A new chitinozoan assemblage from the Middle Devonian Los Monos Formation (sub-Andean basin, southern Bolivia) and its biozonal implications for Western Gondwana (original) (raw)
Related papers
Journal of South American Earth Sciences, 2021
Palynological and organic geochemical analyses have been performed on an Early to Middle Devonian clastic marine sedimentary succession of the TCB X-1001-Tacobo borehole, in the Foothills of the southern sub-Andean ranges of Bolivia. The studied subsurface section encompasses shallow marine deposits of the Icla, Huamampampa and Los Monos formations. Eighteen from the twenty-three cutting samples available were productive, yielding variable abundance, diversity and preservation of organic-walled phytoplankton and miospores, with an increasing trend of terrestrial palynomorphs transpiring towards the younger beds. The palynological assemblage of the Icla Formation contains Bimerga nuda, Cordobesia cf. C. uruguayensis, Duvernaysphaera angelae, and Dibolisporites echinaceus. The Huamampampa Formation includes Polyedryxium sp. cf. P. condensum, Umbellasphaeridium deflandrei and Acinosporites eumammillatus. Arkonites bilixus, Maranhites mosesii, Polyedryxium "talus", Stellinium comptun, Archaeozonotriletes variabilis, Chelinospora timanica, Convolutispora subtilis, Cymbosporites cyathus, Dibolisporites farraginis, Geminospora lemurata, Grandispora permulta, Samarisporites eximius and Verrucosisporites premnus are among the most relevant taxa of the Los Monos Formation. Based on the organic-walled phytoplankton and the miospores of the studied section, the Icla, Huamampampa and Los Monos formations are assigned to the late Pragian-Emsian, Emsian and Eifelian?-middle Givetian, respectively. The palynomorph distribution, relative abundance and preservation throughout the studied samples support the palaeoenvironment interpretation based on sedimentology and sequence stratigraphy. RockEval pyrolysis, TOC, HI and Tmax data were analysed to determine type and quality of the kerogen and hydrocarbon potential of the stratigraphic units.
Review of Palaeobotany and Palynology, 2002
The chitinozoan biostratigraphy of the Barreirinha Formation in its type area (Tapajo ¤ s River near Itaituba town, Para ¤ State, Amazonas Basin, north Brazil), and of the lower part of the overlying Curiri Formation, is calibrated against the local miospore succession, which in turn can be readily correlated with standard miospore biozonations of Euramerica. The present study is based on 375 samples from a ca. 137-m-thick section in the Caima PH-2 shallow borehole. The 26 chitinozoan species encountered are used to recognize eight biozones in the studied well. The applicability of this zonation is yet to be tested elsewhere in the Amazonas Basin. The zones in ascending stratigraphic order are: the total range zone of Angochitina katzeri n. sp., total range subzone of Ramochitina derbyi n. sp, total range subzone of Lagenochitina avelinoi, interval zone of Urochitina bastosi, total range zone of Angochitina carvalhoi n. sp., interval zone of Angochitina rathbuni n. sp. and Ramochitina praeritae n. sp., total range zone of Ramochitina ritae n. sp., and total range zone of Ramochitina cf. R. ritae. Eleven species are newly described; in order of stratigraphic appearance: Ramochitina derbyi, Angochitina katzeri, Ramochitina hartti, Angochitina carvalhoi, Angochitina rathbuni, Ramochitina praeritae, Ramochitina clarkei, Ramochitina ritae, Angochitina loboziaki, Ramochitina oliveirai, and Ramochitina famennense. ß
Silurian and Lower Devonian Chitinozoan Biostratigraphy of the Parana Basin in Brazil and Paraguay
Palynology, 2000
Silurian and Devonian (Lower Lochkovian) chitinozoans from the Trombetas Group, and the basal Jatapu Member of the Maecuru Formation, have been studied in outcrops and shallow borings from the Amazonas Basin, northern Brazil. Outcrops were examined along the Trombetas River and its tributaries, the Cachorro and Mapuera rivers, situated on the northern margin of the Amazonas Basin, and from shallow borings in the Pitinga Formation along the Xingu River at Altamira and Belo Monte, together with outcrops along Igarapé da Rainha and Igarapé Ipiranga on the southern margin of the Amazonas Basin. In addition, nine deep borings in the central part of the Amazonas Basin were used as reference sections. The chitinozoans confirm a Llandovery (Late Rhuddanian-Late Telychian) to Early Wenlock (Sheinwoodian) age for the lower part of the Pitinga Formation, and a Ludlow to Early Pridoli age for the upper part of the Pitinga Formation. The overlying Manacapuru Formation is comprised of lower Pridoli rocks in the basal part, but middle and upper Pridoli strata are missing. The upper part of the formation and the basal part of the Jatapu Member of the Maecuru Formation consist of Lower Lochkovian rocks. Seven chitinozoan assemblages (designated in ascending stratigraphic order 1-7) can be distinguished. Of the 104 chitinozoan species encountered, 51 are left in open nomenclature, and three are newly described (Ancyrochitina pitingaense, Belonechitina? plumula and Linochitina penequadrata).
