Itaituba Formation Research Articles

Bashkirian-Moscovian (Lower–Middle Pennsylvanian) conodonts from the Amazonas Basin, northern Brazil: Biostratigraphy, biofacies, and paleobiogeographic significance for Western Gondwana

Bashkirian-Moscovian (Lower to Middle Pennsylvanian) Itaituba Formation is well exposed in the Itacimpasa Quarry at the southern platform of the Amazonas Basin, northern Brazil. An abundant and diverse conodont fauna was recovered from this predominantly carbonate formation, with a total of 19 species belonging to 8 genera identified. The following species were documented and systematically described for the first time in the basin: Declinognathodus marginodosus, Declinognathodus donetzianus, Idiognathoides postsulcatus, Idiognathoides fossatus, Diplognathodus benderi, Adetognathus spathus, and Idioprioniodus conjunctus, providing significant stratigraphic and environmental insights into the Bashkirian-Moscovian boundary (BMB) interval. The Declinognathodus marginodosus – Neognathodus atokaensis (upper Bashkirian Stage) and the Declinognathodus donetzianus – Diplognathodus ellesmerensis (lower Moscovian Stage) zones are recognized. The distribution of conodonts studied through cluster analysis reveals the conodont biofacies Idiognathodus/Adetognathus and Declinognathodus/Idiognathoides biofacies. Changes in these conodont biofacies are interpreted as the result of a marine ingression event in Western Gondwana during the BMB interval. The fauna recorded in the studied section shows affinities with conodont faunas reported from Paleo-Tethys Ocean regions indicating a faunal connection of this ocean with the Panthalassa in Western Gondwana. These findings contribute significantly to the refinement of the biostratigraphy and paleobiogeography of the Bashkirian-Moscovian boundary interval in the Amazonas Basin and Western Gondwana.

Pennsylvanian epicontinental sea dynamics in Western Gondwana: Stratigraphic, petrographic, and C, O, and Sr isotopic insights from the Itaituba Formation, Amazonas Basin

During the Pennsylvanian period, an epicontinental sea significantly influenced the paleogeography of Western Gondwana, as evidenced by the Pennsylvanian units of the Tapajós Group (Monte Alegre, Itaituba, and Nova Olinda formations) in the Amazonas Basin, Brazil. The carbonate deposition within the Itaituba Formation represents a Pennsylvanian transgressive event linked to the Panthalassa Ocean. Comprehensive stratigraphic, petrographic, and isotopic analyses were conducted on a carbonate succession in the Itacimpasa Quarry, one of the best-exposed carbonate outcrops in the southern Amazonas Basin, notable for its rich fossil content. The petrographic analysis allowed the identification of eleven microfacies grouped into three facies associations: tidal flat (FA1), lagoon (FA2), and outer platform (FA3) representative an epicontinental carbonate platform system. The general transgressive trend is evidenced by the superimposition of marine facies (FA3) over coastal facies (FA1 and FA2). Fossil content was quantified through detailed petrography, revealing a clearly marine fossiliferous diversity, including brachiopods, echinoderms, bivalves, ostracods, foraminifers, trilobites, and bryozoans. Isotopic data, including carbon, oxygen, and strontium isotopes, refined previous chemostratigraphic framework. δ13C values ranged from +2.15‰ to +4.54‰, and δ18O values spanned −6.99‰–2.82‰, consistent with the expected values for the Pennsylvanian carbonates. An upward δ13C trend within the studied interval suggests significant organic productivity during a predominantly transgressive phase, although minor sea-level falls explain variations in the δ13C trend. The 87Sr/86Sr values indicate epicontinental marine conditions, ranging from 0.70852 to 0.70858. However, samples affected by diagenetic processes can reach up to 0.70940. A representative δ13C curve for the Itaituba Formation was constructed for the first time, integrating isotopic data using a sixth-degree polynomial fit. The resultant curve for the carbonate succession shows a positive upward trend, following the δ13C curve trends of other contemporaneous carbonates from the Panthalassa and Paleo-Tethys oceans and with the global relative sea-level curve. This correlation, in addition to reinforcing the validity of the δ13C trends observed in the Itaituba Formation, also suggest a response to paleoceanographic and paleoenvironmental changes during the Pennsylvanian period linked to a deglaciation-induced transgressive event.

