In the Middle to Late Ordovician a boost of marine biodiversity occurred which is regarded as the most rapid diversity in Earth’s history, and termed the Great Ordovician Biodiversification Event. This time is also unique in that at least four marine meteorite craters with a good record of post-impact sediments are preserved in Baltoscandia. Catastrophic impacts can serve as constructive events and produce wide-ranging environments providing new ecological niches for a diverse biota to occupy. Additionally, they generate distinctive patterns of biological destruction and recovery. This, and the study of distribution and ecospace utilisation of Late Ordovician faunas, has been analysed in two almost contemporary (around 455 million years ago) meteorite craters (Lockne and Tvären, Sweden). Within the confined space of the impact craters environments varied from shallow and reef-like to over 200 m in depth and from well oxygenated to hypoxic. These types of environments favored colonization of different individual groups. In Tvären rhynchonelliformean brachiopod assemblages from the shallow crater rim include a range of morphotypes, not established elsewhere in the crater. Within the crater depression rhynchonelliformean brachiopods were not established until the upper third of the remaining crater fill. Colonization of post-impact faunas varies dependent on topography, depth and susbstrate within the impact craters. This is recognised for scolecodonts in Tvären and for gastropod-like mollusks, linguliform and craniiform brachiopods in both of the craters, as they inhabit a wide range of ecospace. A succession of different taxa is observed from the deepest part of each crater and upwards towards inferably more shallow, higher energy, water settings. The development of new community types and narrowly-defined niches in the craters helped further drive both α and β biodiversity during a critical phase of the Great Ordovician Biodiversification Event.

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Wellbore seismic measurements were recorded in the Lake Bosumtwi impact structure, Ghana, in 2004. A full range of petrophysical measurements were also performed in the laboratory on core samples from the same boreholes. The Vertical Seismic Profile shows low velocities for both P and S waves in the hardrock basement of the crater. Although we were expected to locate fractures within the rock, no upgoing waves were detected. Density and porosity measurements on the core samples indicate higher than normal porosity in the impact damaged rocks. Mercury porosimetry and SEM analysis characterized the pores as impact induced microcracks. These microcracks are most likely the reason for the low velocities observed on the seismic profiles, the in situ sonic logs, and the seismic velocity measurements on the core samples. Furthermore our laboratory P and S velocities measurements indicate a strong heterogeneity within the impactites. / Geophysics

abstract: Both volcanism and impact cratering produce ejecta and associated deposits incorporating a molten rock component. While the heat sources are different (exogenous vs. endogenous), the end results are landforms with similar morphologies including ponds and flows of impact melt and lava around the central crater. Ejecta from both impact and volcanic craters can also include a high percentage of melted rock. Using Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC) images, crucial details of these landforms are finally revealed, suggesting a much more dynamic Moon than is generally appreciated. Impact melt ponds and flows at craters as small as several hundred meters in diameter provide empirical evidence of abundant melting during the impact cratering process (much more than was previously thought), and this melt is mobile on the lunar surface for a significant time before solidifying. Enhanced melt deposit occurrences in the lunar highlands (compared to the mare) suggest that porosity, target composition, and pre-existing topography influence melt production and distribution. Comparatively deep impact craters formed in young melt deposits connote a relatively rapid evolution of materials on the lunar surface. On the other end of the spectrum, volcanic eruptions have produced the vast, plains-style mare basalts. However, little was previously known about the details of small-area eruptions and proximal volcanic deposits due to a lack of resolution. High-resolution images reveal key insights into small volcanic cones (0.5-3 km in diameter) that resemble terrestrial cinder cones. The cones comprise inter-layered materials, spatter deposits, and lava flow breaches. The widespread occurrence of the cones in most nearside mare suggests that basaltic eruptions occur from multiple sources in each basin and/or that rootless eruptions are relatively common. Morphologies of small-area volcanic deposits indicate diversity in eruption behavior of lunar basaltic eruptions driven by magmatic volatiles. Finally, models of polar volatile behavior during impact-heating suggest that chemical alteration of minerals in the presence of liquid water is one possible outcome that was previously not thought possible on the Moon. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2016

