Dissertations / Theses on the topic 'Mesozoico'

Geóloga
En las nacientes del río Huasco en la Región de Atacama aflora una sucesión volcanosedimentaria de edad permotriásica, pertenecientes a la Formación Guanaco Sonso. Ésta se habría depositado en una configuración tectónica de colapso extensional tras un período de engrosamiento cortical relacionado con el desarrollo acrecionario del Paleozoico Superior. El registro de este evento corresponde a una serie de cuencas siliciclásticas cuyo desarrollo fue acompañado de un amplio magmatismo de características propias de una corteza en etapa de adelgazamiento. En este contexto, el estudio del registro geológico de este periodo, particularmente, en las cuencas y sus depósitos, aportará al entendimiento de la paleogeografía y configuración tectónica del margen continental. Este trabajo pretende estudiar una cuenca triásica en particular, la cual albergó los depósitos volcánicos y sedimentarios de la Formación Guanaco Sonso. Para ello, se realizó un análisis de facies piroclásticas y sedimentarias que permite relacionar los procesos sedimentarios, volcanosedimentarios y tectónicos, caracterizando la evolución de la cuenca en el área de estudio. En la zona de estudio, esta formación presenta un espesor mínimo de ca. 400 m, y está compuesta, principalmente, por una serie de capas piroclásticas riolíticas a dacíticas de espesores métricos a decamétricos, intercalados en sedimentitas de origen fluvial, aluvial y lacustre. La depositación de estas unidades estuvo controlada por numerosas fallas normales de poco desplazamiento y corta vida que condicionaron la geometría y distribución de las facies, tanto piroclásticas como sedimentarias. Si bien, se logra establecer que la subsidencia estuvo controlada por numerosas fallas normales, la ausencia de fallas mayores no permiten establecer con seguridad la naturaleza de la cuenca. La configuración tectonoestratigráfica podría ser interpretada como un desarrollo de la etapa inicial de un sistema de rift, o su origen podría estar ligado al colapso de un sistema volcánico, generando cuencas de caldera en un ambiente de intra-arco. Ambas hipótesis están aún por ser probadas, aunque no se descarta que ambos procesos geológicos puedan haber estado presentes a esta longitud durante el permotriásico.
Este trabajo ha sido financiado por el Plan Nacional de Geología de SERNAGEOMIN

L’estudi del registre sedimentari i paleontològic del fini-Carbonífer, Permià i Triàsic continentals dels Pirineus Catalans han permès caracteritzar-ne l’evolució paleoambiental i paleoclimàtica i la seva repercussió sobre els ecosistemes terrestres durnt la transició Paleozoic–Mesozoic. Aquesta transició, marcada per diversos canvis climàtics i extincions en massa, s’ha analitzat mitjançant un estudi multidisciplinari. Les diverses campanyes de camp han resultat en el descobriment de fins a deu noves localitats amb restes fòssils, principalment amb icnites de tetràpodes (de les quals se’n fa especial èmfasi), però també amb restes òssies, traces fòssils d’invertebrats i plantes. Fins al present treball es coneixien molt pocs jaciments de petjades d’aquestes edats als Pirineus Catalans. L’elaboració de columnes estratigràfiques i cartografies de detall ha permès establir la successió espacio-temporal dels jaciments i de les unitats geològiques corresponents (unitats deposicionals definides en treballs anteriors). L’estudi conjunt d’icnites i fàcies contribueixen a realitzar anàlisis paleoambientals. L’estudi del registre fòssil ha implicat l’establiment de diferents biozonacions, que s’ha complementat amb anàlisis paleomagnètiques, cicloestratigràfiques, mineralògiques i elementals. El Carbonífer superior s’ha documentat a partir de l’associació de plantes de la Unitat Grisa, que indiquen una edat d’Estefanià C. Les dades sedimentològiques i de paleosòls indiquen un clima humit amb curts períodes de sequera. El trànsit Carbonífer–Permià (Unitat de Trànsit) ve marcat per un increment en l’estacionalitat i l’aridesa. La manca de marcadors cronològics als afloraments estudiats no permet precisar l’edat de la unitat. El Permià inferior constitueix l’inici de les successions de red-beds. Els paleosòls dels dipòsits volcanosedimentaris de la Unitat Roja Inferior i l’absència de carbó denoten una aridificació del clima i una estacionalitat marcada. Els esporàdics intervals més humits, representats per sistemes fluvials meandriformes i dipòsits derivats d’aigua d’escolament superficial, contenen una icnoassociació de tetràpodes característica de l’Artinskià i constituïda per: Batrachichnus salamandroides, Limnopus isp., cf. Amphisauropus, cf. Ichniotherium, Dromopus isp., cf. Varanopus, Hyloidichnus isp., Dimetropus leisnerianus i tres tipus de Characichnos (traces fòssils de natació). Les traces fòssils d’artròpodes (especialment Rusophycus i Acripes) també són comunes. El registre del Permià mitjà denota unes condicions climàtiques humides i estacionals. El sistema al·luvial distal de la Unitat Roja Superior inferior ha lliurat poques restes fòssils. La presència d’una vèrtebra assignada al grup dels casèids suggereix una edat de Wordià inferior i, juntament amb les icnites de tetràpode documentades en treballs previs, constata un reemplaçament de faunes. El Permià superior es caracteritza per un clima semi-àrid, tal com indiquen les dades sedimentològiques, mineralògiques i elementals de la Unitat Roja Superior superior. El sistema de playa-lake o lacustre efímer mostra un control orbital de la sedimentació. La icnoassociació de tetràpodes documentada marca un reemplaçament de les faunes del Permià mitjà, possiblement lligat a una extinció. El Triàsic Inferior i Mitjà està representat pel sistema fluvial (de rius braided a meandriformes i planes d’inundació) de la unitat en fàcies Buntsandstein, que conté una icnoassociació de tetràpodes formada per: Prorotodactylus mesaxonichnus (erigida com a nova icnoespècie), cf. Rotodactylus, Rhynchosauroides cf. schochardti, Rhynchosauroides i chirotheriids indeterminats, un morfotip indeterminat (Morfotip A) i dos tipus de Characichnos associats a la nova icnoespècie i als chirotheriids. Aquest registre fòssil es complementa amb la presència de dues dents d’arcosauromorf i marca la recuperació dels ecosistemes terrestres després de l’extinció de finals del Permià, amb els arcosauromorfs com a grup cabdal. El registre continu als trànsits Carbonífer–Permià i Permià–Triàsic (fins ara desconegut al sudoest europeu), així com també la inesperada riquesa fòssil, fa dels Pirineus Catalans una regió de referència a nivell global per comprendre alguns dels canvis més dràstics de la història de la Terra.
The sedimentary and paleontological record study of the terrestrial end-Carboniferous, Permian and Triassic from the Catalan Pyrenees allowed to characterize its paleoenvironmental and paleoclimatic evolution and their influence on the terrestrial ecosystems during the Paleozoic–Mesozoic transition. This transition, featured by several climatic changes and mass extinctions, has been analyzed in a multidisciplinary study. Diverse fieldworks have resulted in the discovery of up to ten new fossil localities, mainly bearing tetrapod ichnites (here especially emphasized), but also bearing bone remains, invertebrate trace fossils and plants. Until the present work, few fossil footprint sites were known from these ages in the Catalan Pyrenees. The detailed stratigraphic columns and cartography allowed to establish the spatio-temporal succession of fossil sites and of the corresponding geological units (depositional units defined in previous works). The coupled study of ichnites and facies contribute to carry out paleoenvironmental analyses. The study of the fossil record implied the establishment of different biozonations, which have been complemented with paleomagnetic, cyclostratigraphic, mineralogical and elemental analyses. The late Carboniferous has been documented by the Grey Unit plant assemblage, indicating a Stephanian C age. The sedimentological and paleosol data point to a humid climate with short dry periods. The Carboniferous–Permian transition (Transition Unit) is featured by increases in seasonality and aridity. The lack of chronological markers in the studied outcrop precludes to clarify the age of the unit. The early Permian constitutes the beginning of the red-bed successions. Paleosols developed in the Lower Red Unit volcanosedimentary deposits and the absence of coal denote climate aridification and strong seasonality. Sporadic relatively humid intervals, depicted by meandering fluvial systems and deposits derived from unconfined runoff water, yield a tetrapod ichnoassemblage characteristic of the Artinskian and composed of: Batrachichnus salamandroides, Limnopus isp., cf. Amphisauropus, cf. Ichniotherium, Dromopus isp., cf. Varanopus, Hyloidichnus isp., Dimetropus leisnerianus and three types of Characichnos (swimming trace fossils). Arthropod trace fossils (especially Rusophycus and Acripes) are also common. The middle Permian record denotes humid climatic conditions and seasonality. Few fossil remains have been reported from the lower Upper Red Unit distal alluvial system. The presence of a vertebra assigned to the caseid group suggests an early Wordian age and, together with tetrapod ichnites documented in previous works, a faunal replacement is confirmed. The late Permian is characterized by a semi-arid climate, as indicated by the sedimentological, mineralogical and elemental data of the upper Upper Red Unit. Deposits of the playa-lake or ephemeral lacustrine system show orbital forcing during sedimentation. The documented tetrapod ichnoassemblage marks a replacement of the middle Permian faunas, possibly linked to an extinction. The Early and Middle Triassic is recorded by the fluvial system (from braided to meandering rivers and floodplains) of the Buntsandstein facies unit, which yields a tetrapod ichnoassemblage composed of: Prorotodactylus mesaxonichnus (erected as a new ichnospecies), cf. Rotodactylus, Rhynchosauroides cf. schochardti, undetermined Rhynchosauroides and chirotheriids, an undetermined Morphotype A and two types of Characichnos associated to the new ichnospecies and to chirotheriids. This fossil record is complemented with the presence of two recovered archosauromorph teeth and is indicative of the terrestrial ecosystems recovery after the end-Permian mass extinction, being archosauromorphs a relevant group. The continuous record throughout the Carboniferous–Permian and Permian–Triassic transitions (so far unknown from southwestern Europe), as well as the unsuspected fossil richness, make the Catalan Pyrenees a reference region worldwide to untangle some of the most drastic changes of Earth history.

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Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq)
A Bacia do Parna?ba ocupa uma imensa ?rea na por??o NE do territ?rio brasileiro, abrangendo v?rios estados do Brasil. Ela ? uma sin?clise paleozoica, que contem registros desde a forma??o e desagrega??o do supercontinente Gondwana. A bacia ? sustentada por um embasamento cristalino desenvolvido ap?s a colis?o entre as plataformas Amaz?nica e Brasileira. Em um contexto tect?nico de ruptura do megacontinente Pangeia no Mesozoico, que levou ? abertura do Oceano Atl?ntico, rochas ?gneas intrusivas (diques e soleiras) e extrusivas, de composi??o b?sica, acomodaram-se na Bacia do Parna?ba, que, do ponto de vista estratigr?fico, foram divididas em duas unidades: Forma??o Mosquito Eojur?ssica e Forma??o Sardinha Eocret?cea. A presente pesquisa tem por objetivo principal a cartografia geof?sica regional desses corpos magm?ticos com base em dados aeromagn?ticos e uma t?cnica de mapeamento semiautom?tico (SOM). O Matched Filter foi aplicado com o objetivo de decompor o Campo Magn?tico An?malo (CMA) da bacia em componentes relacionadas a fontes magn?ticas em diferentes profundidades. Com isso, foram obtidos os campos magn?ticos profundo (CMP), intermedi?rio (CMI) e raso (CMR). Como o CMI apresenta principalmente uma contribui??o causada por fontes magn?ticas em profundidades mais rasas na crosta superior, caracter?stica dos corpos magm?ticos da bacia, aplicamos as t?cnicas de filtragem espectral Amplitude do Sinal Anal?tico e Derivada Vertical nas anomalias magn?ticas do CMI, com o objetivo de real?ar ainda mais a resposta geof?sica dessas fontes magn?ticas, aumentando a resolu??o espacial do m?todo investigativo. Com base nas anomalias de alta amplitude e curto comprimento de onda, delimitamos dom?nios e lineamentos magn?ticos nos mapas aeromagn?ticos, correlacionando-os com os poss?veis corpos causadores. Assim, integrando os mapas geof?sicos com essas assinaturas magn?ticas ao SOM e ao mapa geol?gico, ? apresentado um mapa interpretativo com a distribui??o superficial das anomalias magn?ticas associadas ao Magmatismo Mesozoico da bacia. Os resultados indicaram que o Magmatismo Mosquito tem grande ocorr?ncia nas bordas oeste e sul da bacia, e o Magmatismo Sardinha est? concentrado nas por??es centro-leste e nordeste. Os dados de susceptibilidade magn?tica medidos nas rochas vulc?nicas da bacia individualizaram o Magmatismo Mesozoico, constatando que a Forma??o Sardinha exibe susceptibilidade magn?tica m?dia de 25,2 x 10-3 SI, aproximadamente duas vezes maior que a susceptibilidade magn?tica m?dia da Forma??o Mosquito de 11,46 x 10-3 SI, revelando uma diferencia??o composicional destes dois eventos magm?ticos. Associa??es entre as se??es s?smicas, os dados magn?ticos e o mapa geol?gico demonstraram que as anomalias do CMA e da ASA est?o relacionadas ?s soleiras e diques intrusivos, geralmente nos grupos Serra Grande, Canind? e Balsas, e s?o sensivelmente influenciadas por rochas ?gneas aflorantes ou subaflorantes. Por fim, as dire??es dos lineamentos magn?ticos revelaram que riftes de dire??es ENE-WSW e NNE-SSW, associados ? desagrega??o do Gondwana Oeste, e trends estruturais E-W e NE-SW, associados ? Zona de Cisalhamento Transbrasiliano, exerceram controle estrutural sobre o Magmatismo Mesozoico da bacia do Parna?ba.
The Parna?ba Basin occupies a large area in the NE portion of Brazil, covering several states. It is a Paleozoic syneclise that contains records from the formation and break-up of the Gondwana supercontinent. The basin is supported by a crystalline basement developed after the collision between the Amazonian and Brazilian platforms. During the Mesozoic break-up of the Pangea megacontinent, which contributed to the opening of the Atlantic Ocean, intrusive igneous (dykes and sills) and extrusive rocks took place in the Parna?ba Basin. In the stratigraphic context, those igneous rocks were divided into two units: Early Jurassic Mosquito and Early Cretaceous Sardinha formations. The main objective of this research is a regional geophysical mapping of these magmatic bodies based on aeromagnetic data and self-organizing map technique (SOM). Matched Filter was applied in order to decompose the Total Magnetic Intensity anomalies (TMI) of the basin in their components related to magnetic sources at different depths: Deep (DMF), Intermediate (IMF), and Shallow Magnetic Fields (SMF). As the IMF anomalies mainly present contributions from magnetic sources at shallower depths in the upper crust, characteristics of such magmatic bodies, spectral filtering techniques (Analytic Signal Amplitude and Vertical Derivative) were applied to IMF data in order to enhance the geophysical response of these magnetic sources, increasing the spatial resolution of the investigative method. Based on high amplitude and short wavelength anomalies, magnetic domains and lineaments were delimited in aeromagnetic maps and correlated with the possible causative bodies. Thus, the correlation of the geophysical maps with SOM solutions and the geological map allowed to propose an interpretive map with the surface distribution of magnetic anomalies associated with Mesozoic Magmatism in the Parna?ba basin. The results indicated that the Mosquito Magmatism has great occurrence at the western and southern basin edges and the Sardinha Magmatism is located at the centraleastern and northeastern parts. Magnetic susceptibility data, measured in the magmatic rocks, permitted individualizing the Mesozoic Magmatism.The Sardinha Formation displays average magnetic susceptibility of 25.2 x 10-3 SI, about two times higher than the values of 11.46 x 10 -3 SI obtained to Formation Mosquito, revealing a compositional differentiation of these two magmatic events. Associations between seismic sections, magnetic data and geological map showed that the high amplitude anomalies in the Analytic Signal and TMI maps are associated with sills and dykes intruded usually within Balsas, Canind? and Serra Grande groups, and are significantly influenced by outcropping or at near-surface buried igneous rocks. Finally, the directions of the magnetic lineaments revealed that ENE-WSW and NNE-SSW oriented rifts, associated with the break-up of West Gondwana, and E-W and NE-SW structural trends, associated with Transbrasiliano Shear Zone, exercised structural control over the Mesozoic Magmatism of the Parna?ba basin.

