Botucatu Formation Research Articles

Contribution of Lab Radon Flux Measurements for Evaluating Submarine Groundwater Discharge in Coastal Areas

Laboratory-scale experiments were conducted on Carboniferous Limestone gravels from the Mendip Hills area, England; sandstones from the Pirambóia and Botucatu formations, Paraná sedimentary basin, Brazil; samples of schist and quartzite from Caldas Novas Hydrothermal Complex, Brazil; and the minerals tantalite, cassiterite, and columbite from mining areas at Rio Grande do Norte State, Brazil, with the purpose of evaluating the release of 222Rn to the water phase. The specific surface area of the samples corresponded to 1.69–81.36 cm2g−1, which provided values of 0.001–1.68 dpm/g and 3.18 × 10−6 to 0.59 for the radon released and radon emanation coefficient, respectively. These results allowed us to calculate the radon flux with respect to the radon leakage, which corresponded to values of 0.00016–0.00158 Bq/m2/d for the denser materials and 0.018–0.43 Bq/m2/d for limestones and sandstones. They also permitted us to find an inverse, significant relationship between the radon generated by the minerals/rocks and the radon flux into the water phase, which was tested for sediments in coastal and inland Brazilian areas, demonstrating utility for evaluating the diffusive radon flux from the sediments, which is an important parameter to monitor submarine groundwater discharge (SGD) by means of radon as a natural tracer.

MORE THAN FOSSILS: PALEOBURROWS AS GEOHERITAGE AND PALEOENVIRONMENTAL ARCHIVES IN THE CAMINHOS DOS CÂNIONS DO SUL UNESCO GLOBAL GEOPARK, SOUTHERN BRAZIL

The paleoburrows (paleotocas) are ichnofossils produced by the autochthonous megafauna of South America. The Caminhos dos Cânions do Sul UNESCO Global Geopark (CCSUGG), Southern Brazil, contains a large amount of these ichnofossils, which are regarded as internationally relevant. This article aims to discuss paleoburrows as geoheritage and paleoenvironmental records, using the examples present in the CCSUGG. For this purpose, bibliographic research, paleoburrows cataloguing fieldwork and mapping routine were carried out. So far, 24 paleoburrows have been compiled. Mostly found in sedimentary friable rocks, such as the Botucatu Formation sandstones, can also occur in harder, weathered lithologies in a smaller amount. Some bioerosive structures show claw scrapping and digging signs, attributed to the Pliocene-Pleistocene South American megafauna, such as the giant sloths and the giant armadillos. Despite these 24 paleoburrows, four of them are recognized as geosites of regional and international value. These ichnofossils provide geological and paleontological values, considering their builders are already extinct and their presence allows to infer paleoenvironmental changes and megamammals distributions. Besides tangible values, these burrows evoke myths and histories about indigenous people and settlers who used these burrows as shelter, representing intangible cultural heritage. Even though these values, paleoburrows face threats that endanger their conservation, like unguided visitors, water flow and block falls. Hence, there are geoeducational efforts to preserve these ichnofossils for future generations. All these processes are evident in geosites with scientific, scenic and touristic values, the paleotocas giant paleoburrows.

Rock anchor testing on sandstone from the Botucatu Formation, Paraná River Basin, Brazil: Insights for climbing safety procedures at the Corumbataí Geopark Project

The Corumbataí Geopark Project, located in São Paulo state, southeast Brazil, features valuable geosites that represent Earth's heritage and attract visitors with geoturism activities such as climbing. Rock anchors are crucial for ensuring climbers' safety in case of falls. This study reveals that the load capacity performance of expansion rock anchors is influenced by the applied torque, the physical-mechanical properties of the rock, and the weathering-induced strength degradation over time. The sandstone of Botucatu Formation, the predominant lithotype at these geosites, was assessed through petrographic analysis, non-destructive testing, physical and mechanical assessments, and pull-out tests of the anchors. Our findings indicate that the sandstone generally meets the geotechnical properties requirements for load capacities outlined in international climbing guidelines, a threshold of 80 MPa is recommended for effective rock anchor performance. However, prolonged exposure leads to rock degradation, compromising safety. Consequently, anchors should not be used in weathered rock and regular maintenance is strong recommended for climbing safety, approximately every 6 six years. This study provides a novel approach to characterizing rock-anchor interactions, supporting the development of effective management plans for outdoor activities.