Nova ocorrência de Crinoidea no Pensilvaniano da Formação Itaituba, Pedreira Caltarém, norte da Bacia do Amazonas

Crinoidea from the Pennsylvanian deposits of the Itaituba Formation, Northern Amazonas Basin. The Itaituba Formation comprises part of the marine section of the Tapajós Group in the Amazonas Basin. This unit mainly comprises Pennsylvanian carbonate deposits associated with various marine invertebrate fossils. In this work, we present new records of crinoids in the Itaituba Formation in the Caltarém quarry, north platform of the Amazonas Basin. There are described and taxonomically identified, two genera of crinoids, through the study of columnals and pluricolumnals, in addition to the interpretation of the depositional environment through the analysis of carbonate microfacies. The identified specimens correspond to the species Cyclocaudex aff. typicus Moore & Jeffords, and to the genus Pentaridica Moore & Jeffords (first record in the Itaituba Formation). The textural, compositional, and paleontological analysis suggests four standard microfacies MPF 09, 10, 16, 23) and two faciological zones (ZF 7 E 8). The bioturbated bioclastic wackestones (MFP 09) and bioclastic wackestones/packstones (MFP 10) microfacies, with fossils of brachiopods, crinoids, echinoids, miliolid and fusulinid foraminifera, trilobites, and bryozoans, characterize an interior shelf environment, with a connection to an open marine circulation (ZF 7). The peloidal wackestones (MFP 16) and mudstones (MFP 23) microfacies, with a fossiliferous assemblage limited to brachiopods, echinoids and miliolid foraminifera, characterize a restricted lagoon environment (ZF 8). Paleontological data and microfacies analysis indicate the development of a lagoon environment with a diverse paleofauna of marine invertebrates in the carbonate platform of the northern bord of the Amazonas Basin, in the Monte Alegre County, during the Pennsylvanian. Keywords: taxonomy, echinoderms, microfacies, paleoenvironment, Pennsylvanian.

Taxonomic revision of conodonts of Piauí formation, Parnaíba basin, updating to late Bashkirian age and biostratigraphic – Paleoecologic correlation with the Itaituba formation, Amazonas basin

This study analyzed conodont elements retrieved from Mocambo Carbonates, marine portion of the Piauí Formation, Parnaíba Basin, Northeast Brazil, West Gondwana. This manuscript aims i) to update the conodont fauna and, ii) to refine the biostratigraphic and paleoecological data of the marine portion, according to new conodont occurrences. The description of the conodont species Diplognathodus orphanus, Idiognathodus incurvus and Adetognathus lautus, suggests a late Bashkirian age. In addition, the presence of adults and juvenile Diplognathodus orphanus and Idiognathodus incurvus, as well as fern sporangia, ostracods, benthic foraminifers, and fish teeth, indicate a very shallow marine platform, of neritic tidal facies. The Mocambo Carbonates are traditionally recognized as Pennsylvanian in age, and thus, with our conodont contribution is refined to late Bashkirian. Paleoecologically, this sequence is interpreted as very shallow marine facies. We also correlate the marine carbonate sequence of the Piauí Formation, Parnaíba Basin, with the marine shallow waters from the Itaituba Formation, Amazonas Basin. This is well-positioned with international biozones from North America, China and Europe, allowing the correlation of the Piauí marine portion with the transgressive-regressive epicontinental Itaituba-Piauí Sea in Northwest South America, Western Gondwana, during the Late Paleozoic.

Protobranch bivalves from the Piauí Formation (Middle Pennsylvanian), Parnaíba Basin, Brazil

