Basin Southern Brazil Research Articles

Desertic siliciclastic stromatolites in the Upper Jurassic Guará Formation from southwestern Gondwana: Trapping and binding in a non-marine setting

Siliciclastic stromatolites are rare in the geologic record, and their occurrence recorded in the literature is restricted to marine and coastal environments. The Upper Jurassic Guará Formation, from the Paraná Basin in southern Brazil, hosts unique non-marine siliciclastic stromatolites, providing a rare opportunity to study trapping and binding mechanisms by microbial mats in a continental setting. These microbialites occur interbedded with eolian and fluvial facies. The structural layering of the stromatolite domes is formed by the intercalation of sandy layers, resulting from trapping and binding of siliciclastic grains by microbial mats and in situ precipitation of amorphous to cryptocrystalline silica, which directly replaced the microbial colonies. The silica layers contain partially preserved spherical to ovoid bodies interpreted as colonies of coccoid microorganisms. These siliciclastic stromatolites were formed due to a specific balance of environmental factors, namely water chemistry and sediment supply, which enhanced the processes of trapping and binding and in situ precipitation. They record the presence of microbial life in a non-marine, silica-rich, fluvial-eolian environment in which there were no previous published occurrences of agglutinated stromatolites. These specimens record macroscopically identifiable evidence of microbial life in a continental environment that must be accounted for in the search for ancient life on Earth and Mars.

Sociogeomorphological Analysis in a Headwater Basin in Southern Brazil with Emphasis on Land Use and Land Cover Change

Effects of natural processes on community building and the modification of nature by man’s hands are an intrinsic part of the co-production of the landscape between man and nature. However, the interactions of this co-production have scarcely been analyzed. Based on data from the MapBiomas project, an analysis of the variation in land use and cover over 35 years in the Quilombola São Roque and Mãe dos Homens communities in southern Brazil was carried out. The sociogeomorphological units in the study area were established, and its geomorphological units and social units were analyzed and described. There is a prevalence of more than 50% of forest formation. Cluster analysis classified the analyzed variables into two groups, with the first corresponding to forest and grassland formations associated with more natural landscape features. The second group is formed by anthropogenic activities. Social units including traditional communities seem to be more related to the stimulation of forest formation. The action of conservation units influences the variation in land use and land cover. There is a Supplementary Material which explains abbreviations concerning the manuscript.

Petunia toropiensis (Solanaceae): A surprising new species endemic from Toropi river basin in southern Brazil

Petunia toropiensis (Solanaceae): A surprising new species endemic from Toropi river basin in southern Brazil

A New Species of Silverside of the Genus Odontesthes (Atheriniformes: Atherinopsidae) with Hypertrophic Lips from a High-Altitude Basin in Southern Brazil

Odontesthes crossognathos, espécie nova, é descrita da bacia do rio Pelotas, alto rio Uruguai, sul do Brasil. A nova espécie é facilmente diagnosticável por possuir lábios hipertrofiados com numerosas papilas dérmicas, caráter ausente em outras espécies do gênero. A nova espécie também se distingue das congêneres, exceto de O. humensis, por ter a mandíbula superior distintamente mais longa do que a inferior e a boca subterminal. Essas adaptações na morfologia da boca provavelmente estão relacionadas ao comportamento de forrageamento da nova espécie, que habita rios de corredeiras e fundos rochosos em uma bacia de altitude elevada.

Flood analysis in the Canoas, Sertão, and Mampituba rivers in the South of Brazil through hydrological and hydrodynamic modeling

