Contribuição ao estudo da Bacia do Amazonas e seu embasamento através da magnetometria e gravimetria

Orientador: Prof. Dr. Francisco Jose Fonseca FerreiraTese (doutorado) - Universidade Federal do Paraná, Setor de Setor de Ciências da Terra, Programa de Pós-Graduação em Geologia. Defesa: Curitiba, 26/08/2011Inclui bibliografiaÁrea de concentração: Geologia exploratóriaResumo: Na presente tese foi realizado um estudo multiescala de dados magnéticos, gravimétricos e de sensores remotos da Bacia do Amazonas e das subáreas Tapajós, Xingu e Monte Alegre. Este estudo resultou em proposições de arcabouços geofísico-estruturais, os quais refletem estruturas do embasamento exposto que traspassam a bacia. Foi gerado, inicialmente, um mapa magnético residual a partir da integração de dados de oito levantamentos aerogeofísicos sobre o embasamento exposto e de onze levantamentos sobre a bacia, além de um mapa gravimétrico Bouguer, com base em um único banco de dados. Com o objetivo de facilitar a visualização e a interpretação qualitativa das estruturas geológicas, refletidas nos mapas de campos potenciais, foram aplicados diversos métodos de realce propostos na literatura, além de uma nova técnica desenvolvida durante a pesquisa. O desempenho dos métodos foi avaliado, para diferentes inclinações magnéticas, através de modelos sintéticos 3D obtidos a partir de um programa para geração de anomalias gravimétricas e magnéticas de corpos prismáticos com dimensões, densidades e magnetizações arbitrárias, também elaborado no transcorrer da pesquisa. A integração das informações obtidas através dos diferentes métodos de realce, testados nos modelos sintéticos, possibilitou avançar no conhecimento das estruturas interpretadas a partir dos dados de campos potenciais. Esta interpretação permitiu a delimitação de um arcabouço geofísico integrado para as áreas de estudo, o qual foi corroborado pelas principais feições de superfície, descritas na literatura. Foram realizadas também interpretações semi-quantitativas através do espectro de potência radial e da deconvolução de Euler. A análise dos resultados obtidos a partir dos métodos descritos acima permitiu verificar que o quadro tectônico do embasamento é caracterizado por tendências NW, enquanto o da Bacia do Amazonas revela direções NE. Os lineamentos NE são vinculados as direções do depocentro e das linhas de charneira da bacia, sendo marcadamente segmentados por lineamentos NW. Na subárea Tapajós, verificou-se que as tendências NW, presentes no embasamento e por vezes adentrando a bacia, são mais antigas do que as feições NE e EW. Na subárea Xingu, também se notou a presença de estruturas NW do embasamento que adentram a bacia. Na subárea Monte Alegre, o posicionamento do domo homônimo é controlado pela interseção de tendências NW, NE e NS, interpretadas como zonas de fraqueza do embasamento. Todas as áreas de estudo revelam estimativas de profundidade das estruturas compatíveis com dados da literatura. Interpretações sobre a reativação destas estruturas durante o Fanerozóico permitiram avaliar suas implicações na compartimentação e na evolução tectônica da Bacia do Amazonas.Abstract: This thesis presents a multiscale study of magnetic, gravity and remote sensors data, for the Amazon Basin and three sub-areas whitin it: Tapajós, Xingu and Monte Alegre. The study has allowed proposing geophysical-structural frameworks, which reflect the exposed basement structures that cross the basin. First, a residual magnetic map was generated using eight aerogeophysical databases, over the basement and eleven databases over the basin, as well as, a Bouguer gravity map, generated from a single database. In order to facilitate the visualization and qualitative interpretation of geological structures from the potential field data, several enhancement methods proposed in the literature have been used, as well as, a new enhancing technique developed as part of this work. The performance of each method has been evaluated at different magnetic inclinations using 3D synthetic models generated by a program for calculation of magnetic and gravity anomalies from prismatic bodies having arbitrary dimensions, densities and magnetizations, which was designed in the course of this research. The integrated information obtained by the different enhancement methods, tested on synthetic models, led to an improvement in the knowledge of the geological structures interpreted from the potential-field data. Such a methodology contributed to the elaboration of an integrated geophysical framework for the study areas, which corroborates the main surface features previously reported in the literature. A semi-quantitative interpretation has also been performed using spectral techniques and Euler deconvolution. The results obtained from the methods described above indicate that the tectonic basement framework is characterized by NW tendencies, while on the basin NE directions are dominant. The NE lineaments are approximately parallel to the basin depocenter and the hinge lines, being strongly segmented by NW lineaments. In the Tapajós subarea, it is observed that NW trends, existent in the basement and occasionally entering into the basin, are older than the NE and EW lineaments. In the Xingu subarea it is remarkable the presence of NW basement structures that enter the basin. In the Monte Alegre subarea, the position of the Monte Alegre dome is controlled by intersecting trends in NW, NE and NS directions, which are interpreted as weakness zones in the basement. In all the studied areas, depth estimates for the structures are compatible with the data found in the literature. Finally, reactivation of geological structures during the Phanerozoic and its implication for the tectonic evolution and compartmentalization of the Amazon Basin have been evaluated

