Alessandro Batezelli

Arquitetura e mecanismos deposicionais em sistemas aluviais holocênicos de clima árido no oeste argentino e comparação com depósitos neocretáceos brasileiros

The Pre-Cordillera in the northwest of Argentine is characterized by geomorphological features formed during Miocene Andes Cordillera uplifting. The arid weather and compressive tectonic regime propitiated the origin of countless sedimentary basins filled by alluvial fans and playa-lakes deposits. Because of the outcrops abundance and their qualities these basins are important sites for direct observation of depositional alluvial architectures and facies analyses. The description of some deposits in the Rio Jachal valley (neighborhood of San Jose de Jachal), and Pie de Palo desert alluvial plain in San Juan, allowed the recognition of main depositional mechanisms in these environments. The analyses were based in the longitudinal cross sections that show intertonguing of the alluvial fans, playa-lakes and eolian deposits. It was characterized the internal and external geometries of the bodies by hierarchical surfaces and macroforms analyses to make the interpretation of the sedimentary process and the depositional dynamics. The facies variation from proximal to distal deposits recorded the evolution of confined or unconfined non-cohesive debris flow to turbulent and laminar flows, resulting by the transport stream energy decrease of ephemeral torrential currents associated with storm periods. Due to the annual low pluviosity (70 mm/y), the sedimentation rate is very low, mainly suggested by the vegetation and soil developed. Although this study has been made in a restrict area with a very recent sedimentary history initiated only in the Late Pleistocene to Holocene, the facies distribution and the depositional mechanisms conditioned by geomorphologic positions in the alluvial fan systems and the sedimentologic characteristics conditioned by the arid climate allow to compare these deposits with the Brazilian neocretaceous, in the Bauru Basin, that shows similar sedimentologic and architecture characteristics.

ANÁLISE DE FÁCIES DA FORMAÇÃO CORUMBATAÍ (GRUPO PASSA DOIS - BACIA DO PARANÁ, NEOPERMIANO), COM VISTA AO EMPREGO NA INDÚSTRIA DE REVESTIMENTO CERÂMICO

The mud rocks from Corumbatai Formation, Neopermian unity of Parana Basin, are at the moment, the principal font of raw material for floor tiles industries in Brazil. In this paper we are applied the lithofacies concept, mineralogical and chemical composition data and ceramic characteristics for define exploration places. It was identify five lithofacies (Massive, Laminated, Intercalated I, Intercalated II and Alterated) all they grouped in two associations (sandy siltstone and argillaceous silstone). The data was plotted in map 1:50,000 scale. This method permits get a best control on raw material, consequently better quality and chipper. It was important the statistical method application (Tendency Surface Analysis) for define the probable areas for future exploration.

Inventário e avaliação do patrimônio natural geológico da região de Rio Claro (SP)

This paper discusses the methodological approach used in the inventory and evaluation of geosites in the Rio Claro region, one of the first studies on this topic in the state of Sao Paulo. This region is characterized by a rich geodiversity, including relevant geosites with speleological, stratigraphical, geomorphological, palaeoenvironmental, paleontological and sedimentological content. The absence of a proposal for a systematic inventory of geological heritage at state or national level, considering the geological history of the area studied, made it difficult to inventory and evaluate the geosites. The methodology used in this study, already applied in European countries, was adapted for the study area and identified eleven geosites with great scientific value and broad potential use. Four out of the eleven geosites are in accordance with the UNESCO proposal for conservation of the world natural heritage and can be included in national and international inventories. Therefore, the first steps toward the development of a strategy for the conservation of the geological heritage of the study area are presented in this paper. These steps are very important since this area is currently under threat and public policies are needed for its better management.

A Late Cretaceous mammal from Brazil and the first radioisotopic age for the Bauru Group

In the last three decades, records of tribosphenidan mammals from India, continental Africa, Madagascar and South America have challenged the notion of a strictly Laurasian distribution of the group during the Cretaceous. Here, we describe a lower premolar from the Late Cretaceous Adamantina Formation, São Paulo State, Brazil. It differs from all known fossil mammals, except for a putative eutherian from the same geologic unity and Deccanolestes hislopi, from the Maastrichtian of India. The incompleteness of the material precludes narrowing down its taxonomic attribution further than Tribosphenida, but it is larger than most coeval mammals and shows a thin layer of parallel crystallite enamel. The new taxon helps filling two major gaps in the fossil record: the paucity of Mesozoic mammals in more northern parts of South America and of tribosphenidans in the Cretaceous of that continent. In addition, high-precision U-Pb geochronology provided a post-Turonian maximal age (≤87.8 Ma) for the type stratum, which is overlain by the dinosaur-bearing Marília Formation, constraining the age of the Adamantina Formation at the site to late Coniacian–late Maastrichtian. This represents the first radioisotopic age for the Bauru Group, a key stratigraphic unit for the study of Cretaceous tetrapods in Gondwana.

The mineralogy of paleosols in the Marília Formation and their importance in the environmental evolution of the Maastrichtian of the Bauru Basin in southeastern Brazil

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 Marilia Formation, Maastrichtian of Bauru Basin. Three sections have been described (A1, A2, A3) in the Marilia Formation. The mineralogy was determined by x-ray diffraction, and mineral quantification was obtained through the Rietveld refinement method. The calcretes of the Marilia 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.

3-D Geological modelling: a siliciclastic reservoir case study from Campos Basin, Brazil

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.