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Abstract Geological structures influence the formation and evolution of sedimentary rocks. The Minas do Camaquã fault zone is a primary structure of the Camaquã Basin, controlling the uplift of the ore-bearing units of the Santa Bárbara Group. To the south of the Camaquã River, the fault zone deforms alluvial and eolian sequences attributed either to the Santa Bárbara or Guaritas groups. In this study, a facies and petrographic composition and diagenetic analysis are presented to understand the evolution of the fault zone. Facies analysis was accomplished using high-resolution orthophoto mosaics and field surveys. Seven sedimentary facies were defined, grouped into three facies associations. Facies associations correspond to a succession of climate-influenced depositional environments. The transition from humid to dry conditions occurs from a fluvial (facies association 1) to eolian environments (facies association 2). These deposits are overlaid at the top by a high energy environment deposits characterized by amalgamated gravelly and sandy bodies, corresponding to an alluvial environment (facies association 3). Despite a small compositional variation, sandstones present a continental block provenance which may be related to mixed anorogenic or orogenic provenance. Diagenetic features are similar in the three facies associations, suggesting the same burial history for the sedimentary deposits separated by the fault zone. The Minas do Camaquã fault zone in the study area is an intraformational structure, as analyzed sequences are attributed to the Guaritas Group, implying a relatively high degree of deformation late after its deposition. Highlights • Fault zone separates steeply inclined from horizontal sequences. • Three facies associations were interpreted from field and remote sensing data. • Sandstones detrital composition indicates continental block and mixed provenance. • Fault zone does not limit diagenetic variations suggesting a single burial history. • Units separated by the fault zone correspond to the Guaritas Group. [ABSTRACT FROM AUTHOR]

A variational Gaussian process (VGP) model for implicit geological modeling is proposed, capable of modeling linear and non-linear trends. A new likelihood capable of honoring geological boundaries is introduced, and its performance is compared with the radial basis function (RBF) model. The model is tested on two case studies in mining, one of which relies only on photogrammetric data. The new approach generates more realistic surfaces on qualitative terms and provides an uncertainty measure. It is available as an open-source Python package. • A variational Gaussian process model for implicit geological modeling. • The model uses only discrete labels, not needing signed distances. • Anisotropy parameters can be learned semi-automatically. • Support for linear and non-linear trends. • A data-driven uncertainty measure is provided. [ABSTRACT FROM AUTHOR]

Paleoproterozoic to Mesoproterozoic cratonic basins in the São Francisco Craton are classified into three megasequences: Statherian, Calymmian–early Ectasian, and Stenian–early Tonian sequences. The location, depositional age, and provenance of these sequences are reflected in their detrital zircon U–Pb age distributions. A minimum of five detrital zircon age distributions are distinguishable: i) the Archean and Rhyacian distribution, which is restricted to the Calymmian interval at Chapada Diamantina; ii) the Rhyacian distribution, which occurs in the Statherian, Calymmian, and Stenian intervals and generally precedes the Proterozoic distribution; iii) the Proterozoic distribution, which always succeeds the Rhyacian distribution and appears in the Brasília Belt and Southern Espinhaço; iv) the mixed Archean and Proterozoic distribution, restricted to the Stenian interval at the Southern Brasília Belt; and v) the Statherian distribution, which is present in the Statherian interval at Espinhaço Basin and is recycled into the Calymmian and Stenian intervals at Chapada Diamantina. Based on the Hf isotope compositions of the detrital zircons, most of the sequences are predominantly sourced from Archean juvenile terrains and from Archean and Paleoproterozoic evolved terrains. The exception is the Paranoá Group, western São Francisco Craton, whose positive ɛHf(t) values suggest juvenile Paleoproterozoic sources such as the Goiás Massif. The Archean zircons from Chapada Diamantina have Hf depleted mantle model ages ranging from Paleoarchean to Neoarchean and are mainly derived from the Gavião Block within northeastern São Francisco Craton. The model unify a dataset spanning hundreds of millions of years of the depositional record over a large area of central and eastern Brazil. The records will assist researchers in unraveling the sedimentary and tectonic history of the Archean and Paleoproterozoic continents from new data collected regionally and in other continents. [ABSTRACT FROM AUTHOR]

The U–Pb data from the volcanic and detrital zircon grains of the Tombador Formation in Chapada Diamantina, Bahia, provide the depositional age of the top of this unit and define the main sedimentary sources of the Archean, Paleoproterozoic and Mesoproterozoic Eras. The lithofacies, petrographic and geochemical data from crystal-tuff samples indicated that a volcanic source was located to the east of the Chapada Diamantina region. The available zircon data defined three first-order intracratonic basinal cycles, including the Lower (Statherian), Middle (Calymmian) and Upper (Stenian–early Tonian) Espinhaço basins. These sequences are well exposed at the Espinhaço Supergroup type-section in the Chapada Diamantina region. The zircon Hf isotope data from the 1.4 Ga crystal-tuff in the Middle Espinhaço and the 1.2 Ga tuffaceous rock in the Upper Espinhaço suggested different sources, with model ages of 2.1 to 1.9 Ga and < 1.9 Ga, respectively. The tectonic development of these Paleoproterozoic to Mesoproterozoic intracratonic basins can be explained by the far-field stress at the paleoplate margins, which has been shown in other Phanerozoic intracratonic basins. The data presented here support a tectonic scenario in which the Congo–São Francisco paleoplate interior recorded the main global events related to the geodynamic processes after the Columbia supercontinent collage and the formation and fragmentation of the Rodinia supercontinent. [ABSTRACT FROM AUTHOR]

