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.

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.

Integrated conodont biostratigraphy and carbon isotope chemostratigraphy in the Lower–Middle Ordovician of southern Sweden reveals a complete record of the MDICE

2016 ◽  
Vol 154 (2) ◽  
pp. 334-353 ◽  
Author(s):  
RONGCHANG WU ◽  
MIKAEL CALNER ◽  
OLIVER LEHNERT
Keyword(s):  
North America ◽  
Carbon Isotope ◽  
South China ◽  
North China ◽  
Southern Sweden ◽  
Conodont Biostratigraphy ◽  
Middle Ordovician ◽  
The Core ◽  
Core Section ◽  
Argentine Precordillera

AbstractOne of the few and most complete records of the MDICE (Middle Darriwilian Isotope Carbon Excursion) is herein documented from Baltoscandia. Based on a core section penetrating the condensed Lower–Middle Ordovician succession (~46 m) on the island of Öland, southeastern Sweden, we provide an integrated scheme for carbon isotope chemostratigraphy (313 samples) and conodont biostratigraphy (29 samples) for this period. The carbonate succession in the Tingskullen core records 12 conodont zones and 6 subzones, including theOepikodus evae, Trapezognathus diprion, Baltoniodus triangularis, B. navis, B. norrlandicus, Lenodus antivariabilis, L. variabilis, Yangtzeplacognathus crassus, Eoplacognathus pseudoplanus(Microzarkodina hagetianaandMicrozarkodina ozarkodellasubzones),E. suecicus, Pygodus serra(E. foliaceus, E. reclinatus, E. robustusandE. lindstroemisubzones) andPygodus anserinuszones in ascending order. The δ13Ccarbrecord reveals an apparently complete record of the MDICE, including a rising limb, a well-defined peak and a falling limb. The anomaly covers a thickness ofc. 27 m in the core and spans theEoplacognathus pseudoplanus, E. suecicus, Pygodus serraandP. anserinusconodont zones. Combined with the new, detailed conodont biostratigraphy, the MDICE in the Tingskullen core can be used for detailed correlation with successions from Baltica, North America, the Argentine Precordillera, South China and North China.

The Cambrian Fauna of the Leny Limestone, Perthshire, Scotland

2007 ◽  
Vol 98 (02) ◽  
pp. 199-218 ◽  
Author(s):  
Terence P. Fletcher ◽  
Adrian W. A. Rushton
Keyword(s):  
New York ◽  
North American ◽  
Lower Cambrian ◽  
Outer Edge ◽  
Open Ocean ◽  
Middle Cambrian ◽  
Middle Ordovician ◽  
The North ◽  
Appalachian Orogen ◽  
Selection Of

ABSTRACTDark limestones in the old quarries at Leny, Perthshire contain sparse beds with tiny fossils. They are poorly preserved and, though barely affected by the Ordovician Grampian Event tectonism, there is some taphonomic distortion and many are corroded along stylolitised horizons. The fauna mainly comprises trilobites of two types, open-ocean miomerids and polymerid shelf dwellers. MiomeridsCondylopygecf.eliandKiskinella cristataindicate a stratigraphical position equivalent to the base of the paradoxidid Amgan Stage of Siberia; traditionally regarded as ‘Middle Cambrian’. However, the bulk of the Leny miomerids, notably species ofPagetides, are forms described from the outer edge of Laurentia, within theBonnia–OlenellusZone, where it is considered to be ‘Lower Cambrian’. The Leny polymerids were likely transported off-shelf and some are conspecific with taxa in the Laurentian allochthonous Quebec and New York successions of the Early–Middle Ordovician (Taconic) Appalachian Orogen. The Leny Limestone and Shale Member of the Keltie Water Grit Formation is part of the Dalradian Supergroup deposited in an off-shelf Caledonide Grampian Terrane of the Humber Tectonostratigraphical Zone, midway between the North American successions and the Greenland Caledonides.Additional to the trilobites, brachiopods, sponges, hyoliths, bradoriids and a selection of indeterminable organic fragments occur; none of which has any particular age significance.