Three-dimensional model and environmental fragility in the Guarani Aquifer system, SE-Brazil

The Guarani Aquifer System (GAS) is a vast transboundary continental sedimentary basin in southern South America, encompassing sedimentary rocks and basalt flows across Uruguay, Paraguay, Argentina, and Brazil. It serves as a crucial water resource for urban supply and irrigation. This study aims to propose geophysical, geometric, and fragility models of the GAS in a critical exploitation area, utilizing geological data, geophysical logs, geomorphometry, and information from tubular wells. The models define distinct geophysical ranges for each formation and identify contacts between sedimentary and basaltic rocks. Integration of horizontal and vertical spatial distributions of geophysical and geological data forms a 3D model, revealing basaltic flows and intrusions distribution in fragile areas between formations, and potentially connecting aquifer layers. Natural fragility zones, characterized by high fracture densities, are observed in the central-east region, while outcrop and recharge areas of the main aquifer hydrofacies are found in the north. The 3D model highlights similarities between the topography of the Botucatu Formation (KJb – eolian sandstones) and the potentiometry of GAS at local scales, and overexploitation zones in Ribeirão Preto's city center. The assessment prioritizes areas at risk and conservation strategies for sedimentary aquifers, emphasizing interactions between surface and groundwater and addressing issues of overexploitation, identifying high-impact risks on GAS hydrodynamics and water quality.

Provenance of volcano-sedimentary features using tourmaline and REE compositional analysis, in the Paraná Basin, southern Brazil

The present research focuses on sediments' compositional analysis, in the Paraná Basin, to demonstrate provenance contributions for the volcano-sedimentary features distributed along three regions of the Basin's border. In this context, the analyzed sediments, which are generally attributed to the Botucatu Formation, interact with volcanic lava flows from the Serra Geral Formation, establishing a volcano-sedimentary interaction. Nonetheless, the classic description for the Botucatu Formation comprehends almost ubiquitous fine to medium sandstones, while the herein sedimentary rocks vary from fine-grained to very coarse sediments. The granulometry difference raises questions about unexplained events during the Cretaceous volcanism (Serra Geral Formation) over the Botucatu desert. Accordingly, the studied area is distributed into regions A, B, and C from the center to the eastern of the state respectively, covering the Paraná basin's border where the volcano-sedimentary rocks can be outcropped. The methodologies employed involve the analysis of tourmaline compositions and REE patterns. These analytical tools help identify provenance variations and the development of local processes. As a result, the data indicate the predominance of meta-pelites and metapsammites in region A, while in region C there is a prevalence of granitoids contribution, while region B is a transition area showing contributions of both meta-pelites, metapsammites, and granitoids that are attributed to some units of the Sul-Rio-Grandense Shield.

Stratigraphic and cartographic review in the western part of Bauru Basin – Brazil - (Upper Cretaceous): implications for the depositional model

ABSTRACT Bauru Basin (Upper Cretaceous) spans 190,000 km² in western segment, Mato Grosso do Sul and Goiás states, Brazil. The Supersequence is a predominantly sandy siliciclastic unit. In Mato Grosso do Sul state a substantial portion of the sedimentary supersequence was considered indivisible. This research, based on regional field surveys, presents updates to the geological map, depositional model, and lithostratigraphic chart of the western Bauru Basin. In Mato Grosso do Sul, the Rio Paraná Formation was identified, directly overlaying the Serra Geral Group in the south/southwest, and the Botucatu Formation on north/central region. The Santo Anastácio Formation outcrop area was found to be smaller than previously mapped, showing lateral contacts with the Rio Paraná and Vale do Rio do Peixe formations. The Vale do Rio do Peixe Formation, conversely, now exhibits a larger mapped area. Additionally, the Marília Formation were discovered in São Gabriel do Oeste-MS, previously marked as detrital-lateritic cover.