Mawsoniidae é uma família de actinístios fósseis, conhecidos popularmente como celacanto, sendo encontrados em paleoambientes continental e marinho. O táxon foi proposto na década de 1990, apresentando, a partir de então, alguns estudos abordando sua filogenia num contexto cladístico. Trata-se de um grupo monofilético, sendo representado por cinco gêneros inquestionáveis (i. e., Axelrodichthys, Chinlea, Diplurus, Mawsonia e Parnaibaia), além de outros dez que possuem alguma discordância na sistemática (i. e., Alcoveria, Garnbergia, Heptanema, Indocoelacanthus, Libys, Lualabaea, Megalocoelacanthus, Moenkopia, Rhipis e Trachymetopon). Cabe ressaltar que nem todos estes gêneros foram contemplados nas análises cladísticas de Mawsoniidae. Mawsoniidae possui considerável interesse biogeográfico, considerando sua extensa amplitude temporal (Triássico Médio ao Cretáceo Superior) e ampla distribuição geográfica (Américas do Sul e do Norte, África e Europa). Os gêneros restritos à América do Norte (Diplurus e Chinlea) e Europa (Alcoveria) possuem os registros mais antigos (Triássico Médio-Jurássico Inferior). Já os gêneros restritos ao Hemisfério Sul (Mawsonia, Axelrodichthys e Parnaibaia) distribuem-se do Jurássico Superior ao Cretáceo Superior, no Brasil e na África. A presente dissertação propôs analisar a Biogeografia Histórica de todos os gêneros (os válidos e os de posicionamento taxonômico controverso) de Mawsoniidae, aplicando o método panbiogeográfico de análise de traços. A partir desta análise, foram obtidos 11 traços individuais das espécies e três traços generalizados (TGs). O TG1, que foi denominado Newark Nordeste, ocorre nos estratos do Grupo Newark (Triássico Superior); o TG2, que foi denominado Centro-oeste gondwânico, ocorre na Formação Lualaba (Jurássico Superior); e o TG3, que foi denominado Itapecuru-Alcântara-Santana, ocorre nas formações Itapecuru-Alcântara-Santana (Cretáceo Inferior). Com base no padrão de distribuição encontrado, sugere-se que a origem do grupo ocorreu a partir do Triássico Médio/Superior na Pangeia Oriental, com subsequente expansão no Jurássico Inferior, corroborada por registros de Indocoelacanthus e Trachymetopon. A expansão do grupo em direção à Gondwana Ocidental ocorreu a partir do Cretáceo Inferior, com registros dos gêneros Mawsonia e Axelrodichthys. A análise panbiogeográfica também foi aplicada para produzir traços individuais para os gêneros em determinados períodos geológicos, os quais mostraram congruência com os traços individuais das espécies. Os resultados aqui obtidos reforçaram o potential do método panbiogeográfico na obtenção dos padrões de distribuição e, consequentemente, nas áreas de endemismo de Mawsoniidae, ao longo de todo o Mesozoico.
Mawsoniidae is a fossil family of actinistians popularly known as coelacanth, being found in continental and marine paleoenvironments. The taxon was proposed in the 1990 and, since then, some studies on its phylogeny in a cladistic context were accomplished. It is considered monophyletic in the most recent reviews and includes five unquestionable genera (i. e., Axelrodichthys, Chinlea, Diplurus, Mawsonia, and Parnaibaia), besides ten others with some taxonomical controversy (i. e., Alcoveria, Garnbergia, Heptanema, Indocoelacanthus, Libys, Lualabaea, Megalocoelacanthus, Moenkopia, Rhipis, and Trachymetopon). Notwithstanding, not all of these genera were included in the cladistic analysis of Mawsoniidae. Mawsoniidae possesses a remarkable biogeographical significance due to its extensive temporal range, from the Middle Triassic to the Late Cretaceous, and a wide geographical distribution in the South and North Americas, Africa, and Europe. The genera restrict to the North America (Diplurus and Chinlea) and Europe (Alcoveria) possess the oldest records (Middle Triassic-Early Jurassic), whereas those found in the South Hemisphere (Mawsonia, Axelrodichthys, and Parnaibaia) extend from Late Jurassic to Late Cretaceous, in Brazil and Africa. This study proposed to analyze the Historical Biogeography of Mawsoniidae, including the valid genera as well as those of controverse systematic position, applying the panbiogeographical method of track analysis. Based on this analysis, 11 individual tracks of the species and three generalized tracks (GTs) were obtained. The GT1, named Northeastern Newark, occurs in strata of the Newark Group (Upper Triassic); GT2, named Midwest Gondwana, occurs in the Lualaba Formation (Upper Jurassic); and GT2, named Itapecuru-Alcântara-Santana, occurs in the Itapecuru-Alcântara-Santana formations (Lower Cretaceous). Regarding the distribution pattern herein found, the origin of the probably occurred from the Middle/Upper Triassic in the Eastern Pangeia, with subsequent expansion in the Lower Jurassic, corroborated by records of Indocoelacanthus and Trachymetopon. The expansion of the group towards the Western Gondwana occurred in the Lower Cretaceous, with records of Mawsonia and Axelrodichthys. The panbiogeographical analysis was also applied to produce individual tracks of the genera by certain geological periods, which showed congruence with the individual tracks of the species. The results herein obtained accentuated the potential of the panbiogeographical method for obtaining the distribution patterns and, consequently, the areas of endemism of Mawsoniidae, throughout all Mesozoic.

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CNPQ
É apresentado um estudo sistemático dos fósseis de invertebrados, micro-vertebrados, microfósseis (ostracodes) e icnofósseis coletados na porção superior da Formação Candeias, Cretáceo Inferior da Bacia de Jatobá, Grupo Santo Amaro (Andar Rio da Serra), na região do município de Ibimirim, Estado de Pernambuco. Nessa localidade foram identificados um conjunto de arenitos finos a grossos, com níveis de arenitos calcíferos, que estão mapeados como pertencentes ao Grupo Santo Amaro, e que por sua características litológicas, são relacionados à Formação Candeias. Foram processados quimicamente por ácido acético 5 kg de arenitos calcíferos (que totalizaram 30 Kg brutos), onde foram coletados numerosos restos de invertebrados e vertebrados. Os ostracodes coletados foram classificados como Cypridea cf. vulgaris e ?Reconcavona. Vertebrados estão representados por dentes isolados e escamas de peixes ósseos, identificados como “Stephanodus” sp. 1, Actinopterygii gen. et sp. indet. 1, 2, 3, e 4, Osteichthyes indet. 1 e 2, peixes cartilaginosos como o Hybodontidae Egertonodus aff. basanus e Diapsida indet. Os icnofósseis estão representados por coprólitos de peixes e traços de Taenidium barreti. Exceto pelos registros de Cypridea cf. vulgaris, ?Reconcavona e Egertonodus aff. basanus, que mostram afinidades com táxons do Cretáceo Inferior, os vertebrados registrados não mostram relações próximas em nível específico com os inúmeros taxa descritos para o Jurássico Superior da Bacia de Jatobá (Formação Aliança), peixes Semionotidae do Cretáceo Inferior da Bacia do Recôncavo ou com aqueles descritos para o Albiano-Aptiano das Bacias interiores do Nordeste do Brasil. Em termos de bioestratigrafia, o registro de Cypridea cf. vulgaris constitui um ótimo dado de correlação com o Cretáceo Inferior, pois sua amplitude (Coimbra et al., 2002, sensu stricto) é atribuída ao intervalo que vai da Sub-Zona Paracypridea maacki (NRT-004.4) a Sub-Zona Paracypridea elegans elegans (NRT-005.2), mas como um grupo de espécies intimamente relacionadas, sua amplitude é maior, distribuindo-se entre as zonas de Paracypridea brasiliensis (NRT-004) e Paracypridea obovata obovata (NRT-005) (Estágios locais Rio da Serra e Aratu).
It is presented a systematic study of fossil invertebrates, microvertebrates, microfossils (ostracods) and ichnofossils recovered from the lower Cretaceous upper Candeias Formation, Jatobá basin, Santo Amaro group, in the municipality of Ibimirim, Campos locality. In this locality were identified fine and coarse sandstones, and calcarenite levels, that were attributed to the Santo Amaro group, and because its lithogical features are related to the Candeias formation. Fossils were recovered by processing of approximately 5 Kg (30 Kg gross weight) of lithified calciferous sand with acetic acid, where numeral microvertebrates and microinvertebrates were recovered. The ostracods recovered were assigned to genus Cypridea and ?Reconcavona. Vertebrates are represented by isolated teeth and fish scales from the bony fishes, identified as “Stephanodus” sp., Actinopterygii gen. et sp. indet. 1, 2, 3, and 4, Osteichthyes indet. 1 and 2, cartilaginous fishes as Hybodontidae, Egertonodus aff. basanus and Diapsida indet. Except by the record of Cypridea cf.vulgaris and ?Reconcavona, which show closer affinities with lower Cretaceous species described for the Reconcavo basin, the vertebrates recorded do not show affinities with the numeral taxa described for the late Jurassic of the Jatobá basin (Aliança Formation), Semionotidae fishes from the lower Cretaceous of the Recôncavo basin or with that described for the Albian-Aptian of the interior basins of northeastern Brazil. Concerning the biostratigraphy, the record of Cypridea cf. vulgaris constitutes an important element of correlation with the early Cretaceous, take in account that its amplitude (Coimbra et al., 2002, sensu stricto) is assigned to interval encompassing the Sub-Zone Paracypridea maacki (NRT-004.4) to the Sub-Zone Paracypridea elegans elegans (NRT-005.2), but if a species group is concerned, its amplitude is larger, ranging between the Paracypridea brasiliensis (NRT-004) and Paracypridea obovata obovata (NRT-005) zones (Rio da Serra and Aratu local stages).

Magíster en Ciencias, Mención Geología
La Sierra Limón Verde (SLV), ubicada al sur de Calama (22,5º- 22,8°S) es el elemento topográfico más elevado de la Cordillera de Domeyko. Se caracteriza por la ocurrencia de afloramientos de rocas metamórficas, sedimentarias, volcánicas e intrusivas paleozoicas, que forman una serie de slivers o lentes de cizalle limitados por fallas con una probable componente de rumbo y cuya actividad se mantuvo en parte hasta el Cenozoico superior. Aunque la geología de la SLV ha sido motivo de numerosos estudios, el significado tectónico y regional de las unidades que allí afloran es aún incierto. En esta Tesis se presenta un estudio detallado de las unidades pre-mesozoicas de la SLV, basado en un mapeo regional a escala 1:50.000 acompañado de nuevas dataciones U-Pb en circones (por el método LA ICP - MS) de las unidades intrusivas y análisis de las poblaciones de circones detríticos de las unidades metamórficas. La mayor parte de la SLV está constituida por un complejo intrusivo del Paleozoico superior que incluye desde gabros hasta granitos y pórfidos riolíticos, cuyas edades U-Pb en circones permiten separarlos en dos grupos principales: Carbonífero Inferior, (ca. 322 - 325 Ma) y Carbonífero Pérmico (ca. 287 - 300 Ma), estas últimas similares a las obtenidas en los niveles volcánicos de la Formación Agua Dulce, emplazadas en forma sincrónica. Las rocas ígneas de la SLV, que representan eventos reconocidos en otros sectores del cinturón magmático del Paleozoico superior del Norte de Chile, intruyen o cubren en discordancia a secuencias metasedimentarias más antiguas. Éstas fueron consideradas, anteriormente, parte del Complejo Metamórfico Limón Verde formado por rocas de alto grado metamórfico. Esta unidad constituida por esquistos micáceos de granate y anfibolitas afectadas, según estudios recientes por metamorfismo de alta P/T en el Pérmico (ca. 288 Ma) aflora exclusivamente al oeste de la SLV y de la Falla Limón Verde. La unidad más antigua expuesta dentro de la SLV corresponde, en cambio, a una serie de conglomerados monomícticos matriz soportados (Diamictitas de Limón Verde) con edad máxima de depósito de ca. 1.060 Ma (U-Pb LA ICP - MS en circones detríticos) y que probablemente corresponden a depósitos de origen glaciar de edad Neoproterozoica (Criogénica), los cuales representarían los primeros depósitos de este tipo reconocidos en Chile. Junto a ellas, formando también enclaves dentro de los intrusivos del Paleozoico superior, aflora una unidad de metacuarcitas foliadas y metabasitas (Estratos de Pampa Quenante) y otra constituida por grauvacas y conglomerados (Estratos de Cerro Limón Verde) afectadas por metamorfismo de bajo grado y cuyas poblaciones de circones detríticos indican una edad máxima de depósito Ordovícica (ca. 470 - 480 Ma). Su espectro de edades de circones detríticos se puede comparar al de sucesiones sedimentarias del Devónico Carbonífero inferior aflorantes en la Cordillera de la Costa de la región de Antofagasta, aunque una edad más antigua no puede ser descartada del todo. La Tesis incluye, como capítulo final, una discusión en cuanto al significado de las unidades expuestas en la SLV para los modelos tectónicos propuestos para la evolución paleozoica del norte de Chile.