Dolomitic limestones of the upper Piauí Formation of the Parnaíba Basin, Northern Brazil, preserve a rich and diversified invertebrate fauna of Middle Pennsylvanian age. The fauna shows affinities with the Pennsylvanian Itaituba Formation of the Amazon Basin, Brazil, and with Upper Paleozoic Andean faunas of the Cerro Prieto Formation and Tarma Group of Peru, and the Caño Indio Formation of Venezuela. In North America similar faunas are present in the Mississippian-Pennsylvanian Amsden Formation and in the Desmoinesian of Missouri. The Piauí fauna thus shows a clear "Tethyan" (boreal) affinity in contrast with other Late Paleozoic assemblages from southern South America. Bivalves comprise the majority of the fauna (60%, 31 species), followed by gastropods (17%, 9 species) and brachiopods (17%, 9 species). Other invertebrates including a cephalopod, a trilobite and a bryozoan make up the remainder of the fauna (6%, 3 species). Three species of protobranch bivalves, Polidevcia bellistriata, Nuculavus levatiformis and Solemya (Janeia) radiata are described here in. Obesity and elongation indexes as well as the external ornamentation and muscle scars of the nuculoid species here recovered are consistent with their interpretation as rapid (P. bellistriata) and slow, shallowly burrowing (N. levatiformis) deposit feeders. S. (Janeia) radiata, a slow shallow burrower, deposit feeder, is preserved in life position. This is the first of three publications that aim to ameliorate the present lack of paleontologic and paleobiogeographic knowledge on the Carboniferous of northern South America.

Paleoenvironment, chemostratigraphy, and age of Pennsylvanian carbonate platform succession of the Amazonas basin, northern Brazil, Uruará region

Extensive Pennsylvanian carbonate platforms are the main transgressive successions recorded on Laurasia and Gondwana continents. The western Gondwana was one of the important sites of these transgressive carbonate accumulation exposed on several basins in Amazonia. Carbonate platform successions are exceptionally preserved in the southern border of the Amazonas Basin, northern Brazil, represented by the Pennsylvanian Itaituba Formation, previously interpreted as tidal flat, lagoon, and carbonate subtidal deposits. Microfacies and petrographic analysis of ~32 m-thick succession of core F5 allowed the definition of nine microfacies grouped in three facies associations: lagoon (FA1), bioclastic bars (FA2) and open carbonate platform (FA3). The FA1 is composed by massive lime-mudstones and dolostones with silt to sand-size terrigenous grains, brachiopods, echinoderms, and rare foraminifers. The lagoon deposits represent a low energy environment with intense micrite precipitation, low diversity of fossils, but that indicates a marine connection, mainly because of the presence of echinoderm and brachiopods. The FA2 is composed of massive grainstone with ooids, intraclasts, brachiopods, echinoderms, corals, bivalves, and foraminifers cemented by granular calcite. The bioclastic bars are affected by wave actions and currents that reworked the carbonate substrate. The FA3 is composed of wackestone and lime-mudstone with micritic matrix, terrigenous, pyrite, brachiopods, bivalves, echinoderms, foraminifers, and ostracods. The Itaituba carbonate platform deposits indicate sedimentation under warm climate, normal salinity and were directly connected with the ocean by the record of benthic organisms. δ13C and δ18O, were obtained for these carbonate rocks and the determination of alteration degree was assisted by Rb/Sr, Fe/Sr, Ca/Mg, and Fe/Sr ratios assisted by digenetic indicators. The Ca and Mg become constant between 30 and 40% in the succession while the Si, Al, and Fe contents decrease upward coincident with the transgressive trend of the succession revealing low continental inflow. Diagenetic processes are represented mainly by stylolitization, cementation, micritization, dolomitization, fracturing, and pyritization that partially modify the framework of carbonate rocks, attesting low diagenetic alteration. The δ13C and δ18O range from +1.60‰ to +5.42‰, and −8.73‰ to +0.80‰ respectively. These values show wide dispersion (non-covariance), suggesting the circulation of diagenetic fluids through these rocks was not able to modify the original composition of δ13C. The carbon and oxygen data coincide with values obtained for carboniferous marine deposits, and the positive data of δ13C in FA2 and FA3 indicates intense organic productivity, similar to that recorded in transgressive deposits associated with the Panthalassa Ocean. The strontium ratios values vary from 0. 708466 ± 0. 000011 to 0. 708417 ± 0. 000009 with 30–299 μg/g in the carbonate platform and presents three age intervals of deposition with a range varying between 293 and 303 Ma (Bashkirian to Kasimovian stages). These data are analogous to the palynomorphs and conodonts ages from the Pennsylvanian of the Amazonas Basin positioned the basal part of the Pennsylvanian succession in the Bashkirian stage.

