Associações naturais de conodontes Mesogondolella spp., Grupo Itararé, Cisuraliano da Bacia do Paraná

Itarare Group represents the glacial record of Gondwana Continent in the intracratonic Parana Basin, encompassing regions of Southern Brazil, Eastern Paraguay, Northeast Argentina and Northern Paraguay. Itarare Group is the thickest sedimentary package of Parana Basin, and was deposited over 36 million years during the end of the Carboniferous and the beginning of the Permian. However, in relation to its paleoenvironmental evolution, it is generally understood that more research is necessary, in order to better understand the genesis of the Itarare Group in different places. The present work entailed mapping facies associations for the Itarare Group in the city of Salto, in Sao Paulo State, by identifying and classifying sedimentary facies that, in turn, were utilized to develop a paleoenvironmental evolution model. This model was based on geological mapping carried out over 125 km². Petrological and petrographic descriptions of 32 outcrops of Itarare Group also were studied. These results were compared with subsurface data obtained by Sistema de Informacoes de Aguas Subterrâneas, Servicos Geologicos do Brasil (SIAGAS-CPRM; System Water Information Groundwater, Geological Survey of Brazil). Through lithofacies and petrographic analyses and making a comparison between five column sections, surface and subsurface data, a stratigraphic correlation model was established for the region. Through this model was possible to identify four facies associations, which, together, indicate how the paleoenvironmental evolution of the region occurred. The first three associations (A, B, C) were interpreted as being formed in subaqueous environment, being related to sandy lobe systems, followed by the last association (D), pertaining to a fluvial system. doi: 10.12957/jse.2016.21956

Drilling in the Parana basin of Brazil in the mid-1980s discovered gas and condensate in the Itarare Group, and showed that glacial deposits in Brazil can contain hydrocarbons. The reservoir potential of the Carboniferous-Permian Itarare Group of the basin is analyzed using new subsurface data from 20 deep wells drilled in the early to middle 1980s. Central to the analysis was the construction of over 3000 km of cross sections based on more than 100 wells, the description of more than 400 m of core, and study of 95 thin sections. Subsurface exploration and mapping of the Itarare are greatly aided by the recognition of three recently defined and described formations and four members, which are traceable for hundreds of kilometers. These units belong to three major glacial cycles in which the pebbly mudstones and shales are seals and glacially related sandstones are reservoirs. The best sandstone reservoirs in the deep subsurface belong to the Rio Segredo Member, the uppermost sandy unit of the Itarare. The Rio Segredo Member is the best petroleum target because it is overlain by thick seals and massive pebbly mudstones and shales, and because it is shallower and less compacted than underlying, more deeply buried sandstones. This member has little detrital matrix and much of its porosity is secondary, developed by carboxylic acid and CO[2] generated when Jurassic-Cretaceous basalts, sills, and dikes were intruded into the Parana basin as Gondwana broke up.

SUMMARY A detailed magnetostratigraphic and rock-magnetism study of two Late Palaeozoic rhythmite exposures (Itu and Rio do Sul) from the Itarare Group (Parana Basin, Brazil) is presented in this paper. After stepwise alterning-field procedures and thermal cleaning were performed, samples from both collections show reversed characteristic magnetization components, which is expected for Late Palaeozoic rocks. However, the Itu rocks presented an odd, flat inclination pattern that could not be corrected with mathematical methods based on the virtual geomagnetic pole (VGP) distributions. Correlation tests between the maximum anisotropy of the magnetic susceptibility axis (K1) and the magnetic declination indicated a possible mechanical influence on the remanence acquisition. The Rio do Sul sequence displayed medium to high inclinations and provided a high-quality palaeomagnetic pole (after shallowing corrections of f = 0.8) of 347.5°E 63.2°S (N = 119; A95 = 3.3; K = 31), which is in accordance with the Palaeozoic apparent wander pole path of South America. The angular dispersion (Sb) for the distribution of the VGPs calculated on the basis of both the 45° cut-off angle and Vandamme method was compared to the best-fit Model G for mid-latitudes. Both of the Sb results are in reasonable agreement with the predicted (palaeo) latitudinal S-λ relationship during the Cretaceous Normal Superchron (CNS), although the Sb value after the Vandamme cut-off has been applied is a little lower than expected. This result, in addition to those for low palaeolatitudes during the Permo-Carboniferous Reversed Superchron (PCRS) previously reported, indicates that the low secular variation regime for the geodynamo that has already been discovered in the CNS might have also been predominant during the PCRS.