Floods that occur in hydrographic basins with high slopes are more susceptible to natural hazards due to the occurrence of high intensity hydrological events and the type of sloping relief. These two associated factors contribute to an increase in the destructive potential of these regions, causing economic damage and loss of life for people and animals. This study sought to assess the floodplain areas in the Canoas, Sertão, and Mampituba Rivers that contribute to the Mampituba River basin in southern Brazil, to support emergency procedures for dealing with floods and contribute to the territorial management of these spaces. From the hydrological data of the Mampituba River basin, a hydrological model was used, which generated flows that were inserted as input to a hydrodynamic model, resulting in flood patches in the plains of the modeled rivers. The calibration and integration studies of the models were carried out on a computational platform that employs the hydrometeorological knowledge represented by the models of the basin under study. The hydrodynamic modeling represented in the maps indicated that the flooding patches occur within the river channels and in the plains occupied by agriculture, with a predominance of irrigated rice paddies, pasture fields, forestry, urbanized areas, and native vegetation. In the urban region along the floodplains of the Praia Grande and Mampituba Cities, there are inns, restaurants, and residences which can suffer structural damage and expose people to the danger of a flood event of this magnitude. The results achieved allow us to infer that the integrated modeling system proved to be capable of performing efficient hydrological and hydrodynamic simulations. The methods used can be replicated in other basins and the results can support public managers for greater assertiveness in decision-making when facing the dangers of extreme weather events.

Suitability Zoning for Sustainable Drainage Systems (SuDSs): Application in a Basin in Southern Brazil

The objective of this study was to propose a set of procedures to assess areas regarding the suitability of sustainable drainage systems (SuDSs) with application in a basin in the urban area of São Carlos (Brazil). The assessment was based on an analysis of 39 attributes reflecting the infiltration conditions that control the functional and constructive aspects of the systems, including subsurface drainability, stability, and groundwater contamination potential, which control the degree of suitability of each plot of land. The data obtained through engineering geological mapping procedures and physical principles were used to characterize the area, which resulted in the division of the basin into five SuDS suitability zones, ranging from favorable to restrictive. The proposed procedures proved to be efficient for analyzing the suitability of different SuDS types and the zoning of an area into terrain units. This approach can help planners identify the most appropriate SuDS types for a given unit, optimize the efficiency/cost relationship, and foresee potential environmental and construction-related challenges. In other words, this procedure enables the assessment of the suitability of SuDSs for different unit terrain types with inexpensive and environmentally efficient technological procedures and resources and can be applied at a fine geographic scale.

Far from urban areas: plastic uptake in fish populations of subtropical headwater streams.

This study investigated the occurrence of plastic particles in the digestive tracts of fish from headwater streams in a human-thinly populated region of the subtropical Sinos River basin in southern Brazil. In total, 258 individuals from 17 species were collected using electric fishing. Thirty-eight percent (38%) of the specimens contained plastic particles. All of them were fibers, with a maximum count of 43 per individual. Plastic fibers were the fourth most abundant food category. Results showed that the uptake of these plastic particles was proportional to the number of ingested food items. Fiber counts in the guts correlated with the uptake of Trichoptera, which are invertebrates using plastic particles to construct their protective cases. No significant difference in plastic uptake was detected between benthic and water column fish. No evidence of bioaccumulation of plastic particles was found in the intestines. The distance from urban areas was not related to the number of ingested plastic particles, concluding that plastics are ubiquitous and available to biota, even in remote locations. The most probable source of these particles is residences close to the streams which discharge the sewage of washing machines without any treatment.

Geochemical study on fossil vertebrates from some specific Permian and Triassic beds of the Paraná Basin (Brazil): A preliminary approach