Detrital zircon and tourmaline unravel polycyclic provenance of sedimentary infill of the Cretaceous Tupanciretã formation, southern Brazil

The recognition and evaluation of polycyclic processes in sedimentary units are critical for proper provenance analysis and sedimentary system interpretation. The chemical composition and textural maturity of detrital tourmalines and zircons allow identification of sediment source areas, transport, and deposition. This study investigates the origin and history of post-Gondwanan sediments of the Tupanciretã Formation in southern Brazil, which lacks provenance studies. The Tupanciretã Formation is in a similar setting of the Bauru Supersequence at the uppermost portion of the Paraná Basin. Detrital zircon ages indicate sediment provenance from the Transamazonian, Grenvillian, and Brasiliano orogenic cycles of the Rio Grande do Sul Shield and younger grains (280-128 Ma) record contribution from the Choiyoi and Serra Geral igneous events, with a maximum deposition age of 127 Ma. Detrital tourmaline chemical analyses points to the Sul-riograndense Shield as the ultimate source, with metapelitic, metapsamitic and granitic origins. The predominant degrees of roundness are well rounded to rounded suggest evidence of sediment recycling from sedimentary units of the Paraná Basin, with important aeolian reworking involved. Zircon U–Pb signatures are compatible with the eastern sector of the Botucatu Formation in Rio Grande do Sul as the immediate source and the northeastern Sul-riograndense Shield as the ultimate source. Intermediate sources between the Sul-riograndense Shield and the Tupanciretã Formation were Gondwanan sedimentary units of the Paraná Basin, with possible participation from the Camaquã Basin.

Optimization of enhanced oil recovery using ASP solution

Many studies have been conducted to focused on developing an optimal alkali/surfactant/polymer (ASP) composition to increase the recovered fraction of oil in reservoirs that have already undergone water injection. To analyze the effect of alkali (Na2CO3), surfactant (lauryl sodium sulfate), and polymer (commercial xanthan gum) concentration on oil recovery, a complete factorial experimental design was performed with combinations of three variables (alkali, surfactant, and polymer) and three central point replications (2³ + 3). The experiments were carried out on a core holder using rock samples from the Botucatu formation. The simulated oil reservoirs have an average permeability of 348 mD and a temperature of 60 °C. The crude oil was acquired from the Carmópolis field, with 25.72 °API. Synthetic production water containing 40,000 mg L−1 of NaCl and 13,000 mg L−1 of Na2SO4 was injected through an HPLC pump to saturate the rock samples and to recover the oil in the secondary step. From the experimental results, it was verified that the surfactant and polymer concentrations are the most statistically significant independent variables and that first-order interactions are not statistically significant for the process. The oil recovery factors in the secondary stage ranged between 30 and 36 % of the OOIP, which are within the range reported in the literature. The optimal composition of the ASP fluid obtained a recovered fraction of oil of 62 % in the advanced step. Other combinations reported in the literature used higher concentrations of alkali, surfactant, and polymer with lower recoveries and higher cost in the injection design. Thus, the present study highlights the necessity to investigate the performance of each component of the ASP solution. In addition, the results obtained in this study are very attractive for possible full-scale applications.

Farlowichnus rapidus new ichnogen., new ichnosp.: A speedy and small theropod in the Early Cretaceous Botucatu paleodesert (Paraná Basin), Brazil