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The study of Brazilian sedimentary basins concentrates on their rift phase, whereas the Post-rift phase has been considered a tectonic quiescent period. The post-rift sequence of the Potiguar Basin, in the far northeastern Brazil, was once considered little deformed, however several studies have shown how that it was affected by major fault systems. The purpose of this thesis is to characterize the post-rift tectonic. The specific objectives are: to characterize the Neogene and Quaternary sedimentary units that outcrop of the Potiguar Basin; to show how the NW-SEtrending Afonso Bezerra Faults System deformed outcrop rocks in the Basin; to describe soft-sediment deformation in gravels of the Quaternary Alluvial Deposits from A?u River. Facies analyses, grain-size studies, luminescence dating, remote sensing, structural mapping, shallow geophysics (georadar), paleostress and petrography were carried out. The structural mapping and the georadar sections indicated that the Carnaubais and Afonso Bezerra fault systems formed fractures, silicified and non-silicified faults or deformation bands, affecting mainly the A?u, Janda?ra and Barreiras formations. The petrographic data indicate that the strong silicification resulted in a sealant character of the faults. Paleostress analysis indicates that two stress fields affected the Basin: the first presented N-S-trending compression, occurred from the Neocretaceous to the Miocene; the second stress field presents E-W-trending compression, acts from the Miocene to the present. It was verified once the Afonso Bezerra System Faults was reactivated in periods post-Campanian and affects all post-rift lithostratigraphic units of Potiguar Basin, including Quaternary sedimentary covers. The study about soft-sediment deformation structures indicates that they are similar in morphology and size to modern examples of seismically-induced deformation strutures in coarse sediments. TL and OSL ages indicate that sediment deposition and associated soft-sediment deformation occurred at least six times from ~352 Ka to ~9 Ka. Finally these studies demonstrate how recent is tectonics in the Basin Potiguar
Os estudos sobre as bacias sedimentares brasileiras se concentram em sua fase rifte, enquanto a fase p?s-rifte tem sido considerada um per?odo de pouca atividade. A sequ?ncia p?s-rifte da Bacia Potiguar, no extremo nordeste brasileiro, j? foi considerada pouco deformada, contudo, in?meros trabalhos v?m demonstrando como ela ? afetada por importantes sistemas de falhas. A finalidade geral desta tese ? caracterizar a tect?nica p?s-rifte na Bacia Potiguar. Os objetivos espec?ficos s?o: caracterizar as unidades sedimentares cenozoicas aflorantes e a tect?nica associada; evidenciar como o Sistema de Falhas de Afonso Bezerra deformou rochas aflorantes da Bacia; descrever deforma??o em sedimentos inconsolidados nos conglomerados dos Dep?sitos Aluviais quatern?rios do Rio A?u. An?lises de f?cies, estudos granulom?tricos, data??o por luminesc?ncia, sensoriamento remoto, mapeamento estrutural, geof?sica rasa (georadar), an?lises de paleotens?es e petrografia foram realizados. O mapeamento estrutural e as sec??es de georadar indicaram que os sistemas de falhas Carnaubais e Afonso Bezerra formaram juntas, falhas silicificadas e n?o-silicificadas e bandas de deforma??o, afetando principalmente as forma??es A?u, Janda?ra e Barreiras. Os dados petrogr?ficos indicam que a forte silicifica??o deu ?s falhas um car?ter selante. O estudo de paleotens?es indica dois campos de tens?es afetando a Bacia: o primeiro, com compress?o N-S, atuou do Neocret?ceo ao Mioceno; o segundo, com compress?o E-W, atua do Mioceno ao presente. Constatou-se que o Sistema de Falhas de Afonso Bezerra foi reativado em per?odos p?s-campanianos e afeta todas as unidades litoestratigr?ficas p?s-rifte da Bacia Potiguar, inclusive as coberturas quatern?rias. O estudo sobre deforma??o em sedimentos inconsolidados indica que esta ? similar na morfologia e no tamanho aos exemplos modernos de estruturas de deforma??o sismicamente induzida em sedimentos grossos. Idades por TL e LOE indicam que a deposi??o dos sedimentos e a deforma??o associada ocorreram pelo menos em seis eventos entre aproximadamente 352 Ka e 9 Ka. Enfim estes estudos demonstram qu?o recente ? a tect?nica na Bacia Potiguar

Magíster en Ciencias, Mención Geología
La Zona Volcánica Sur presenta una clara disminución de la elevación y del espesor cortical hacia el sur, atribuido a la gradual disminución del acortamiento tectónico medido desde 25% (~25 km) a 35º30 S hasta 12% (~10 km) a 36º17 S. Este estudio pretende caracterizar y determinar los procesos tectónicos que producen el desarrollo de la Cordillera del Maule, en el contexto de la orogénesis en los Andes Centrales del Sur. En la región andina del Maule aflora una serie de depósitos sedimentarios continentales (Formación. Río Damas y Colimapu) y marinos del Cretácico Inferior (Formación. Baños del Flaco), sobreyacidos en discordancia angular por rocas sedimentarias y volcano-sedimentarias Cenozoicas continentales de la Formación Abanico, caracterizadas por una fuerte deformación, cubiertos en discordancia por depósitos volcánicos del Neógeno Superior. La evolución de la estratigrafía se superpone a una serie de eventos extensionales y compresivos, los que se evidencian en los principales rasgos estructurales de la región. Las estructuras presentes en la región se agrupan en dos dominios estructurales, con orientaciones principales N-S a NNE-SSW. El Dominio de la cuenca de trasarco Mesozoica (al este) consiste en estructuras inversas de vergencia Este, la Falla La Invernada y el anticlinal La Araña (asimétrico y de gran longitud de onda). El Dominio de la Cuenca de Abanico consiste en estructuras inversas de vergencia Este y Oeste (Falla Cipreses, Falla Las Corrientes, Falla García y Falla Las Garzas), caracterizadas por formar una serie de pliegues de diversa longitud de onda, amplitud y vergencia. La relación entre ambos dominios se puede explicar mediante una transferencia de la deformación desde el occidente (Dominio Cuenca de Abanico) hacia el oriente (Dominio de la cuenca de trasarco Mesozoica), a través de estructuras con un nivel de despegue de aprox. 10 km de profundidad. El acortamiento generado en la región es de 9 km, equivalente a un 24%, explicado por tectonismo compresivo neógeno. Estudios en U/Pb con circones detríticos sugieren la existencia de un evento compresivo Cretácico Superior, relacionado con la discordancia Mesozoico-Cenozoico, confirmando el inicio del alzamiento andino posterior a ~120 Ma en esta región de la cordillera. La evolución estructural de la zona de estudio, realizada a partir del análisis estructural, logró establecer la existencia de tres eventos compresivos para el flanco occidental de la Cordillera Principal en la zona de estudio. El primer evento compresivo evidenciado actuó en el Cretácico Superior, observado en el contacto discordante entre las rocas Mesozoicas y Cenozoicas (~ 20°), asociado al inicio del alzamiento de los Andes, posterior a ~120 Ma. El segundo evento compresivo ocurrió en el Mioceno medio, con la inversión de la Cuenca de Abanico. El tercer evento compresivo actuó en el Mioceno Superior, transfiriendo la deformación al Este a través de la Falla La Invernada. La distribución homogénea de acortamiento entre el sector oeste y este de la cordillera permite explicar la elevación media actual a esta latitud. Estas características difieren de la asimetría reportada más al norte, donde se planteó un modelo de cizalle simple como mecanismo de alzamiento de la cordillera, mientras que las características de la región de estudio permiten proponer, más bien, un mecanismo de cizalle puro como controlador del alzamiento andino a 36°S.

