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Carbonate reservoirs are of great economic importance due to their frequent association with high permeability and hydrocarbon storage capacity. One of the most significant discoveries of this type of reservoir in recent decades has been the Brazilian Pre-salt. This deep reservoir has unusual depositional features, consisting of a wide variety of textures with different compositions, influenced by diagenetic overprinting that modify most of its mechanical, elastic and petrophysical properties. Despite the marked heterogeneity, these carbonates are characterized by excellent reservoir quality. The objective of this study is to establish a correlation between geomechanical behavior and sedimentary facies and its implications for the definition of flow units in the Barra Velha Formation, the main reservoir of the Brazilian Pre-salt. Thus, using a database from the Buzios field composed of well logs (conventional and advanced), well tests, thin sections, and laboratory petrophysics, geomechanical facies (GMFs) were defined using dynamic geomechanical modeling and an unsupervised algorithm (K-mean clutering), followed by textural classification of sedimentary facies and definition of flow units (FUs) on the decametric scale. These classifications were compared using frequency histograms. The geomechanical model revealed that the in-situ stress state exhibits a dual regime, between normal and strike slip. In addition, it was found that the direction of the maximum horizontal stress is in the NE-SW azimuth. In this context, four geomechanical facies were defined, which showed a notorious variation in mechanical strength. The strongest GMFs consisted mainly of well-cemented Grainstones and Packstones with no apparent porosity or microcrystalline porosity and correlated with the FU with the worst production rates. On the other hand, the weaker GMFs were mainly composed of Grainstones and Spherulistones with high intergranular porosity generated by dissolution processes, with higher risk of pore collapse and correlated with the FUs with the best production rates. However, this classification also identified laminated mudstones with microporosities associated with FUs that act as flow barriers. Geomechanical facies have also been incorporated into reservoir development by evaluating wellbore stability, fault reactivation risk, and brittleness index for future CO 2 injection projects. • Stress regime duality in the Búzios field (Normal to Strike-slip failure regime). • Low to intermediate mechanical strength of Brazilian pre-salt reservoir. • The sedimentary facies show a great variety of textures, and porosities, influencing the geomechanical behavior. • Lateral and vertical variations of the geomechanical properties using K-means clustering defined by facies. • Comparison between flow units and geomechanical facies. [ABSTRACT FROM AUTHOR]

During the Cretaceous, the Brazilian Intracratonic Sanfranciscana Basin was characterised by fluvial and aeolian deposition, whose facies, palaeosols, and stratigraphic architecture indicate significant changes in tectonics and climate. This work proposes a low-frequency sequence stratigraphic model, using the facies and palaeosols distribution as the stratigraphic proxy for identifying variations in the accommodation space, sediment supply, and their relationship with the tectonic and climatic events. The Unconformity U-0 was generated by the extensional tectonic processes during the Gondwana breakup in the Early Cretaceous and marked the initial continental sedimentation. The Lower Cretaceous Sequence SF1 overlies this unconformity, constituted by fluvial and lacustrine deposits. From south to north, the unconformity U-1 truncates the top of the Lower Cretaceous Sequence SF1 and the Precambrian basement, respectively. Overlaying Unconformity U-1 are the Upper Cretaceous volcanic rocks, fluvial, and aeolian deposits of the Sequence SF2. Because of the vertical and lateral changes, Sequence SF2 is divided into two sequences, SF2A and SF2B, separated by the regional Unconformity U-2, representing climatic and tectonic changes in the basin. During the late stage of sedimentation of Sequence SF1, the ratio between accommodation (A) and sediment supply (S) was positive in the south and negative in the basin's north. The evolution of Sequence SF2A records a negative A/S ratio, followed by an abrupt change to a positive A/S ratio in Sequence SF2B, leading to the genesis of the regional erosive surface of Unconformity U-2. Sequence SF2B also records increased humidity from arid climatic conditions, marked by the 3D regional distribution of facies and palaeosols, linked to the climatic changes detected in South America for the Late Cretaceous. • Proposes low-frequency sequence stratigraphy analysis. • The 3D regional distribution of facies and palaeosols approach. • The Brazilian Intracratonic Sanfranciscana Basin. • Variations in the accommodation space, sediment supply, and their relationship with the tectonic events. • Late Cretaceous climatic changes. [ABSTRACT FROM AUTHOR]

Distributive Fluvial Systems (DFS) are fan-shaped landforms constituted by a radial system of channels that diverge downstream from an active apex, where the drainage emerges from the confinement valley. In such landforms, elevation, distance from fluvial channels, sedimentation rates, surface stability, and plant cover control weathering processes and soil development, but these features are obliterated within geological time. Thus, the micromorphological analysis of paleosols can be helpful for paleoenvironmental reconstruction of ancient DFS, improving the knowledge of soil genesis in these depositional landforms. Here, we describe macro and micromorphological features of twenty paleosols developed under arid to semiarid climates along the proximal to the medial zone of an Upper Cretaceous DFS in the Marília Formation, Bauru Basin, Brazil. Paleosols on the proximal zone typically showed features consistent with poor drainage, namely Bg, Btg and Bss horizons, and reddish Bt horizons in higher positions. Conversely, paleosols on the medial zone commonly showed reddish colours and pronounced secondary carbonate accumulation, consistent with a predominantly arid climate. Based on this distribution, we elaborated an evolution landscape model for the proximal and medial zone of the Bauru DFS, including allogenic and authigenic controls of soil development during the Campanian to the Maastrichtian epochs of southeastern Brazil. • Macro and micromorphological analysis of paleosols. • Identify the mainly paleosol-forming processes, such as palaeohydrology and palaeotopography conditions. • Soil Paleocatena. • Allogenic control in soil development and geomorphic relationships. • Conceptual framework for recognition criteria for paleosols and geomorphic evolution in distributive fluvial systems (DFS). [ABSTRACT FROM AUTHOR]

The Marília Formation is a lithostratigraphic unit positioned at the top of the Bauru Group of Maastrichtian age. The present work presents a provenance study of the Marília Formation sandstones through the combined dating of the fission‐track method (FTM) and U–Pb, in which individual zircon grains are simultaneously dated by these two methods. Thirty‐one zircons were dated in the C5 sample and 26 in the C7 sample for a total of 57 grains. The data demonstrated a wide range of U–Pb ages, presenting maximum and minimum ages, respectively: 2,905 ± 11 and 128 ± 1 Ma for the C7 sample and 2,676 ± 10 and 455 ± 5 Ma for the C5 sample. Regarding the fission‐track (FT) ages, they have been grouped into three time intervals, which are associated to geological events relatively well recognized in the published literature: ages younger than 250 Ma (Wealdenian Reactivation); between 250 and 470 Ma (Palaeozoic orogenesis—Ocloyic, Precordilleran, Chanic, and Sanrafaelic); and older than 470 (Precambrian collisions—Brasiliano I, II, and III). There is a predominance of results of Precambrian age using the U–Pb dating, mainly in the Neopalaeoproterozoic, and with FT dating corresponding to the Ocloyic, Precordilleran, Chanic, and Sanrafaelic orogeneses. From the comparison of the results between the two dating methods, the age variations suggest that the zircons originated during the main south‐western orogenesis of Gondwana and were reworked during the Palaeozoic and Mesozoic geological episodes. The ages associated to the Upper Cretaceous are related to the tectonic and magmatic activity of the Alto Paranaiba Uplift. [ABSTRACT FROM AUTHOR]