Swidden fallow management to increase landscape-level Brazil nut productivity.

Brazil nut (Bertholletia excelsa Bonpl.) is considered the cornerstone non-timber species of Amazonian conservation. Nuts (or seeds) of this massive tree are harvested by local people living in and near old growth forests, supporting local livelihoods and regional economies. Secondary forests, however, particularly plots previously used for agriculture (swidden fallows), present better B. excelsa seedling and sapling recruitment than mature forest. This study examines the extent to which forest residents could increase nut productivity by allowing their fallows to grow into Brazil nut rich forests. We conducted B. excelsa inventories in the Brazilian state of Acre in abandoned swidden fallows of different ages. We also conducted interviews to determine landowner perspectives on the fallow potential for increasing nut production. An individual-based model, based on in-situ inventories and primary and secondary datasets from prior fieldwork, simulated growth, survivorship and production from the 250 inventoried trees in 18 fallows of varying sizes (from 0.41 to 4.18 ha) and different regrowth stages (12 to 60 years old). These simulation model predictions showed that after 10 years, 2.4% of existing trees would be productive, with an average of 68.6 ± 21.5 fruits per reproductively mature tree in the four fallows that most quickly yielded productive trees. By the final projected time interval (40 years), predictions suggest all fallows will produce fruits with cumulative production averaging 1475 ± 359 fruits ha?1, suggesting an increase in landowner income of US$55.1 ± 13.4 per hectare of fallow. Our simulation model is the first to explore fruit productivity of Brazil nut in secondary forest. It likely underpredicts B. excelsa growth and nut production, considering that swidden fallows provide better resource availability than the forest-derived datasets we used to construct the model equations. In conclusion, our findings support previous research that suggests that higher B. excelsa recruitment rates observed in abandoned swidden fallows could indeed translate into greater adult densities and thus potentially, higher nut production – a conclusion mirrored by most participant landowners