Facies, petrophysical and geochemical properties of gravity-flow deposits in reservoir analogs from the Itararé Group (late Carboniferous), Paraná Basin, Brazil

This study presents a methodology of data preparation for cyclostratigraphic analysis, using core and gamma ray log data from two wells drilled by CPRM (Companhia de Pesquisa de Recursos Minerais) to coal research, one in Santa Catarina state (7-RL-04-SC) and other in Rio Grande do Sui state (IB-93-RS). The wells sampled rocks from Lower Permian Itarare Group, Parana Basin, originally deposited in glacial, periglacial and marine environments. The distance between the original locations of the cores (about 380 km) made it possible to test, after ward (Cyclostratigraphy of Lower Permian - Case Study in Itarare Group, Parana Basin (PART II), in this same publication), the astronomic forcing in different locations of the basin. Two methods ofdata sampling were used, according to data scale and the possible forcing: the gamma ray logs were digitized and sampled at 1 em intervals, in order to test the presence oforbital forcing (20,000 to 400,000 years) or other forcing phenomena (3,000 to 10,000 years), and the cores were scanned in the intervals with rhythmites and transformed in gray scale data sampled equally (0.2538 mm), in order to search for annual to millenarian cycles. The process of core data preparation before scanning required a detailed elimination of small fractures and sedimentary structures as ripples, to avoid distortions in the final results

A análise do material proveniente do afloramento de Rio da Estiva, Formação Rio Bonito, Permiano Inferior da Bacia do Paraná, em Santa Catarina, possibilitou a avaliação das glossopterídeas ali existentes. O conteúdo paleobotânico compreendia, até este trabalho, formas apresentadas apenas em nível genérico, como Glossopteris sp. e Samaropsis sp., frutificações como Ottokaria sp., Arberia minasica, Arberia sp. e Hirsutum sp., além de restos não identificados, tais como caules e prováveis folhas de licófitas. Novas análises, realizadas com exemplares melhor preservados, possibilitaram a separação dos espécimes atribuídos ao gênero Glossopteris em três morfoespécies distintas: Glossopteris communis, Glossopteris cf. G. indica e G. occidentalis. Além disso, confirmou-se o primeiro registro de folhas do tipo Gangamopteris na flora de Rio da Estiva (G. obovata), além da presença de frutificações do tipo Ottokaria e sementes do tipo Cardiocarpus, o que aumentou a diversidade desta associação e a possibilidade de correlação com outras floras pertencentes ao mesmo intervalo na Bacia do Paraná.

The Parana Basin was developed on one of the younger areas of the South American platform, and its basement cratonization had continued up till the Eopaleozoic. The Brazilian South-Southeast folded belt, with a NE-SW strike in Upper Pre-Cambrian, probably had watched the development of subsequent aulacogenic trenches with NW-SE trends in the Cambro-Ordovician. extending easterly from the present Andean belt. These type zones had controlled the pericratonic sedimentation on the western border area of the present basin during the Silurian. During the Devonian, a portion of the future Parana Basin, belonging to the present Andean belt, had been divided into sections by the uplift of the Asuncion arch. However, the NW·SE weakness zones, which were previously impressed on the basin basement, had strongly controlled the Devonian sedimentation, the Lower Carboniferous tectonic reactivation and erosion, and the very early Permocarboniferous sedimentation. In these espisodes, the vertical movements had been controlled by the old pattern which is related to the aulacogenic channels in the basement. The basin had acquired an intracratonic sineclise character, which was clearly defined during the Middle-Upper Permian and which was maintened up till the Lower Triassic. In southern Brazil, a wide uplift of the crust, which had begun in the Jurassic-Cretaceous, had caused the vulcanism phenomenon and the old aulacogen zones of weekness and fault had been the tracks for the extrusion of the lava. The consequent shrinking of this crustal uplift area had controlled, subsequently, the subsidence process of the coastal basins, such as Campos and Santos, as well as the reactivation and the sedimentation of the Bauru Group at the continent. The successive boundaries of this contracting movement in the domic area were controlled by the NE-SW alignments. The rift phase of the coastal basins of that time had caused the elevation of the coastal margin of the old NE-SW folded belt and step faults were formed in both direction through the marginal basins and through the continental interior. The structures of Piratininga. Agudos, Artemis, Anhembi, etc, are examples of these step fault structures. Contemporaneously, the Upper Cretaceous sedimentation had begun in the northern area of the basin. The zones of NW-SE alignments had subdivided the Parana Basin, and had controlled the areas of maximum sedimentation, until the Tertiary, when the basin had been even more subdivided by the reactivation of these zones. This subdivision included the northern area which is still receiving sedimentation at the present time. The riff control of the basement, especially during the early Paleozoic sedimentation and reactivation and the strong influence during the Mesozoic evolution, allows the classification of the Parana Basin as an intracontinental, cratonic, type 2A complex basin, similar to the west Siberian basins.