The Late Cretaceous Marília Formation located in the central-southern portion of Brazil is characterized by a succession of sandstones, conglomerates, and paleosols. The paleosols constitute more than 60% of this formation, providing significant information about pedogenetic processes as well as paleoenvironmental and paleoclimate implications. The paleosols of the Marília Formation have been studied principally from a stratigraphical, sedimentological and paleopedological point of view; however, there are no studies addressing in detail the geochemical behavior of the paleosols. Therefore, we used a robust geochemical dataset combined with stratigraphical and macromorphological interpretations as well as clay mineralogy to conduct a paleoenvironmental and paleoclimate analysis of the Marília Formation in the western portion of the state of Minas Gerais in Brazil. The results indicate that the paleosols of the Marília Formation can be divided into three pedotypes and pedochemical units based on their geochemical variations and are limited at the base and top by pedochemical markers. Moreover, X-ray diffraction identified quartz and calcite as primary minerals associated with montmorillonite, smectite, illite and palygorskite, indicating wet periods combined with dry stages associated principally with dry and arid environments. The paleosol distribution and weathering index allow us to interpret the paleoenvironmental evolution of the Late Cretaceous Marília Formation, suggesting an increase in humidity from east to west in the study area. • A new approach using pedochemistry analysis was used. • Three pedochemical units and geochemical markers were identified. • Seasonal variations based on weathering indexes were observed. • Paleoenvironmental and paleoclimate conditions indicate arid to semiarid climate. [ABSTRACT FROM AUTHOR]

Abstract The Eastern Marlim oilfield, located in the northeastern offshore of the Campos Basin, is a portion of the Marlim Complex, one of the most important oil accumulations ever found in Brazil. This paper presents findings from lithofacies, sequence stratigraphy and petrophysical analyses for the Oligocene-Miocene section of the Eastern Marlim oilfield. Here, we evaluate at least four main lithofacies associations and three major zones recognized in the latter section, presenting sedimentological and stratigraphical interpretations based on stratigraphic correlations, distribution and sand proportion maps, and accompanying petrophysical analysis. Our findings suggest at least two bipartite turbiditic flows representing different stages of deposition associated with a deep-water turbidite sequence, composing the elements of a submarine lobe complex. Massive unconsolidated amalgamated sandstone bodies, displaying very good porosity, lateral and vertical continuity, reflecting excellent reservoirs. The final depositional model of the studied Oligocene-Miocene interval in this work is part of the first-order Highstand System Tract (HST) of the Campos Basin, which in turn represents a second-order, exploration-scale depositional sequence. Finally, the sequence stratigraphic model of the Oligocene-Miocene section of the Eastern Marlim oilfield has an architecture similar to those that have been developed from Oligocene-Miocene global sea level changes. Highlights • A lithofacies, sequence stratigraphic and petrophysical evaluation is proposed for the Eastern Marlim oilfield. • Four main lithofacies and three major zones were recognized. • Two-bipartite turbiditic flows represent different stages of deposition. • A deep-water submarine lobe complex was identified. • The studied section represent a first order HST and a second order depositional sequence. [ABSTRACT FROM AUTHOR]

The Upper Cretaceous Bauru Group in south‐east Brazil consists of alluvial strata whose characteristics and distribution indicate a fluvial system developed in a semi‐arid to arid climate. Sections exposed within a 90 000 km2 study area in Minas Gerais State (in south‐eastern Brazil) were evaluated using facies and palaeosol analysis to formulate depositional and pedogenic models that may account for geomorphic and climate features. From east to west, the study succession records a gradual decrease in grain size, an increase in the width/thickness ratio in channels, a decrease in the lateral and vertical connectivity of channel deposits, and an increase in overbank deposits. The fluvial architecture indicates a braided channel belt, ephemeral ribbon–channels, and an unconfined fluvial facies from east to west in the study area. The lateral and vertical distribution of facies, stratigraphic architecture and palaeocurrent data suggest proximal, medial and distal portions of a progradational distributive fluvial system. The sedimentary dynamics were marked by the building and abandonment of channels related to processes of aggradation, vegetation growth and palaeosol generation. Macromorphological and micromorphological analyses have identified pedological and mineralogical features that indicate an arid to semi‐arid climate with a provenance from the north‐eastern part of the basin (Alto Paranaiba Uplift). From the proximal to the distal portions of the distributive fluvial system, the palaeosol development is different. In the proximal portion, the palaeosols are absent or poorly developed, allowing a possible general comparison with the present soil order: Inceptisols and Aridisols. In the medial portion of the fluvial system, the palaeosols are well‐developed and characterized by Bt, Btk, C and Ck horizons (Alfisols, Aridisols, Inceptisols and Entisols). Poorly drained to well‐drained palaeosols from the base to the top in the distal plain (Aridisols and Inceptisols) are associated with geomorphic and hydromorphic changes in the fluvial system due to progradational evolution. The genetic relationship between the fluvial architecture and the palaeosols enhances the understanding that the sedimentation and pedogenesis that occurs in different portions of the distributive fluvial system are related to the tectonic and climatic evolution of the basin. [ABSTRACT FROM AUTHOR]

Abstract Rhizoliths are organosedimentary structures produced by plants and are an important proxy for paleoenvironmental reconstructions because the differences in the morphology of rhizoliths and their rooting depths can be used to interpret soil humidity regimes, overall biomass at the soil surface, and the behavior of the water table. With the objective of advancing knowledge on rhizoliths, a study was performed on the macromorphological and micromorphological characterizations of the rhizoliths preserved in the thirty-one paleosols of the Marília Formation in Minas Gerais, southeastern Brazil. Based on the topological and architectural attributes of rhizoliths, and on their possible functional adaptations, such as mycorrhizal associations, three different types of rhizoliths are described in this study and represent at least three different plants: rhizohaloes, root casts and rhizocretions. Well-developed paleosols with nodular horizons contain the higher density of long root casts, indicating a seasonally dry environment, because the root casts present two meters in length. These adaptations are associated with an exploitation of a lowered water table during most times of the year. The higher density of rhizoliths indicates an area with agglomerated arboreous arbustive vegetation cover. Paleosols with chalky horizons also show a high density of root casts, indicating a landscape with high plant density that is adapted to drained soils, but with a seasonally elevated water table or the influence of ephemeral flows, given the proximity to the flow channels. The poorly drained paleosols with redoximorphic features show the lowest density of rhizoliths, thus indicating an incipient vegetation in response to near-surface water table and waterlogged soils in a distal floodplain. The rhizogenic laminar horizons have developed near fluvial channels with frequent sedimentary input, resulting in a sequence of laminar horizons composed of rhizocretions that are separated by sandy deposits or poorly developed pedogenic horizons. The micromorphological analysis on the rhizogenic laminar calcretes showed biogenic features, such as alveolar septal structures, calcified filaments, microcodium, calcified cells and pisoliths. Despite the scarce paleobotanical findings in the Marília Formation, the results obtained indicate an ecosystem that was composed of plants varying from herbaceous to arboreous, with an environment similar to modern semiarid shrublands. Graphical abstract Unlabelled Image Highlights • The architecture and geometry of rhizoliths indicate different types of paleosols. • The preservation of rhizoliths are linked to the paleosols characteristics. • A link between the type of rhizolith and paleotopography was established. [ABSTRACT FROM AUTHOR]

Abstract The current research was performed in the eastern portion of the Marlim oilfield to identify the hydrocarbon-generating potential of the Albian-Oligocene sequences (Macaé Group, Ubatuba and Carapebus formations) in the Campos Basin, Brazil. On the basis of petroleum geochemical proxies, an integrated approach was developed using source rock characterizations to establish the distribution of source rock properties, such as organic matter content, hydrocarbon-generating potential, thermal maturity and stratigraphic thickness. The outcomes of a comprehensive petroleum geochemical characterization were integrated with cuttings and core sample descriptions, biostratigraphic controls, well log analyses and 2-D/3-D seismic interpretations. Our results reveal that for the Albian-Oligocene deposits, the key geochemical properties required to develop hydrocarbon source kitchens converge in specific locations, demonstrating a variable hydrocarbon potential ranging from poor to excellent and suggesting the existence of local generation pods in the central and principally northern portions of the research area. The accumulation and preservation of the organic matter were influenced by the paleo-topography and tectonic controls, and the lowest concentrations of organic carbon were attributed to significant siliciclastic dilution taking place mostly toward the middle and southern portions of the Eastern Marlim oilfield. Lateral variations in both the lithofacies and organic facies are the main conditions controlling the behavior of the petroleum potential in the investigated sediments. Our results indicate that the Macaé Group has sufficient source-rock potential, maturation patterns, and hydrocarbon-generating potential to be considered as an active source rock in the Eastern Marlim oilfield, where the petroleum geochemical properties converge and are adequate to generate hydrocarbon compounds. In addition, the Ubatuba and Carapebus formations are also likely to generate oil and/or gas, but due to their relatively low maturity, it is difficult to establish that these rocks can be active source rocks in the study area. Graphical abstract Image 1 Highlights • A petroleum geochemical characterization is proposed in the Eastern Marlim oilfield. • Local generation pods were recognized in the northern portion of the study area. • Significant siliciclastic dilution takes place mostly toward the south of the field. • Paleotopography and tectonic controls influenced the behavior of the organic matter. • The Macaé Group may have significant hydrocarbon generation potential. [ABSTRACT FROM AUTHOR]