ANÁLISE DE DADOS DE DEFORMAÇÃO A PARTIR DE SENSORES DISTRIBUÍDOS DE FIBRA ÓPTICA INSTALADOS EM UMA ENCOSTA

O presente trabalho expõe uma metodologia de análise de dados de monitoramento de deformações de uma encosta natural atravessada por um duto pertencente a PETROBRAS, a partir de sensores distribuídos de fibra óptica. A encosta em questão localiza-se na Serra do Mar, município de Morretes (PR), distante a 40 km da cidade de Curitiba (PR) sob as posições geográficas UTM (716.332E - 7.172.000N) e (720.000E - 7.173.000N). Devido a uma ruptura na encosta, o duto sofreu esforços de tração rompendo em fevereiro de 2001. Tal ocorrência resultou no vazamento de aproximadamente 145 m³ de óleo diesel no meio ambiente. Em agosto de 2014 os institutos Lactec procederam com a instalação de sensores distribuídos de fibra óptica na encosta para o monitoramento de movimentos de massa. Essas atividades foram desenvolvidas no contexto de um P&D em parceria com a PETROBRAS/CENPES. Os dados obtidos através dos sensores distribuídos de fibra óptica correspondem a dados de deformação e temperatura, os quais permitem verificar possíveis deslocamentos que podem resultar em movimentos de massa. Os dados foram coletados no período entre janeiro de 2015 a maio de 2016 com um interrogador DTSS e tratados pelos softwares MatLab, Excel e Surfer. Em janeiro de 2015 foram realizados ajustes nos sensores ópticos, a fim de melhorar a qualidade do sinal, resultando em uma campanha de leituras de referência para as análises posteriores, denominada 7ª campanha. Os dados coletados nas campanhas de monitoramento a partir da 7ª campanha até a 12ª campanha, realizada em maio de 2016, indicaram que a encosta apresentou deformações na ordem de 784 µɛ a -515 µɛ. Sendo que os valores de deformação registrados foram relativamente baixos e a metodologia de análise dos dados de deformação obtidos encontrava-se ainda em fase experimental, não foi possível afirmar que as deformações registradas correspondessem a possíveis deslocamentos na encosta. Portanto, na continuidade destes trabalhos, a metodologia aqui apresentada pode gerar mais informações ao longo do seu desenvolvimento, possibilitando uma correlação mais precisa entre deformação e deslocamento

Izu-Bonin-Mariana Rear Arc - The missing half of the subduction factory, 30 March – 30 May 2014

International Ocean Discovery Program (IODP) Hole U1436A (proposed Site IBM-4GT) lies in the western part of the Izu fore-arc basin, ~60 km east of the arc-front volcano Aogashima, ~170 km west of the axis of the Izu-Bonin Trench, 1.5 km west of Ocean Drilling Program (ODP) Site 792, and at 1776 meters below sea level (mbsl). It was drilled as a 150 m deep geotechnical test hole for potential future deep drilling (5500 meters below seafloor [mbsf]) at proposed Site IBM-4 using the D/V Chikyu. Core from Site U1436 yielded a rich record of Late Pleistocene explosive volcanism, including distinctive black glassy mafic ash layers that may record large-volume eruptions on the Izu arc front. Because of the importance of this discovery, Site U1436 was drilled in three additional holes (U1436B, U1436C, and U1436D), as part of a contingency operation, in an attempt to get better recovery on the black glassy mafic ash layers and enclosing sediments and to better constrain