The Botucatu Formation (Paraná Basin, Brazil and the southern neighboring countries) comprises one of the richest tetrapod ichnological deposits of the Lower Cretaceous in South America. The ichnofossils are found in reddish sandstones lithofacies -interpreted to be dune and interdune deposits. The sandstones of Botucatu Formation originally covered a surface estimated in at least 1,300,000 km2, the largest known fossil desert in the Earth's history. The distribution area of the Botucatu paleodesert presents one of the world's largest megatracksites. The tetrapod ichnofauna from the Botucatu Formation comprises minor bipedal dinosaur tracks (almost all attributable to theropods, with one exception, a doubt ornithopod trackway) along with many thousands of footprints of early mammals, and a single trackway of a lacertiform reptile. Among the bipedal dinosaur footprints, the most common and typical are considered theropod tracks, with long strides and high step angle and always with an acuminate termination. These trackways are straight and very narrow, with long strides and step angles showing high values. The footprints have a relatively large and very wide III digit and small, short, pointed, bladelike outer digits. The most special characteristic is that the II digit is longer and more important than the IV digit. Because of this morphology, the general outline of the footprint often reminds that of a waterdrop and, although it is structurally tridactyl, it usually looks like functionally monodactylous. These tracks are herein assigned to small theropods adapted to desert life with a prevalently cursorial gait, probably ancestors of clades such as noasaurs and velocisaurs. Due its unique morphological aspects it is defined a new ichnogenus and ichnospecies, Farlowichnus rapidus new ichnogen., new ichnosp.

Volcano-sedimentary interactions – A key to understand Cretaceous paleoenvironments in the Paraná basin (southern Brazil)

The Lower Cretaceous in the Paraná Basin record a large volcanic event (Serra Geral Formation) that covered an active sedimentary system (Botucatu Formation), before the fragmentation of the southern Gondwana. Therefore, the fluvial-aeolian deposits underlying aeolian deposits of residual dunes, were gradually covered by volcanic flows. Intense basic and minor acidic magmatism covered an extensive continental aeolian environment. The interface between the two units shows an aeolian environment during the early stages of volcanism forming deposits and volcano-sedimentary features overlying and underlying the flows. In six outcrops on the southern portion of the current border of Paraná Basin, in Rio Grande do Sul state, these deposits and features were recognized, showing the complexity of the environment and the processes associated with lava flows and sediments. They were formed by the interaction of consolidated or unconsolidated sediments, saturated or not in the water, with basaltic or dacitic flows. Interaction features and deposits synchronous to volcanism (volcanoclastic), later or in intervals between volcanic events (epiclastic) and only cover, with absence of interactions, were identified. Through the distinctive characteristics of the interaction processes between the volcanic rocks and the sediments analyzed in the volcanic-sedimentary features and deposits, the morphology of the aeolian environment of Botucatu Formation could be, by analogy, compared to the current aeolian environments. The proposed paleoenvironment indicates a sedimentary environment with different domains, categorized by their water saturation. The different siliciclastic components found in each domain allowed the generation of different features and volcanic-sedimentary deposits evidencing aspects related to the presence or absence of water among the proposed domains.

Volcanoclastic and epiclastic diagenesis of sandstones associated with volcano-sedimentary deposits from the upper Jurassic, Lower cretaceous, Paraná Basin, southern Brazil

The opening of South Atlantic Ocean produced an immense volume of lava that covered an active aeolian system during Lower Cretaceous. The contact of Botucatu Formation sandstones with the Serra Geral volcanic flows generated a variety of volcano-sedimentary features and deposits. During volcanism, the temperature contrast between lava and wet or water-saturated sediments formed volcanoclastic features and related sedimentary deposits. In moments of magmatic quiescence, epiclastic deposits were generated due to the return of sedimentation. Volcanoclastic deposits include volcanic breccias with sandy matrix, and epiclastic deposits include conglomerates and conglomeratic sandstones with intraclasts. Quantitative petrography of the sandy matrix samples of these deposits was analyzed, in order to discuss the paragenesis of volcano-sedimentary interactions. Regular burial diagenetic processes were discussed for epiclastic sandstones and contact diagenesis processes for volcanoclastic sandstones. The original composition of volcanoclastic and epiclastic sandstones is heterogeneous. However, the main difference between them is the presence of textural fluidization indicators found in the volcanoclastic sandstones, along the lava-sediment interface. These textural characteristics indicate that the unconsolidated sediments were probably wet or saturated in water during the interaction with the volcanic flow. Epiclastic sandstones have infiltrated clays and neoformed smectites as their main diagenetic constituent due to alteration of available volcanic lithoclasts. For volcanoclastic sandstones, the formation of opal, chalcedony and megaquartz cements through burial is unlikely, due to the intergranular volume occupied by these cements, indicating near-surface early diagenetic conditions. Therefore, the mechanisms of dissolution and repreciptation of the siliceous fluids, incorporated in the system, formed mainly the chalcedony cementation. Furthermore, zeolite cementation, which occurs along the lava-sediment contact, is another important indicator of contact diagenesis for volcanoclastic sandstones. During telodiagenesis, the formation of secondary porosity by dissolution of volcanic lithoclasts and detrital K-feldspar grains was of great importance in volcanoclastic and epiclastic sandstones.