Trilobites, scolecodonts and fish remains occurrence and the depositional paleoenvironment of the upper Monte Alegre and lower Itaituba formations, Lower – Middle Pennsylvanian of the Amazonas Basin, Brazil

This study aims to characterize the scolecodonts, trilobite pygidium fragments and fish remains of an outcropped region in the southern Amazonas Basin, comprising the uppermost section of the Monte Alegre Formation and the basal section of the Itaituba Formation. These, correspond to part of the marine portion of the Tapajós Group, related to an intracratonic carbonate platform. The Monte Alegre Formation includes a deposition of fluvial-deltaic and aeolian sandstones, siltstones and shales of interdunes and lakes, intercalated with transgressive carbonates of a shallow restrict nearshore marine environment. The Itaituba Formation comprises a thickest deposit of marine carbonates, representing the establishment of widespread marine conditions, and is the richest interval containing organisms of shallow marine environment in the Pennsylvanian of the Amazonas Basin. The associated fauna includes brachiopods, bivalves, gastropods, crinoids, echinoids, bryozoans, corals, foraminifers, sponges, ostracods, trilobites, scolecodonts, fish remains and conodonts, mainly in the packstones, and subordinately in the wackestones and mudstones. Conodonts Neognathodus atokaensis, Diplognathodus orphanus, Idiognathodus incurvus, and foraminifers Millerella extensa, Millerella pressa, Millerella marblensis, Eostaffella ampla, Eostaffella pinguis and Eostaffella advena characterizes a predominant Atokan age to the analyzed profile. The fossil association herein presented is taxonomically diversified and biologically interesting, comprising an important and well preserved, for the first time occurrence of two molds and two fragments of Proetida trilobites. Well preserved Eunicida and Phyllodocida scolecodonts and paleonisciform fish remains. These fossils help in the paleoenvironmental establishment of the studied interval in the Amazonas Basin and as a potential biostratigraphic and paleoecological tool to correlate regionally and globally the Pennsylvanian.

Taphofacies of Lower-Middle Pennsylvanian marine invertebrates from the Monte Alegre and Itaituba formations, part of the outcropped marine sequence of the Tapajós Group (Southern Amazonas Basin, Brazil) – regional palaeoecological models

One of the most relevant characteristics of the Pennsylvanian shallow-water carbonates of the Amazonas Basin is its diverse and well preserved invertebrate fossiliferous assemblages. In order to better understand the origin of these fossil concentrations, taphonomic data were obtained along well exposed areas of the uppermost part of the Monte Alegre Formation and basal part of the Itaituba Formation, which, based on conodonts, fusulinids and palynomorphs is of Atokan age. The taphonomic data focused on invertebrate organisms were supported by petrographic analysis. The understanding of the stacking pattern of the strata in the studied section allowed the identification of five type taphofacies, which contributed in the development of regional palaeoecological models, expressed as block-diagrams. These characterize the distribution of the environmental parameters, the composition of the faunal associations and the distribution and amplitude of the taphonomic processes that created the taphonomic signatures of the bioclastic elements throughout the supratidal to lower intertidal/deep subtidal depositional environments pertinent to the studied depositional environment. The regional palaeoecological models here presented are related to the particularities of the depositional environments of the studied rocks and are exclusive for the characterization of this intracratonic basin set influenced by high frequency climatic variations. Lithofacies, biofacies and taphofacies associations also reflect depositional conditions pertinent to the studied regional context, differing from the elements observed in modern intracratonic contexts analogous to the one studied, from different sedimentary basins around the world. Therefore, invertebrate taphonomy, supported by the analysis of sedimentary facies, fulfills the purposes recommended in this work, demonstrating its potential as a tool for palaeoecological analysis in the Pennsylvanian outcropping section in the southern platform of the Amazonas Basin.

Conodont biostratigraphy and paleoecology of the marine sequence of the Tapajós Group, Early-Middle Pennsylvanian of Amazonas Basin, Brazil