Access to the geochemical conditions of paleoenvironments is made through the analysis of the chemical composition of the hydroxyapatite of fossil bones. This is because the bones were able to incorporate chemical elements from adjacent fluids into their pores and channels during the fossildiagenesis process, and as a result, have their original apatite substituted. The main goal of the present study was to seek geochemical signatures in bones and related sedimentary rocks from three well-known fossiliferous units of the Paraná Basin in southern Brazil: Irati Formation, Cisuralian (three bones/rocks sampled); Rio do Rasto Formation, Guadalupian (three bones/rocks sampled) and Santa Maria Supersequence, Late Ladinian–Early Norian (nine bones/rocks sampled). Fossils and rocks were analyzed by ICP-MS. Although the Permian fossil and rock samples (from Irati + Rio do Rasto Formations) have variations among them, some geochemical parameters are common (high Be–Co–Cu–Zn–Y–W–Pb contents). This composition differentiates them from the Triassic fossils and rocks (from Santa Maria Supersequence - high contents of V–As–Ba). The P content (essential in apatite) was used to determine the degree of preservation of the studied material. The better-preserved Permian specimen has a mean = 434.19 ratio (P content of fossil bones/P content of rock) and the lowest ratio = 1.87. Within the Triassic specimens, the better preserved has ratio = 205.64 and lowest = 2.24. In Permian specimens, Y shares similar ionic radio with Ca. For Triassic specimens, Y replaces Ca and As either replaces P or is associated with minerals in bone cavities. So, Y and As substitute Ca in the analyzed material. Therefore, the Permian samples are better preserved than the Triassic ones based on their P contents; Y and As can be used as indicators to differentiate Permian fossils (high Y values) from Triassic ones (high As values). These geochemical signatures can help in forensic cases, such as robbery or illegal transport of fossils.

Assessment of environmental degradation due to anthropogenic processes based on critical zones: a study in a basin in southern Brazil

Different land uses imposed by human activities have affected biotic and abiotic components, modifying the natural environment according to population growth and increasing the environmental impact over time. As a consequence, the relevance of studies to evaluate the magnitude and aspects of environmental changes is increasing. In this context, the Ribeirao do Pinheirinho Basin (Sao Paulo state, southeastern Brazil) was selected for this study, since it is part of a region that recharges a set of drainage channels that provide water to several municipalities (approximately 2 million people), primarily during dry seasons. Additionally, this basin has been intensively used for agricultural purposes over the last 50 years. To determine the current characteristics and to analyze the environmental changes, this study was based on temporal and spatial analyses of the components of the basin’s critical zone at a scale of 1:10,000. In association, due to water availability issues, the HOST (hydrology of soil types) classification was adopted, as well as previous data, satellite images, aerial photos and results of laboratory and field tests. As a result, anthropogenic activities have changed the depth, areal distribution, and environmental functions of geological materials. These activities have affected the relationship between rainfall, infiltration and surface runoff, resulting in a lower groundwater level and decreasing water availability. In conclusion, the adopted methodology aids in the assessment of the changes in the environmental area of study. This could be useful for environmental recovery projects as well as the establishment of environmental policies.

Structural architecture and the episodic evolution of the ediacaran Campo Alegre Basin (southern Brazil): Implications for the development of a synorogenic foreland rift and a post-collisional caldera-volcano

During the last decades, tectonic models provided new insight into the evolution of the Luis Alves, Curitiba, and Paranaguá terranes, which are all limited by thrust and transpressive shear zones, nowadays outcropping only as deep crustal horizons and presenting poorly known lateral displacements. An essential puzzle piece to understanding the juxtaposition processes and evolution of these blocks in the Neoproterozoic lies in the Campo Alegre Basin in Southern Brazil, a volcano-sedimentary sequence deposited during the middle to late Ediacaran. Based on new U–Pb geochronological, structural, and aero-geophysical data, at least two main stages of filling and subsidence have been identified in this region, namely the basin and the caldera stages. In the Basin Stage, the regional collisional tectonics triggered the far-field stress resulting in a local extension at ~605 ± 5 Ma through the reactivation of NNW-SSE inherited basement structures. The deposition of the sedimentary basin finishes with the Initial Volcanic Activity, corresponding to a bimodal mildly alkaline, predominantly mafic and effusive volcanism. After the transition to a post-collisional setting, probably at ca. 595 Ma, regional extension led to the Caldera Stage of the basin, which had its volcanic peak at ca. 583-580 Ma, contemporaneous with the intrusive A-type magmatism of the nearby Graciosa Province. The Main Volcanic Activity corresponds to a predominantly alkaline silica-saturated, effusive to explosive magmatic manifestation culminating with the formation of a caldera-volcano. The volcanic products from both the initial and the main volcanic activities were raised to the surface mainly through NNW-SSE and ENE-WSW oriented conduits, respectively reactivated and neo-formed during the collisional process. The crustal-scaled discontinuities associated with the development of the sedimentary basin have further controlled the subsidence of the caldera structure, which might be the main mechanism of preservation for these ancient volcano-sedimentary sequences in the evolution of the Campo Alegre Basin.