Chitinozoans from the Late Silurian (Prídolí s.l.) and Devonian, and miospores from the Middle and Late Devonian, have been investigated from the Solimões Basin in northern Brazil. Of the 37 chitinozoan species encountered, 16 are retained in open nomenclature, because of an insufficient number of well-preserved specimens, and Ramochitina jutaiense is newly described. Three or four miospore zones have been recognized: the LE - LN and VH zones of late to latest Famennian age, and a poorly characterized interval not older than the AP zone of latest Emsian - early Eifelian age. A regional chitinozoan biozonation, consisting of six zones, is proposed for the investigated interval. These zones are, from the oldest to the youngest: concurrent range zone of Ancyrochitina ancyrea and Ancyrochitina aff. A. libyensis (Pr ˇídolí s.l.); interval range zone of Angochitina filosa (early Lochkovian); concurrent range zone of Urochitina loboi and Ramochitina jutaiense sp. nov. (late Lochkovian); co...
2005
Silurian and Early Devonian chitinozoans and miospores have been identified from samples of the Serra Grande Group, Parnaíba Basin, northeast Brazil. The chitinozoans indicate a Llandovery (late Aeronian-early Telychian) age for the uppermost Ipu, Tianguá and lowermost Jaicós formations. The upper part of the Jaicós Formation yielded chitinozoan species similar to those from the latest Pragian age strata in Bohemia. The miospore age detenninations agree with those based on chitinozoans. The Laevolancis divellomedia Subzone is recognized from the Early Silurian interval, and the Su (Dictyotriletes subgranifer) I n t e~a l Zone (latest Pragian-earliest Emsian) in the uppermost Jaicós Formation. The overlying Itaim Formation is separated from the Serra Grande Group by a hiatus comprising a yet undetermined amount of Emsian time. Therefore the total age range of palyniferous parts of the Serra Grande Group is Early Silurian (Llandovery) through possibly earliest Emsian. Three chitinozoan species, Angochitina gurupiense, Pogonochitina tianguaense and Sphaerochitina palestinaense, are newly described. Two chitinozoan biozones are defined: the Interval Zone of Pogonochitina tianguaense n. sp. (late middle-early late Llandovery, equivalent to the upper part of the L. divellomedia Subzone) and the Assemblage Zone of Ramochitina sp. A and Ramochitina sp. B (latest Pragian or possibly earliest Emsian, equivalent to the older part of the Su Interval Zone).