This study was undertaken in the south and western regions of the Amazonas Basin to describe the conodont biostratigraphy and paleoecology of Pennsylvanian carbonate rocks of the marine portion of the Tapajós Group comprising the upper Monte Alegre, Itaituba, and lower Nova Olinda formations.The analyzed area includes one outcrop along the Tapajós river (TAP), two carbonate quarries (QI, QII), and 18 wells (dots 1–18). The conodont fauna is dominated by Idiognathoides sinuatus and Neognathodus symmetricus in the Monte Alegre Formation, followed by Idiognathodus incurvus, Diplognathodus coloradoensis and Neognathodus bassleri in the Itaituba and Nova Olinda formations. The conodont association suggests an Early to Middle Pennsylvanian age to the analyzed section. Relative ages attributed to the three lithostratigraphic units using conodonts, palynomorphs, and foraminifers are consistent.Herein are proposed one local taxon-range zone of Idiognathodus incurvus in the Itaituba and lower part of the Nova Olinda Formation and one local taxon-range subzone of Diplognathodus coloradoensis in the Itaituba Formation, suggesting a late Bashkirian – Moscovian (Atokan – early Desmoinesian) age to these strata.The Itaituba Formation marks the establishment of large Pennsylvanian marine conditions in the Amazonas Basin and is composed primarily of marine carbonates of abundant fossil content, tidal flat evaporites and siliciclastic thin intervals. Its lower limit, with the Monte Alegre Formation, is characterized by the predominant occurrence of fluvial-deltaic sandstones superimposed on an extensive sequence of aeolian sandstones, siltstones and shales intercalated with the interdune and lakes. From the upper strata of Itaituba Formation the faunal and lithological characteristics indicate the occurrence of a regressive phase culminating in a restricted environment, arid which indicates the Nova Olinda Formation. This is characterized by the occurrence of evaporites increasingly abundant to the top of carbonates, also shales and siltstones intercalated with the sabkha plain. The carbonate strata have similar marine fossils to those of Itaituba Formation, however, the fauna becomes impoverished in abundance and diversity. The conodont fauna of Early-Middle Pennsylvanian of Amazonas Basin suggests similarities of species with the North American Midcontinent region and the Illinois Basin indicating their probable cosmopolitism; however in a slightly different paleogeographic context, probably due to latitudinal differences, coal deposits are present in North America, whereas widespread evaporitic deposits are registered to the Tapajós Group, Amazonas Basin.

Depósitos de plataforma mista, Neocarbonífero da Bacia do Amazonas, região de Uruará, estado do Pará

Rochas carbonáticas são amplamente registradas na região oeste e centro-oeste do Estado do Pará, borda Sul da Bacia do Amazonas, correspondentes ao período Neocarbonífero. Esses depósitos são incluídos na sequência pensilvaniana-permiana correspondente a uma super sequência de segunda ordem representada pelo Grupo Tapajós. A Formação Itaituba corresponde à porção transgressiva que precedeu a expressiva continentalização e formação de Pangeia. Essa unidade é constituída de carbonatos fossilíferos, arenito com estratificação cruzada e subordinadamente folhelhos e evaporitos de ambiente marinho costeiro. Dezenove fácies e microfácies foram agrupadas em cinco associações de fácies (AF) correspondentes a depósitos de planície de maré (AF1), canal de maré (AF2), laguna (AF3), barra bioclástica (AF4) e plataforma externa (AF5). A AF1 compreende ciclos de exposição subaérea com formação de gretas de contração e deposição subaquosa, composta de brecha dolomítica, dolomito fino laminado e dolomudstone com terrígenos separados por arenito maciço piritoso e dolomito fino silicificado. A AF2 consiste em arenito fino com laminação cruzada de base reta e recobrimento pelítico nos foresets, siltito argiloso com laminação cruzada, marga com laminação cruzada cavalgante e arenito grosso com estratificação cruzada com recobrimento pelítico nos foresets. Falhas sinsedimentares afetam os arenitos e siltitos. A AF3 é constituída de siltito maciço avermelhado, mudstone fossilífero, floatstone com braquiópode e folhelho negro piritoso maciço. A AF4 é representada por grainstone oolítico fossilífero e grainstone com terrígenos e fósseis de braquiópodes, equinodermas, bivalves, moluscos e subordinadamente artrópodes, briozoários e foraminíferos. A AF5 associa-se a uma plataforma composta de wackestone fossilífero, wackestone fossilífero com terrígenos e mudstone maciço. A assembleia fossilífera é representada por foraminíferos, braquiópodes, bivalves e, subordinadamente, briozoários e equinodermas, que atestam um ambiente costeiro de salinidade moderada e profundidade baixa com intensa proliferação de organismos bentônicos. O modelo deposicional da Formação Itaituba, na região de Uruará, foi atribuído a um sistema lagunar e de planície de maré conectado a um sistema de plataforma marinha carbonática. As lagunas eram bordejadas por planície de maré na porção mais continental e periodicamente supridas por aporte de terrígeno fino (silte) que inibia a precipitação carbonática. Barras bioclásticas cortadas por canais de maré (inlet) separavam a laguna da plataforma rasa com maior abundância de fósseis marinhos bentônicos, registrando o início de uma transgressão marinha neocarbonífera na Bacia do Amazonas advinda de NNW.