Palaeosols can be used as stratigraphic proxies, palaeosurface indicators, and palaeorelief reconstitution tools, as they reflect a complex interrelationship between sedimentation, erosion, non-deposition, and pedogenesis. The objective of the article was to estimate the relative time of formation of palaeosols of the Marília Formation, to determine the periods of non-deposition and non-erosion, indicative of stabilities on the surfaces, and to interpret the profiles as markers of palaeosurfaces in distributive fluvial systems (DFS) of the Late Cretaceous of Brazil. Eleven sections of the Marília Formation (S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, and S11) were described, comprising forty-three profiles. The pedotypes classification (polygenic, compound, and cumulative) and the determination of palaeosols' relative formation time and residence time were based on the specialized literature. The reconstitution of pedosedimentary cycles considered the dynamics of sedimentation, erosion, and pedogenesis. Eight sedimentary cycles and 45 pedosedimentary cycles were interpreted. All the Maastrichtian pedosedimentary cycles of the Bauru Basin corresponded to depositional cycles interspersed with erosive and pedogenic processes. Palaeosols with argillic (Btk, Bt, Bss) and calcic (Bkm) horizons, developed from fluvial sandstones, evolved in processes predominantly after the deposits, with later erosive processes. However, although most of the profiles developed in periods between deposits and erosion, pedogenic processes also occurred concomitantly with the sedimentary cycles, favouring the formation of polygenetic profiles, which presented the longest pedogenic cycles in chronological terms. Palaeosols with argillic horizons can be important stratigraphic landmarks. They represent stopping moments in erosion and sedimentation of up to 1.374 My, thus consisting of the closing of high-frequency depositional cycles. Although palaeosols can demonstrate relief inversion and pedotypes with Bt-horizons can indicate ancient regional surfaces, the complete reconstitution of the topography becomes more possible at the local level, in a palaeoslope approach, due to the variability of pedofacies. • Palaeosols represent moments of non-deposition and non-erosion, indicative of landscape stability. • Compound and polygenetic palaeosols with Bt and Btk horizons correspond to the largest intervals of non-erosion, non-deposition, of topographical and tectonic stability in the evolution of the Maastrichtian palaeolandscape of the Bauru Basin. • The palaeosols represent relief inversion and the pedotypes with Bt-horizons indicate ancient regional surfaces, providing the reconstitution of palaeoslopes. [ABSTRACT FROM AUTHOR]

This is the first report of trace fossils potentially associated with insect social behavior in sandy and well-drained paleosols of the Upper Cretaceous continental sequence of Brazil. The trace fossils consist of dozens of lobed and vertical structures cemented by CaCO 3 and preserved mainly in full relief in paleosols of the Marilia Formation (Bauru Basin) in the state of Minas Gerais. The described ichnofossils are predominantly vertical, up to 2 m long, and are composed of horizontal lobed structures connected by vertical tunnel-like structures that intersect in the center and at the edges. The lobed structures range from 3 to 15 cm long and 2–6 cm thick. Two different hypotheses are analyzed to explain the origin of the trace fossils; the less probable one is that the structures are laminar calcretes associated with rhizoliths and rhizoconcretions. The hypothesis involving social insects was considered because the trace fossils described herein partially resemble a modern ant nest and the ichnofossil Daimoniobarax. The micromorphological analysis of the lobed and tunnel-like structures indicates modifications of the walls, such as the presence of inorganic fluidized linings, dark linings and oriented grains, supporting the hypothesis that they are chambers and shafts. The architecture and size of the reported nests suggest the possibility that social insect colonies existed during the Maastrichtian and are direct evidence of the social behavior and reproductive strategies of the Cretaceous pedofauna. [ABSTRACT FROM AUTHOR]

The Barra Velha carbonates are widely known for their complexity regarding facies, diagenetic features, and depositional history. The absence of recent analogues representing the depositional setting of these rock formations leaves many uncertainties concerning the sedimentary process that generated them. The present work aims to propose a model for the depositional environment of the Barra Velha Formation based on sedimentary features identified through facies description and interpretation. The employed data consists of 645 m of core descriptions, 2300photomicrographs, 1201 plug samples, and 44 thin sectionsdistributed throughout 34 wells in two Santos Basin oil fields. Fourteen facies were identified and classified into four categories: in situ, microbial, reworked, and altered. The in situ facies are composed of spherulites, shrubs, and mud. Sedimentological evidence points out that spherulites and shrubs precipitated within layers of mud, as a post depositional process. Microbial facies have several characteristics that refer to stromatolites and occur laterally and vertically associated with in situ facies. The spatial association between them indicates that in situ and microbial facies formed in the lower energy portions of the lake. Reworked facies were formed by grain fragmentation and transportation, indicating an energetic lake-littoral zone, where grainstones and packstones formed in the shallowest portions, and wackestones formed in the less energetic portion of the littoral zone. The altered category comprises the weathering profiles. These profiles resemble soils and developed in response to periods of strong evaporation, when lake brines would become dense enough to infiltrate into the groundwaters, leading to the precipitation of the dolocretes in the mixing zone. The spatial distribution of the facies corroborates the sedimentological interpretations. In situ and microbial facies are frequently found in the structurally lower regions of the study area. In contrast, reworked facies and weathering profiles are more common on structural highs. • The Barra Velha Formation comprises 14 facies, that were grouped in 4 categories: in situ, reworked, microbial and altered. • The in-situ facies are composed by spherulites, shrubs and mud, and were formed in the limnetic zone of the lake. • Reworked facies were formed in lake littoral zone, and indicated the occurrence of an energetic lake shoreline. • Microbial facies occur spatially associated with in situ facies indicating that they formed submerged in the lake water. • Altered facies resemble soils and were formed in a palustrine setting due to lake level fluctuations and evaporation. [ABSTRACT FROM AUTHOR]

The reactivation of faults may directly modify their permeability and the integrity of the petroleum system seal. Thus, this understanding is fundamental for decision-making in the petroleum industry at different levels while developing, for example, hydraulic fracturing projects, fracture networking, Enhanced Hydrocarbon Recovery (EOR), and CO 2 storage. The identification of the stress field based on elastic properties, failure criterion, rock strength, and in-situ principal stresses allow to understand the geomechanical behavior of stratigraphic units. This process becomes complex in carbonate reservoirs because they present high geomechanical variability related to the sedimentary and diagenetic processes they undergo. In this context, the present work aims to study the potential for fault reactivation in the pre-salt Barra Velha and Itapema Formations and in the Camboriu Formation in the study area, Santos Basin, Brazil, based on geomechanical modeling. Data from 28 wells with basic geophysical well-logs and wellbore image logs, absorption and formation pressure tests, and 3D pre-stack seismic data were used. The results indicate an abnormally high fluid pore pressure (9.49 ppg) concerning hydrostatic pressure (8.34 ppg). Three structural compartments delimited by interpreted seismic horizons and faults were defined. Three fault regimes were defined based on minimum and maximum horizontal stresses gradients: a double normal-transcurrent regime for the Barra Velha and Itapema Formations; a normal regime for the Piçarras Formation; and a double transcurrent-inverse regime for the Camboriu Formation. Finally, based on the stress polygon, scenarios of fault reactivation in the structural compartments were estimated. With increases between 16% and 28.1% of the pore pressure by fluid injection, the transcurrent movement of the faults can be generated. The reverse faults of a shallower structural compartment have the highest probability of reactivation and movement. • Contrasting mechanical behaviors were observed in the pre-salt carbonate rocks and in the igneous rocks • An abnormally high behavior of Ppore with respect to Ph was identified for different saturation intervals. • The orientation of the in-situ horizontal stresses is NW-SE for S hmin and NE-SW for S HMax coinciding with the azimuth of the faults (NE-SW). • A rotation of the stress fields along some wells relative to the main trend was identified. • Due to the magnitudes of the stresses S v , S hmin and S HMax , different fault regimes were identified in the formation of interest. • Fault reactivation in the BVE100 can occur under a transcurrent stress regime. • A direct relationship between the depth of fluid injection and the increase of Ppore was identified. / OTHER HIGHLITH --> A correlation was defined between the orientation of movement of the reactivated faults and the azimuth of the faults. [ABSTRACT FROM AUTHOR]

