the Upper Vendian in the updated stratigraphic scheme of the East European Platform.

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