First occurrence of Ellisonia, Gondolella and Ubinates (Conodonts) in Itaituba Formation, Pennsylvanian of Amazonas Basin, Brazil

This paper analyzes and describes a fi rst occurrence of the conodonts Ellisonia, Gondolella and Ubinates in Amazonas Basin, North of Brazil. The recovered material comes from two outcrops along the Tapajos River and from a limestone quarry of Itaituba Formation, whose levels are included in the Itaituba Formation, with a Pennsylvanian age. Those conodonts are relevant paleoecological indicators of water depth, salinity and environmental energy and have implications in the Late Carboniferous to Triassic biostratigraphy. The fossil remains represent M and S conodont elements, associated to Pa elements of the Idiognathodus, Idiognathoides, Neognathodus, Adetognathus, Hindeodus and Diplognathodus genus. Key words: conodonts, Amazonas Basin, Itaituba Formation, Pennsylvanian.

Primeira ocorrência dos gêneros Ellisonia, Gondolella e Ubinates (Conodonts) para a Formação Itaituba, Pensilvaniano da Bacia do Amazonas, Brasil

This paper analyzes and describes a fi rst occurrence of the conodonts Ellisonia, Gondolella and Ubinates in Amazonas Basin, North of Brazil. The recovered material comes from two outcrops along the Tapajos River and from a limestone quarry of Itaituba Formation, whose levels are included in the Itaituba Formation, with a Pennsylvanian age. Those conodonts are relevant paleoecological indicators of water depth, salinity and environmental energy and have implications in the Late Carboniferous to Triassic biostratigraphy. The fossil remains represent M and S conodont elements, associated to Pa elements of the Idiognathodus, Idiognathoides, Neognathodus, Adetognathus, Hindeodus and Diplognathodus genus . Key words: conodonts, Amazonas Basin, Itaituba Formation, Pennsylvanian.

Diplognathodus occurrence in the Itaituba Formation, Amazonas Basin, Brazil

203 ABSTRACT - The Itaituba Formation contains the most abundant and diverse fossiliferous deposits of the Tapajos Group Pennsylvanian of the Amazonas Basin with a rich fauna of normal marine organisms, including conodonts, fish remains, foraminifers, brachiopods, echinoids, gastropods, bryozoans, trilobites, corals, ostracodes, scolecodonts, sponges. Palynomorphs are also common. Conodonts are widely distributed. Genera like Rhachistognathus, Neognathodus, Idiognathodus and Diplognathodus are among the most important to calibrate the age and to correlate the studied deposits. The occurrence of Diplognathodus coloradoensis, D. orphanus, and the first appearance of D. ellesmerensis in the Itaituba Formation, Pennsylvanian of the Amazonas Basin are reported, which suggest an Atokan age to this interval. RESUMO - A Formacao Itaituba possui os estratos carbonaticos mais espessos do Grupo Tapajos. Esta formacao contem os depositos fossiliferos mais diversos e abundantes do Pensilvaniano da Bacia do Amazonas com organismos que representam uma fauna de ambiente marinho normal, incluindo conodontes, fragmentos de peixes, foraminiferos, braquiopodes, equinodermos, gastropodes, briozoarios, trilobitas, corais, ostracodes, escolecodontes, esponjas e flora caracterizada por palinomorfos. Os conodontes tem sido amplamente encontra- dos. Generos como Rhachistognathus, Neognathodus, Idiognathodus e Diplognathodus estao entre os mais importantes para o refinamento das idades e a correlacao dos estratos estudados. Este trabalho tem por objetivo reportar a presenca de Diplognathodus coloradoensis, D. orphanus, e a primeira ocorrencia de D. ellesmerensis na Formacao Itaituba, Pensilvaniano da Bacia do Amazonas, as quais sugerem uma idade Atokana para o intervalo estudado.