Soils and paleosols reflect the complex interplay between sedimentation, erosion and non-deposition. An analysis of the mineralogical components of paleosols is critical for the reconstitution of the factors, processes and environments in which they were formed. The recognition of mineralogical assemblages can reveal the environmental conditions during pedogenesis and through quantitative analysis it is possible to identify a vertical variation in mineral concentration or leaching over the paleosol profiles, indirectly pointing to environmental processes that dominated during the pedogenetic evolution. The objective of this study is to discuss the significance of mineral phases and to quantify the environmental evolution and degree of development of paleosols of the Marília Formation, Maastrichtian of Bauru Basin. Three sections have been described (A1, A2, A3) in the Marília Formation. The mineralogy was determined by x-ray diffraction, and mineral quantification was obtained through the Rietveld refinement method. The calcretes of the Marília Formation are pedogenic, mostly authigenic minerals. The variation of quartz, calcite, palygorskite and smectite, the micromorphology, and the diversity of subsurface horizons (Bkm, Btkm, Bt) indicate that the studied paleosols did develop in semi-arid conditions, with episodes of higher rainfall rates, humidity, leaching and desilication. [ABSTRACT FROM AUTHOR]

The application of sequence stratigraphy concepts to continental deposits lacking the referece provided sea level has been a challenge, mainly because the temporal relationships between stratigraphic surfaces and systems tracts depend on the tectonic and climatic evolution of the area. Using the concept of accommodation space (A) and sediment supply (S), we identify specific stacking patterns of aeolian, lacustrine, fluvial and alluvial systems that correspond to the particular tectonic and climatic evolution of the southeastern portion of South America. With the end of the Early Cretaceous volcanism (133 Ma), the southeastern portion of South America underwent tectonic restructuring, which generated basins that encompassed continental sedimentary sequences. The tectonic events responsible for the accumulation of these sequences occurred during two primary phases. The first phase is related to Early Cretaceous thermal subsidence, which was more pronounced in the regions where the thickest Serra Geral Formation basaltic successions are found, resulting in the formation of Bauru Basin. The second phase was related to the Late Cretaceous uplift in southeastern Brazil as a result of magmatic/volcanic activity associated with the Trindade Mantle Plume. Stratigraphic analysis based on well-logs and outcrops and aided by petrographic studies identified three sequences that are bounded by regional unconformities that record important changes in the Bauru Basin's tectonic and paleoenvironmental conditions. The unconformity K-0 is related to the origin of the Bauru Basin in the Early Cretaceous. The Early Cretaceous Sequence 1 (Caiuá Group) is interpreted as a second- order sequence, formed by aeolian and fluvial deposits and constituting a Fluvial-Aeolian Systems Tract. Unconformity K-1 that was generated in the Late Cretaceous (Cenomanian - Campanian?) is related to the tectonic evolution of the basin and source area. Overlying Unconformity K-1, lacustrine, fluvial and alluvial deposits display progradational characteristics of the two-third- order sequences: Sequences 2A and 2B, constituted by the Fluvial-Lacustrine and Alluvial Systems Tracts, respectively, and separated by the Unconformity K-1A. Sedimentological characteristics, paleosols and stratigraphic architecture, suggest that A/S ratio was neutral in the late stage of the Sequence 1, whereas in the Sequence 2 there was an increase (Sequence 2A) followed by a decrease in the A/S ratio (Sequence 2B). Aeolian facies and paleosol P1 (Sequence 1), fluvial-lacustrine facies and hydromorphic soils (Sequence 2A), and alluvial facies and Paleosol P2 (Sequence 2B), indicate climatic changes in the South American during the Cretaceous. The stratigraphic framework, subaerial unconformities and paleosols provide key elements for subdividing of the Brazilian continental sequence into third-order sequences and systems tracts, for identification of allocyclic and autocyclic patterns in time and space. [ABSTRACT FROM AUTHOR]

Reservoir static modelling plays a fundamental role in the evaluation phase of a petroleum field. Integrated modelling allows a better understanding of how the local geology and depositional systems are related through the distribution of facies and petrophysical properties within the reservoir. In this study, geological static models of the siliciclastic Carapebus Formation of Campos Basin were built using subsurface data. The applied methodology was divided into five phases: (1) establishment of a conceptual model, (2) building of a structural model, (3) generation of 100 realizations of lithofacies using sequential indicator simulation, (4) generation of 100 realizations of porosity and permeability using sequential Gaussian simulation, and (5) validation of models by targeting both statistical and geological consistency. The obtained models are consistent and honor the conditioning data. A lithofacies constraint is crucial to better characterize the petrophysical properties distribution of the reservoir. A Dykstra-Parsons coefficient of V=0.52 characterizes this reservoir as moderately homogeneous. [ABSTRACT FROM AUTHOR]

Despite the vast crocodyliform fossil record, little is known about the reproductive biology and nesting strategies of the extinct members of the group. Here we report a large accumulation of crocodilian fossil eggs from the type-locality of the baurusuchid Pissarrachampsa sera . Sedimentary facies and architectural elements of the site support a palaeoenvironmental model with a shallow lacustrine, playa-lake system interacting to ephemeral braided fluvial channels, with aeolian influence and development of sandy soils. The presence of pedogenic calcretes in the palaeosols indicates arid to semi-arid conditions. The crocodilian affinity of the eggs is supported by the thin eggshell which bears wedge-shaped shell units with tabular microstructures. Furthermore, taphonomic data support an autochthonous assemblage of eggs and skeletal remains, hinting at a monotypical stratigraphic horizon and suggesting P. sera as the egg-laying taxon. The repeated pattern of four (eventually five) eggs per clutch at the site demonstrates that P. sera laid fewer eggs compared to modern crocodilians, indicating that k-selected reproductive strategy pattern is pervasive in the fossil record of Notosuchia. In the crocodyliform phylogenetic framework, the k-strategy and the “egg clutch sizes” optimization of Notosuchia is opposite to the strategy with larger clutches consistently occurring in modern Crocodylia and Neosuchia, the sister clade to Notosuchia. Yet, the lack of data on more early-branching taxa renders unclear which pattern is plesiomorphic for Crocodyliformes as a whole. [ABSTRACT FROM AUTHOR]