This work presents a Gaussian process model (a Bayesian derivation of kriging) for the interpolation of structural field data (dip and strike measurements). The structural data are treated as the directional derivatives of a latent potential field. The latent field's isosurfaces characterize the general structural trend in a region, and the predictive variance can be used as a measure of uncertainty. The model's parameters are optimized via maximum likelihood, avoiding the need for a variogram analysis. The model is tested using the orientation vectors of metamorphic foliation in meta-volcanic rocks of the Passo Feio Metamorphic Complex, in southern Brazil. An open-source implementation is available. • A potential field is modeled from orientation data alone with the Gaussian process. • Structural surfaces correspond to isovalues of the modeled field. • Covariance parameters are trained through maximum likelihood. • Open-source implementation available. [ABSTRACT FROM AUTHOR]

This paper presents the geomorphological features of four areas of subtropical, southernmost Brazil displaying striking landforms developed upon Precambrian Camaquã Basin conglomerates in the southern Brazilian shield areas. The distinctive and unique features of the Serra do Segredo cuesta, the Rincão do Inferno canyon, the Casa de Pedra inselberg, and the Pedra da Cruz cap-shaped hills are important examples of such conglomerate geomorphology in South America and in Brazil, where few occurrences were available so far. They are the first documented conglomerate landforms in southernmost Brazil, widening the distribution of such terrains in South America and in the subtropical, southern hemisphere areas, considering recent global reviews. Besides the high scientific relevance for geomorphology as a whole, such features are important also for (1) evidencing the decisive role of lithology, structure, and water flows in the formation of such landforms; as well as (2) ecology and tourism, being distributed within and in the vicinity of the Caçapava UNESCO Global Geopark of southernmost Brazil. • Novel description of conglomerate geomorphology developed upon Ediacaran alluvial/fluvial deposits of the Camaquã Basin in subtropical, southernmost Brazil. • Different landforms developed according to bed tilting and arrangement, as well as to tectonic structures "pre-design". • Decisive role of lithology and water in shaping ranges and hills. • Contribution to a global distribution of conglomerate landforms, especially in humid, subtropical areas. • Geological heritage potential, features within and in the surroundings of the Caçapava UNESCO Global Geopark. [ABSTRACT FROM AUTHOR]

Implicit modeling has experienced a rise in popularity over the last decade due to its advantages in terms of speed and reproducibility in comparison with manual digitization of geological structures. The potential-field method consists in interpolating a scalar function that indicates to which side of a geological boundary a given point belongs to, based on cokriging of point data and structural orientations. This work proposes a vector potential-field solution from a machine learning perspective, recasting the problem as multi-class classification, which alleviates some of the original method's assumptions. The potentials related to each geological class are interpreted in a compositional data framework. Variogram modeling is avoided through the use of maximum likelihood to train the model, and an uncertainty measure is introduced. The methodology was applied to the modeling of a sample dataset provided with the software Move™. The calculations were implemented in the R language and 3D visualizations were prepared with the rgl package. [ABSTRACT FROM AUTHOR]

The visualization, analysis and interpretation of sedimentary data can be optimized with techniques such as the Digital Outcrop Models (DOMs) generated with the Structure from Motion – Multi-View Stereo (SfM-MVS) technique. In this paper, to demonstrate the usage of DOMs in the characterization of the depositional architecture of a braided fluvial system, we developed a case study in Jaicós Formation, Parnaíba Basin, NE Brazil, where a high-resolution stratigraphic analysis of a braided fluvial system was performed, and the potentials and limitations of the method were evaluated. This multi-scale reservoir analysis allowed the identification, description and interpretation of facies, bounding surfaces and architectural elements. In addition, it was also possible to predict quantitative attributes of the fluvial system that deposited this sequence and evaluate the potential of this formation as a reservoir. • The usage of Virtual Outcrop Models in High Resolution Stratigraphy. • Analysis of facies, bounding surfaces and architectural elements. • Quantitative estimation of the fluvial system that deposited Jaicós Formation. [ABSTRACT FROM AUTHOR]