Tree community patterns along pond-upland topographic gradients, upper Uruguay River basin, southern Brazil

We investigated the interrelations between environmental variables (proxies for water availability and soil physico-chemical properties) and tree community patterns (diversity, composition and structure) along pond-upland topographic gradients within depressional watersheds in the upper Uruguay River basin in southern Brazil. Sampling plots were allocated in four topographic habitats: (1) inside ponds (wetland sites) and (2) immediately outside them, and in areas with (3) 60 cm and (4) 120 cm of elevation in relation to their limits (upland sites). Environmental conditions and forest composition varied along pond-upland gradients, but the diversity and structure of tree communities did not. Species turnover was associated with changes in topography-driven environmental conditions, notably water availability. Depressional watersheds show regionally unique abiotic and biotic features but are virtually unprotected by Brazilian private land legislation.

<i>Contracaecum<i> spp. (NEMATODA: ANISAKIDAE) AND <i>Eustrongylides<i> spp. (NEMATODA: DIOCTOPHYMATIDAE) NEMATODE LARVAE WITH ZOONOTIC POTENCIAL FOUND IN TWO FISH SPECIES FROM TRAMANDAÍ RIVER BASIN, SOUTHERN BRAZIL

Parasitic nematodes can infect both wild and cultivated fish species and may be the source of many diseases. The consumption of raw fish meat in many countries has been the responsible of nematode related zoonosis. Knowing the risk of consumption of contaminated fish by the local communities, the main goal of this paper is to quantify and report the presence of larvae with zoonotic potential of Contracaecum spp. and Eustrongylides spp. found in two exotic fish species from the Tramandaí­­ River Basin in southern Brazil. The sample sites were two lagoons of the basin, the Itapeva lagoon and Palmital lagoon, sampled in the period of April 2018. Forty specimens of Acestrorhynchus pantaneiro and twenty specimens of Trachelyopterus lucenai were examined. A. pantaneiro presented a 58% and 4% prevalence and a mean intensity of 3.17 and 1 for Contracaecum spp. and Eustrongylides spp., respectively. Meanwhile T. lucenai presented a prevalence of 70% and 5% and a mean intensity of 1.92 and 1 of Contracaecum spp. larvae and Eustrongylides spp. larvae, respectively. Although larvae of Contracaeucum spp. are reported only in the literature in experimental infections, they were able to complete their biological cycle in some mammals with certain pathogeneses. However, larvae of Eustrongylides spp. infect humans, as reported in the literature, causing severe damage to the intestinal tract. Knowing that local populations may be at risk, we recommend that all prophylactic measures be taken in relation to fish consumption. This study also contributes to the knowledge concerning the parasitic fauna of the host species studied.

Functional trophic groups and spatial variation of aquatic insects in a hydrographic basin of Southern Brazil

In Brazil hydrographic basins are geographical unities used to environmental and hydric resources management, but few studies focus in the biodiversity variation within these unities. Here we present the results of spatial variation of aquatic insects in streams of a hydrographic basin in Southern Brazil. The insect composition was analyzed in relation to abundance of the families, functional trophic group and environmental evaluation indexes proposed by literature. The insects had a heterogeneous distribution in the sampling areas of the hydrographic basin. The most abundant families were Hydropsychidae, Philopotamidae and Leptophlebiidae, which demonstrate a good oxygenation of the water in the sampling streams. The most abundant functional trophic groups were gatherer-collector (20%) and scraper (18.92%). The indexes demonstrated the riverbeds of the streams are stable, with a high presence of fine particulate organic matter and they were considered heterotrophic. However, they also indicated a low abundance of shredders, which may be related to poor environmental conditions in the riparian forests. Therefore, here we found spatial variation of aquatic insects and indexes performed indicated the main human impacts as deforestation and inadequate land use. The data obtained also contributed to reinforce the importance of hydrographic basin as geographical unities for environmental conservation.