The first recorded decline of the Malvinokaffric Devonian fauna in the Paraná Basin (southern Brazil) and its cause; taphonomic and fossil evidences

Two late Paleozoic glacial rhythmite successions from the Itarare Group (Parana Basin, Brazil) were examined for paleoclimate variations. Paleomagnetic (characteristic remanent magnetization, ChRM) and magnetic susceptibility (K z ) measurements taken from the rhythmites are interpreted as paleoclimatic proxies. Ratios of low-frequency components in the K z variations suggest Milankovitch periodicities; this leads to recognition of other, millennial-scale variations reminiscent of abrupt climate changes during late Quaternary time, and are suggestive of Bond cycles and the 2.4 k.y. solar cycle. We infer from these patterns that millennial-scale climate change is not restricted to the Quaternary Period, and that millennial forcing mechanisms may have been prevalent throughout geologic time.

Como contribuição a um projeto de pesquisa abrangente de modelos análogos a reservatórios fraturados (Projeto Modres), foram realizados ensaios geoelétricos nos arenitos do Grupo Itararé, Bacia do Paraná. O principal objetivo deste estudo consiste em determinar as respostas de resistividade dos arenitos fraturados do Grupo Itararé. Particularmente interessa a detecção de fraturas e seu comportamento hidráulico (atuando como barreiras ou condutos) influenciando a resistividade, e, neste contexto, apresenta uma nova contribuição ao entendimento do Grupo Itararé. A área de estudo envolve a Fazenda Rivadávia, localizada perto do Parque Estadual de Vila Velha. Geologicamente a área é formada por rochas da Formação Campo Mourão, Grupo Itararé, Bacia do Paraná, sendo representadas por uma porção sedimentar arenosa chamada informalmente de “Arenitos Lapa-Vila Velha”. O levantamento de campo foi realizado sobre uma malha com quinze linhas paralelas e distanciadas 10 metros. Vários espaçamentos foram utilizados no arranjo dipolo-dipolo, incluindo 5, 10, 20, 30 e 40 metros. O processamento dos dados iniciou-se com a plotagem em pseudo-seções de resistividade aparente, seguida da geração das seções modelos de resistividade através de inversão 2D. Os resultados obtidos permitem correlacionar os valores de resistividade com diversas feições geológicas, mais especificadamente com a geometria das camadas e o contato entre litologias diferentes. De maneira geral, foi observado que o condicionamento estrutural, representado pelas fraturas, influenciam os valores de resistividade. Altos de resistividade foram correlacionados a fraturas mapeadas, possivelmente indicando que estas se encontram fechadas, enquanto que baixos podem indicar fraturas mais abertas, maior porosidade e com conseqüente maior facilidade de percolação de água. Os resultados mostram valores muito altos (milhares de Ohm.m), até certo ponto distribuídos de forma uniforme, mesmo nos níveis mais arenosos, indicando que a permeabilidade dos arenitos é muito baixa.

A small and poorly diversified bivalve fauna from Taciba Formation, Itarare Group, Parana Basin (State of Santa Catarina, Mafra Municipality), is described in this paper for the first time, based on new findings. The fauna is recorded in a 30 cm thick interval of fine sandstone locally at the top of Taciba Formation, in the Butia quarry. The studied fossil-bearing sandstone bed is a marine intercalation recording a brief eustatic rise in sea-level, probably following glacier retreat and climate amelioration at the end of a broad glacial scenario. The fauna is mainly dominated by productid brachiopods, which are not described here, and rare mollusk shells (bivalves and gastropods). Two bivalve species were identified: Myonia argentinensis (Harrington, 1955), and Aviculopecten multiscalptus (Thomas, 1928). The presence of Myonia argentinensis is noteworthy since this species is also present in the Baitaca assemblage found in marine siltstones (Baitaca assemblage) of the Rio do Sul Formation, cropping out at the Teixeira Soares region, Parana State. This species is also recorded in the bivalve fauna from the Bonete Formation, Pillahinco Group, Sauce Grande Basin, Buenos Aires Province, in Argentina. Hence, the marine bivalves of the Taciba Formation are associated with the transgressive event that characterizes the Eurydesma fauna, indicating a Late Asselian-Sakmarian age for the bivalve fauna. Presence of the Myonia argentinensis megadesmid species reinforces the Gondwanic nature of the studied fauna.