Orientadores: Carlos Roberto de Souza Filho, Cristiano de Carvalho Lana / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-23T13:22:26Z (GMT). No. of bitstreams: 1 Silva_Dailto_D.pdf: 6673922 bytes, checksum: ad586d69e4694b3e81cab5a383dfef3f (MD5) Previous issue date: 2013 / Resumo: A pesquisa foi realizada na cratera de impacto de meteorito de Araguainha (Goiás / Mato Grosso, Brasil) e compreendeu três desenvolvimentos científicos principais. O primeiro engloba a petrografia e geoquímica de rochas graníticas parcialmente fundidas do núcleo da cratera de impacto. Foi possível separar, por petrografia e posicionamento geográfico, os litotipos do granito preservado (GP) dos litotipos de fusão (granito parcialmente fundido (GPF), veios de fusão (VF) e capa de fusão (CF)). Contudo, estes litotipos apresentam características geoquímicas muito semelhantes para elementos maiores, menores, traços e terras raras. O diagrama que se mostrou o melhor discriminante entre os litotipos de fusão e os granitos preservados foi o Th/U x TiO2, que indica enriquecimento relativo na razão Th/U nos granitos. O granito preservado é também rico em quartzo e apresenta empobrecimento em elementos como Ti, Zr, Ce, Y, Eu, Nb e elementos terras raras. Essas características permitem postular uma possível influência hidrotermal na geração dos litotipos de fusão. O segundo desenvolvimento aborda a mobilidade dos elementos traço e geração de fusões félsicas na crosta terrestre durante o impacto de meteoritos e implicações para a evolução da crosta Hadeana. Nesse caso, o processo de acresção crustal por impacto pode ser um mecanismo complementar, capaz de explicar uma importante modificação da crosta terrestre Hadeana ocorrida entre 3.9-4.5 Ga. O terceiro desenvolvimento trata dos efeitos do impacto na indução de fusão incongruente da crosta da Terra, tendo como base a fusão da biotita. O estudo mostrou que a biotita pré-impacto é distinta daquela pós-impacto, com texturas, estrutura e quimismo contrastantes. Demonstrou-se que até 9% do granito de Araguainha é produto de cristalização a partir da quebra da biotita. A biotita funde incongruentemente durante o processo de impacto, produzindo uma fusão aluminosa, que preenche bolsões e rede de fraturas nas rochas. Impactos do tamanho de Araguainha ou maiores são capazes de gerar volumes substanciais de fundidos aluminosos na crosta / Abstract: The focus of this PhD thesis is on granitic targets impacted by meteorites and felsic melting generation in the crust during impacts. Key features of the Araguainha impact crater (Goiás / Mato Grosso, Brazil) were employed as a control. Field, petrographic and analytical data collected in the study area were grouped into three, central scientific developments. The first comprises the petrography and geochemistry of partially melted granitic rocks observed in the core of the Araguainha crater. The work shows that it is possible to separate, by petrography and geographical positioning, preserved granite rocks from melt rock types, such as the partially melted granite (GPF), the melted veins (VF), and the melted caps (CF). These rock types have very similar geochemical characteristics regarding major, minor, trace and rare earth elements. However, melt rock types are readily discriminated from preserved granites in Th/U x TiO2 scatergrams; granites show relative enrichment in the ratio Th/U. Another noteworthy feature is that the preserved granite rich in quartz is depleted in Ti, Zr, Ce, Y, I, Nb and REE, indicating a possible influence of hydrothermal systems in the formation of melt products. The second development provides clues on the mobility of trace elements and generation of felsic melts in the crust during the meteorite impact, and implications for the evolution of the Hadean crust. It is argued that process of crustal accretion by impacts may have been one of the mechanisms that can explain important modification of the Earth's crust during the Hadean (3.9-4.5 Ga). The third development deals with the effects of shock-induced incongruent melting within Earth's crust, using the case of biotite melting. It was demonstrated that pre-impact and pos-impact biotites found in Araguainha show distinct textures, structures and chemistry. Results show that up to 9% of Araguainha granite is a product of magma crystallization from breakdown of biotite. The biotite melts incongruently during the impact process, producing an aluminous fusion, which fulfills pockets and fracture networks of the rocks. Impacts of the size of Araguainha or larger seem to be capable of generating substantial amounts of aluminous melt in the crust / Doutorado / Geologia e Recursos Naturais / Doutor em Ciências

No description available.

No description available.

<p>Digital elevation models (DEM) can be used for a multitude of applications. Under ideal circumstances, calibration of a remotely acquired estimate of topographic elevation is calibrated through use of ground control points (GCP) which would be ubiquitous, seamlessly joining remotely sensed data and high accuracy check points. In reality there are many areas on the earth’s surface which are difficult, expensive, or dangerous to access. Under these circumstances, the acquisition of GCPs may not be realistic and relative DEMs must be used. Innovative methods must then be used to determine the relative error associated with a DEM in a given study area. The method presented in this paper compares three DEMs (ASTER, CDED, SRTM) derived from independent acquisition systems to determine their relative errors.</p> <p>The ASTER DEM data was chosen for a lineament analysis study in north central Ontario, Canada. This study used a quantitative digital approach to determine the density of lineaments mimicking the geometry of the northern Sudbury Igneous Complex contact (SIC). The study revealed a lineament density at ~25km north of the northern SIC contact, suggesting a ring structure from an ancient multi-ring impact basin. This argument is supported by findings of the pattern of plagioclase clouding intensities in Matachewan dykes in the vicinity of the ring structure. The orientation of the dykes may have some connection to the faulting and block rotation caused by crater wall collapse.</p> <p>Paleomagnetic data from the norite in the SIC and Foy Offset dyke combined with an unconstrained magnetic inversion of the Foy Offset dyke suggest that the Sudbury Structure has not been folded, but instead has been deformed by brittle deformation.</p> / Master of Science (MSc)