Improving the use of ground-based radar rainfall data for monitoring and predicting floods in the Iguaçu river basin

This study investigates the efficiency of correcting radar rainfall estimates using a stochastic error model in the upper Iguaçu river basin in Southern Brazil for improving streamflow simulations. The 2-Dimensional Satellite Rainfall Error Model (SREM2D) is adopted here and modified to account for topographic complexity, seasonality, and distance from the radar. SREM2D was used to correct the radar rainfall estimates and produce an ensemble of equally probable rainfall fields, that were then used to force a distributed hydrological model. Systematic and random errors in simulated streamflow were evaluated for a cascade of sub-basins of the Iguaçu catchment, with drainage area ranging from 1,808 to 21,536 km2). Results showed an improvement in the statistical metrics when the SREM2D ensemble was used as input to the hydrological model in place of the radar rainfall estimates in most sub-basins. Specifically, SREM2D was able to remove the relative bias (up to 50%) in the radar rainfall dataset regardless of the basin dimension, whereas the random error was reduced more prominently in the larger basins (up to 100 m3 s−1). An event scale evaluation was also performed for nine selected flood events in three sub-basins. SREM2D reduced the overestimation in the cumulative rainfall and streamflow volumes during these events.

Geological and geotechnical land zoning for potential Hortonian overland flow in a basin in southern Brazil

This paper presents a new procedure to perform geological and geotechnical land zoning at the 1:50,000 scale for potential Hortonian overland flow (Rpot values). The procedure was applied to the Ribeirão do Feijão Basin, São Paulo State, Brazil. The zoning was conducted using a procedure that combines rainfall data, engineering geological mapping, infiltration modelling, and anthropogenic and geomorphic aspects. The association between the geological-geotechnical units defined by the engineering geological mapping and the land use types generated 29 different infiltration condition categories, which were used to divide the basin into 94 territorial units. The in situ infiltration test and geotechnical data for each infiltration condition category combined with several rainfall event types were used as inputs to the Philip model to obtain the values of the Rpot and infiltration values. The Rpot and infiltration values estimated by the proposed procedure agreed well with the values estimated by the Chu model. The 94 territorial units were grouped into 4 classes based on the variability and magnitude of the potential Hortonian overland flow. The first class represents the areas where infiltration predominates (59 km2) for all selected rainfall events, and the second class represents areas of infiltration and flooding (11 km2). Infiltration is predominant in the third class; however, overland flow can be generated (133 km2) depending on the intensity and duration of the rainfall event. The fourth class represents the main source areas of overland flow generation and runoff (40 km2). The areas considered in the third and fourth classes are affected by erosion processes due to the potential generation of Hortonian overland flow. The results indicated that the proposed procedure is adequate for identifying, characterizing, classifying and dividing a region into units with distinct geological and geotechnical zones that are associated with potential Hortonian overland flow. Therefore, the procedure is an appropriate tool for regional planning and water management at the 1:50,000 scale because the results define land units with specific environmental characteristics. The application of the procedure is not expensive and uses common equipment but requires experienced or trained professionals to perform the field and laboratory work.

Mapping groundwater pollution vulnerability with application in a basin in southern Brazil