the thickness of the mafic ash layers. IODP Site U1437 is located in the Izu rear arc, ~330 km west of the axis of the Izu-Bonin Trench and ~90 km west of the arc-front volcanoes Myojinsho and Myojin Knoll, at 2117 mbsl. The primary scientific objective for Site U1437 was to characterize “the missing half of the subduction factory”; this was because numerous ODP/Integrated Ocean Drilling Program sites had been drilled in the arc to fore-arc region (i.e., ODP Site 782A Leg 126), but this was the first site to be drilled in the rear part of the Izu arc. A complete view of the arc system is needed to understand the formation of oceanic arc crust and its evolution into continental crust. Site U1437 on the rear arc had excellent core recovery in Holes U1437B and U1437D, and we succeeded in hanging the longest casing ever in the history of R/V JOIDES Resolution scientific drilling (1085.6 m) in Hole U1437E and cored to 1806.5 mbsf. The stratigraphy at Site U1437 was divided into seven lithostratigraphic units (I–VII) that were distinguished from each other based on the proportions and characteristics of tuffaceous mud/mudstone and interbedded tuff, lapilli tuff, and tuff breccia. The section is much more mud rich than expected, with ~60% tuffaceous mud for the section as a whole (89% in the uppermost 433 m) and high sedimentation rates of 100–260 m/My for the upper 1320 m (Units I–V). The proportion (40%) and grain size of tephra are much smaller than expected for an intra-arc basin, composed half of ash/tuff and half of lapilli tuff of fine grain size (clasts < 3 cm). These were deposited by suspension settling through water and from density currents, in relatively distal settings. Volcanic blocks are only sparsely scattered through the lowermost 25% of the section (Units VI and VII, 1320–1806.5 mbsf), which includes hyaloclastite, in situ quench-fragmented blocks, and a rhyolite peperite intrusion (i.e., proximal deposits). The transition from unconsolidated to lithified rocks occurred progressively; however, sediments were considered lithified from 427 mbsf (top of Hole U1437D) downward. Alteration resulted in destruction of fresh glass from ~750 mbsf downward, but minerals are less altered. Because of the alteration, the deepest biostratigraphic datum was at ~850 mbsf and the deepest paleomagnetic datum was at ~1300 mbsf. Additional age control deeper than this depth is provided by an age range of 10.97–11.85 Ma inferred from a nannofossil assemblage at ~1403 mbsf and a preliminary U-Pb zircon concordia intercept age of 13.6 +1.6/–1.7 Ma, measured postcruise on a rhyolite peperite in Unit VI at ~1390 mbsf. Based on the seismic profiles, the Miocene–Oligocene hiatus (~17–23 Ma) was predicted to lie at ~1250 mbsf, but strata at that depth (Unit V, 1120–1312 mbsf) are much younger (~9 Ma), indicating that we recovered a thicker Neogene section of volcaniclastics and associated igneous rocks than anticipated. Our preliminary interpretation of shipboard geochemistry is that arc-front versus rear-arc sources can be distinguished in the upper, relatively distal 1320 m of section (Units I–V), whereas the lower, proximal 25% of the section (Units VI–VII) may be geochemically heterogeneous, suggesting that the rear-arc magmas only fully compositionally diverged after ~13 Ma