UPPERMOST MISSISSIPPIAN BRACHIOPODS FROM THE BASAL ITAITUBA FORMATION OF THE AMAZON BASIN, BRAZIL

This paper describes 19 brachiopod species (including six indeterminate species) in 15 genera and one indeterminate genus from the basal Itaituba Formation at the Caima Quarry 1 section of Itaituba, Amazon Basin, Brazil. The faunal correlations of the brachiopods and the associated fusulinids and conodonts indicate a late Chesterian (late Serpukhovian) age for the described fauna, therefore confirming for the first time the presence of uppermost Mississippian rocks in the Amazon Basin. A new species, Composita caimaensis, is created, and two species, Inflatia cf. gracilis and Marginovatia cf. catinulus, are described for the first time from the Amazon Basin. The Amazon brachiopods appear to be of strong affinity with coeval faunas of the North American midcontinent.

Pennsylvanian (Carboniferous) brachiopods from the Itaituba Formation of the Amazon Basin, Brazil

A new brachiopod fauna is described from the lower Itaituba Formation at the Caima Quarry 2 section in the Itaituba area, Amazon Basin, Brazil. The Amazonoproductus amazonensis-Anthracospirifer oliveirai Assemblage is proposed for this fauna, which is considered early Pennsylvanian (Morrowan) as constrained by associated conodont and fusulinacean faunas. Nine brachiopod taxa are described herein, including Amazonoproductus amazonensis gen. et sp. nov., and Buxtonioides itaitubensis sp. nov. and Linoproductus caima sp. nov. The new tribe Marginovatini of the Linoproductoidea (the Productida) is also proposed.

Stratigraphic and palaeoenvironmental significance of a Pennsylvanian (Upper Carboniferous) palynoflora from the Piaui Formation, Parnaiba Basin, northeastern Brazil

A well-preserved palynoflora is reported from within a cored interval of a coal-exploratory borehole (1-UN-23-PI of the Geological Survey of Brazil) in the southern part of the Parnaiba Basin, northeastern Brazil. The sample studied is from the lower portion of the Piaui Formation. Its palynoflora is characterized by particular abundance of the trilete cavate/pseudosaccate miospores Spelaeotriletes triangulus Neves and Owens, 1966 and S. arenaceus Neves and Owens, 1966, together with cingulizonate forms mainly attributable to Vallatisporites Hacquebard, 1957 and Cristatisporites R. Potonie and Kremp emend. Butterworth et al., 1964. Radially and bilaterally symmetrical monosaccate pollen grains are also well-represented, chiefly by Plicatipollenites Lele, 1964 and Potonieisporites Bhardwaj, 1954, respectively. Taeniate grains (i.e., monosaccates and bisaccates) are relatively minor constituents of the palynoflora; no marine microplankton were encountered. Several species are described in detail : the trilete apiculate spores Brevitriletes levis (Balme and Hennelly) Bharadwaj and Srivastava, 1969 and Horriditriletes uruguaiensis (Marques-Toigo) Archangelsky and Gamerro, 1979; and the taeniate pollen grains Meristocorpus ostentus sp. nov. and Lahirites segmentatus sp. nov. A Pennsylvanian (Late Carboniferous : late Westphalian) age is adduced for the palynoflora via its correlation with part of the Tapajos Group (specifically, the upper Itaituba Formation) of the Amazonas Basin in northern Brazil. The entirely land-derived palynomorphs, associated with abundant plant debris, corroborate previous suggestions that the lower part of the Piaui Formation accumulated in a nonmarine setting under conditions of aridity.

Acanthodian and Actinopterygian fish remains from the Itaituba Formation, Late Carboniferous of the Amazon Basin, Brazil, with a note on acanthodian ganoin

Acanthodian and Actinopterygian fish remains from the Itaituba Formation, Late Carboniferous of the Amazon Basin, Brazil, with a note on acanthodian ganoin

Habitat of Petroleum in the Paleozoic Basins of Brazil: A Look Back, a Comparison, a Look Forward