A pesquisa tem como objetivo compreender a evolução da drenagem e do relevo na cratera de Colônia e entorno, no setor meridional do Planalto Paulistano, em São Paulo-SP. Parte-se da hipótese de que o relevo da área resulta da degradação de uma zona de estruturas concêntricas, formada em conjunto com a cratera, por impacto de bólido extraterrestre. Essas estruturas seriam atribuídas a um ou mais mecanismos, entre eles: a) controle exercido por um sistema de falhas radiais e concêntricos, b) estratificação do alvo, c) pico anelar em cratera complexa, d) ejecta fluidificada e e) fluidificação de finos, que resultaram na geração de uma zona de formas concêntricas no entorno da cratera. Após sua formação, o relevo da cratera e seu entorno foram degradados pela drenagem, que promoveu trabalho erosivo mais intenso a leste que a oeste, produzindo níveis hipsométricos menores a leste. Com base na proposta metodológica de Oliveira (2003), elabora-se uma descrição do relevo e da drenagem para identificar elementos sugestivos de condicionamento geológico produzido pela estrutura de impacto, por meio de fotointerpretação, trabalhos de campo e morfometria. A partir dos dados de hipsometria, rupturas de declividade e lineamentos da drenagem, descartam-se os mecanismos de estratificação do alvo, pico anelar e ejecta fluidificada, restando apenas o sistema de falhas radiais e concêntricos e a fluidificação de finos como possibilidades em aberto, cujo teste definitivo dependerá da disponibilidade de dados geofísicos detalhados. Os dados de morfometria, por sua vez, sugerem maior trabalho erosivo efetuado pelos rios da bacia do Jurubatuba que do Embu-Guaçu, respondendo pela assimetria altimétrica leste-oeste da zona de formas concêntricas e do anel colinoso da cratera de impacto e pela abertura da drenagem a leste, em conjunto com o condicionamento dado pelas linhas estruturais geradas tectonicamente. A presença de anomalias de drenagem e sua correlação com as integrais hipsométricas, por sua vez, são indicativas de modificação tectônica da drenagem, posterior à sua delineação condicionada pela estrutura de impacto. / This research aims to comprehend the relief and drainage evolution in the Colônia crater and surrounding areas, in the southern sector of the Paulistano Plateau, São Paulo-SP. We advance a hypothesis such as the morphology of the area results from degradation of a zone of concentric structures, originated at the same time as the crater, by extraterrestrial bolide impact. These structures are due to one or more mechanisms, among them: a) system of concentric and radial fractures, b) target stratification, c) peak ring in a complex impact structure, d) fluidized ejecta and e) fluidization of fine sediments, which generated a zone of concentric forms around the crater. After its formation, the relief of the crater and surroundings was degraded by drainage, which promoted a more intense erosive work to East than West, producing lower hypsometric levels to East. Based on the methodological proposal of Oliveira (2003), we elaborated a description of the topography and drainage to indentify suggestive elements for geological conditioning produced by the impact structure, by means of photointerpretation, fieldwork and morphometric measurements. From hypsometric data and slope break and drainage lineations analysis, we discard the hypothesis of: target stratification, peak ring and fluidized ejecta, leaving only those of concentric and radial fractures and fluidization of fine sediments, as open possibilities, whose final test will depend on the availability of detailed geophysical data. The morphometric data suggest greater erosive work performed by the Jurubatuba drainage basin than by Embu-Guaçu, responding by hypsometric East-West asymmetry of the craters raised ring and surroundings. This still accounts for the position of its drainage exutory, to East, together with structural lines tectonically generated. The presence of drainage anomalies and their correlation with the hypsometric integrals are indicative of tectonic modification of drainage, after its delineation conducted by the impact structure.