This study presents the criteria and conditions that supported the development of a proposed vulnerability index and its application in the Corrego do Ribeirao do Feijao Basin, which is located in the central portion of the state of Sao Paulo, southeastern Brazil. This basin was selected, because it is representative of very large areas in the south, west, and southeast regions of Brazil, is the main source of freshwater for the municipality of Sao Carlos, and has been undergoing accelerated changes due to diversified anthropogenic activities, thus increasing the number of contaminant sources. The proposed index is based on a hierarchy of information that includes a total of 46 attributes categorized into groups (4 rainfall attributes, 6 point contaminant sources, 5 non-point contaminant sources, 5 unconsolidated material 1, 4 unconsolidated material 2, 4 rock substrate 1, 4 rock substrate 2, 1 relief, 6 unconsolidated material 3, 4 rock substrate 3, and 3 groundwater), which were obtained from principles and procedures of engineering geological mapping and laboratory tests. The final vulnerability index for each land unit was obtained as a percentage using the total vulnerability index, which is the sum of the partial indices (these indices are normalized eigenvectors of the unit) and the maximum value that a unit can reach, considering the classes of maximum influence in vulnerability. The basin was divided into 29 categories controlled by engineering geological units and types of land uses, resulting in 94 land units, of which 17 were classified as Class 1, with the highest vulnerability; 41, 23, and 13 were classified as Classes 2, 3, and 4, respectively, with decreasing degrees of vulnerability. The results verify that the proposed index enables an adequate subdivision of the region and classification of the units, respecting the natural variability and the anthropogenic aspects. The attributes associated with land units and the datasheet used for data treatment permit a dynamic vulnerability analysis, because it is easier to identify and characterize the anthropogenic changes (mainly related to contaminant sources) per land unit in situ and to obtain new results that will require new control or planning measures.

Ichnology applied to sequence stratigraphic analysis of Siluro-Devonian mud-dominated shelf deposits, Paraná Basin, Brazil

Previous studies of the Paraná Supersequence (Furnas and Ponta Grossa formations) of the Paraná Basin in southern Brazil have yielded disparate sequence stratigraphic interpretations. An integrated sedimentological, paleontological, and ichnological model was created to establish a refined sequence stratigraphic framework for this succession, focusing on the Ponta Grossa Formation. Twenty-nine ichnotaxa are recognized in the Ponta Grossa Formation, recurring assemblages of which define five trace fossil suites that represent various expressions of the Skolithos, Glossifungites and Cruziana ichnofacies. Physical sedimentologic characteristics and associated softground ichnofacies provide the basis for recognizing seven facies that reflect a passive relationship to bathymetric gradients from shallow marine (shoreface) to offshore deposition. The vertical distribution of facies provides the basis for dividing the Ponta Grossa Formation into three major (3rd-order) depositional sequences— Siluro-Devonian and Devonian I and II—each containing a record of three to seven higher-order relative sea-level cycles. Major sequence boundaries, commonly coinciding with hiatuses recognized from previously published biostratigraphic data, are locally marked by firmground Glossifungites Ichnofacies associated with submarine erosion. Maximum transgressive horizons are prominently marked by unbioturbated or weakly bioturbated black shales. By integrating observations of the Ponta Grossa Formation with those recently made on the underlying marginal- to shallow-marine Furnas Formation, the entire Paraná Supersequence can be divided into four disconformity-bound sequences: a Lower Silurian (Llandovery-Wenlock) sequence, corresponding to lower and middle units of the Furnas; a Siluro-Devonian sequence (?Pridoli-Early Emsian), and Devonian sequences I (Late Emsian-Late Eifelian) and II (Late Eifelian-Early Givetian). Stratigraphic positions of sequence boundaries generally coincide with regressive phases on established global sea-level curves for the Silurian-Devonian.

DNA barcoding as a useful tool for identifying non-native species of freshwater ichthyoplankton in the neotropics

The objective of our study was to evaluate the efficacy of DNA barcoding as a tool to identify non-native fish in their early stages of life. Specimens were collected from 14 sites in the lower and middle regions of the Paranapanema River—the main tributary of the Upper Parana River basin in southern Brazil. Over three reproductive periods from 2012 and 2015, 75 eggs and 170 larvae from 13 non-native fish species were identified. The most abundant species were Plagioscion squamosissimus (75 specimens) and Serrasalmus marginatus (68 specimens). The highest abundance was found near the Rosana hydroelectric plant reservoir. The removal of the natural physical barrier is the main reason that fish are introduced into the Paranapanema River basin with higher occurrence in the Rosana reservoir. P. squamosissimus was found in all reservoirs. DNA barcoding is a useful tool for identifying non-native fish during their reproductive phase. Furthermore, recording the presence of potentially invasive species in their early development stages may provide information useful for the rapid and effective control.