Bench X-ray microtomography of water-salt solution/oil injected into samples of the Botucatu formation

This paper provides a report on the utilization of the X-ray microtomography to obtain images of the internal microstructure of natural sandstone samples from the Botucatu Formation. Its primary objective was to identify the different phases of fluids when injected into the samples to evaluate the various phases through grayscale histograms obtained from 2-D images, quantification of fluid phases, and generation of 3-D images of them. The fluids used in the experiments comprised one type of commercial oil, one type of industrial oil, and an water-salt solution. Quantitative results from 2-D and 3-D analyzes are presented and compared to the volume of injected solution and the measured volume. The phase size distributions indicated which pore radii had a more relevant participation in the percolation of fluids through the samples. Projections in conjunction with 2-D images and profiles of average percentages of air-filled pores indicated the occurrence of preferential percolation flow paths. The 2-D images allowed the measurement of the contact angle between the phases present in the sample containing industrial oil. Different measurements taken from the sample containing commercial oil showed capillary effects indicated by the average percentage profiles of air-filled pores in the 2-D images.

Revisiting the southernmost occurrence of Brasilichnium elusivum Leonardi, 1981 with comments on the tetrapod track record of eolian environments

Mammalian lineage is deep rooted in Mesozoic, with several taxa and ichnotaxa described worldwide. One of the most prolific mammaliaform ichnospecies is Brasilichnium elusivum, which is extremely abundant in the Lower Cretaceous Botucatu Formation of the Brazilian Paraná Basin, as well as in other Mesozoic ichnofaunas of North America and Africa. In this contribution, we revisited the proposed southernmost occurrence of B. elusivum using both classical and photogrammetric (3D digitization) approaches. The flagstone containing the studied material was found ex situ, in a sidewalk at Santa Cruz do Sul Municipality (the Rio Grande do Sul State, Brazil), and the results of the performed analysis showed that the tracks cannot be assigned to any ichnotaxon. Lastly, some significant issues related to ichnological research of ex situ track-bearing flagstones and large eolian deposits are discussed. Keywords: Early Cretaceous, Botucatu Formation, mesozoic mammals, South America, vertebrate ichnology.

GEOLOGY OF THE FRONTEIRA OESTE RIFT, SOUTHERNMOST BRAZIL – A FIELD GUIDE

The Fronteira Oeste Rift located in the state of Rio Grande do Sul, southern Brazil, covers an area of 15,000 km2 and constitutes both a rhombohedral structural province and a paleohot spring field. These major features can be observed during a two-day field trip. A 4x4 vehicle is recommended. The weather is cold (freezing), humid climate during winter and hot (35 °C), varying from humid to dry during summer-. Excellent access to the outcrops is possible through paved and unpaved roads. Outcrops described in this field guide are stratigraphically located above the Botucatu Formation (paleoerg) and below the Serra Geral Group (volcanics) of the Paraná Basin. Sandstones of the Botucatu Formation were quickly filled by rainwater and after covered by a basalt (Mata Olho Flow) and a quartz andesite (Catalán Flow), thus originating the Guarani Paleoaquifer. The third Cordillera Flow (basaltic andesite) occurs in places, eventually covered by the Muralha Flow (basaltic andesite). Two additional basaltic andesites (UR13 and Coxilha Flows) were described in a drill hole. Aquifer heating by raised geothermal gradient led to pre-compaction cementation of sandstones by iron-rich minerals. Eolian quartz-rich sediments were deformed and hydrothermally altered in the composite paleodunes, showing thousands of circular, elliptical and curvilinear structures. Compaction caused upward motion of hot water + liquefied sand leading to the formation of many sand injectites and extrudites. Simultaneous doming of overlying rocks caused both large- and small-scale rhombi in sandstones and volcanic rocks. Post-compaction silicification occurred together with the formation of a myriad of 0.1-1.0 m-large hydrothermal vents at the surface of the paleoerg and also the first three lava flows. Features resulting from these processes can be visited, as described in this Geological Field Guide. A shorter geotrail is also described.