Located on the Brazilian Equatorial Margin, the Mundaú Sub-Basin is the only offshore hydrocarbon-producing region of the Ceará Basin. The origin and evolution of the Mundaú Sub-basin are a consequence of the rupture of the Pangea supercontinent during the Early Cretaceous, which led to the opening and development of the Equatorial Atlantic Ocean. This area has been considered a new exploration frontier, promoting research to be developed in recent years. However, the interactions between transtensive events and spatial-temporal distributions of tectonic subsidence have been poorly studied. To cover this gap, fifty-seven wells and approximately 5800 km of 2D seismic lines were analyzed to understand these events. From these data, stratigraphic and structural interpretations were performed throughout the sub-basin, enabling the construction of 43 pseudo-wells. Using descompactation of the wells and pseudo-wells using the backstripping method, it was possible to reconstruct seven tectonic phases for the Sub-Basin, which correspond to the rift sequence (RP01, RP02, and RP03), the transition sequence (BP01), and the drift sequence (DP01, DP02, and DP03). Four sets of faults of three zones of the three zones (WZ, CZ and EZ) proposed for the Mundaú Sub-Basin were also analyzed. The faults are distributed in two orthogonal families, formed in two distinct events. Older R and P faults, respectively trending NWW-SEE and NNESSW, formed during RP01 (first event). Younger R and P faults, respectively trending NNW-SSE and NEE-SWW, formed during RP02 (second event). Tectonic reconstruction revealed the diachronic formation of two depocenters, one in the West Zone (WZ) during RP01, and the other in the Central Zone (CZ) during RP02. Despite the intense tectonic activity in WZ and CZ, the East Zone (EZ) showed low subsidence rates and little development during the entire rift phase. In turn, BP01 showed faster subsidence rates when compared to RP03, indicating tectonic influence even during the breakup phase. Finally, the drift phase showed the lowest subsidence rates, spatially distributed in an opposite pattern to the rift phase. From these results, a rotation of the Principal Displacement Zone (PDZ) was identified, with initial parallel motion vectors, forming the WZ depocenter and generating the first fault family during RP01; after RP02, motion vectors were oblique, forming the second depocenter in CZ and generating the second fault family. Significant thermal control associated with magmatic events was identified during the drift phase. This study also describes the main structures formed along with the overlap of parallel and oblique PDZ displacement. [Display omitted] • This study provides new insights into the Mundaú Sub-Basin geodynamic evolution. • Tectonic stress and subsidence patterns from Early Aptian to Holocene. • Strike-slip features from seismic and subsidence rates obtained from decompression of well and pseudo-well data. • Evidence of the superposition of parallel and oblique Principal Displacement Zone. • Tectonic, thermal, and basement inheritance controls acting during rift, breakup and drift phases. [ABSTRACT FROM AUTHOR]

With the breakup of the supercontinent Gondwana, the South American Plate has undergone an intense process of tectonic restructuring that led to the genesis of the interior basins that encompassed continental sedimentary sequences. The Brazilian Bauru, Sanfranciscana and Parecis basins during Late Cretaceous have had their evolution linked to this process of structuring and therefore have very similar sedimentary characteristics. The purpose of this study is to establish a detailed understanding of alluvial sedimentary processes and architecture within a stratigraphic sequence framework using the concept of the stratigraphic base level or the ratio between the accommodation space and sediment supply. The integration of the stratigraphic and facies data contributed to defining the stratigraphic architecture of the Bauru, Sanfranciscana and Parecis Basins, supporting a model for continental sequences that depicts qualitative changes in the sedimentation rate (S) and accommodation space (A) that occurred during the Cretaceous. This study discusses the origin of the unconformity surfaces (K-0, K-1 and K-1A) that separate Sequences 1, 2A and 2B and the sedimentary characteristics of the Bauru, Sanfranciscana and Parecis Basins from the Aptian to the Maastrichtian, comparing the results with other Cretaceous Brazilian basins. The lower Cretaceous Sequence 1 (Caiuá and Areado groups) is interpreted as a low-accommodation systems tract compound by fluvial and aeolian systems. The upper Cretaceous lacustrine, braided river-dominated alluvial fan and aeolian systems display characteristics of the evolution from high-to low-accommodation systems tracts (Sequences 2A and 2B). Unconformity K-0 is related to the origin of the Bauru Basin itself in the Early Cretaceous. In Sanfranciscana and Parecis basins, the unconformity K-0 marks the contact between aeolian deposits from Lower Cretaceous and Upper Cretaceous alluvial systems (Sequences 1 and 2). Unconformity K-1, which was generated in the Late Cretaceous, is related to an increase of the A/S ratio, whereas Unconformity K-1A is the result of the decrease in the A/S ratio. Unconformity K-1A bound Sequence 2A (lacustrine and fluvial systems) and Sequence 2B (alluvial deposits) in Bauru Basin whereas in the Sanfranciscana and Parecis basins this unconformity marks the transition from alluvial system to aeolian system (Sequences 2A and 2B). Changes in depositional style in both basins correspond to two distinct tectonic moments occurring within the South American plate. The first associated with post-volcanic thermal subsidence of the Early Cretaceous (Serra Geral and Tapirapuã volcanismos), and the second moment associated with the uplift occurred in the Late Cretaceous (Alto Paranaíba, Vilhena and Serra Formosa Arcs). [ABSTRACT FROM AUTHOR]

Flow units (FUs) have been widely used for rock typing in many reservoirs, especially where there is no direct correlation between petrophysical properties and geological characteristics. This scenario is extremely common in carbonate rocks that are likely to be shaped and modified by pedo-diagenetic processes forming heterogeneous reservoirs with geological and petrophysical properties varying in all scales. The present work aimed to test different well-established petrophysical rock-typing methods in complex carbonate reservoirs and integrate them with geological-driven rock classifications. The goal was to find a correlation between facies, diagenesis and the quality of the reservoir as well as understand how different rock-typing methods behave in complex reservoirs. This study was implemented on the carbonates of the Barra Velha Formation which are known for their complexity regarding facies, diagenetic features, and petrophysics. The study was performed in two oilfields of Santos Basin (Brazil) and employed data from 44 wells, including routine core analyses and well logs, along with core and thin section high-resolution images. As a result, 13 facies were identified and grouped into six facies associations representing different zones of a lacustrine environment: Deep Lake, Lower Shoreface, Upper Shoreface, Lower Foreshore, Upper Foreshore, and Backshore. Three rock-typing methods were tested for the flow units identification: FZI, Winland R35 and Aguilera R35. The Barra Velha Formation was subdivided into 4 flow units. All methods reveal that the Deep Lake and Lower Shoreface Facies Associations comprise the poorer reservoirs of the Barra Velha Formation and that the Lower and Upper Foreshore Facies Associations concentrate the best reservoirs. Shrubstones were the facies with the highest R35s and FZIs values followed by the grainstones. The FZI methodology was the most optimistic and Winland R35 the least. Aguilera R35 presented the highest correlation with permeability, proving to be a reliable method for application in complex carbonate reservoirs. The approach and equations obtained in the Pre-salt reservoirs can be employed for different oilfields. Therefore, for a more accurate result, we recommend the calculation of the constants using data from the studied field. • Barra Velha Formation comprises in situ, reworked, and altered facies that were subdivided into 6 facies associations. • The formation was subdivided into 4 flow units based in 3 different rock typing methods: FZI, Winland R35 and Aguilera R35. • FZI had the most optimistic results and Winland R35 the least. Aguilera R35 had the highest correlation with permeability. • Shrubstone and Grainstone are the most frequent facies in flow unit 4, which comprises the best reservoirs of the formation. • The methodology presented in this work can be applied to segment flow units in other locations. [ABSTRACT FROM AUTHOR]

The Cretaceous climate was characterized by arid and semiarid conditions in different parts of the world. Climatic changes for the Early to Late Cretaceous had been reported by many authors in North America, East Asia, Africa, and South America due to the geological evolution of Laurasia and Gondwana. In South America, the Bauru Basin, located in Brazil, is one of the most critical places to develop paleoclimatic reconstructions due to the presence of well-preserved Cretaceous sedimentary sequences, as well as abundant fossil content and paleosol profiles. The transition between the Lower and Upper Cretaceous in the Bauru Basin is represented by the Santo Anastácio and Araçatuba formations, which are characterized by a succession of sandstones, claystones, and paleosols. The paleosols are well distributed in the basin, providing valuable information about the paleoenvironmental conditions and insights about the tectonic and climatic changes in the Cretaceous Period. Since the 1960's decade, the Cretaceous paleosols of the Bauru Basin have been used as stratigraphic and sedimentological proxies providing paleoenvironmental and paleoclimatic insights, principally for the Late Cretaceous Period. This study, based on macromorphological descriptions, clay mineralogy (X-ray diffraction and scanning electron microscopy - SEM), and geochemical of paleosols, identified environmental and climatic patterns from the Lower and Upper Cretaceous. Results allowed to elaborate maps of paleoclimatic evolution that indicate changes occurred from Lower to Upper Cretaceous sequences of the Bauru Basin. These changes were compared and correlated with other continental basins in West Gondwana and Laurasia around the world, contributing to the understanding of the Cretaceous paleoclimatic context of South America. • A first interpretation of the Early Cretaceous climate using geochemistry was made. • The Early Cretaceous Period displayed predominantly arid to semi-arid conditions. • The Late Cretaceous indicated some rainfalls intervals and an increase in humidity. [ABSTRACT FROM AUTHOR]