Expedition 350 summary

International Ocean Discovery Program (IODP) Hole U1436A (proposed Site IBM-4GT) lies in the western part of the Izu fore-arc basin, ~60 km east of the arc-front volcano Aogashima, ~170 km west of the axis of the Izu-Bonin Trench, and 1.5 km west of Ocean Drilling Program (ODP) Site 792, at 1776 meters below sea level (mbsl). It was drilled as a 150 m deep geotechnical test hole for potential future deep drilling (5500 meters below seafloor [mbsf]) at proposed Site IBM-4 using the D/V Chikyu. Core from Site U1436 yielded a rich record of Late Pleistocene explosive volcanism, including a distinctive black glassy mafic ash layer that may record a large-volume subaqueous eruption on the Izu arc front. Because of the importance of this discovery, Site U1436 was drilled in three additional holes (U1436B, U1436C, and U1436D), as part of a contingency operation, in an attempt to get better recovery on the black glassy mafic ash layer and its enclosing sediments and to better constrain its thickness. IODP Site U1437 is located in the Izu rear arc, ~330 km west of the axis of the Izu-Bonin Trench and ~90 km west of the arc-front volcanoes Myojinsho and Myojin Knoll, at 2117 mbsl. The primary scientific objective for Site U1437 was to characterize “the missing half of the subduction factory” because numerous ODP/Integrated Ocean Drilling Program sites had been drilled in the arc-front to fore-arc region (i.e., ODP Site 782A Leg 126), but this was the first site to be drilled in the rear-arc region of the Izu arc. A complete view of the arc system is needed to understand the formation of oceanic arc crust and its evolution into continental crust. Site U1437 on the rear arc had excellent core recovery in Holes U1437B and U1437D, and we succeeded in hanging the longest casing ever in the history of R/V JOIDES Resolution scientific drilling (1085.6 m) in Hole U1437E and cored to 1806.5 mbsf. The stratigraphy at Site U1437 was divided into seven lithostratigraphic units (I–VII) that were distinguished from each other based on the proportions and characteristics of tuffaceous mud/mudstone and interbedded tuff, lapilli-tuff, and tuff-breccia. The section is much more mud rich than expected, with ~60% tuffaceous mud for the section as a whole (89% in the uppermost 433 m) and high sedimentation rates of 100–260 m/My for the upper 1320 m (Units I–V). The proportion (40%) and grain size of volcaniclastics are much smaller than expected for an intra-arc basin, composed half of ash/tuff and half of lapilli-tuff of fine grain size (clasts <3 cm). These volcaniclastics were deposited by suspension settling through water and from density currents, in relatively distal settings. Volcanic blocks are only sparsely scattered through the lowermost 25% of the section (Units VI and VII, 1320–1806.5 mbsf), which includes hyaloclastite, in situ quench-fragmented blocks, and a rhyolite peperite intrusion (i.e., proximal deposits). The transition from unconsolidated to lithified rocks occurred progressively; however, sediments were considered lithified from 427 mbsf (top of Hole U1437D) downward. Alteration resulted in destruction of fresh glass from ~750 mbsf downward, but minerals are less altered. Because of the alteration, the deepest biostratigraphic datum was at ~850 mbsf and the deepest paleomagnetic datum was at ~1300 mbsf. Additional age control deeper than ~1300 mbsf is provided by an age range of 10.97–11.85 Ma inferred from a nannofossil assemblage at ~1403 mbsf and a preliminary U-Pb zircon concordia intercept age of 13.6 +1.6/−1.7 Ma, measured postcruise on a rhyolite peperite in Unit VI at ~1390 mbsf. Based on the seismic profiles, the Miocene–Oligocene hiatus (~17–23 Ma) was predicted to lie at ~1250 mbsf, but strata at that depth (Unit V, 1120–1312 mbsf) are much younger (~9 Ma), indicating that we recovered a thicker Neogene section of volcaniclastics and associated igneous rocks than anticipated. Our preliminary interpretation of shipboard geochemistry of solids is that arc-front versus rear-arc sources can be distinguished for individual intervals in the upper, relatively distal 1320 m of the section (Units I–V), whereas data for the lower, proximal 25% of the section (Units VI–VII) overlap and exceed the compositional fields for Neogene rear-arc seamounts and Quaternary arc-front volcanoes. This suggests that the compositional divergence between arc-front and rear-arc magmas only fully developed after ~13 Ma

Expedition 350 methods

Introduction This chapter of the International Ocean Discovery Program (IODP) Expedition 350 Proceedings volume documents the procedures and tools employed in the various shipboard laboratories of the R/V JOIDES Resolution during Expedition 350. This information applies only to shipboard work described in the Expedition Reports section of this volume. Methods for shore-based analyses of Expedition 350 samples and data will be described in the individual scientific contributions to be published in the open literature or in the Expedition Research Results section of this volume. This section describes procedures and equipment used for drilling, coring, and hole completion; core handling; computation of depth for samples and measurements; and sequence of shipboard analyses. Subsequent sections describe specific laboratory procedures and instruments in more details

Expedition 350 Methods

This chapter of the International Ocean Discovery Program (IODP) Expedition 350 Proceedings volume documents the procedures and tools employed in the various shipboard laboratories of the R/V JOIDES Resolution during Expedition 350. This information applies only to shipboard work described in the Expedition Reports section of this volume. Methods for shore-based analyses of Expedition 350 samples and data will be described in the individual scientific contributions to be published in the open literature or in the Expedition Research Results section of this volume. This section describes procedures and equipment used for drilling, coring, and hole completion; core handling; computation of depth for samples and measurements; and sequence of shipboard analyses. Subsequent sections describe specific laboratory procedures and instruments in more details