Analysis of Kinetics Parameters of Oil Shale Pyrolysis

The composition of the shale is a mixture of kerogen contained in the shale of organic matter and various mineral compounds. The limits between the kerogen and the mineral compounds can only be broken by the pyrolysis process, being very complex due to the structure of the kerogen generating many reactions. These reactions involve the breaking of chemical bonds with different energies in the organic phase and between the organic phase and the mineral matter. New alternatives are being studied for oil recovery between the use of shale. As a new requirement of an alternative for improvements in shale processing, is to optimize the pyrolysis process, through literature models are calculated kinetic parameters. Thus, kinetic parameters were determined from dynamic thermogravimetric analysis (TGA) in the temperature range of 323 K to 1,173 K, using different methods proposed by the literature. One of the most common places for extracting bituminous shale is the Irati basin in southern Brazil. The extraction was carried out by Petrobras / SIX in the city of Sao Mateus do Sul, Parana, Brazil. The kinetic parameters, as well as the activation energy and the pre- exponential factor were calculated using Friedman, Kissinger, Kissinger-Akahira-Sunose (KAS) methods and the Flynn-Wall-Ozawa (FWO) method. In addition, it was studied the characterization of shale behavior for a better evaluation.

Ar-Ar ages, Sr-Nd isotope geochemistry, and implications for the origin of the silicate rocks of the Jacupiranga ultramafic-alkaline complex (Brazil)

The Jacupiranga Complex is one of several Meso-Cenozoic alkaline intrusive complexes along the margins of the intracratonic Paraná Basin in southern Brazil. The complex encompasses a wide range of rock-types, including dunites, wehrlites, clinopyroxenites, melteigites-ijolites, feldspar-bearing rocks (diorites, syenites, and monzonites), lamprophyres and apatite-rich carbonatites. While carbonatites have been extensively investigated over the last decades, little attention has been paid to the silicate rocks. This study presents new geochonological and geochemical data on the Jacupiranga Complex, with particular emphasis on the silicate lithotypes. 40Ar/39Ar ages for different lithotypes range from 133.7 ± 0.5 Ma to 131.4 ± 0.5 Ma, while monzonite zircon analyzed by SHRIMP yields a U-Pb concordia age of 134.9 ± 1.3 Ma. These ages indicate a narrow time frame for the Jacupiranga Complex emplacement, contemporaneous with the Paraná Magmatic Province. Most of the Jacupiranga rocks are SiO2-undersaturated, except for a quartz-normative monzonite. Based on geochemical compositions, the Jacupiranga silicate lithotypes may be separated into two magma-evolution trends: (1) a strongly silica-undersaturated series, comprising part of the clinopyroxenites and the ijolitic rocks, probably related to nephelinite melts and (2) a mildly silica-undersaturated series, related to basanite parental magmas and comprising the feldspar-bearing rocks, phonolites, lamprophyres, and part of the clinopyroxenites. Dunites and wehrlites are characterized by olivine compositionally restricted to the Fo83-84 interval and concentrations of CaO (0.13–0.54 wt%) and NiO (0.19–0.33 wt%) consistent with derivation by fractional crystallization, although it is not clear whether these rocks belong to the nephelinite or basanite series. Lamprophyre dikes within the complex are considered as good representatives of the basanite parental magma. Compositions of calculated melts in equilibrium with diopside cores from clinopyroxenites are quite similar to those of the lamprophyres, suggesting that at least a part of the clinopyroxenites is related to the basanite series. Some feldspar-bearing rocks (i.e. meladiorite and monzonite) show petrographic features and geochemical and isotope compositions indicative of crustal assimilation, although this may be relegated to a local process. Relatively high CaO/Al2O3 and La/Zr and low Ti/Eu ratios from the lamprophyres and calculated melts in equilibrium with cumulus clinopyroxene point to a lithospheric mantle metasomatized by CO2-rich fluids, suggesting vein-plus-wall-rock melting mechanisms. The chemical differences among those liquids are thought to reflect both variable contributions of melting resulting from veins and variable clinopyroxene/garnet proportions of the source.