Paleosols are soils that were formed on an ancient landscape. They may be buried soils and/or soils incorporated into the sedimentary sequences, exhumed soils, or soils developed on ancient relief surfaces (relict soils). Exposed on the surface and influenced by later environmental changes, paleosols reveal ancient environments and contain records regarding the climate, vegetation, landforms, organisms, parent material, time, intensity of pedogenesis, and sedimentation rates in effect during their training. In the Marília Formation, the paleosols, exhumed and buried, developed on sandstones have argic (Btk, Bt and Bss), hydromorphic (Cg) and calcic (Bk) horizons with different degrees of cementation, forming mainly calcretes. The objective of this study was to characterize the genesis of the paleosols of the Marília Formation, addressing the dynamics of their formation factors and processes at local and regional levels in order to reconstitute the conditions of environmental evolution of the Maastrichtian of the Bauru Basin. Eleven sections (S1, S2, S3, S4, S5, S6, S7, S8, S9, S10 and S11) of the Marília Formation were described and collected on nine sample profiles. Micromorphological, mineralogical and geochemical analyses were performed according to the specialized literature. In the Marília Formation, sedimentation, erosion and pedogenesis are processes that occurred together, concomitantly or subsequently, in view of the fluvial paleoenvironmental dynamics. The paleosols indicate the end of depositional cycles, with differentiated rates, intensities and duration. The paleosols of the Marília Formation comprise well-drained (Bt-horizon) and poorly drained or hydromorphic (Cg-horizon) pedotypes, of drier conditions (Bkm-horizon) and pedotypes indicative of drier periods alternated with periods of higher humidity (Bss-horizon). The profiles were classified as Luvisols (Bt and Btk horizons), Calcisols (Bk and Ck horizons), Arenosols (C-horizons) and Vertisols (Bss-horizons). Paleosols developed on the flatter and lower portions of the slopes and floodplains and were commonly influenced by the oscillation of the groundwater and the seasonality of the climate. Sandstone with allochthonous and autochthonous carbonate cementation constituted the main parent material of the paleosols. The predominant climate during the Maastrichtian was semi-arid, with seasonality and variations in precipitation patterns and a precipitation-evapotranspiration relationship that provided conditions for the formation of paleosols with Bk, Btk, Bss, Bg and Bt horizons. The time of formation of these diagnostic horizons was dependent on climatic and edaphic factors. However, the time factor lasted until approximately 200,000 years, allowing paleosols to develop with Bt-horizons and prismatic and block structures. Calcification and argilluviation were the formation processes responsible for the genesis and evolution of paleosols during the Maastrichtian of the Bauru Basin. Weathering indexes have shown that paleosols with Bt-horizons are more weathered than are those with Btk and Bk horizons. The paleosols with Bk-horizons reflect periods with more arid conditions in the general context of the semi-arid paleoclimate of the Maastrichtian of the Bauru Basin. • The calcretes of the Marília Formation are of pedogenic origin. • The calcretes (paleosols) developed in situ by the weathering of sandstones. • These paleosols were formed in flatter slopes of relief, under semi-arid environment. • Calcification and argilluviation acted in the evolution of the paleosols. • Paleosols with Bt-horizon are more weathered than those with Btk and Bk horizons. [ABSTRACT FROM AUTHOR]

Tectonic rejuvenation has been widely described in ancient rifting areas of intraplate settings, despite extensive active tectonics being discontinued long ago. Various models have been invoked to justify such tectonic rejuvenation, suggesting that the long-term deformation in intraplate interiors may be more complex than once supposed. Inherited weakness zones, e.g., pre-existing faults are stress concentrators. However, not all weakness zones in plate interiors show tectonic rejuvenation and recognizing intraplate fault reactivation remains puzzling. Bedrock channels play an essential role in tectonically unstable landscapes and therefore they may unveil which pre-existing structures have been rejuvenated. Here we explore the Cinzas Catchment in order to investigate the interactions between tectonic rejuvenation, bedrock inheritance and geomorphic river signatures in an important Brazilian rifting feature, the Ponta Grossa Arch. We perform a geomorphic analysis combined with fieldwork, dating techniques and existing data to evaluate whether the geomorphic responses of the major rivers show perturbations related to the bedrock inheritance and post-rift rejuvenation. We also show that the interactions between river signatures and the bedrock fault zones are responses to post-rifting rejuvenation coupled with bedrock inheritance. This post-rifting rejuvenation is consistent with a mosaic of superimposed mechanisms which have been invoked by previous studies. [ABSTRACT FROM AUTHOR]

The sedimentary basins in the Continental Rift of Southeastern Brazil (CRSB) provide an opportunity for ichnological analyses due to its well-known facies relationships and paleoenvironmental interpretations. This study reports invertebrate trace fossils from the Neogene fluvial deposits (Floriano Formation) and applies integrated ichnological and facies analyses to reconstruct the environmental conditions recorded in this lithostratigraphic unit. Fieldworks revealed a rich ichnofauna in the Floriano Formation, whose facies associations have been interpreted as indicative of meandering river environments. Four sedimentary facies were identified, including bioturbated sandstone, horizontally stratified sandstone, laminated sandstone, and mudstone. Six ichnogenera were identified, Arenicolites, Beaconites, Camborygma, Palaeophycus, Skolithos, and Taenidium. Those ichnogenera occur as Skolithos, Taenidium, and Beaconites ichnocoenoses. The Skolithos ichnocoenosis is primarily represented within sand bar deposits, indicating arthropod colonization in abandoned channels. The Taenidium ichnocoenosis, which is observed within mudstone layers and presents Camborygma burrows, suggests transitional environments between aquatic and subaerial conditions, locally with high water table levels. The Beaconites ichnocoenosis indicates changes in substrate consistency associated with progressive desiccation and extended exposure time. Therefore, the identified ichnocoenoses, combined with the analysis of physical sedimentary structures, suggest generally humid conditions during colonization by invertebrates of the meandering river deposits of the Floriano Formation. [ABSTRACT FROM AUTHOR]

Soils are good indicators of the stability of environmental systems. In meandering river floodplains, they assess river channel morphology, incision process, groundwater level dynamics, and avulsion processes. The morphological properties and physicochemical attributes give gleysols unique characteristics about formation conditions and evolution degrees related to fluvial dynamics, thus allowing elaborate models of floodplain evolution in meandering rivers. This manuscript aimed to analyze the relationship between gleysols evolution and fluvial dynamics, in the quaternary floodplain of a meandering river, in the Mogi Guaçu River basin in the State of Minas Gerais. We described three profiles, in concave and convex margins of the river, identifying facies and considering the morphological characteristics of the gley horizons. Physicochemical analyses, determination of major and minor elements, and oxides were carried out on the samples of horizons and deposits of the profiles. For the characterization of the river channel, morphometric parameters were measured. Concentrations of silica, titanium dioxide, alumina, ferric and manganese oxides, plus the molar relations of provenance (P), leaching (L), parent material (M1 and M2), oxidation (O), hydrolysis (H), and the alteration geochemical index (CIA-K) were determined to compare the profiles pedological evolution. The three analyzed profiles were classified as typic Dystrophic Tb Haplic Gleysol (P1 and P2) and typic Alic Tb Haplic Gleysol (P3) so that the relation silt/clay demonstrated profile 3 to be the most evolved (weathered). Concentrations and behavior of oxides, associated with molar relations and conditions of the surfaces S II and S III of the flat floodplains morphological, demonstrated that the meandering process, with avulsion linked to erosion and deposition, affects gleysols evolution, suggesting genesis with compound or polygenetic profiles. Under a cyclical interpretation, the evolution of gleysol profiles, with truncation and horizon overlaying, reflects processes of avulsion, incision, and floods, as well as are proxies for interpreting the quaternary evolution of the Mogi Guaçu River meandering process. • The meandering process, with avulsion associated with erosion and deposition, influences the evolution of gleysols, providing for the genesis of compound or polygenetic profiles. • The genesis of different pedotypes of gleysols are reflections of the process of avulsion and incision of the river channel. • The Gci, Sh, Sl, Sm, and Fm facies, along with intense mottling in the horizons, demonstrate oscillations in the groundwater level and changes in the channel's energy gradient. [ABSTRACT FROM AUTHOR]