Dissertação (mestrado)—Universidade de Brasília, Instituto de Geociências, Programa de Pós-Graduação em Geologia, 2017.
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A margem ocidental de América do Sul é comumente considerada como um exemplo de margem oceano - continental convergente, constituindo a antigo Oeste do Gondwana antes de sua dispersão no Cretáceo. O segmento norte de América do Sul experimento a mudanças drásticas desde o desenvolvimento como bacia de trás-arco no Triássico-Jurássico até formar uma retro-bacia de ante-país no contexto atual andino. Uma maneira para determinar essas mudanças nos eventos geodinâmicos que afetam o segmento norte da América do Sul é estudando a proveniência das rochas sedimentares e reconstruir a evolução do paleodrenagem. Este estudo analisa a proveniência das rochas sedimentares que compõem o intervalo Triássico-Mioceno depositados na Bacia do Huallaga. Foram utilizados os métodos de U-Pb em zircão detrítico e isotopia de Nd-Sr. Os resultados mostram quatro mudanças da proveniência associados a eventos locais e regionais que afetam a bacia de ante-pais do norte de Peru. As rochas sedimentares do Triássico-Jurássico foram depositadas em um contexto de bacia de back-arc. Os valores de εNd (0) são de - 7,9 a -10 associada com um arco juvenil junto com idades U-Pb em zircão detritico que representam as províncias de Greenville- Sunsás (1.3-0.9 Ga), Brasiliano (0.5-0.7 Ga) e Maroni-Itacaiúnas (2-2.2 Ga). Estes resultados sugerem uma fonte de proveniência mista vindo do Arco Vulcânico Mesozoico (Arco Misahuallí-Colán) e rochas Pré-cambrianas da Cordilheira Oriental do Peru e Cordilheira Real do Equador. As rochas sedimentares do Cretáceo (Albiano-Maastrichtiano) têm valores de εNd (0) entre -16 a -18 com picos de idades U-Pb em zircão detritico representando as províncias de Rondônia-San Ignácio (1.3-1.54 Ga), Rio Negro-Juruena (1.54-1.82 Ga) e Ventuari Tapajós (1.82-2 Ga). Estes resultados sugerem uma fonte das áreas do Cráton Amazonico onde o transporte de sedimentos foi realizado no sentido Oeste para Leste durante o Albiano-Maastrichtiano e dominou todo o segmento norte de América do Sul. As rochas sedimentares do Paleoceno Inferior- Eoceno têm valores εNd (0) de - 5,58 a -10,35 com picos de idades U-Pb em zircão detritico que representam as províncias de Greenville-Sunsás (1.3- 0.9 Ga), Brasiliano (0.5-0.7 Ga) e Rio Negro-Juruena (1.54-1.82 Ga) junto com as primeiras populações de zircões com idades mais jovens que 120 Ma. Essas idades representam os primeiros zircões da região dos Andes e corresponde ao segmento da Cordilheira Ocidental. As rochas sedimentares do Oligoceno têm valores de εNd (0) entre -7,7 a -9,9 junto com um pico principal de idades U-Pb entre 23-29 Ma (Oligoceno). Estes resultados mostram uma predominância de fonte de arco vulcânico Paleógeno-Neógeno (Arco Vulcânico Calipuy- Saraguro) que se desenvolve na Cordilheira Ocidental do Equador e do Peru. As rochas sedimentares do Miocene apresentam valores de εNd (0) entre -5,8 a -12,6 junto com idades U-Pb em zircão detritico principais pertencem às províncias Greenville-Sunsás (1.3-0.9 Ga), Brasiliano (0.5-0.7 Ga), Arco Magmático Paleozóico (0.4-0.26 Ga) e Rift Permo-Triassico (0.25-0.15 Ga). Estas rochas apresentam uma fonte mista vindo dos segmentos da Cordilheira Ocidental e Oriental dos Andes Centrais. O desenvolvimento da Cordilheira Oriental gera uma barreira evita o transporte dos sedimentos que veim da Cordilheira Ocidental.
The Andean margin of South America is considered as the type example of an ocean - continental convergent margin, located along the west margin of Gondwana prior to its dispersion during to Cretaceous. The north segment of South America undergoes severe changes from the passage of a back-arc basin during the Triassic-Jurassic to a retro-foreland basin in the current Andean context. One way to constraint the changes of these geodynamical proccesses and the way it affected the northern part of South America is to study the sedimentary provenance and reconstruct its paleodrainage evolution. This study analyzes the sedimentary rocks of the Triassic-Miocene interval deposited in the Huallaga basin that has part of the northern Peruvian Amazonian basin. We performed sedimentary analyzes using the methods of, U-Pb in detrital zircon and Sr-Nd isotopes. The results show 4 changes in provenance associated with regional and local events that affect the northern Peruvian Amazonian basin. The Triassic-Jurassic is characterized by deposition of sediments in back-arc basin context. The Triassic-Jurassic sediments present εNd (0) values of -7.9 to - 10 associated with a young arc along with zircon population age from the representing the provinces of Greenville-Sunsás (1.3-0.9 Ga), Brasiliano (0.5-0.7 Ga) e Maroni-Itacaiúnas (2- 2.2 Ga). These results suggest a mixed source between volcanic arc (Misahuallí-Colán Arc) and Pre-cambrian rocks of the Eastern Cordillera of Peru and Cordillera Real of Ecuador. The sedimentary rocks of the Cretaceous (Albian-Maastrichtian) present εNd (0) values of - 16 to -18 along with zircon population age from the representing the provinces of Rondonia- San Ignácio (1.3-1.54 Ga), Rio Negro-Juruena (1.54-1.82 Ga) e Ventuari-Tapajós (1.82-2 Ga). These results suggest a source of Amazon Craton, where the transport of sediments developed westward from the drainage systems during the Albian-Maastrichtian and dominated the entire northern segment of South America. The Early Paleocene to Eocene sedimentary rocks presents εNd (0) values of – 5.58 to -10.35 with zircon population age from the representing the provinces of Greenville-Sunsás (1.3-0.9 Ga), Brasiliano (0.5-0.7 Ga) e Rio Negro-Juruena (1.54-1.82 Ga) with population age younger than 120 Ma. These ages represent the first zircons from the Andean mountains and correspond to the segment of the Western Cordillera. The Oligocene sedimentary rocks present εNd (0) values of -7.7 to - 9.9 with a main peak of zircon population ages between 23-29 Ma (Oligocene). These results show a predominance of the Paleogene-Neogene volcanic arc (Calipuy-Saraguro Volcanic Arc) source that is developed in the Western Cordillera of Peru and Ecuador. The Miocene sediments present εNd (0) values of -5.8 to -12.6 located in the sediments area of the Altiplano-Eastern Cordillera associated to a mixture sources of volcanic arc and recycled sediments of Phanerozoic and Pre-cambrian rocks. The main peaks of U-Pb ages belong to the Greenville-Sunsás (1.3-0.9 Ga), Brasiliano (0.5-0.7 Ga), Arco Magmático Paleozóico (0.4-0.26 Ga) e Rift Permo-Triassico (0.25-0.15 Ga). These sediments present a mixed source from the segments of the Western and Eastern Cordillera of the Central Andes. Te uplift of the Eastern Cordillera generates a barrier that avoids the transportation of the sediment that comes from the Western Cordillera.
El margen occidental andino sudamericano es comúnmente considerado como un ejemplo de margen océano - continental convergente, constituyendo el antiguo margen Oeste de Gondwana antes a su dispersión en el Cretáceo. El segmento norte de América del Sur experimenta cambios desde el desarrollo de una cuenca de tras-arco durante el Triásico- Jurásico hasta formar una retro-cuenca de ante-país en el actual contexto andino. Una manera para determinar estos cambios en la geodinámica que afectan el segmento norte de Sudamérica es estudiando la procedencia de los sedimentos y reconstruir la evolución de paleodrenaje. El presente estudio de procedencia analiza las rocas sedimentarias que componen el intervalo Triásico-Mioceno depositado en la Cuenca Huallaga que forma parte de la Cuenca Amazónica Norte del Perú. Para este estudio fueron utilizados dataciones U-Pb en circón detrítico e isotopia de Sr-Nd. Los resultados muestran cuatro cambios de procedencia asociados con eventos regionales y locales que afectan la retro-cuenca de antepaís al norte de Perú. Las rocas sedimentarias del Triásico-Jurásico fueron depositads en un contexto de cuenca tras-arco. Los valores de εNd (0) oscilan entre - 7.9 a -10 asociados a un arco juvenil junto con edades principales de U-Pb que representan las provincias Greenville- Sunsás (1.3-0.9 Ga), Brasiliano (0.5-0.7 Ga) e Maroni-Itacaiúnas (2-2.2 Ga). Estos resultados sugieren una fuente mixta entre arco volcánico (Arco Misahuallí-Colán) y rocas Precambrianas de la Cordillera Oriental de Perú y Cordillera Real de Ecuador. Las rocas sedimentarias del Cretáceo Superior (Albiano-Maastrichtiano) presentan valores de εNd (0) entre -16 a -18 junto con picos de edades U-Pb que representan las provincias de Rondônia- San Ignácio (1.3-1.54 Ga), Rio Negro-Juruena (1.54-1.82 Ga) e Ventuari-Tapajós (1.82-2 Ga). Estos resultados sugieren una fuente de Cratón Amazónico donde el transporte de sedimentos se desarrolló en dirección Este para el Oeste durante el Albiano-Maastrichtiano y dominó todo el segmento norte de América del Sur. Las rocas sedimentarias del Paleoceno Temprano-Eoceno presentan valores de εNd (0) entre – 5.58 a -10.35 con principales edades U-Pb que representan las provincias Greenville-Sunsás (1.3-0.9 Ga), Brasiliano (0.5-0.7 Ga) e Rio Negro-Juruena (1.54-1.82 Ga) junto con las primeras poblaciones de edades menores a 120 Ma. Estas edades representan los primeros circones procedentes de la zona andina y corresponde al segmento de la Cordillera Occidental. Los rocas sedimentarias del Oligoceno son caracterizados por presentar valores εNd (0) entre -7.7 a -9.9 junto con un pico principal de edades de U-Pb entre 23-29 Ma (Oligoceno). Estos resultados muestran un predominio de fuente de arco volcánico Paleógeno-Neógeno (Arco Volcánico Calpiuy-Saraguro) que se desarrolla en la Cordillera Occidental de Perú y Ecuador. Las rocas sedimentarias del Mioceno presentan valores εNd (0) entre -5.8 a -12.6 junto con idades U-Pb principales que pertenecen a las provincias Greenville-Sunsás (1.3-0.9 Ga), Brasiliano (0.5-0.7 Ga), Arco Magmático Paleozóico (0.4-0.26 Ga) e Rift Permo-Triassico (0.25-0.15 Ga). Estos sedimentos presentan una fuente mixta procedente de los segmentos de la Cordillera Occidental y Cordillera Oriental de los Andes Centrales. Durante el desarrollo de a Cordillera Oriental genera una barrera que impide el transporte de sedimentos procedentes de la Cordillera Ocidental

O Gabro José Fernandes é um corpo com cerca de 3 km², representante do magmatismo alcalino da Província Magmática Paraná-Etendeka na região do Arco de Ponta Grossa. A intrusão está encaixada em rochas metassedimentares proterozoicas do Grupo Votuverava e apresenta considerável variedade litológica definida por rochas gabróicas, em parte cumuláticas, cortadas por diques alcalinos. A intrusão foi datada em 134.93±0.16 Ma pelo método U-Pb TIMS em zircão. Um dique de basalto com alto TiP-Sr apresenta idade U-Pb de 133.95±0.16 Ma, idêntica à idade \'ANTPOT.40 Ar\'/\'ANTPOT.39 Ar\' step-heating em flogopita de dique de lamprófiro (133.7±0.1 Ma), indicando com dados robustos que o magmatismo toleítico e alcalino do Cretáceo Inferior são contemporâneos na região. A idade de cristalização de um dique de basalto andesítico é um pouco mais jovem (131.31±0.13 Ma), e está de acordo com dados \'ANTPOT.40 Ar\'/\'ANTPOT.39 Ar\' step-heating da literatura, confirmando que o magmatismo básico toleítico perdurou por pelo menos 3 m.y. no Arco de Ponta Grossa. As rochas do Gabro José Fernandes mostram evidências petrográficas, geoquímicas e isotópicas de evolução magmática em sistema aberto com acentuada contribuição crustal. As evidências petrográficas incluem zoneamentos minerais e texturas de desequilíbrio com a formação de Fe-enstatita em bordas de reação de olivina. A cristalização fracionada é um importante processo na evolução das rochas, e a correlação positiva entre \'SiO IND.2\' e razões isotópicas de Sr-Pb e negativa com \'épsilon\'Nd indicam contaminação progressiva do magma com o fracionamento. As variações isotópicas identificadas em diques e rochas gabróicas indicam a existência de pulsos magmáticos com diferentes contribuições crustais. O zoneamento de elementos maiores observado em minerais é acompanhado pelos elementos traços. Bordas mais ricas em Fe e Ti de cristais de clinopiroxênio também apresentam maior concentração de elementos HFS e LILE. A isotopia in situ de Sr em plagioclásio mostra variações nas razões \'ANTPOT.87 Sr\'/\'ANTPOT.86 \'Sr IND.i\'\', interpretadas como evidências de recargas da câmara magmática, enquanto os dados para clinopiroxênio revelam núcleos com textura de reabsorção com razões \'ANTPOT.87 Sr\'/\'ANTPOT.86 \'Sr IND.i\'\' mais baixas (<0.705) interpretadas como relíquias de antecristais que podem apresentar relação com o magma parental. De fato, as assinaturas isotópicas desses núcleos são compatíveis com as de fenocristais de diques de basanito, fornecendo indicações de um magma parental alcalino basanítico. A composição química do líquido em equilíbrio com núcleos de fenocristais de clinopiroxênio em diques de basanito é mais alcalina, com maiores teores de Nb e elementos terras raras em relação à estimada para os gabroscumuláticos. A natureza do contaminante é consistente com rochas (meta)-sedimentares proterozoicas, como indicado pelo aumento das razões K2O/Na2O, Th/La e Th/Nb; a menor razão Th/U é indicativa de crosta superior e as idades modelo Nd \'T IND.DM\' mais antigas (1400-1200 Ma) indicam assimilação de crosta pré-cambriana. Modelamentos de assimilação e cristalização fracionada mostram que a diversidade isotópica é compatível com a curva de mistura entre magma inicial alcalino basanítico e rochas metassedimentares do Grupo Votuverava.
The José Fernandes Gabbro is a ~3 km² intrusion related to the alkaline magmatism of the Paraná-Etendeka Magmatic Province in the region of the Ponta Grossa Arch, Brazil. The intrusion is enclosed in Proterozoic metasedimentary rocks of the Votuverava Group and is composed of varied types of gabbroic rocks, including cumulates, cut by alkaline dykes. It was dated at 134.93±0.16 Ma (TIMS U-Pb zircon). A high Ti-P-Sr basalt dyke has a U-Pb age of 133.95±0.16 Ma, identical to the phlogopite \'ANTPOT.40 Ar\'/\'ANTPOT. 39 Ar\' step-heating age of a lamprophyre dyke (133.7±0.1 Ma), indicating with robust data that tholeiitic and alkaline magmatism are coeval in the region. The crystallization age of a basaltic andesite dyke is slightly younger (131.31±0.13 Ma), in agreement with previous \'ANTPOT.40 Ar\'/\'ANTPOT.39 Ar\' step-heating data from literature, confirming that the basic tholeiitic magmatism persisted for at least 3 m.y. in the Ponta Grossa Arch. The José Fernandes Gabbro rocks show petrographic, geochemical and isotopic evidence for open-system processes with significant crustal contribution. The petrographic evidence includes mineral zoning and disequilibrium textures with the development of Fe-enstatite in reaction rims of olivine. Fractional crystallization is an important process in the evolution of the intrusion and positive correlation of SiO2 with Sr-Pb initial ratios and negative correlation with \'épsilon\'Nd indicate a progressive contamination of the magma with fractionation. The variation of isotopic ratios identified in dykes and gabbroic rocks indicates the existence of magmatic pulses with distinct crustal contributions. The major element chemical zoning observed in minerals is coupled with variations in trace elements. Fe-Ti enriched rims from clinopyroxene show higher concentrations of other HFS elements and LILE. In situ Sr isotope determinations in plagioclase crystals locally show variations in \'ANTPOT.87 Sr\'/\'ANTPOT. 86 \'Sr IND.i\' interpreted as evidence for recharges in the magma chamber, while similar data for clinopyroxene show that cores with resorbed textures may have lower \'ANTPOT. 87 Sr\'/\'ANTPOT. 86 \'Sr IND.i\' (<0.705) interpreted as relicts of antecrysts that can be related with the parental magma. In fact, the isotopic signatures of these relicts are compatible with those of phenocrysts from basanite dykes, suggesting a basanitic parental magma. The composition of the liquid in equilibrium with phenocrysts from basanite dykes is more alkaline, with more concentration of Nb and rare earth elements, relative to that estimated for the cumulatic gabbros. The nature of the contaminant is consistent with (meta)-sedimentary rocks, as revealed by higher K2O/Na2O, Th/La and Th/Nb; lower Th/U is indicative of upper crust, and the older NdTDM model ages (1400-1200 Ma) indicate assimilation of Precambrian crust. Assimilation fractional crystallization-mixing modelling shows that the isotopic diversity is consistent with a curve of mixing between a starting alkaline basanitic magma and metasedimentary rocks of the Votuverava Group.

Geología
En este trabajo se describe la estratigrafía de rocas volcánicas y sedimentarias del Jurásico Superior al Cretácico Superior, en las cercanías del valle del río del Carmen, entre los 28°50´ y los 29°15´S, con el fin de obtener datos sobre la actividad tectónica ocurrida durante el Mesozoico Superior. Esta zona se caracteriza por ser el límite entre los dos dominios estructurales principales a lo largo de la III Región. El dominio occidental, caracterizado por poseer deformación de escama delgada, con gran longitud de onda, sobre una cobertura principalmente mesozoica, abarca la Cordillera de la Costa y la Precordillera; por otro lado el dominio oriental, se caracteriza por mostrar deformación de escama gruesa y fallas inversas de alto ángulo, que permiten la exhumación de basamento en la Cordillera Frontal. El estudio estratigráfico de las secuencias mesozoicas fue realizado mediante tres columnas estratigráficas a lo largo del área de estudio, acompañadas de datos geocronológicos realizados por el Servicio Nacional del Geología y Minería. Estas columnas abarcan secuencias de rocas volcánicas del Jurásico Superior correspondientes a la Formación Algarrobal y rocas volcánicas andesíticas, con base sedimentaria continental, correspondientes a la Formación Cerrillos del Cretácico Superior. Los resultados estratigráficos y geocronológicos obtenidos permiten determinar un fuerte volcanismo entre los 152,7 ± 2,3 y 144 ± 1,9 Ma, donde se depositaron grandes espesores de rocas volcánicas, de al menos 1420 m, correspondientes a la Formación Algarrobal, los cuales podrían haber sido acomodados mediante la acción de una falla normal. Sobre la Formación Algarrobal se encuentran secuencias de rocas sedimentarias con edades máximas de depositación entre 90-91 Ma. Estas unidades son cubiertas en discordancia y concordancia por rocas volcánicas de edades entre 80 y 85 Ma. El estudio petrográfico y geocronológico U-Pb de circones detríticos permite reconocer que los aportes en las rocas sedimentarias corresponden a la Formación Algarrobal y al Complejo Plutónico Chanchoquín del Pérmico Inferior, que serían aportes provenientes desde el este, por otro lado, por su lado oeste, estos depósitos recibirían aportes de intrusivos del Cretácico Inferior. Esto indica que se produjo la exhumación de rocas de la Formación Algarrobal y del Complejo Plutónico Chanchoquín en el Cretácico Superior (91-85 Ma). Esta fase de exhumación, sumada a los antecedentes de discordancias angulares reconocidas en las secuencias del Cretácico Superior, puede ser asociada con una fase compresiva que afectó toda el área, permitió el alzamiento de un bloque oriental y coincidiría con el desarrollo de la Fase Peruana, reconocida ampliamente en el norte de Chile. Este evento además, permitió la formación de un depocentro de carácter local en torno a los 29°05´S donde se depositaron sedimentos provenientes del alzamiento desde el este, hasta que la reactivación del volcanismo hace 85 Ma, cubrió esos depósitos sedimentarios del Cretácico Superior.