scholarly journals Conodont biostratigraphy and correlation of the San Juan Formation at the Cerro La Silla section, middle Tremadocian-lower Dapingian, Central Precordillera, Argentina

2020 ◽  
Vol 47 (3) ◽  
pp. 577
Author(s):  
Matías J. Mango ◽  
Guillermo L. Albanesi
Keyword(s):  
Species Distribution ◽  
North American ◽  
Carbonate Rocks ◽  
Basal Part ◽  
San Juan ◽  
Conodont Biostratigraphy ◽  
Original Definition ◽  
The Baltic

This study deals with the conodont biostratigraphy from the uppermost part of La Silla Formation (9.6 m) and the overlying San Juan Formation (264.7 m), at the Cerro La Silla section, Central Precordillera of San Juan, Argentina. The 41 samples of carbonate rocks that were digested for microfossils yielded 11,388 conodont elements corresponding to 78 species. The Paltodus deltifer deltifer Subzone of the Paltodus deltifer Zone from the Baltic biostratigraphic scheme is represented at the top stratum of the La Silla Formation and the basal part of the San Juan Formation (28.4 m), which correlates with the Macerodus dianae Zone (middle Tremadocian) of the Precordilleran and North American schemes. Following upwards, the Paroistodus proteus, Prioniodus elegans, Oepikodus evae, Oepikodus intermedius and Baltoniodus triangularis-Tripodus laevis zones (middle Tremadocian-lower Dapingian) are recorded in the San Juan Formation. The Baltoniodus triangularis-Tripodus laevis Zone is recognized from the second reef level (177.3 m from the base of the San Juan Formation) up to the top stratum in the section, in contrast to previous interpretations that assigned the referred interval to the Baltoniodus navis, Paroistodus originalis and Microzarkodina parva zones of the Baltic biostratigraphic scheme. The division of the Oepikodus evae Zone in subzones, according to its original definition for the Precordillera, is not applicable at the Cerro La Silla section due to the particular species distribution. The conodont elements show a brown alteration color (CAI 2-2.5), which indicates a burial paleotemperature of 60-155°C for the bearer strata.

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.

Ontogeny and relationships of the Ordovician odontopleurid trilobite Ceratocara, with new species from Argentina and New York

1997 ◽  
Vol 71 (1) ◽  
pp. 108-125 ◽  
Author(s):  
Brian D. E. Chatterton ◽  
Gregory D. Edgecombe ◽  
Norberto E. Vaccari ◽  
Beatriz G. Waisfeld
Keyword(s):  
New York ◽  
Phylogenetic Analysis ◽  
New Species ◽  
San Juan ◽  
Growth Stages ◽  
Upper Ordovician ◽  
Growth Series ◽  
Middle Ordovician ◽  
Argentine Precordillera ◽  
A New Species

A growth series is described for a new species of Ceratocara Ramsköld, 1991, C. argentina, from the Upper Ordovician (Caradoc) part of the Las Aguaditas Formation, near Jáchal in San Juan Province, Argentine Precordillera. Another new species of Ceratocara, C. shawi, is described from the Middle Ordovician (lower Chazy) Crown Point Formation of New York. A phylogenetic analysis is presented for these species, other well-known Ordovician species of Ceratocara, and some Ordovician species of Ceratocephala, with Ceratocephalina tridens Whittington, 1956, as outgroup. The analysis presented supports the monophyly of both Ceratocara and Ceratocephala Warder, 1838, their divergence having occurred by the middle Arenig. The ontogenies of the Ceratocara species from Argentina and New York, complete from protaspid to holaspid growth stages, are some of the best preserved odontopleurid ontogenies described to date. Material of Ceratocephala triacantheis Whittington and Evitt, 1954, from the Crown Point Formation of the Chazy Group of New York, is discriminated from that of Ceratocara shawi.

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.

Sign in / Sign up

Export Citation Format

Share Document