The structural framework and tectonic evolution of the sedimentary basins along the eastern margin of the South American continent are closely associated with the tectonic framework and crustal heterogeneities inherited from the Precambrian basement. However, the role of NW-SE and NNW-SSE structures observed at the outcropping basement in Southeastern Brazil and its impact over the development of those basins have not been closely investigated. In the continental region adjacent to the Campos Basin, we described a geological feature with NNW-SSE orientation, named in this paper as the Alegre Fracture Zone (AFZ), which is observed in the onshore basement and can be projected to the offshore basin. The main goal of this work was to study this structural lineament and its influence on the tectonic evolution of the central portion of the Campos Basin and adjacent mainland. The onshore area was investigated through remote sensing data joint with field observations, and the offshore area was studied through the interpretation of 2-D seismic data calibrated by geophysical well logs. We concluded that the AFZ occurs in both onshore and offshore as a brittle deformation zone formed by multiple sets of fractures that originated in the Cambrian and were reactivated mainly as normal faults during the rift phase and in the Cenozoic. In the Campos Basin, the AFZ delimitates the western side of the Corvina-Parati Low, composing a complex fault system with the NE-SW faults and the NW-SE transfer faults. [ABSTRACT FROM AUTHOR]

The pedogenic carbonates found in Pleistocene units of the coastal Brazilian Pampa, informally designated as 'Caliche Cordão', include rhizocretions, soft masses and isolated or coalescent nodules, either isolated within the sediment or forming discrete horizons, the most developed horizons (Ca-01 and Ca-02) stretching for hundreds of meters along the banks of Chuy Creek. Petrographic analyses show micritic (Alpha-type) matrix in most samples, with few signs of recrystallization as circumgranular spar rims or cracked sand grains. Stable carbon (δ13C) and oxygen (δ18O) isotope values in samples from the lower horizon Ca-01 exhibit small variation and indicate C3-dominated plant assemblages and carbonate precipitation from relatively 18O-enriched water, whereas the δ13C and δ18O in samples from the upper horizon (Ca-02) exhibit wider variation, higher proportion of C4 plants and precipitation from 18O-depleted water in some samples. The δ18O variations can be explained by variable degrees of evaporative enrichment, or to relative contributions of 18O-depleted (tropical) or 18O-enriched (subtropical) rainfall, based on the similarity with estimates from fossils of mastodons. Nodules from other sites are similar, but larger isotopic variations indicate carbonate precipitation at distinct times and environmental conditions, and a few exhibit partial recrystallization as larger spar calcite crystals. Luminescence ages of ∼74.7 and ∼71.3 ka of quartz grains in two nodules from Ca-01 indicate precipitation during MIS 4, whereas ages of ∼52 ka from Ca-02, and ≥30 ka in nodules from the shores of Mirim Lagoon indicate carbonate formation between MIS 3 and MIS 2. The probable source of carbonate was calcium released from eolian-sourced silty dust produced by Andean glaciers and transported from loess deposits in Argentina during cold and dry intervals of the last glacial, when arid/semiarid environments expanded from Patagonia across the Pampas up to southern Brazil. The variations of δ13C in calcretes formed between MIS 4 and 2 point to changes in plant assemblages that could have contributed for the local extinction of the mammalian megafauna. • Pleistocene calcretes indicate dry paleoenvironments in the coastal Brazilian Pampa. • The carbonates include nodules and rhizocretions developed in Pleistocene sediments. • OSL ages indicate calcrete formation during the last glacial stage (MIS 4 to MIS2). • The calcretes record changes in the relative proportions of C3 and C4 plants. • Calcretes formed from highly evaporated water or 18O-enriched subtropical rainfall. [ABSTRACT FROM AUTHOR]

Cu- and Pb–Zn-hosting sedimentary units of the upper part of the Camaquã Basin (Ediacaran-Lower Ordovician) in the Dom Feliciano Belt of southernmost Brazil were formed during the late stages of the West Gondwana amalgamation and were controlled by large left-handed strike-slip shear zones. Integration of structural geology, stratigraphy and thermochronology allow recognition of five structural events (D1, Ediacaran-Lower Cambrian, through D5, Cretaceous). D1 structures are related to a N30E-trending, sinistral strike-slip shear zone that controlled the deposition of the mineralized sedimentary unit and its overlying units, the Santa Barbara and Guaritas Groups, respectively, in a transtensional setting. Based on U–Pb in situ methods, it is possible (a) to establish a maximum depositional age of 566 ± 6.9 Ma for the basal section of the Santa Barbara Group and, therefore, a minimum age of ca. 566 Ma for D1, and (b) to recognize two main zircon populations, Neoproterozoic and Paleoproterozoic, with sources from the eastern and southern parts of the Dom Feliciano Belt and reworking of older units of the Camaquã Basin. The D2 structures are mainly N-trending shear zones that developed after the deposition of the Guaritas Group during the Cambrian. During the Phanerozoic (post-Cambrian), the recognized structures were connected to compressional and extensional events that affected West Gondwana and the South America Platform. Thermochronological fission track analyses on apatite revealed four main age populations. The first three are interpreted to have formed during tectonic processes at the Gondwana Margin, namely the Famatinian and Gondwanides orogenies, and can be related to the D3 and D4 tectonic events in the basin. The last age population formed from thermal heating by the Upper Cretaceous continental flood basalts, which are represented in the area by volcanic intrusions, that were related to the separation of Africa and South America. [ABSTRACT FROM AUTHOR]