Lacertoid tracks from the Botucatu Formation (Lower Cretaceous) with different locomotor behaviors: A new trackmaker with novel paleoecological implications

The Botucatu Formation (Paraná Basin) is an eolian deposit that represents an extensive paleoerg that existed in the south-central Gondwana during the Early Cretaceous. The fossil record of the unit is almost exclusively constituted of ichnofossils, including numerous tracks and burrows of vertebrates and invertebrates. The greatest trace fossil diversity of the Botucatu Formation is reported at the Ouro ichnosite, located in the Araraquara municipality region, São Paulo State, Brazil. This site comprises a faunal-rich setting of greater humidity in the ancient desert. In this work, a new footprint morphotype is reported for the Ouro ichnosite. Five trackways including tracks with an elongated anteroposterior axis associated with tail drag marks are described. The morphology of the autopodia and geometry of the trackways indicate an affinity with a lizard-like trackmaker. Furthermore, at least three different modes of locomotion were recognized: a typical walking gait, a pause-walking gait, and sideways drifting. The current report suggests Lepidosauria may have inhabited the ancient Botucatu desert, a group never reported before in this geological context. This finding expands the knowledge about the Botucatu Formation paleofauna and adds more complexity to its ecological network. Squamata and Sphenodontia are plausible candidates to have produced the described fossil tracks.

PIRATARIA FLUVIAL NA SERRA DO ESPIGÃO: DIVISÓRIA DOS RIOS URUGUAI E IGUAÇU-AMÉRICA DO SUL

Stream capture is a drainage rearrangement where a flux transference occurs and a contribution area from a drainage basin is incorporated to another. It is about expanding a river system over another one, caused by erosive advantage earned by conditioning factors such as lithostructure, pluviometric regime, topographic gradient, and base level. However, in the southern region of Brazil, a rare dynamic of stream piracy was verified between the drainage basins of the Uruguay and Iguazu (Paraná) rivers. Stream captures were observed along the Serra of Espigão, part of the drainage divide between the two basins. Still, it was not possible to identify which basin was advancing over the other. This paper investigated the occurrence of stream captures, identifying which factors are responsible for this atypical stream dynamic. Mapping the stream captures by remote sensing and further validation with fieldwork, it was verified that there is stream piracy for both sides of the drainage divide. Still, it is not clear which basin is behaving more aggressively. A longitudinal profile analysis of the channels involved in the stream captures showed a local control in the drainage network. This control sets a local base level to the Iguazu river tributaries. It indicates the lithostructural limit between two different geological units: the Serra Geral group basalts and the Botucatu formation sandstones. Depending on the geographic location of this base level, channels that drain to the Iguazu (Paraná) river become more aggressive or less aggressive than the ones that drain to the Uruguai basin, and so they capture or lose area for the other basin. Therefore, it is impossible to identify a river basin that exclusively pirates the other, prevailing, in this case, a mutual competition between the Uruguai and Iguazu (Paraná) rivers basins. This fact highlights the significance of local base levels to promote stream capture processes.

Comment on “Resurfaced paleodunes from the Botucatu erg amid Cretaceous Paraná volcanics”, by Hartmann and Cerva-Alves (2021)

Hartmann and Cerva-Alves (2021) describe a field of silicified Cretaceous Paleodunes of the Botucatu Formation present in southernmost Brazil. In this comment, we explore pressing problems of their study and demonstrate that the authors inadequately use their data to support their conclusions. We evidence that: (1) the methodology misses basic information about the used datasets, as well as petrography and geochemistry data of the Botucatu sandstones; (2) the proposed silicification model is not supported by any petrographic or geochemical data; (3) the interpretations about dune morphology, wind pattern and direction are incorrect and differ from the available eolian record for the study region; and (4) the ‘explosive’ hydrothermal hypothesis for Cerro do Jarau site is based upon a not sustainable hydrothermal model that neglects substantial evidence for an impact origin for Cerro do Jarau and is broadly inconsistent with physical constraints.