Geóloga
A los 33°S, en territorio chileno y argentino, existe una fragmentación de las franjas batolíticas representativas del arco magmático del Paleozoico tardío. Al norte de 33°S, en la Cordillera Frontal, aflora el Batolito Elqui-Limarí, de edad Misisípico Superior - Triásico Superior, mientras que al sur de 33°S, en la costa, aflora el Batolito Costero, entre 33°-39°S, de edad, esencialmente, Pensilvánico. La presencia de enclaves graníticos de edad Carbonífero tardío, incluidos en un dique máfico mesozoico emplazado en el Complejo Metamórfico del Choapa, en el sector costero de Huentelauquén (31°30 S), podría sugerir la prolongación del Batolito Costero hacia el norte, bajo la cobertura meso-cenozoica. Este trabajo presenta un estudio detallado de las características petrográficas y geoquímicas, además de dataciones U-Pb e isotopía de Hf en circones, mediante el método LA-ICP-MS, de una muestra de enclave, con el fin de aportar nuevos antecedentes para la evolución tectono-magmática del margen occidental de Gondwana, durante el Paleozoico tardío. El enclave corresponde a un monzo-sienogranito, hololeucocrático, con microclina, sin máficos primarios frescos y con texturas de intercrecimiento y magmáticas tardías. Los resultados geoquímicos en roca total de elementos mayores y elementos traza indican que correspondería a un granito desarrollado en un ambiente de margen típico de subducción, con magmatismo de arco asociado, fraccionamiento de piroxeno y plagioclasa durante su cristalización, sin la influencia de granate, a partir de un protolito ígneo. Las dataciones U-Pb en circones de la muestra de enclave arrojan una edad de cristalización pensilvánica de 318.6±2 Ma, con un rango de edades entre 305 y 335 Ma. Las determinaciones isotópicas de Lu-Hf en la muestra de enclave entregan valores ℇHf(i) entre 0 y +7, mostrando una componente juvenil predominante y edades modelo tDM desde el Mesoproterozoico tardío al Neoproterozoico temprano (tDM=1.22-0.85 Ga). La concordancia de estas características, excepto en las isotópicas, con las conocidas para el Batolito Costero parecen confirmar la idea de una prolongación de éste hacia el norte, bajo la cobertura meso-cenozoica y el basamento metamórfico. Asimismo, mediante el estudio geocronológico e isotópico en circones heredados en lavas y plutones cenozoicos en la Alta Cordillera (34°S), se sugiere que las componentes pensilvánicas del Batolito Elqui-Limarí se extenderían hacia el sur, en subsuperficie, hasta, por lo menos, estas latitudes. Se propone que, durante el Misisípico Superior-Pensilvánico, se habrían desarrollado dos arcos simultáneos, paralelos e independientes, representados por el Batolito Elqui-Limarí, en la Alta Cordillera, y el Batolito Costero, en la costa, emplazados en la litósfera como una zona de tipo MASH, cuya fuente principal sería una corteza continental antigua y reciclada, con pulsos discretos provenientes de la astenósfera, en zonas de debilidades corticales heredadas, representadas, por ejemplo, por los magmas de los enclaves graníticos. Estos dos arcos simultáneos se habrían desarrollado por la migración de un terreno alóctono o para-alóctono desde el W hacia el margen occidental de Gondwana, que correspondería al Terreno X, o Terreno de Atacama o de Domeyko, como se lo nombra en este estudio, separado de Chilenia por una sucesión alineada de afloramientos de metamorfitas interpretadas como remanentes de un prisma de acreción. El arco de la Alta Cordillera se habría desarrollado en el borde trasero de Chilenia, mientras que el arco de la Cordillera de la Costa se habría desarrollado en el borde W del Terreno Atacama o Domeyko.

The Maestrat basin was one of the most subsident basins of the Iberian Rift System, which experienced two main rifting events: Late Permian-Late Triassic and Late Jurassic-Early Cretaceous. Its inversion during the Cenozoic Alpine orogeny generated the E-W-trending, N-verging Portalrubio–Vandellòs fold-and-thrust belt in the Linking Zone between the NW-SE-trending Iberian Chain, and the NE-SW-trending Catalan Coastal Chain, detached in the Triassic evaporites, while southwards it also involved the Variscan Basement. The study area is located in the central part of the fold-and-thrust belt. The objectives of this thesis are to characterize the structures developed during the different deformation events, as well as to characterize the transition from thin to thick-skinned areas. Finally, it aims to propose a kinematic evolutionary model for the northern margin of the basin based on the interpretation of subsurface data and new field data. During the first stage of extensional activity a high angle normal fault system developed, which fragmented the Variscan Basement into a system of horsts, grabens and half-grabens. Those faults were active during the deposition of the Buntsandstein facies and lasted until the lower part of the Middle Muschelkalk facies was deposited, filling the system of horsts and grabens and generating depositional thickness variations. The fault system was overstepped by the upper part of the Middle Muschelkalk, indicating a decrease in the extensional activity that lasted until the carbonates of the Upper Muschelkalk facies were deposited, as they present nearly constant thickness. During the Keuper facies deposition, the extensional activity of some normal faults in the acoustic basement resumed, triggering the Middle Muschelkalk salt flow, which developed salt anticlines and welds, increasing the thickness variations of this facies. The age of the salt flow is deduced from the Keuper facies reflectors lapping on the folded Upper Muschelkalk above the salt accumulations. Growth-strata above some Upper Muschelkalk forced folds are also recognized, developed above some reactivated normal faults in the basement. During the second stage of extensional activity, a system of segmented listric normal faults, connected by relay ramps developed bounding the different sub-basins. The Maestrat basin filling (Upper Jurassic-Lower Cretaceous) broadly becomes thinner towards the north, towards the northern boundary of the basin, although locally it becomes thicker northwards, towards the hanging wall of the S-dipping main normal faults. Major extension occurred during the Barremian, as units of this age display bigger thickness variations, while the Aptian units show more constant thicknesses. During the Cenozoic Alpine orogeny, the Maestrat basin was inverted. The E-W-trending, N-verging Maestrat Basement Thrust developed, traversing the entire basin, as a result of the inversion of the Mesozoic fault system within the basement. As this thrust reached the Mesozoic cover, it propagated across the Middle Muschelkalk detachment level, transporting the supra-salt cover, and the normal fault segments within it, about 12km towards the North. The basement thrust is deduced to have a ramp-flat geometry, with a low-dip ramp which reaches about 8km depth, rooted in the upper crust. The displacement of the basement in the hanging wall of this ramp generated a 40km-wide uplifted area, in the N-S direction, bounded to the N by the Calders monocline, interpreted as a fault-bend-fold adapted to the ramp to flat transition in the basement thrust. It also indicates the transition from a thick-skinned style of deformation in the S, to a thin-skinned style to the N. The superficial shortening accumulated in the northern margin of the basin, containing the thinnest Mesozoic cover, developing the Portalrubio-Vandellòs fold-and-thrust belt.
La Conca del Maestrat va ser una de les més subsidents del Sistema de Rift Ibèric Mesozoic, el qual va experimentar dos episodis de rift principals: el primer durant el Permià superior-Triàsic i el segon durant el Juràssic superior-Cretaci inferior. La conca del Maestrat es va formar durant el segon episodi de rift, per un sistema de falles normals lístriques que la van dividir en sub-conques. Es va invertir durant l’Orogènia Alpina Cenozoica, formant la Zona d’Enllaç entre la Serralada Ibèrica, d’orientació NW-SE, i la Cadena Costanera Catalana, d’orientació NE-SW. Durant la inversió es va formar, en el marge nord de la conca, el cinturó de plecs i encavalcaments de Portalrubio-Vandellòs, d’orientació predominant E-W i vergència cap al N, desenganxat a les evaporites Triàsiques, però que cap al S passa a involucrar el sòcol Varisc. La zona d’estudi es situa al marge nord de la Conca del Maestrat, a la part central del cinturó de plecs i encavalcaments de Portalrubio-Vandellòs, i inclou la zona de trànsit d’un estil de deformació de pell fina (N) a un de pell gruixuda (S). Els principals objectius d'aquesta tesi s6n caracteritzar les estructures formades durant l'extensi6 Mesozoica i durant la contracci6 Cenozoica, i la influencia de les primeres en la formació de les darreres, així com caracteritzar com es produeix el trànsit d’una zona amb deformació de pell fina a una de pell gruixuda. Finalment, preten proposar un model d'evoluci6 cinematica del marge nord de la conca i una reconstrucció de la geometria de l’Encavalcament de Sòcol del Maestrat. Aquest estudi està basat en la interpretació de dades de subsòl (sísmica 2D i sondeigs d’exploració) i dades noves de camp. Pel que fa a l’estructura Mesozoica, durant la primera etapa de rift (Permià superior-Triàsic superior) es va formar un sistema de falles normals d’alt angle que va fragmentar el sòcol Varisc en un sistema de horsts, grabens i semi-grabens. Aquestes falles foren actives durant el depòsit de la fàcies Buntsandstein, fins que es va dipositar la part inferior de la facies Muschelkalk mitja, reomplint el sistema de horst i grabens i donant lloc a diferències de gruix deposicionals en aquesta unitat evaporítica. La part alta del Muschelkalk mitjà va sobrepassar i cobrir el sistema de falles, indicant una disminució de l’activitat extensiva, que va durar fins que es van dipositar els carbonats de la facies Muschelkalk superior, que presenta un gruix quasi constant a tota la conca. Mentre es dipositava la fàcies Keuper es va reactivar l'activitat extensiva d'algunes falles normals del socol acustic o infra-salf, desencadenant el flux de la sal del Muschelkalk mitjà, que va formar anticlinals de sal i welds, incrementant les diferències de gruix d'aquesta facies. L'edat del flux de sal es dedueix a partir dels reflectors sfsmics del Keuper, que es disposen en onlap a sobre del Muschelkalk superior plegat sobre les acumulacions de sal. Alguns ventalls de capes també es poden reconèixer sobre plecs forçats del Muschelkalk superior a sobre d’algunes falles normals reactivades en el sòcol acústic. La càrrega diferencial exercida pel Keuper hauria incrementat o afavorit el flux de sal. Durant el segon episodi de rift (Juràssic superior- Cretaci inferior) es va formar un sistema de falles normals lístriques segmentades i connectades per rampes de relleu, que separaven les diferents sub- conques, tal i com suggereix la distribució de les roques del Cretaci inferior i de les estructures extensives en la zona d’estudi, que presenten diverses orientacions. El rebliment de la conca del Maestrat a grans trets s’aprima cap al Nord, cap al marge de la conca. Tot i això, el Cretaci inferior de la sub-conca de la Selzedella – la més extensa de la conca del Maestrat – presenta una geometria de tascó que s’engruixeix progressivament cap al Nord, de 350m a 1100m, cap al bloc superior del sistema de falles normals inclinades cap al S. Durant el Barremià, l’activitat extensiva va ser major que durant l’Aptià, ja que les unitats barremianes presenten variacions de gruix més acusades, mentre que les aptianes presenten gruixos més constants. Durant l’orogènia alpina cenozoica, la conca del Maestrat es va invertir. La inversió del sistema de falles normals Mesozoiques, en el seu segment a través del sòcol acústic, va generar l’Encavalcament de Sòcol del Maestrat, d’orientació aproximadament E-W i vergència cap al N, que travessa tota la conca. Al rerepaís de la Zona d’Enllaç es pot observar una extensa zona elevada, d’uns 40km d’amplada en direcció N-S, que conté roques del Cretaci superior i del Cenozoic poc deformades i sub-horitzontals, que es situen a cotes entre 1400 i 2000m. A la zona d’estudi, aquesta zona elevada està limitada al nord pel Monoclinal de Calders, d'orientaci6 E-W i vergencia cap al N, que te un flanc basculat cap al N uns 5º amb una amplada màxima d’uns 13km a la part central, i que genera un esglaó tectònic vertical de 800-1200m. Aquest monoclinal s’interpreta com un plec d’adaptació, a partir del qual se’n dedueix una geometria de replà-rampa-replà per a l’Encavalcament de Sòcol del Maestrat. La xarnera sinforme septentrional del Monoclinal de Calders coincideix a grans trets amb el pas d’un estil de deformació de pell gruixuda al Sud, a un estil de deformaci6 de pell fina al Nord. El baix angle del flanc inclinat del Monoclinal de Calders, i la gran extensi6 de la zona aixecada suggereixen un baix angle per a l’encavalcament basal en el sòcol, que estaria arrelat a l’escorça superior. Aquest encavalcament tindria una rampa de baix angle (~9º), que es propagaria més de 40km cap al S, arribant a una profunditat d’uns 7.5km sota el nivell del mar. Quan aquest encavalcament va arribar a la cobertora Mesozoica cap a l’avant-país, es va propagar a través del nivell de desenganxament del Muschelkalk mitjà salí, generant un short-cut quasi horitzontal que va transportar la cobertora supra- salina i els segments de les falles normals a través d’aquesta uns 12km cap al NNE. El desplaçament del sòcol en el bloc superior de la rampa de baix-angle va generar l’extensa zona aixecada, d’uns 40km d'amplada, mentre que l'escur,:ament en superffcie es va acumular a la zona externa de la conca, situada al N, que conté la cobertora Mesozoica més prima, formant el cinturó de plecs i encavalcament de Portalrubio-Vandellòs. L’estructura del cinturó de plecs i encavalcament de Portalrubio-Vandellòs presenta, a la zona d’estudi, una geometria arquejada, convexa cap a l’avantpaís, cap al NNE, en el sentit del transport. La formació d’aquesta geometría es pot atribuir a diversos factors: a la presència d’un nivell de desenganxament salí (Muschelkalk mitjà) que acaba lateralment, cap a l’Oest; a un alt de basament (Anticlinal de Montalbán) que hauria interactuat amb la propagació cap al Nord del front d’encavalcaments d’orientació E-O, a l’oest de la zona estudiada, i per últim a l’herència de l’orientació de les falles normals Mesozoiques.
La Cuenca del Maestrat fue una de las más subsidentes del Sistema de Rift Ibérico mesozoico, el cual experimentó dos episodios de rift principales: el primero durante el Pérmico superior-Triásico y el segundo durante el Jurásico superior-Cretácico inferior. La Cuenca del Maestrat se formó durante el segundo episodio de rift, por un sistema de fallas normales lístricas que la dividieron en sub-cuencas. Se invirtió durante la Orogenia Alpina cenozoica, formando la Zona de Enlace entre la Cadena Ibérica, de orientación NW-SE, y la Cadena Costera Catalana, de orientación NE-SW. Durante la inversión, se formó en el margen norte de la cuenca el cinturón de pliegues y cabalgamientos de Portalrubio-Vandellòs, de orientación predominante E-W y vergencia hacia el N, despegado en las evaporitas triásicas, que hacia el S pasa a involucrar el zócalo varisco. La zona de estudio se sitúa en el margen norte de la cuenca del Maestrat, en la parte central del cinturón de pliegues y cabalgamientos de Portalrubio-Vandellòs, e incluye la zona de tránsito de un estilo de deformaci6n de piel fina (N) a piel gruesa (S). Los principales objetivos de esta tesis son caracterizar las estructuras formadas durante la extensión mesozoica y durante la contracción cenozoica, y la influencia de las primeras en la formaci6n de las segundas, asf como caracterizar c6mo se produce el transito de una zona con deformaci6n de piel fina a una de piel gruesa. Finalmente, se pretende proponer un modelo de evolución cinemática del margen norte de la cuenca y una reconstrucción de la geometría del Cabalgamiento de Zócalo del Maestrat. Este estudio está basado en la interpretación de datos de subsuelo (sísmica 2D y sondeos de exploración) y de nuevos datos de campo. En cuanto a la estructura Mesozoica, durante la primera etapa de rift (Pérmico superior-Triásico superior) se formó un sistema de fallas normales de alto ángulo que fragmentaron el zócalo varisco en un sistema de horsts, grabens y semi-grabens. Estas fallas fueron activas durante el depósito de la facies Buntsandstein, hasta que se depositó la parte inferior de la facies Muschelkalk medio, rellenando el sistema de horsts y grabens, y dando lugar a diferencias de espesor deposicionales en esta unidad evaporítica. La parte superior de la facies Muschelkalk medio sobrepasó y cubrió el sistema de fallas, indicando una disminución de la actividad extensiva, que duró hasta que se depositaron los carbonatos de la facies Muschelkalk superior, que presentan una potencia casi constante en toda la cuenca. Mientras se depositaba la facies Keuper, se reactivó la actividad extensiva de algunas fallas normales en el zócalo acustico o infra-salino, desencadenando el flujo de la sal del Muschelkalk medio, que form6 anticlinales de sal y welds, incrementando las diferencias de espesor de esta facies. La edad del flujo de sal se deduce a partir de los reflectores sfsmicos del Keuper, que se disponen en onlap sobre el Muschelkalk superior plegado sobre las acumulaciones de sal. Algunos abanicos de capas también pueden reconocerse sobre pliegues forzados del Muschelkalk superior sobre algunas fallas normales reactivadas en el zócalo acustico. La carga diferencial ejercida por el Keuper habrfa incrementado o favorecido el flujo de sal. Durante el segundo episodio de rift (Jurásico superior-Cretácico inferior) se formó un sistema de fallas normales lístricas segmentadas y conectadas por rampas de relevo, que separaban las diferentes sub-cuencas, tal y como sugiere la distribución de las rocas del Cretácico inferior y de las estructuras extensivas en la zona de estudio, que presentan diversas orientaciones. El relleno de la cuenca del Maestrat, a grandes rasgos se adelgaza hacia el norte, hacia el margen de la cuenca. Aun así, el Cretácico inferior de la sub-cuenca de la Salzedella – la más extensa de la cuenca del Maestrat – presenta una geometría de cuña que se engrosa progresivamente hacia el norte, de 350m a 1100m, hacia el bloque superior del sistema de fallas normales inclinadas hacia el S. Durante el Barremiense la actividad extensiva fue mayor que durante el Aptiense, ya que las unidades barremienses presentan variaciones de espesor más acentuadas, mientras que las aptienses presentan espesores más constantes. Durante la Orogenia Alpina cenozoica la cuenca del Maestrat se invirtió. La inversión del sistema de fallas normales mesozoicas, en su segmento a través del zócalo acústico, generó el Cabalgamiento de Zócalo del Maestrat, de orientación aproximadamente E-W y vergencia hacia el N, que atraviesa toda la cuenca. En el postpaís de la Zona de Enlace se puede observar una extensa zona elevada, de unos 40km de anchura en dirección N-S, que contiene rocas del Cretácico superior y del Cenozoico podo deformadas y sub-horizontales, que se sitúan en cotas entre 1400 y 2000m. En la zona de estudio, esta zona elevada está limitada al norte por el Monoclinal de Calders, de orientación E-W y vergencia hacia el N, que tiene un flanco inclinado hacia el N unos SQ, con una anchura maxima de unos 13km en su parte central, y que genera un escalón tectónico vertical de 800-1200m. Este monoclinal se interpreta como un pliegue de adaptación, a partir del que se deduce una geometría de rellano-rampa-rellano del Cabalgamiento de Zócalo del Maestrat. La charnela sinforme septentrional del Monoclinal de Calders coincide, a grandes rasgos, con el paso de un estilo de deformación de piel gruesa al Sur, a un estilo de deformación de piel fina al Norte. El bajo angulo del flanco inclinado del Monoclinal de Calders, y la gran extensi6n de la zona levantada sugieren un bajo ángulo para el cabalgamiento basal en el zócalo, que estaría enraizado en la corteza superior. Este cabalgamiento tendría una rampa de bajo ángulo (~9º), que se propagaría más de 40km hacia el S, alcanzando una profundidad de unos 7,5km bajo el nivel del mar. Cuando este cabalgamiento llegó a la cobertera mesozoica hacia el antepaís, se propagó a través del nivel de despegue del Muschelkalk medio salino, generando un short-cut casi horizontal, que transportó la cobertera supra-salina y los segmentos de las fallas normales a través de ésta unos 12km hacia el NNE. El desplazamiento del zócalo en el bloque superior de la rampa de bajo ángulo generó la extensa zona elevada, de unos 40km de ancho, mientras que el acortamiento en superficie se acumul6 en la zona externa de la cuenca, situada al N, que contiene la cobertera mesozoica más delgada, formando el cinturón de pliegues y cabalgamientos de Portalrubio-Vandellòs. La estructura del cinturón de pliegues y cabalgamientos de Portalrubio-Vandellòs presenta, en la zona de estudio, una geometría arqueada, convexa hacia el antepaís, hacia el NNE, en el sentido del transporte. La formación de esta geometría se puede atribuir a varios factores: a la presencia de un nivel de despegue salino (Muschelkalk medio) que termina lateralmente, hacia el Oeste; a un alto de basamento (Anticlinal de Montalbán) que habría interactuado con la propagación hacia el norte del frente de cabalgamientos E-W, al oeste de la zona estudiada, y por último a la herencia de la orientación de las fallas normales mesozoicas.