Comptes Rendus de l'Académie des Sciences - Series IIA - Earth and Planetary Science, 2000
A new fossil fish fauna from western Venezuela provides the first South American Devonian record of antiarch and phyllolepid placoderms, and sarcopterygians including lungfishes, groups widely distributed on other continents. Endemic elements in the fish fauna indicate Gondwana affinities, and the age of the phyllolepid placoderm occurrence is consistent with a model of biotic dispersal between Gondwana and Euramerica near the Frasnian-Famennian boundary. A narrow marine barrier separating northern and southern landmasses is indicated, in contrast to the wide equatorial ocean for the Late Devonian postulated from palaeomagnetic data. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SAS Venezuela / Frasnian-Famennian / Devonian fishes / biogeography / palaeogeography Résumé-Nouvelles découvertes de vertébrés dévoniens en Amérique du Sud et leurs implications dans le contact entre le Gondwana et l'Euramérique. Une nouvelle ichthyofaune fossile, découverte dans l'Ouest du Venezuela, constitue la première mention, en Amérique du Sud, de certains groupes majeurs de vertébrés dévoniens : les placodermes (antiarches et phyllolépides), et les dipneustes. Des éléments endémiques appartenant aux vertébrés indiquent des affinités gondwaniennes. L'âge des phyllolépides permet d'émettre une hypothèse sur la dispersion biotique entre le Gondwana et l'Euramérique à la limite entre le Frasnien et le Famennien. La reconstitution d'une barrière marine étroite séparant les masses continentales du Nord et du Sud est préférable à celle qui préconise, pour cette même région, un large océan équatorial, ainsi que le suggèrent les données paléomagnétiques du Dévonien terminal. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SAS Venezuela / Frasnien-Famennien / poissons dévoniens / biogéographie / paléogéographie Version abrégée
Late Tremadocian chitinozoans and acritarchs from northwestern Argentina (Western Gondwana)
Review of Palaeobotany and Palynology, 2009
Chitinozoans and acritarchs are recorded from the Saladillo and Parcha formations of the Pascha-Incamayo area (Salta Province), Cordillera Oriental, northwestern Argentina. These organic microfossils coexist with graptolites of the Kiaerograptus, Araneograptus murrayi and Hunnegraptus copiosus biozones of early late Tremadocian and late Tremadocian age respectively. This is the oldest chitinozoan record from western Gondwana, and one of the few Tremadocian chitinozoan assemblages documented in the world. The stratigraphical range and the palaeobiogeographic affinities of the recovered acritarchs (messaoudensistrifidum association) and the chitinozoans assemblages are discussed at regional and at global scale. A new chitinozoan species, Euconochitina paschaensis, is described.
Geologica Acta
The palynological analysis of the 2548-3628 m interval of the San Antonio x-1 Borehole in northwestern Argentina is presented. The illustrated palynoflora is composed of 96 species represented by diverse palynological groups such as trilete spores and cryptospores (46 species), microplankton (39 species), chitinozoans (7 species), scolecodonts, and some remaining specimens in open nomenclature and as incertae sedis. One new species, Retusotriletes ottonei, is described. Thirty-four species are first records in the Argentinean Devonian. Three assemblages (SA1, SA2, and SA3) are defined based on the presence, absence, or abundance of groups of taxa. The presence of Grandispora protea and Grandispora douglastownense among others in the assemblage SA1 is indicative of a late Emsian to mid-Eifelian age. The concurrence of Acinosporites macrospinosus and A. acanthomammillatus in the assemblage SA2 is indicative of a late Eifelian-mid Givetian and is also supported by the appearance of sev...
Paleobiogeography of Lower-Middle Devonian Conulariids from southwest Gondwana
The bioregionalization of the Devonian fauna in southwest Gondwana has been extensively studied, focusing on the occurrences of brachiopods and trilobites, however, little attention has been given to Conulariids. The main goal of this paper is to propose a bioregionalization for the Conulariids (Conularia albertensis, C. quichua, C. sp., Paraconularia africana, P. ulrichana, and Reticulaconularia baini) from the Lower-Middle Devonian in southwest Gondwana. After a clustering analysis and diversity tests we have identified two distinct bioregions for Conulariids: the Amazon and southwest Gondwana, in the Amazon region the diversity is low, and can be attributed to scarcity of palaeontological data on the area. On the other hand, in the southwest Gondwana bioregion, diversity ranges from moderate to relatively high, which helps define a second-order bioregion, the Andeo-South Africa and Interior Gondwana. The first includes areas where diversity has higher values bordering southwest Gondwana (Bolivian Chaco-Peru, Zorritas-NOA-South Bolivia, South Africa and Malvinas areas). Further, in the Interior Gondwana bioregion are the Parnaíba (Parnaíba Basin), Alto Garças (north and northwest of Paraná Basin), Paraná (south of Paraná Basin, Uruguay and Paraguay) areas, where the diversity is slightly lower when compared to the Andeo-South Africa bioregion.