Study of single-phase polymer-alkaline-microemulsion flooding for enhancing oil recovery in sandstone reservoirs

Enhanced oil recovery methods (EOR) are designed to increase reservoir productivity by facilitating oil displacement in the porous media. Due to its physicochemical properties capable of reducing the interfacial tension and inverting rock wettability, microemulsion flooding has been studied as a chemical EOR method. In this work, we studied the injection of polymer, surfactant, and alkali as single microemulsion media. A microemulsion formulation was selected with high water content and a composition of 1.5% of active matter, 0.05% of oil phase (OP), and 98.39% of aqueous phase (AP) prepared with 1.5% of Na2CO3 and 0.06% of the polymer. The systems obtained were characterized according to droplet diameter, pH, surface tension, and viscosity. We studied the rock-fluid interaction mechanism, evaluating the reservoir rock's wettability before and after contact with the microemulsion in a Botucatu sandstone rock. The microemulsions studied promoted a significant reduction in surface tension and changed the sandstone wettability from oil to water-wet. Coreflooding experiment results proved the potential of microemulsions prepared with alkali and polymer in the EOR process, achieving up to 97% of the oil recovery factor.

Numerical modeling and 3D-gravity inversion of the Vargeão impact structure formed in a mixed basalt/sandstone target, Paraná Basin, Brazil

Terrestrial impact structures formed in basaltic targets are suitable analogues for analyzing cratering processes in other planetary bodies where basalt is abundant. However, such structures are remarkably scarce on Earth. The Vargeão impact structure in the Santa Catarina state, Brazil, is one of the rare cases of such structures. It was formed in the Paraná-Etendeka Large Igneous Province, in the region that currently corresponds to the Paraná Basin, in southern Brazil. Local stratigraphy comprises volcanic rocks of the Jurassic-Cretaceous Serra Geral Formation, mostly basalts intermixed with rhyodacites, lying on top of sandstones of the Piramboia (Triassic) and Botucatu (Jurassic) formations. We analyzed the dynamics of crater formation through numerical simulations, focusing on the resistance to deformation under high pressure of a very tick basalt (>1 km) layer overlaying clastic sedimentary sequences. We then compared the crater morphology obtained from the model with the results of a 3D-gravity inversion based on the Preconditioned Conjugate Gradient (PCG) algorithm. We used this method to estimate the depth of the sandstones underneath the basaltic layer, and to better understand the complex structural relationship between both lithologies, especially in the central uplift area. Our results showed that the Vargeão crater was likely formed in ca. 130 sec., by a projectile of approximately 1,400 m in diameter, which produced a transient crater of ~14 km diameter, with a subdued topographic high at the center. We also point out that the negative Bouguer anomaly observed at the center was a consequence of the structural uplift of the sandstones by ~500 m, together with pre-Triassic sedimentary sequences underneath the sandstones. Both models support the formation of a final crater with a relatively subtle central peak.

CHEMICAL AND PHYSICAL ANALYSIS OF SANDSTONE ROCK FROM BOTUCATU FORMATION

The productive capacity of the Guarani Aquifer System is subject to variations along its length, due to its complex structural and compositional heterogeneity. Several parameters may influence the quality of this reservoir rock, such as its mineralogical and textural constitution, as well as the physicochemical processes, since its diagenesis is not the same throughout the aquifer, influencing the water productivity in wells in different locations. Such parameters are useful in the geoscience studies for the elaboration of diagenetic models for the prediction of the reservoir quality. In this work, several properties of the sandstone rock from Botucatu Formation were determined using different techniques, such as geotechnical tests, optical microscopy (MO), electron scanning microscopy (SEM), X-ray Fluorescence and X-ray diffraction. The results indicate that the studied sandstones have characteristics of the reservoir rocks, with potential for water storage.