Submitted by Eunice Novais (enovais@uepg.br) on 2017-09-01T17:05:55Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Marco Aurelio R Hundsdorfer.pdf: 5023740 bytes, checksum: 41becfa0989c009ce106bfe85691cddd (MD5) / Made available in DSpace on 2017-09-01T17:05:55Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Marco Aurelio R Hundsdorfer.pdf: 5023740 bytes, checksum: 41becfa0989c009ce106bfe85691cddd (MD5) Previous issue date: 2017-07-11 / Em Coronel Vivida (PR), no distrito de Vista Alegre, foi identificada um cratera de impacto de meteorito em 2004, que posteriormente foi tombada como patrimônio geológico-geomorfológico paranaense. A cratera se situa a 12 quilômetros da sede do município e apresenta 9,5 quilômetros de diâmetro. É considerada rara por ser uma das sete crateras de impacto conhecidas no Brasil, e uma das quatro existentes sobre derrames de lava basáltica no mundo. Sua descoberta fomentou estudos científicos sobre o geossítio que, porém, estiveram restritos ao meio acadêmico e não chegaram à população paranaense e à comunidade local com o alcance desejado. O impacto aconteceu há aproximadamente 115 milhões de anos e deixou registros geológico-geomorfológicos na paisagem, que sofreram modificações ao longo destes últimos milênios. A análise realizada neste trabalho, a partir de estudos teóricos e levantamento de campo, envolve discussões sobre a origem de asteroides e meteoritos, sua importância na história do planeta e investiga o contexto de evolução da cratera de impacto de Vista Alegre. O desconhecimento das características do geossítio e seu valor tende a colocar em risco a preservação do patrimônio científico-cultural. Ações de divulgação e subsídios para fomentar o turismo foram implantadas no local a partir de 2007, como a instalação de painéis explicativos e a distribuição de folhetos. Em 2016 foi construído um mirante para a contemplação da paisagem da cratera, buscando fortalecer o geoturismo e divulgar o geossítio. Entretanto, não há um sentimento de pertencimento por parte da população local e o geossítio é pouco valorizado como patrimônio estadual, muito em função da ausência de disseminação de uma cultura de conhecimento científico. Este trabalho busca, por meio da educação não formal, a difusão pública do conteúdo geocientífico referente ao geossítio, procurando sua valorização como patrimônio por parte da comunidade. Com este escopo foi elaborado um vídeo-documentário que apresenta: a origem de asteroides e sua interação com a Terra através de impactos; o contexto geológico antes do impacto que ocasionou a cratera; o evento que a formou, sua idade e sua evolução, incluindo também fatores antrópicos. São correlacionados aspectos astronômicos, geológicos e climáticos para um melhor entendimento da raridade desta feição geológica e a necessidade de sua preservação. O vídeo foi disponibilizado na internet e aplicado, em caráter experimental, a um público de universitários e professores da rede pública estadual com questionários que buscaram avaliar sua eficácia na compreensão do tema. As informações resultantes apontaram que o vídeo não é suficiente para amplo aprendizado sobre o tema, mas induz o interesse e promove conscientização patrimonial. Estatísticas da divulgação na internet mostraram cerca de três mil visitas em três meses de exposição, o que sugere avanços no conhecimento mínimo sobre o geossítio em médio e longo prazo. / In Coronel Vivida (PR), in the district of Vista Alegre, a crater of meteorite impact was identified in 2004, which later was classified as geological-geomorphological heritage of Paraná. The crater is located 12 kilometers far from the county seat and is 9.5 kilometers in diameter. It is considered rare because it is one of the seven impact craters known in Brazil, and one of the four existing on basalt lava flows in the world. His discovery fostered scientific studies on the geosite which, however, were restricted to the academic milieu and did not reach the population of Paraná and the local community as desired. The impact occurred about 115 million years ago and left geological-geomorphological records in the landscape, which have undergone modifications over the past few millennia. The analysis carried out in this work, from theoretical studies and field survey, involves discussions about the origin of asteroids and meteorites, their importance in the history of the planet and investigates the evolution context of the Vista Alegre impact crater. Ignorance of the characteristics of the geosite and its value tends to jeopardize the preservation of the scientific-cultural heritage. Publicity actions and subsidies to promote tourism were implemented in the place from 2007, such as the installation of explanatory panels and the distribution of leaflets. In 2016 a gazebo was built to contemplate the landscape of the crater, seeking to strengthen geotourism and disseminate the geosite. However, there is no sense of belonging on the part of the local population and the geosite is little valued as state patrimony, much due to the lack of dissemination of a culture of scientific knowledge. This work seeks, through non-formal education, the public diffusion of the geoscientific content referring to the geosite, seeking its valuation as patrimony by the community. With this scope was elaborated a video documentary that presents: the origin of asteroids and their interaction with the Earth through impacts; The geological context before the impact caused by the crater; The event that formed it, its age and its evolution, including also human factors. Astronomical, geological and climatic aspects are correlated for a better understanding of the rarity of this geological feature and the need for its preservation. The video was made available on the internet and applied, on an experimental basis, to a public of university students and teachers of the state public network with questionnaires that sought to evaluate its effectiveness in understanding the theme. The resulting information pointed out that the video is not enough for extensive learning on the subject, but it induces interest and promotes equity awareness. Internet dissemination statistics showed about three thousand visits in three months of exposure, which suggests advances in the minimum knowledge about the geosite in medium and long term.