Les structures extensives d'âge Mésozoïque tardif (Crétacé) sont très répandues en Eurasie orientale, depuis la Transbaïkalie en Russie jusqu'à l'intérieur de la Chine du Sud. Elles constituent la plus grande province de distension crustale dans le monde. Cette thèse a sélectionné des structures développées dans trois endroits différents du bloc de Chine du sud en utilisant les méthodes de la géologie structurale, de l'anisotropie de la susceptibilité magnétique et de la géochronologie (U-Pb sur zircon et titanite, U-Th-Pb sur monazite et Ar-Ar sur micas et amphiboles). L'expression des structures extensives diffère selon les endroits étudiés: (1) la ceinture orogénique de HP/UHP Tongbai-Dabie, le long de la bordure nord du bloc de Chine du sud a été remaniée par au Crétacé par la formation d'un antiforme ou d'un dôme métamorphique extensif. Contemporaine de la migmatisation et du magmatisme syntectonique, le régime extensif a commencé à environ 145 Ma et s'est approché de son point culminant vers 130 Ma. Ce qui a été interprété comme le résultat de la suppression de la racine orogénique. Localement, un nouvel épisode de distension vers 110-90 Ma a également été enregistré; (2) le batholite de Dayunshan-Mufushan intrudif dans l'orogène Neoproterozoic Jiangnan se compose de deux phases d'intrusions granitiques d'âge Jurassique (ca. 150 Ma) et Crétacé inférieur (ca. 132 Ma). Le pluton le plus récent s'est mis en place dans un contexte d'extension NW-SE correspondant au processus amincissement crustal du Crétacé inférieur, avec une faille de détachement développée le long de sa bordure ouest; (3) l'anticlinal de Huangling dans le craton du Yangtze est un pli asymétrique d'axe N-S formé entre le Jurassique et le Crétacé inférieur. Sur les deux flancs, la couverture sédimentaire a participé à une série de plis d'effondrement de vergence opposée et de glissements banc-sur-banc des couches. Les exemples étudiés ci-dessus représentent une série de structures d'extension d'âge Crétacé développées dans différents niveaux structuraux: exhumation de croûte inférieure et moyenne de accommodée par un fort étirement, mise en place syntectonique de plutons granitiques avec étirement limité, déformation de la couverture sédimentaire sous une faible extension. Ils indiquent que la Chine du Sud a également participé au régime extensif bien connu en Chine du Nord. Ces résultats apportent des données nouvelles de première main permettant de discuter le cadre tectonique et géodynamiques spatio-temporel du régime extensif du Crétacé sur la marge orientale de l'Eurasie
Late Mesozoic extensional structures are widespread in eastern Eurasia (from Transbaikalia region in Russia to inland South China). They constitute the largest crustal extensional province in the world. This thesis selected extensional structures developed in three different tectonic settings in the South China block. Detailed studies including structural geology, anisotropy of magnetic susceptibility and geochronology (zircon and titanite U-Pb, monazite U-Th-Pb, and mica Ar-Ar) were conducted. The expression of these extensional structures is not the same for each area: (1) the Tongbai-Dabie HP/UHP orogenic belt along the northern edge of the South China block was reworked by Cretaceous extensional antiform or metamorphic core complex. Coeval with migmatization and syntectonic magmatism, the extensional regime started at ca. 145 Ma, and approached its climax at ca. 130 Ma that was signaled by removal of the orogenic root. Locally, a late (110-90 Ma) extensional event was also recorded; (2) the Dayunshan-Mufushan batholith intruding the Neoproterozoic Jiangnan orogen is composed of two phases of granitic intrusions with Late Jurassic (ca. 150 Ma) and Early Cretaceous (ca. 132 Ma) ages, respectively. The late pluton emplaced under a NW-SE extensional setting corresponding to the Early Cretaceous crustal thinning process, with a detachment fault developed along its western margin; (3) the Huangling anticline within the Yangtze craton is a nearly N-S striking asymmetric dome formed between the Late Jurassic and Early Cretaceous. The sedimentary cover on the two flanks was involved in a series of oppositely-directed collapse folding and layer-parallel slipping. These examples of Cretaceous extensional structures in different tectonic levels (exhumation of middle-lower crust by strong stretching, syn-tectonic emplacement of granitic pluton with limited stretching, deformation of sedimentary cover under a weak extension) indicates that South China also was involved into the regional extensional regime coeval with the destruction of the North China craton. These results provide first-hand new structural evidence for further discussing the temporal-spatial framework and geodynamic setting of the Cretaceous extensional tectonics on the eastern margin of Eurasia

The presence of spicule pseudomorphs and an aquiferous filtration system in Mesozoic stromatoporoids confirms poriferan affinity for this previously problematic group. The form, and postulated original siliceous nature of most of the spicules, indicates that the possessors of these were calcified demosponges; others with originally calcareous spicules were calcareans. Different spicule types and arrangements indicate that the possession of a calcareous skeleton is a convergent feature. Previous defining characteristics are found to be invalid and Mesozoic stromatoporoids are redefined as calcified sponges, so that the term 'stromatoporoid' now only refers to a grade of organisation of the calcareous skeleton and not a taxonomic grouping. 'Chaetetids', 'sphinctozoans' and 'sclerosponges' are also polyphyletic groupings, representing grades, where some members of which are calcified demosponges. These groupings should no longer be considered in isolation, as this has previously obscured their true nature. The original mineralogy of late Mesozoic stromatoporoids was probably low-Mg. calcite. Spicule and calcareous skeleton diagenetic lineages are given to enable workers to determine original microstructures. Analogies with Recent calcified demosponges, suggests that the fossil stromatoporoid demosponges produced a primary framework of siliceous spicules bound together with an organic matrix, which probably provided the nucleation sites for subsequent precipitation of the calcareous skeleton. A new taxonomic scheme is presented based on spicule type, arrangement and relationship of this framework to the microstructure of the calcareous skeleton. On the basis of spicule criteria, calcareous microstructure alone is found to be convergent and can no longer be used as a high-level taxonomic feature. Spiculate species are therefore redescribed and placed within the Recent poriferan classification framework. Synonyms are documented and intra-specific variation discussed. The present cnidarian-based nomenclature is replaced by one modified from Recent poriferan terminology. The possession of a calcareous skeleton is probably a relict feature of a previously widespread calcified sponge fauna. It appears that the calcareous skeleton was acquired independently in a number of lineages in the early Palaeozoic, and has subsequently been lost in many.