The Late Albian-Early Turonian succession on the Arabian Platform stands out as one of the world's richest hydrocarbon provinces. This study delves into the Seismic Sequence Stratigraphy (SSS) of these successions to unravel reservoir characterization and characterized potential hydrocarbon plays. Utilizing data from five exploration wells, including well logs, selected core data, biostratigraphical information, and chemostratigraphy analysis, alongside a comprehensive 3D seismic volume, enabled the identification of four 3rd-order sequences and multiple 4th-order sequences within the studied successions. Sequence-1 (DS-I), dating back to the Late Albian age, features mudstone and bioclast wackestone in an open marine environment. DS-I is a key sequence, notably witnessing the disappearance of siliciclastic input from west to east in the study area. DS-II (Early Cenomanian) and DS-III (Mid-Cenomanian) were deposited on carbonate platforms with grain-supported facies in shoal and lagoonal depositional environments. A distinct regional unconformity at the Turonian base, evident on seismic sections, aligns with depleted δ18O values on the Cenomanian-Turonian Boundary. The maximum flooding surfaces of DS-I and DS-II are characterized by continuous reflectors with negative amplitude. Furthermore, the lateral grading of reservoir facies and their intercalation with non-reservoir facies within 4th-order sequences suggest that reservoir facies heterogeneity is strongly influenced by depositional processes at this scale. Potential reservoirs, particularly in the Highstand System Tract (HST) of each 3rd sequence, are highlighted, with DC-III's HST standing out, hosting patch reef facies resulting from local tectonic activities and carbonate build-up movements. • High resolution seismic sequence stratigraphy was applied to Reservoir characteristics. • New insight to distinguished petroleum play by using HRSS approaches. • Biostratigraphy and chemostratigraphy analysis to detect Sequence boundaries. • 3rd and 4th sequences were characterized within the Late Albian-Early Turonian successions. • Heterogeneity is strongly controlled by the depositional processes operated at the scale of 4th-order cycles. [ABSTRACT FROM AUTHOR]

Burrowing behavior is an important adaptation of animals that live in arid and semi-arid conditions. In this paper, we describe examples of vertebrate burrows from the Upper Cretaceous (Maastrichtian) Adamantina Formation of the Bauru Basin, Brazil, most likely produced by turtles. The Adamantina Formation preserves abundant and diverse turtle body fossils such as Bauruemys elegans (Testudines: Pleurodira); however turtle burrows have not been previously documented. The newly reported burrows are preserved in fluvial sandstone facies and exposed in sections that partially preserve their three-dimensional geometry. Burrows are simple J-shaped tunnels with a cross-sectional shape that is semicircular (half-dome) with a flattened floor. Such burrows show a partially preserved entrance with an inclined ramp angle (22°), and grooves and ridges up to 1 cm in width preserved along the burrows walls and floor. The architecture and sedimentary facies of the host sandstone body, together with the occurrence of Taenidium barretti and the absence of rhizoliths, suggest that the burrow was excavated by scratch digging into an exposed point bar of a meandering river channel. Based on burrow morphology, dimensions, as well as ridges,and grooves in the walls and floor, we propose that burrows were formed by a chelonian (such as a freshwater turtle) during aestivation. We highlight that these are first examples of turtle burrows reported from the Cretaceous, and their occurrence reinforces the hypothesis that the original function of turtle shells was as an adaptation to fossorial behavior. [Display omitted] • The first freshwater turtle burrows from Cretaceous of South America. • The burrows occur in fluvial point bars of Adamantina Formation. • Evidence of fossorial and aestivation behavior in turtles during Cretaceous. • Results reinforce the hypothesis of fossorial behavior in stem turtles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Weathering pattern is mainly determined by the bimodality of aeolian deposits. • Dissolution features and booklets of kaolinite reveal monosiallitisation process. • Kaolinization processes suggest an increase in moisture between Albian and Cenomanian. The work investigated the paleoenvironmental significance of kaolinite-rich weathering fronts developed during the Cretaceous in stabilized dune fields of Sanfranciscana Basin in Brazil. To this, was conducted a multi-scale analysis from the outcrops of paleosols to mineral grains and soil pores. The macro and micromorphology of paleoweathering fronts allow recognizing weathering features and estimating the porosity and hydraulic parameters (permeability, capillary pressure, and saturated hydraulic conductivity). Scanning electron microscope analyses were conducted to investigate surface microtextures of quartz grains for weathering process characterization based on dissolution microfeatures. Energy-dispersive X-ray spectrometry was utilized to identify chemical elements of clay minerals. The major and trace elements were analyzed using a Philips X-ray fluorescence (XRF) spectrometer (PW 2440). Our results showed that weathering fronts expand through preferential water paths (pipe and finger flow) in bedding planes in response to textural and porosity contrasts related to the bimodality (i.e., the difference of grain size distribution between overlapped sedimentary structures) of aeolian deposits. The dissolution features present in quartz grains, such as etching, pitting, total dissolution of grains, iron coatings, and booklets of well-developed kaolinite, reveal an increase in humidity and the pedogenetic kaolinization process typical of a humid tropical environment. These weathering patterns coincide with cooling events between the Albian and the Cenomanian report in the literature. Our study indicates that during the Cretaceous, the Sanfransicana Basin underwent climatic amelioration and a rise in water table level, which likely enhanced dune stabilization and the formation of an extensive geomorphic surface. [ABSTRACT FROM AUTHOR]

• Pedogenetic processes involved in the argillic horizon (Marília Formation) have been studied. • Argillic horizons show clay illuviation, accumulation of carbonates and gleyic properties. • Argillic horizons developed in a semi-arid environment. A study of paleosols with argillic horizons found in the Marília Formation associated with Maastrichtian in the Cretaceous is presented herein. This study aims to investigate the polygenetic processes involved in argillic horizon formation under paleoclimatic conditions from arid to semiarid in the Brazilian Cretaceous and considers morphological soil attributes, such as evidence of cementation, macromorphological data (horizons, matrix color, structure, clay coatings, nodules, and bioturbations), micromorphological data (coarse/fine patterns, b-fabric, clay coatings, infillings, and nodules), and water table oscillation. Seven representative profiles of paleosols were selected in the São Paulo state, Brazil, and soil samples of lithified paleosols were collected to determine their macromorphological–micromorphological and chemical properties. Clay illuviation, carbonate accumulation, and gleization were dominant processes in the paleosols. Clay illuviation was identified from clay coatings along grain and ped surfaces. Carbonates occurred as nodules and rhizoliths and as coatings on peds. Red mottles, gray rhizohaloes with red oxidation rims, oxidic nodules, an iron-depleted matrix, and iron oxide depletion hypocoatings confirmed gleization. The argillic horizon polygenesis in the Marília Formation is usually interpreted as evidence of high-moisture events under arid/semiarid climates or climate change toward moister conditions than arid/semiarid. Thus, argillic horizon paleosols in the sedimentary records of the Marília Formation are not necessarily reliquial characteristics of wet paleoenvironments but are associated with changes in dominant granulometry, types of macroaggregates–microaggregates, carbonate accumulation in horizons, and/or water table oscillation. Thus, the presence of Bt horizons does not necessarily imply wet conditions with changes in the depositional system, as proposed by some authors. [ABSTRACT FROM AUTHOR]