It took almost a century of intermittent petroleum exploration in Brazil's vast Paleozoic basins before continuous production of about 5000 bbl per day of light oil, together with gas, could be established in one of them. Proved volumes of oil equivalent in place so far discovered in Paleozoic reservoirs amount to only 0.6% of the domestic total, but hopes of substantial new finds are great. In the Rio Urucu field of Solimoes basin (Upper Amazon), hydrocarbons are being produced from Early Carboniferous Monte Alegre formation sandstones roofed by evaporites and carbonates of the Carboniferous Itaituba formation which were intruded by thick Juro-Triassic igneous sills and folded during a Cretaceous reactivation event into the present-day shape of gentle anticlinal trends controlled by reverse faulting. The widespread occurrence of igneous intrusions and extrusions in the Solimoes, Amazonas, Parnaiba, and Parana basins is a major problem met by explorationists throughout the years but can be faced with presently available technology, seismic and other. Further investigations in these four basins are needed in order to better define details of basin architecture, configuration of basement, location of the oil kitchens, main carrier beds, windows in the dyke walls through which hydrocarbons could find their waymore » to the traps, etc. Examples from the various basins, along with a comparison to some successful exploration cases in the USA, suggest that the habitat of other commercial oil and gas in the Paleozoic basins of Brazil may be localized in the deeper basinal positions - like in the Rio Urucu trend - but also in the shallow flank areas, where igneous rocks tend to be scarcer and exploration baroquely started.« less

Atomic Absorption Spectrometry in GeologyE.E. Angino and G.K. Billings, 1973. Elsevier, Amsterdam/London/New York, N.Y., 2nd rev. ed., x + 191 pp., Dfl. 32.50

This study aims to characterize the scolecodonts, trilobite pygidium fragments and fish remains of an outcropped region in the southern Amazonas Basin, comprising the uppermost section of the Monte Alegre Formation and the basal section of the Itaituba Formation. These, correspond to part of the marine portion of the Tapajós Group, related to an intracratonic carbonate platform. The Monte Alegre Formation includes a deposition of fluvial-deltaic and aeolian sandstones, siltstones and shales of interdunes and lakes, intercalated with transgressive carbonates of a shallow restrict nearshore marine environment. The Itaituba Formation comprises a thickest deposit of marine carbonates, representing the establishment of widespread marine conditions, and is the richest interval containing organisms of shallow marine environment in the Pennsylvanian of the Amazonas Basin. The associated fauna includes brachiopods, bivalves, gastropods, crinoids, echinoids, bryozoans, corals, foraminifers, sponges, ostracods, trilobites, scolecodonts, fish remains and conodonts, mainly in the packstones, and subordinately in the wackestones and mudstones. Conodonts Neognathodus atokaensis, Diplognathodus orphanus, Idiognathodus incurvus, and foraminifers Millerella extensa, Millerella pressa, Millerella marblensis, Eostaffella ampla, Eostaffella pinguis and Eostaffella advena characterizes a predominant Atokan age to the analyzed profile. The fossil association herein presented is taxonomically diversified and biologically interesting, comprising an important and well preserved, for the first time occurrence of two molds and two fragments of Proetida trilobites. Well preserved Eunicida and Phyllodocida scolecodonts and paleonisciform fish remains. These fossils help in the paleoenvironmental establishment of the studied interval in the Amazonas Basin and as a potential biostratigraphic and paleoecological tool to correlate regionally and globally the Pennsylvanian.

Ocorrências de Foraminíferos Fósseis no Brasil

São descritos pela primeira vez alguns foraminiferos fósseis do Brasil. O artigo inicia com um breve apanhado das informações pré¬ vias sobre ocorrências de foraminiferos fósseis do Brasil. Discute-se material com foraminiferos procedente de Caraparú, Estado do Pará, provavelmente referivel à formação Pirabas de idade miocenica. Não foram atingidas, porém, determinações sistemáticas. Segue-se a descrição de alguns foraminiferos do Paleozoico Superior, procedentes do Rio Parauarí (formação Itaituba). dentre os quais foram genericamente reconhecidos Endothyra e Plectogyra. São considerados, então, foraminiferos cretácicos vindos do Rio Gramane, Estado de Paraiba do Norte e Ponta dos Barcos, Estado de Sergipe. Detem-se o autor mais demoradamente sobre fósseis coletados na Ponta de Pirabas (formação P irabas), cuja idade é considerada miocenica. Descreve: Quinqueloculina sp. a, Q. sp. b., Q. sp. c, Pytgo sp. a, P. sp. b., Peneroplis sp., Discovbis? sp.., “Rotalia ’ sp., Gyroidina? sp., Eponides sp., Nonion sp. a, N . sp. b