This thesis is centred around an anatomical study of the cranial osteology of the Mesozoic sphenodontidans, Asiacephalosaurus wangi, Rarojugalosaurus mcgilli, Dianosaurus petilus and Homoeosaurus maximiliani. The first two are newly discovered and have not been studied previously. The third, previously described only in a preliminary fashion, was misinterpreted as a protorosaur. Although many specimens of H. maximiliani have been described (Cocude-Michel, 1963; Faber, 1981) since the species was first named by Meyer (1845), the newly exposed dorsal part of the skull of a new specimen has provided many new cranial features. Consequently, it was necessary to examine, draw and describe all of these sphenodontidans. The descriptions are all original and present a virtually complete picture of the cranial osteology of these genera for the first time. In addition, the different patterns of the middle ear apparatus of the Sphenodontida and the functional problems of the temporal region in the Lepidosauria have been considered. Although use is made of the literature to obtain background data, the conclusions drawn are original unless explicitly stated otherwise. Finally, the detailed descriptions of the four genera have permitted a reassessment of the phylogeny of the Sphenodontida. After reviewing the literature, original conclusions are given.

In the 1960s Oberhauser and Fuchs (palaeontologists working at the Geologische Bundesanstalt in Vienna) described a range of new taxa from the Triassic of Austria that were thought to be the earliest planktonic foraminifera. The first reactions of the palaeontological community were negative but in the subsequent forty years our knowledge of Jurassic planktonic foraminifera has expanded considerably. A thorough re-evaluation of the Oberhauser and Fuchs collections in Vienna has shown that these species are probably not planktonic and that the first planktonic taxa appeared in the Toarcian. This origination in the centre of Western Tethys was followed by a rapid expansion of planktonic foraminifera throughout Peri-Tethys. This expansion is dominated by the genera Conoglobigerina and Globuligerina and while some believe that their separation is straightforward (based on apertural characters) analysis of large assemblages shows that this differentiation is not reliable and requires further analysis not only of holotypes, paratypes and topotypes but of large assemblages. In Southern Poland, Middle Jurassic limestones in the Pieniny Klippen Belt are described as foraminiferal packstones and represent the first evidence of a foraminiferal ooze on the ocean floor. This indicates that, by the mid-Jurassic, there was an oceanic stratification of the Aragonite and Carbonate Compensation Depths and that the modem ocean system had developed, although the depths of these various layers may have been different to those of the present day. By the Oxfordian a relatively diverse planktonic fauna had expanded throughout Peri- Tethys and, probably, around the globe in the tropics. The fauna expanded further in the early Cretaceous as Gondwana fragmented but data across the important Jurassic to Cretaceous transition is extremely limited and requires further investigation.

This PhD project contains two related parts, both linked by a study of belemnites. The first part is to test the validity and quality of belemnite palaeo-environmental proxies, and the second to investigate the feasibility of U-Pb dating of Mesozoic carbonates. In the first part, a wide range of well-preserved Mesozoic belemnites was analyzed for bulk stable isotope and trace element compositions, so as to access species-specific effects on compositions and to evaluate belemnite palaeo-proxies (notably δ18O, δ13C, Mg/Ca and Sr/Ca) as palaeo-temperature indicators. Then, high-resolution profiles of trace elements (Mg, Ca, Sr, Na, etc.) were obtained from those best-preserved specimens by electron microprobe and laser ablation-ICP-MS, and compared with the bulk analysis for a better understanding of intro-rostral variations. Results of four different belemnite polulations with differing ages and from differing stratigraphic levels show that Mg/Ca ratios in bulk analysis neither correlate with δ18O within one single species nor within one belemnite population. Mg/Ca is therefore not considered as a palaeo-temperature indicator for belemnites. Variations in Mg profiles along belemnite cross-sections are then interpreted to likely reflect the changes of ontogeny and growth rate. Part two is to apply U-Pb dating method to Mesozoic belemnites and other carbonates. An innovative approach of dating carbonates in deep time has been developed, using both laser-ablation MC-ICP-MS and isotope dilution measurements; and ages with the highest achieveable precision (±1%) and accuracy for Mesozoic calcite cements from three separate ammonites have been produced. Part I contains chapters 1 to 8. Chapter 1 gives a brief account of belemnites (e.g. the morphology, biogeography, palaeo-proxies and palaeo-ecology) and problems that need addressing in belemnite studies; and chapters 2-8 then focus on the geochemistry (isotopic ratios and elemental compositions) of belemnites from four different Mesozoic stratigraphic levels of Europe (Pliensbachian of Yorkshire, Toarcian of Dorset, Callovian of Oxfordshire and Valangigian of Vergol, SE Fance). Part II only contains chapter 9 which presents the U-Pb dating work of a range of Mesozoic carbonate samples.

A well preserved, fossiliferous Middle Triassic to Early Cretaceous section lies on the west side of Harrison Lake in the southern Coast Mountains. The study of this area involves a re-evaluation of the stratigraphic nomenclature first described by Crickmay (1925, 1930a) together with a lithologic description of the units and age determinations based on collected, identified and described fossils by the writer. Discussions on the biostratigraphy, paleogeography, regional correlations and structure of the thesis area and an overview of the regional tectonics of southwestern British Columbia and northwestern Washington, help to better understand the relation of this Mesozoic section to other rock assemblages in this geologically complex region. The oldest unit, the Middle Triassic Camp Cove Formation, comprises conglomeratic sandstone, siltstone and minor volcanic rock. Unconformable7 overlying this unit is the Toarcian to Early(?) Bajocian Harrison Lake Formation, divided into four distinct members by the writer, Celia Cove Member (basal conglomerate), West Road Member (siltstone, shale), Weaver Lake Member (flows, pyroclastic rocks, minor sediments) and Echo Island Member (interbedded tuff, siltstone, sandstone). Thickness of this formation is estimated at 3000 m. A hiatus probably is present between this unit and overlying shale, siltstone and sandstone of the Early Callovian Mysterious Creek Formation which is 700 m thick. Conformably above this are 230 m of sandstone and volcaniclastic rock of the Early Oxfordian Billhook Creek Formation. Late Jurassic fluvial conglomerate, sandstone and siltstone of the Kent Formation, perhaps 1000 m thick south of Harrison River, unconformably(?) overlies the last two units mentioned. Berriasian to Valanginian conglomerate and sandstone, 218 m thick, of the Peninsula Formation overlies the Billhook Creek Formation with slight angular unconformity. The Peninsula Formation is conformably overlain by tuffaceous sandstone, volcanic conglomerate, crystal tuff and flows of the Valanginian to Middle Albian Brokenback Hill Formation which is several km thick. Nine Jurassic ammonite genera are identified and described in this report. Triassic radiolaria and conpdonts and Cretaceous ammonites and bivalves are also present in the section. The most significant structure in the thesis area is the post-Albian to pre-Late Eocene Harrison Fault which strikes north-northwest through Harrison Lake, separating the Mesozoic section along the west side from the northern extension of the Cascade Metamorphic Core on the east side of the lake. A strong sub-horizontal stretching lineation within the fault zone may indicate right-lateral strike-slip movement.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate

The Domeyko basin of northern Chile records Late Triassic-Early Cretaceous mixed carbonate and siliciclastic marine deposition along the western margin of Gondwana. The carbonate and siliciclastic ramp environment is characterised by the deposition of siliciclastic-dominated sediments at times of low accommodation space (lowstand and late highstand systems tracts) and carbonate-dominated sediments during periods of high accommodation space (transgressive and early highstand systems tracts). Along strike variations in siliciclastic sediment supply do not overprint the effects of basinwide changes of relative sea-level. Sequence stratigraphical analysis identifies five second-order sequences resulting from changes in accommodation space and hence, relative sea-level. Within these second-order cycles a higher-frequency cyclicity has also been identified. Each second-order sequence is composed of between 3 and 5 high-frequency sequences which results in a second-order composite sequence, but does not produce the "typical" sequence-sets normally associated with composite sequences. Comparison of the relative sea-level fluctuations interpreted from the Domeyko basin succession with those documented from other similar age South American marginal basins and northern hemisphere basins allows the distinction of regional from global events, and a methodology for potentially differentiating between eustatic and tectonic driving mechanisms. The choice of these basins permits an objective analysis of relative sea-level change using basins of different tectonic setting, on different continental plates. Relative sea-level fall in the late Early Sinemurian, earliest Pliensbachian, earliest Aalenian, Early Callovian, earliest Valanginian, and rises in the earliest Hettangian, earliest and Late Toarcian, Early and Late Bajocian, Late Bathonian and earliest Oxfordian of the Dorneyko basin appear time-equivalent to similar events in other southern and northern hemisphere basins and thus are interpreted to be products of eustatically driven, global sea-level cycles. Relative sea-level falls in the earliest Bathonian, Late Oxfordian, earliest Valanginian and rises in the Late Kimmeridgian are interpreted to be tectonically-driven, continental-scale changes in accommodation space. Although the earliest Valanginian relative sea-level fall can also be seen globally the sequence boundary is interpreted to be tectonically-enhanced by documented regional uplift in Chile and Argentina. The Domeyko basin succession appears to be dominantly controlled by global sea-level fluctuations during the Early-Middle Jurassic, interpreted to have been driven by glacio-eustasy, and by continental-scale fluctuations during the Middle Jurassic to mid-Cretaceous. Mesozoic back-arc basins of western South America record both eustatic and subduction-related relative sea-level fluctuations. To date, the latter have been assumed to be driven chiefly by Pacific plate spreading. However, five tectonically-driven sequence boundaries in the Domeyko and Neuquen basins which have no time correlative expressions in northern hemisphere basins display a close temporal association with five major Gondwanan fragmentation phases. They are: (A) the earliest Bathonian (170 Ma) sequence boundary was driven by the separation of Laurasia and Gondwana; (B) the Late Oxfordian (157 Ma) salinity crisis was driven by the separation of west from east Gondwana; (C) the termination of the marine Domeyko basin was driven by the fragmentation of east Gondwana; CD) the termination of the marine Neuquen Basin (114 Mal was driven by the opening of the South Atlantic; and (E) the major basin inversion associated with the Peruvian tectonic event (100 Mal was driven by the final fragmentation phase within east Gondwana. It is deduced that plate reorganisation associated with the initiation of new oceans during Gondwanan fragmentation resulted in increased coupling along the Andean subduction zone producing regional uplift and thus relative sea-level fall. Responses variously involve: basin barring and Kimmeridgian evaporite production; erosively-based fluvial sandstones directly overlying offshore marine deposits; closure of the Rocas Verdes oceanic marginal basin; sequential termination of marine conditions in the Domeyko and Neuquen back-arc basins; sudden influx of arc-derived alluvial conglomerates resulting from the onset of contractional tectonics; and an incremental jump in the eastward propagation of the Andean volcanic arc. Discrete contractional episodes in the otherwise extensional Andean active margin were thus driven by the incremental spreading phases of the supercontinent. Associated thermal signatures are recorded near the centre of Gondwana by kimberlite emplacement frequency maxima in southern Africa. Plate tectonic theory emphasises the dynamic interaction between adjacent plates, whereby relative rates of motion can be fixed to either the underriding or overriding plate as a reference frame. With reference to the circum-Gondwana subduction zone, I believe that in the past an overemphasis has been placed on the motions of oceanic plates in the Pacific region, while overlooking the role that the thermal evolution of the Pangean supercontinent played in driving circum-Pangean subduction. Thus, careful sequence stratigraphical analysis of active margin sedimentary basins provides a high resolution record, presently under-utilised in detecting, identifying and analysing global tectonic events in time.

Studies of Vibroseis reflection profiles over the exposed Triassic-Jurassic Culpeper, Richmond, and Scottsville Basins, and another profile over a probable early Mesozoic basin (Toano) beneath the Atlantic Coastal Plain sediments, in Virginia indicate that resolution of the geometry of the basins is inhibited by small impedance contrasts between the rock units within the basin and those bordering the basin. None of the seismic sections exhibit reflections which can be directly attributed to a Triassic-pre-Triassic interface. Resolution of the geometry of the basin sediments depends upon the presence of anomalously high or low velocity/density rock units within the basin, and similarly the presence of large amplitude reflections from within these and possibly other basins may imply the presence of these units, which include basalt and lignite. A method of analyzing the refracted waves in the seismic reflection data with large receiver offsets for determination of apparent velocities and the geometry of the refraction interface is presented. The Culpeper seismic lines indicate a basin with a maximum thickness of 2500 m along the western side and approximately 1750 m along the eastern side of the basin. The maximum thickness of the Richmond Basin below the seismic line is approximately 2700 m. The Scottsville Basin contains sedimentary strata with a thickness of 1750 m and the seismic data from the Toano Basin indicate a thickness of 3000 m. The compressional wave velocity of the strata within these basins has a range of 4000-5300 m/sec.
M.S.

Marine upwelling occurs when surface currents diverge or are deflected. Deeper water, often nutrient-rich, rises and generates a cascade of biological effects including elevated productivity and a unique assemblage of organisms. Macrofaunal characteristics of upwelling provide key evidence for oxygen-minimum zones, upwelling of cool water, and high productivity and are potentially useful indicators of ancient upwelling. The Upper Triassic Luning Formation in Nevada contains abundant, large ichthyosaurs and was deposited in a back-arc basin that could have experienced upwelling conditions. Luning Formation rocks at West Union Canyon were analyzed for sedimentological, geochemical, and paleontological upwelling indicators. Abundant suspension feeders, lack of corals and calcareous algae, modest total organic carbon and minor element concentrations in deeper marine facies, abundant cosmopolitan molluscs but no taxa restricted to low latitudes, and abundant fecal pellets and clotted fabrics in most facies suggest that upwelling could have influenced Luning deposition. Moderate-scale upwelling likely contributed to eutrophic conditions and ichthyosaur abundance at West Union Canyon. Marine reptiles might have had ties to upwelling areas to provide food, as do modern whales. A relational database containing 817 locality records and 1365 taxon-localities was assembled for ichthyosaurs, plesiosaurs, and mosasaurs. Marine reptile localities were compared with model-predicted upwelling and with upwelling-related lithologies (organic-rich rock, biogenic silica, phosphorite, and glauconite). Marine reptile occurrences intersected predicted upwelling more often than expected by chance for the Upper Cretaceous, Callovian, and Norian stages, and for all of the data together (P = 0.05). For age-restricted data, occurrences of Mosasauridae, Pliosauridae, and Plesiosauria intersected upwelling more often than expected by chance (P = 0.05). Average shortest distances between reptile fossil and upwelling lithology occurrences were smallest (one grid cell adjacent or smaller) for the Pliensbachian and four of five Cretaceous stages. Analytical biases and other aspects of reptile ecology may have affected the results, but overall, upwelling could have influenced marine reptile distribution, particularly for the Upper Cretaceous. Multiple radiations into the high-productivity, top-predator niche over the Mesozoic are suggested by the dominance of different taxa in grid cells containing upwelling lithologies: ichthyosaurs (early Mesozoic), plesiosaurs (middle Mesozoic), and finally mosasaurs (late Mesozoic).

