Search results for "raton"
showing 10 items of 156 documents
Kinematic and sedimentological evolution of the Manyara Rift in northern Tanzania, East Africa
2005
We describe the stratigraphical/sedimentological and structural evolution of the Manyara Rift in the Tanzania Divergence Zone, East Africa. The rift-related Manyara Beds on the shoaling side of the Manyara Rift were deposited between <1.7 and 0.4 Ma and can be separated into a lacustrine lower member and a fluvial upper member. The transition from lacustrine to fluvial sedimentation at ∼ 0.7 Ma appears to be related to a southward shift of major rift faulting. Fault geometry and the kinematics of the faults are consistent with major faulting during NE/E-directed extension. There is also evidence for other extensional directions including radial extension, which might be caused by magmati…
Melt infiltration of the lower lithosphere beneath the Tanzania craton and the Albertine rift inferred from S receiver functions
2012
[1] The transition between the lithosphere and the asthenosphere is subject to numerous contemporary studies as its nature is still poorly understood. The thickest lithosphere is associated with old cratons and platforms and it has been shown that seismic investigations may fail to image the lithosphere-asthenosphere boundary in these areas. Instead, several recent studies have proposed a mid-lithospheric discontinuity of unknown origin existing under several cratons. In this study we investigate the Tanzania craton in East Africa which is enclosed by the eastern and western branches of the East African Rift System. We present evidence from S receiver functions for two consecutive discontin…
Influence of pre-existing fabrics on fault kinematics and rift geometry of interacting segments: Analogue models based on the Albertine Rift (Uganda)…
2011
This study aims at showing how far pre-existing crustal weaknesses left behind by Proterozoic mobile belts, that pass around cratonic Archean shields (Tanzania Craton to the southeast and Congo Craton to the northwest), control the geometry of the Albertine Rift. Focus is laid on the development of the Lake Albert and Lake Edward/George sub-segments and between them the greatly uplifted Rwenzori Mountains, a horst block located within the rift and whose highest peak rises to >5000 m above mean sea level. In particular we study how the southward propagating Lake Albert sub-segment to the north interacts with the northward propagating Lake Edward/George sub-segment south of it, and how this i…
Rift-controlled fluvial/tidal transitional series in the Oukai¨meden Sandstones, High Atlas of Marrakesh (Morocco)
1996
Abstract The Carnian formation of the Oukai¨meden Sandstones was deposited in the northwestern corner of the African craton along tectonic troughs grouped as a WSW-ENE rift system on the southwestern margin of the Tethys. Red sandstones represent mainly distal braided-stream deposits where very extensive sand flats with 3D dunes, 2D sand waves and high-regime horizontally laminated sandstones predominate. The similarities in orientation between current patterns and trough border faulting, the sudden large variations in the thickness of deposits and the occurrence of lateral alluvial fans along the marginal faults are all evidence of the tectonic control of sedimentation. The middle part of …
The building blocks of continental crust: Evidence for a major change in the tectonic setting of continental growth at the end of the Archean
2013
Abstract Oceanic arcs are commonly cited as primary building blocks of continents, yet modern oceanic arcs are mostly subducted. Also, lithosphere buoyancy considerations show that oceanic arcs (even those with a felsic component) should readily subduct. With the exception of the Arabian–Nubian orogen, terranes in post-Archean accretionary orogens comprise 50%) produced in continental arcs. Felsic igneous rocks in oceanic arcs are depleted in incompatible elements compared to average continental crust and to felsic igneous rocks from continental arcs. They have lower Th/Yb, Nb/Yb, Sr/Y and La/Yb ratios, reflecting shallow mantle sources in which garnet did not exist in the restite during m…
Deformation history of the Hengshan Complex: Implications for the tectonic evolution of the Trans-North China Orogen
2007
Abstract Structural analysis indicates that the Hengshan Complex underwent five distinct episodes of deformation (D1–D5). The D1 episode formed small isoclinal folds (F1), penetrative axial planar foliations (S1) and mineral stretching lineations (L1). D1 fabrics were reworked by following D2 deformation. Associated with D2 was the development of NW-verging asymmetric folds and accompanying thrust faults. Both D1 and D2 resulted from crustal thickening and coherent with prograde and peak metamorphism. D2 deformation was followed by transpressional dextral shearing (D3), including top-to-NW oblique-slip shearing and NNE–SSW dextral strike-slip shearing. Ongoing collision led to development o…
Efecto de la hipoxia moderada en la adaptación pulmonar, estado oxidativo y respuesta inflamatoria en ratones nacidos en hipoxia con transición a air…
2022
El oxígeno, necesario para la vida y los procesos metabólicos del organismo, puede causar daño celular y tisular por el incremento de especies reactivas del oxígeno, llegando a producir un estrés oxidativo. De hecho, la propia transición fetal neonatal (TFN) supone un estrés oxidativo fisiológico para el feto que pasa de un ambiente de relativa hipoxemia, de 3,5-4,4 kPa, a 10.5 kPa en el momento del nacimiento, en pocos minutos. Pero este estrés oxidativo, en condiciones normales, es necesario para el desarrollo y funcionamiento del organismo. Es en otras situaciones como el nacimiento prematuro, en el que el sistema antioxidante no está completamente maduro, cuando se produce un desequilib…
Juoksemisen merkitykset suomalaisessa postmodernissa juoksukirjallisuudessa : sisällönanalyysi valmennusoppaasta, elämänkerrasta ja kaunokirjallisest…
2014
Tämän pro gradu -tutkielman tarkoituksena on selvittää, millaisia merkityksiä juoksemiselle annetaan suomalaisessa postmodernissa juoksukirjallisuudessa ja miten nämä merkitykset ilmenevät suhteessa identiteettiin ja elämäntapaan. Lisäksi tutkin elämyksiä, joita juokseminen harrastajalleen tarjoaa sekä sitä, millaiseen fyysiseen ja sosiaaliseen kontekstiin juokseminen sijoittuu. Tutkimusaineistonani toimii kolme postmodernina aikana julkaistua juoksemiseen liittyvää kirjaa. Teokset poikkeavat toisistaan sekä sisällöltään että orientaatioltaan, sillä yksi on valmennusopas, toinen on elämänkerta ja kolmas on essee- ja runotyyliä edustava kaunokirjallinen teos. Tutkimusaineistoon valitut teoks…
Diferencias sexuales en el aprendizaje del Laberinto Hebb-Williams con ratones OF1
2017
espanolEl Laberinto Hebb-Williams es una prueba utilizada para evaluar el aprendizaje espacial en animales. Aunque la capacidad espacial es una funcion cognitiva considerada sexodimorfica, donde los machos muestran una ventaja frente a las hembras, los resultados de los pocos estudios que evaluen diferencias de sexo en esta prueba no son concluyentes. Por ello, en este estudio nos propusimos comprobar si los ratones OF1 machos ejecutaban mejor que las hembras las tareas del Laberinto Hebb-Williams, y si esa ventaja era independiente de la dificultad del laberinto. Se utilizo la version reducida para ratones, la cual consta de 5 laberintos, 3 consi-derados faciles y 2 dificiles. Los resultad…