The Mundaú sub-basin composes the western segment of the Ceará Basin, which is one of a series of basins of the Brazilian Equatorial Margin that resulted from the breakup of Western Gondwana. This study investigates the origin and maturation of the organic matter preserved in the rocks of the middle and outer shelf of the Mundaú sub-basin, in order to assess the source-rock potential for oil and gas generation. The samples selected for this study are representative of the Mundaú, Paracuru, and Ubarana formations, which correlate with the rift, transition, and drift phases of the Western Gondwana breakup. The results indicate moderate to good potential for oil generation and good potential for gas generation for the Mundaú Formation. Fault activity during the rift phase favored sediment supply. Kerogen type III predominates in shallower portions and probably reflects the contribution from the continent. Good to excellent potential for oil and gas generation is indicated for the Paracuru Formation. Kerogen types I and II predominate, having the marine organic matter been deposited in reducing conditions. The most promising interval for hydrocarbon generation is limited by the top of the Trairí Member and the top of the Paracuru Formation. Moderate to good potential for oil and gas generation is suggested for the Uruburetama Member of the Ubarana Formation. The source rocks located in the middle shelf were deposited under reducing conditions in a transgressive marine environment. Kerogen varies from type II, to a mixture of types II and III, and to subordinate type III. Poor to fair potential for oil generation is indicated for the Itapajé Member of the Ubarana Formation. Kerogen type IV (inert or degraded) is typical in the middle shelf, and kerogen type IV and subordinate type III are typical on the outer shelf. The presence of inert kerogen is related to high-energy, oxidizing depositional environments. The hydrocarbon expulsion threshold estimated for the outer shelf is at 2106-m, for the middle shelf at 1635-m, and for the deep waters at 3632-m depths. Source rocks of the middle and outer shelves occur between 561 m and 4080 m, whereas those in deep waters occur between 2754 m and 5007 m of depth. The Active Source Rock Depth Limits (ASDL) estimated for the outer shelf is below 4500 m, whereas for deep waters, this limit is close to 6000 m. These organic geochemical constraints are important guidelines for oil and gas exploration in the Ceará and adjacent basins. [Display omitted] • Source-rock from Mundaú sub-basin, Ceará Basin, Brazilian Equatorial Margin. • Source-rock characterization by means of organic geochemistry. • Distribution of source rocks via transects and isoline maps. • Aptian to Eocene distribution of organic-rich facies. • Oil potential of the Paracuru Formation – transitional phase of the Ceará Basin. [ABSTRACT FROM AUTHOR]

An organic geochemical investigation combined with sequence stratigraphy was performed in the Ceará Basin, an offshore basin located in Northeastern Brazil. The information available from 30 well logs (gamma-ray, resistivity, density), besides geochemical (TOC, and pyrolysis indexes) and isotopic (δ13C) data, aided the preparation of a dataset for this study. The application of sequence-stratigraphic methods helped classify and correlate seismic and organic facies. Four key petroleum source-rock units were identified, from the oldest to the youngest: (1) Mundaú Formation – top of the Rift Sequence (Berriasian-Aptian); (2) Paracuru Formation – Breakup Sequence (Aptian-Albian); (3) Itapajé Member of the Ubarana Formation – Continental Drift Sequence (Albian-Turonian), and (4) Uruburetama Member of the Ubarana Formation – Continental Drift Sequence (Turonian-Maastrichtian). The geochemical characteristics of the Mundaú Formation (high total organic carbon (TOC), hydrogen index (HI), relative hydrocarbon potential (RHP = (S1 + S2)/TOC)) point to a typical transgressive sequence. Six transgressive-regressive (T-R) cycles were recognized in the entire Paracuru Formation. The best geochemical marker is related to the top of the Paracuru Formation. This stratigraphic unit can be correlated to a major anoxic event and is the best source rock of this basin. Evaporitic facies found in this top section, maximum RHP values (anoxic conditions), and maximum flooding surfaces related to transgressive events characterize this interval. Moreover, the wide spatial cover of organic-rich rocks, carbon isotopic data, and the recognition of favorable characteristics for anoxia in other basins of the Equatorial Margin are suggestive of the Aptian-Albian Oceanic Anoxic Event (OAE-1b) occurring in the Ceará Basin. The Ubarana Formation represented by the Uruburetama Member and the Itapajé Member yields the least promising source rocks. However, high TOC values suggest the occurrence of the late Cenomanian–early Turonian Oceanic Anoxic Event (OAE-2), when organic-rich strata started to deposit in deep-water regions. The predominance of a regressive interval in the Uruburetama Member points to oxic or sub-oxic conditions. Additionally, the correlations between the Brazilian Equatorial Margin and its African counterpart, and the organic geochemical characterization allied to the definition of depositional systems for these regions proved to be useful for oil exploration. Flowchart representing the steps of this research. A) Database components. B) Data interpretation. C) Relative hidrocarbom potential (RHP) variations revealing changes in oxic conditions at depth and correlations with gamma-ray (GR) and lithofacies (Facies) stacking patterns. D) Sections showing the results obtained from data interpretation. E) A simplified model for the Paracuru Formation. [Display omitted] • Stratigraphic evolution, organic geochemistry, and Cretaceous Anoxic Events (CAE) were investigated. • Well-log correlations, redox conditions, and modeling to investigate anoxic events occurring in the Ceará Basin. • Relative sea-level fluctuations in 3rd- and 4th-order sequence-stratigraphic contexts are presented. • Relative hydrocarbon potential (RHP) as a geochemical index that reflects oxygenation conditions. • Anoxic markers were defined in the organic-rich, transgressive systems tracts (TST) and condensed section (CS) strata. [ABSTRACT FROM AUTHOR]

• A robust predictive model for bitumen assaying at multi-scale was developed. • The hydrocarbon signature at 2300 nm was found consistent and comparable among scales. • Key variables that control the spectral behavior of bituminous sands was recognized. • Multi-scale imaging spectroscopy has the capability to provide continuous grade data. In this work, oil-sand outcrops of the Anhembi deposit located in the Paraná Basin, Brazil, were investigated using multi-scale imaging spectroscopy. The study incorporated VNIR–SWIR (400–2500 nm) spectroscopic data from imaging (i.e. sisuCHEMA) and nonimaging (i.e. FieldSpec-4) instruments in the lab, an AisaFENIX hyperspectral system on the ground and from the air, and WorldView-3 multispectral instrument. The aim was to assess the usefulness of emerging remote sensing technologies in characterizing hydrocarbon-bearing targets and understand the spatial variability of oil-sands at different scales using multi-source spectroscopic data. The bitumen content of the sands, estimated to be as high as 12 wt. %, was revealed to be unevenly distributed at all scales. Its distribution was shown to be controlled mainly by the clay proportion and permo-porosity of the strata, with the sand sheet facies corresponding to the highest bitumen contents. The ubiquitous clays, identified to be dominantly montmorillonite, were found to be intimately mixed with bitumen at all studied scales. The mean bitumen content was estimated to decrease from ˜ 6 to 4.5% while moving from small-, to deposit-scale as a consequence of the pixel aggregation effect and incremental clay contribution. The study showed that bitumen determination on the ground requires an imaging system with a high signal-to-noise ratio and good illumination conditions. Spectral denoising is also a crucial prerequisite for the extraction of coherent spectral information from the data. WV-3 data was proved capable of resolving HC's feature at 1700 nm wavelength by its SWIR band-4 over targets encompassing >30% of the 7.5 m SWIR pixel; albeit it was not successful in determining the total bitumen content of the sands. This work indicated that HC signatures, particularly the one centered at 2300 nm, is consistent and comparable among scales, and upon employing properly calibrated data, could be used to confidently map the bitumen content of oil-sands at all imaging scales. A multi-scale spectroscopic approach can provide a complete picture of the variations in geologic targets and is able to fill the gap in scale differences across scales that when integrated, would add synergy and help reduce the uncertainties associated with ore grade estimation. [ABSTRACT FROM AUTHOR]