The stratigraphy and sedimentology of Mesozoic carbonate platform-margins cropping out in southern Italy are investigated. New strati graphic data are presented from northern and eastern slopes of the Apennine carbonate platform, based on locallycorrelated field sections. Thin-section petrography is used to demonstrate the spatial and temporal distribution of derived lithoclasts. Results indicate that southern Apennine platforms underwent repeated erosion during Cretaceous time and possible reasons for this are discussed. Petrographic studies also provided outline sediment parageneses for slopes and platforms, with special reference to the detailed geochemistry of secondary dolomite formation on the eastern margin of the Apulian platform, whose growth is indicated by proton microprobe microanalysis to have been influenced by redox changes. The sedimentary facies and sediment geometries of Upper Cretaceous to Lower Tertiary slope sediments mapped in the Frosolone area are discussed in a case-study. Cross-sections showing geometries of key beds are presented, and depositional controls are discussed. Outcrop data suggest an Early to Middle Jurassic age of basin formation of this sector of the Lagonegro-Molise basin. A further case study from the Mesozoic slope in the Gran Sasso shows sediment geometries at reflection seismic scale, and relates them to possible depositional control by relative sea-level fluctuations. Finally, data from southern Apennine platforms and basins are combined in a tentative sequence stratigraphic framework for the Middle Cretaceous. The results of onedimensional subsidence modelling are presented in order to separate and describe the signals of local tectonics and relative sea-level fluctuations affecting the southern passive-margin of Mesozoic Tethys.

La ceinture orogénique de Longmenshan (LMTB) constitue la frontière orientale du plateau tibétain, qui est reconnue par sa topographie escarpée, son activité tectonique intensive ainsi ses la complexité de ses structures. Comme une orogène typique, le LMTB a subi une forte déformation intracontinentale au cours du Mésozoïque. Ainsi, la connaissance sur l’évolution tectonique du Mésozoïque de la LMTB est cruciale pour comprendre l’orogenèse intracontinentale et la surrection du plateau tibétain. Une ceinture de clivage verticaux divise la LMTB en une zone occidentale et une orientale. La Zone orientale présente un top-to-SE cisaillement tandis que la zone occidentale présente un top-to-NW cisaillement. La zone orientale peut être subdivisée en quatre sous-unités avec de foliations orientées du SE au NW. Le granite syntectonique et les données géochronologiques contraignent cette déformation principale au Mésozoïque inférieur (environ 219 Ma). L’analyse structurale, l’AMS, l’étude microstructurale et la modélisation gravimétrique sur le complexe de Pengguan, l’un des complexes de l’orogène néoprotérozoïques au milieu de segment de la LMTB), révèlent une structure des slices du socle imbriquées de la LMTB et la zone adjacente. Les âges connus, l’exhumation rapide localisée et la subsidence du bassin flextual suggèrent que les slices du socle sont imbriquées au cours du Mésozoïque supérieur (166-120 Ma). La LMTB se trouve loin de la limite de la plaque contemporaine, et est absence de matériel ophiolitique, donc elle peut être considéré comme une orogène intracontinentale. Pendant le début du Mésozoïque, le Yangtze plate subductait vers l’ouest en fermant l’océan paléo-Téthys. Cette tectonique a exhumé des matériaux de différentes profondeurs en surface par des chevauchements vers le SE et chevauchements arrières vers le NW. Au cours de la fin du Mésozoïque, le socle a été soulevé davantage en raison de la collision entre les blocs de Lhasa et de l’Eurasie, qui a conduit à une imbrication des slices du socle et épaissi la croûte
The Longmenshan Thrust Belt (LMTB), constituting the eastern boundary of the Tibetan Plateau, is well known by its steep topography, intensive tectonic activities and the complicated structures. As a typical composite orogen, the LMTB experienced extensive intracontinental deformation during the Mesozoic. The knowledge on the Mesozoic tectonic evolution of the LMTB therefore is crucial to understand the intracontinental orogeny and uplifting of the Plateau. The vertical cleavage belt divides the LMTB into a Western Zone and an Eastern Zone. The Eastern Zone displays a top-to-the-SE shearing while the western zone a top-to-the-NW shearing. The Eastern Zone can be further divided into four subunits with foliations deepening from SE to NW. The syntectonic granite and published geochronologic data constrain this main deformation to the Early Mesozoic around 219 Ma. Structural analysis, AMS and microstructural study and gravity modeling on the Pengguan complex, one of the orogen-parallel Neoproterozoic complexes located in the middle segment of the LMTB, reveal a basement-slice imbricated structure of the LMTB and adjacent areas. Published ages, localized fast exhumation rate and flexural subsidence of the foreland basin suggest that the basement-slices imbricated southeastwards during Late Mesozoic (166-120 Ma). The LMTB is far away from the contemporaneous plate boundary and devoid of ophiolite-related material, therefore, it is supposed to be an intracontinental orogen. During the Early Mesozoic, the Yangtze basement underthrusted westwards due to the far-field effect of the Paleo-Tethys’ obliteration, and the materials in different structural levels have been exhumated to the surface by southeastward thrusting and contemporaneous backward thrusting. During the Late Mesozoic, the basement is further underthrusted due to the collision between the Lhasa and Eurasia blocks, which led to SE-ward imbrication of the basementslices that may thicken the crust

The aims of the study were to elucidate the stratigraphy, sedimentology and geochemistry of latest Jurassic - late Cretaceous Campania - Lucania platform carbonates in southern Italy. Eight formations and fifteen biozones have been proposed and described, representing platform carbonates and basin margin sediments. Most formations are isochronous, but the Lower Cretaceous Monte Faito Formation is diachronous, becoming younger and thinner from northwest to southeast across Campania, as a result of tectonically induced differential subsidence. The biostratigraphy indicates a late Cretaceous fauna/floral divergence between the Campania - Lucania and other Periadriatic platforms from a common late Jurassic biota. The sedimentary sequence reflects the development of a Bahamian type epioceanic platform. Restricted environments were characteristic of the late Jurassic and early Cretaceous while open marine, cyclic peritidal sediments were widespread during the late Cretaceous. Basin margin sediments include Jurassic pelagic radiolarian limestones, Cretaceous debris flows and Tertiary planktonic foraminiferal limestones. The western margin of the platform was probably a fault -bounded escarpment. Two large scale transgressive - regressive sequences (late Jurassic - mid Cretaceous) partly correspond to eustatic sea level fluctuations. The relatively simple diagenetic history has been locally complicated by dolomitisation and / or silicification. Early cements are uncommon, locally restricted and are non-luminescent. Late burial cements luminesce dull orange. Fabrics indicate several phases of dolomitisation; early syndepositional types occur but dolomitisation was largely the result of burial diagenesis. Magnesium was probably derived from pore fluids released by the compaction of shales in the Tyrrhenian Basin to the west. Geochemical trends reflect clay minerals and diagenetic history particularly dolomitisation. Palaeogeographically the Campania - Lucania and Latium - Abruzzi platforms were probably part of the same structure during the late Jurassic and early Cretaceous, becoming increasingly separated from each other through the late Cretaceous, during the closure of Tethys.

The primary goal of numerical palaeobiology is to understand the processes that generate and eliminate extinct and extant biodiversity. It is important to examine key clades and adaptive assemblages, whose evolution appears intrinsically related to major events in deep time. Mesozoic marine reptiles represent an excellent candidate for investigation, having ascended to ecological dominance in the aftermath of the Permo-Triassic mass extinction and passed through multiple biotic crises. Observations from the rich Triassic marine reptile fossil record highlight diverse ecologies, providing tentative evidence for an exceptional radiation driven by new trophic opportunities - but quantitative tests for this are scarce. Others have highlighted the potential long-term impacts of extinction, and revealed that ichthyosaur evolution was reset following an extinction interval in the Late Triassic. Although a recent body of research has provided new insights into marine reptile macroevolution, many questions remain unanswered. In this thesis, I present several diverse case studies exploring the impacts of ecological opportunity and biotic perturbations in Mesozoic marine reptile macroevolution. Throughout, focus is placed on examining temporal and group-wide patterns of morphological and functional diversity (disparity) and testing rates of phenotypic evolution. Chapters 2-4 focus on Sauropterygia, the most diverse and ecologically disparate Mesozoic marine reptiles, while chapter 5 incorporates all Mesozoic marine reptiles as an inclusive adaptive assemblage. In brief, results show that the Triassic was a time of unusual diversification and high disparity in marine reptile evolution. Multiple lines of evidence show the Triassic was a time of marked morphological, functional and ecological proliferation. Results herein also reveal that sauropterygians, and marine reptiles as a whole, passed through a macroevolutionary bottleneck during the Late Triassic, similar to that identified for ichthyosaurs previously. Overall, this thesis supports the idea that major extinction events can have disproportionate effects on macroevolution, by catalysing exceptional radiations in their aftermath.

Through the first detail geochronological, sedimentological and stratigraphic analysis, this thesis provides new insights into the depositional and tectonic history of the Late Triassic to Middle Jurassic intracontinental basin in southeastern South China, and discusses the geodynamic processes that controlled rapid continental vertical movements. Stratigraphic evolution, basin filling pattern and accompanied magmatism are interpreted to be the consequence of a flat subduction and subsequent delamination and foundering of an oceanic plateau.

Mesozoic tectonic inversion in the Neuquen Basin of west-central Argentina produced two main fault systems: (1) deep faults that affected basement and syn-rift strata where preexisting faults were selectively reactivated during inversion based on their length and (2) shallow faults that affected post-rift and syn-inversion strata. Normal faults formed at high angle to the reactivated half-graben bounding fault as a result of hangingwall expansion and internal deformation as it accommodated to the shape of the curved footwall during oblique inversion. Contraction during inversion was initially accommodated by folding and internal deformation of syn-rift sedimentary wedges, followed by displacement along half-graben bounding faults. We suspect that late during inversion the weight of the overburden inhibited additional fault displacement and folding became the shortening-accommodating mechanism. A Middle Jurassic inversion event produced synchronous uplift of inversion structures across the central Neuquen Basin. Later inversion events (during Late Jurassic, Early Cretaceous, and Late Cretaceous time) produced an "inversion front" that advanced north of the Huincul Arch. Synchroneity of fault reactivation during the Callovian inversion event may be related to efficient stress transmission north of the Huincul Arch, probably due to easy reactivation of low-dip listric fault segments. This required little strain accumulation along "proximal" inversion structures before shortening was transferred to more distal structures. Later inversion events found harderto- reactivate fault segments, resulting in proximal structures undergoing significant inversion before transferring shortening. The time between the end of rifting and the different inversion events may have affected inversion. Lithosphere was probably thermally weakened at the onset of the initial Callovian inversion phase, allowing stress transmission over a large distance from the Huincul Arch and causing synchronous inversion across the basin. Later inversion affected a colder and more viscous lithosphere. Significant strain needed to accumulate along proximal inversion structures before shortening was transferred to more distal parts of the basin. Timing of inversion events along the central Neuquen Basin suggest a megaregional control by right-lateral displacement motion along the Gastre Fault Zone, an intracontinental megashear zone thought to have been active prior to and during the opening of the South Atlantic Ocean.

Structural restoration has been carried out on the northern North Sea (60-62ºN), based on the reprocessed, interpreted and depth converted seismic lines NSDP84-1 and 2. Two major rifting events have previously been recognized in the area during the Mesozoic: the Permo-Triassic and Jurassic extension phases. Different structures were formed or, in some cases, the same structures were reactivated during the Permo-Triassic and Jurassic rifting phases. Permo-Triassic rifting affected a 125 km wide area from the Oygarden Fault Zone in the east to the Hutton Fault alignment in the west.. By measuring the length of the profiles before and after faulting, the restorations show that the stretching factors for upper crustal stretching during the Permo-Triassic rifting are 1.11 (11%) for NSDP84-1 and 1.10 (10%) for NSDP84-2 respectively. The Jurassic rifting was confined to a narrower zone mainly in the Viking Graben with the major faults formed on the western side of the graben. Low angle faults are identified in the western flank of Viking Graben in the Tampen Spur area. Low angle supra-basement detachments formed in the late Jurassic are found in Gullfaks area, beneath the Gullfaks Sør block and SE of the Visund fault block. Intra-basement detachments are also found in Tampen Spur area. These detachments are formed by normal faults which flatten in the basement. From the restorations, the stretching factor for the Jurassic rifting is calculated to be 1.12 (12%) for NSDP84-1 and 1.19 (19%) for NSDP84-2. The total extensions for the two rifting phases combined are 1.24 (24%) and for NSDP84-1 and 1.30 (30%) for NSDP84-2. Stretching factors (&#946;) can also be measured by crustal thickness changes, stretching is measured before and after rifting for different area (Horda Platform, Shetland Platform, Viking Graben, and Tampen Spur), and &#946;mean calculate for the Permo-Triassicxrifting phase are calculated 1.25 and 1.16 for NSDP84-1 and 2 respectively. For the Jurassic rifting &#946;mean is calculated as 1.16 for NSDP84-1 and 1.17 for NSDP84-2. These values are similar to previous published results using the same methods in the Northern North Sea and represent the minimum amounts of upper crustal extension on large seismically resolved faults.