Abstract. PALYNOSTRATIGRAPHIC ANALYSIS OF PERMIAN DEPOSITS (HN-05-RS AND HN-25-RS BOREHOLES) FROM SOUTHERN PARANA BASIN. This paper presents the palynological results obtained from 133 levels of the HN-05-RS and HN-25-RS wells, drilled in Hulha Negra, southern portion of Rio Grande do Sul State. The sampled levels included the Permian units of the Gondwana I Supersequence (Itarare Group and Rio Bonito, Palermo, Irati, Serra Alta, Teresina and Rio do Rasto formations) from Parana Basin, Brazil. A total of 133 palynomorph species were recorded, corresponding to spores (57), pollen grains (65), besides microplanktonic elements and fungi (11). The stratigraphic distribution of all taxa is presented, as well as the relative frequency of selected levels. The analysis allowed the recovery of palynological associations relatively diverse and abundant from the overlying levels of the Irati Formation, which were generally considered sterile. The associations are related to Vittatina costabilis (Asselian to middle A...

The imposed diagenetic conditions to the sandstones of the Itarare Group during progressive burial, were analyzed through de integration of subsidence history of the basin with mesodiagenetic products evaluation. The burial history and compaction of the sedimentary column was based on regional stratigraphy correlation, using composite logs, thickness variation, lithology content and erosive rate. The geohistory curves with subsidence and uplift phases were based on previous works of stratigraphy. The Itarare Group deposition was related to high subsidence rate in the Parana Basin. This high subsidence rate had great influence in the sandstones porosity, mainly in chemical compacting action, decurrent of pressure and temperature increase conditions for the burial gradual. Is also distinguished the quartz overgrowths development, abundant anhydrite cementation and partial dissolution of the cements and detritics components.

Shallow reflection seismic is applied to image stratigraphic and structural features to help the study of fractured reservoir analog modeling. The outcropping geological unity is composed of sandstone of the Itarare Group, Parana Basin. Fine-grained sedimentary rocks with silt and clay content occur as intercalation in the sandstone so that acoustic impedance variation is expected at the interfaces and consequently reflections be detected. Intense fracturing occurs, rendering the area very interesting for the study. As little has been done in this area, particularly in Brazil, results of tests conducted to determine the acquisition parameters and difficulties encountered are discussed in detail. Although results show apparent correlation between geology and seismic features, this has still to be confirmed by sonic logs and VSP tests, which will be carried on next, in the research project.

Pelagic deep-sea siliceous successions in accretionary complexes preserve precious records of a vast deep seafloor that is now lost due to plate subduction. Microfossils are the key means of age assignment of these successions, but poor preservation due to tectonic deformation and metamorphism at the subduction zone hamper biostratigraphic records. X-ray computed microtomography, while not widely used in biostratigraphic studies until now, allows us to visualize fossils that are impossible or difficult to extract from host rocks due to poor preservation. In this study, we applied this method on conodonts from a pelagic chert–claystone succession in Okoshizawa, Iwaizumi Town, Northeast Japan, using a laboratory-based X-ray microscope. This work is a first close look at conodont biostratigraphy across the Carboniferous–Permian boundary in pelagic deep Panthalassa. We identified conodonts including ten species that are used as zonal markers in intensely studied areas such as around the East European Platform and Midcontinent United States. Based on the occurrence of conodonts, the studied section in Okoshizawa was correlated to the lower Moscovian to middle Artinskian. Confirmation of Moscovian to Artinskian age diagnostic conodonts from pelagic Panthalassa strengthens their role as global biostratigraphic indicators. By identifying more numerous specimens compared to the conventional hydrofluoric acid dissolution method, we were able to obtain information about conodont faunal characteristics around the Carboniferous–Permian boundary in pelagic deep areas of Panthalassa. The dominant taxa changed fromStreptognathodustoMesogondolellain the middle Asselian, probably reflecting an ecological takeover by the latter in the deep waters.