Добірка наукової літератури з теми "Morphogenese quaternaire"

ln the north-west of Portugal, the quaternary glaciation hadn't only reached the mountains of Gerês and Peneda. Also in Cabreira mountain, southward and with low altitude, forms and deposits with origin in the quaternary cold are remarked, even than in a smaller number and of a smaller dimension. This article tries to point out the sheltered character of the glaciation in the culminant massif of Cabreira mountain, as well as to distinguish the two kinds of landscapes present there, derived from an intense gelifraction (slopes with cryoclastic debris) and from glacial morphogenesis.

Abstract The Cévennes are bordering the French Massif Central and the Gulf of Lion margin. The morphogenesis of this area results from an interaction between deep-seated and superficial processes, whose origin and timing is still discussed. We attempt a reconstruction of the surrection and erosion history of the area through a multidisciplinary approach including geology, geomorphology, thermochronology and geochronology. Thermochronology shows that the Cévennes basement underwent some 2 km denudation in mid-Cretaceous time. Analyses of the sediments preserved on uplifted surfaces and in peripheral sedimentary basins indicate a differential surface uplift of the Cevennes, of the surrounding calcareous plateaus, and of the coastal plain, that occurred in several stages during the Tertiary. Early Miocene rifting of the Gulf of Lion margin and opening of the NW Mediterranean drastically modified the drainage network. Geomorphology analyses of the incised rivers and karst network suggest that most of the incision results from uplift that occurred sometime in the Serravalian-Tortonian interval. U/Th dating of calcite concretions in karsts allows to chronologically bracket the formation of some fluvial terraces, and to find very low incision rates during the Pleistocene. Most of the morphogenesis predates the Quaternary. This ongoing study shows an example of polyphased and very slow morphogenesis, with present-day landscape including elements as old as Cretaceous.

Abstract This work is a significant contribution to knowledge of the Quaternary and pre-Quaternary morphogenesis of a wide sector of central Italy, from the Apennine chain to the Adriatic Sea. The goal is achieved through a careful analysis and interpretation of stratigraphic and tectonic data relating to marine and continental sediments and, mostly, through the study of relict limbs of ancient landscapes (erosional surfaces shaped by prevailing planation processes). The most important scientific datum is the definition of the time span in which the modelling of the oldest morphological element (the “summit relict surface”) occurred: it started during Messinian in the westernmost portion and after a significant phase during middle-late Pliocene, ended in the early Pleistocene. During the middle and late Pleistocene, the rapid tectonic uplift of the area and the climate fluctuations favoured the deepening of the hydrographic network and the genesis of three orders of fluvial terraces, thus completing the fundamental features of the landscape. The subsequent Holocene evolution reshaped the minor elements, but not the basic ones.

Les reliefs du sud-ouest tunisien presentent les caracteristiques du relief jurassien avec ses formes d'erosion typiques telles que les combes anticlinales, les monts, les vals, les cluses. . . L'equipement hydrographique des structures de la region montre deux generations hydrographiques : un reseau ante-quaternaire et un reseau quaternaire. Le premier reseau avait ete implique dans la sedimentation neogene du bassin de gafsa. La reconstitution paleomorphologique et l'analyse sedimentologique ont montre que cette region a evolue durant le neogene en bassin sedimentaire quasiment plat qui n'etait pertube que par de modestes bombements. Ce bassin a ete durant le neogene, continuellement comble par differentes nappes detritiques. Au cours de cette periode, le bassin obeissait aux lois du synchronisme subsidence-sedimentation. La sediementation miocene debute par les argiles rouges attribuees a l"aquitanien" puis connait un arret durant le burdigalien-langhien. Les depots de la formation beglia montrent une instabilite des paleoenvironnements. L'orogenese plio-quaternaire met fin au comblement du bassin et engage la region dans une evolution geomorphologique nouvelle
South-western tunisian reliefs show the same jurassian relief characteristics with its typical erosion figures as anticlinal combs, mounts, valleys and cluses. The regional hydrographic structures belong to two generations : a pre-quaternary retwork preceding the quaternary one. The first one was involved in the neogene sedimentation of the gafsa basin ( s-w tunisia). The paleomorphologic reconstitution and the sedimentological analysis proved that this area behaved as a nearly flat basin only disturbed by light deformations. During neogene this basin, was continuously filled with different detrital accumulations thanks to the equilibrium between the rates of subsidence and sediementation. The miocene filling begins with the so called "aquitanian" red shales then marks a stop during the surdigalian-langhian times. The beglia sands deposit, is characterized by the instability of the paleoenvironnement. The plio-quaternary orogeny of the atlasic folding phase puts an end to the gafsa basin filling and inserts the area in a new geomorhological evolution

Ce travail presente l'etude geomorphologique, sedimentologique et paleoenvironnementale du secteur n0 de la serra do ramalho qui correspond un massif carbonate precambrien ou se developpent d'importantes formes karstiques. La caracterisation des domaines geomorphologiques, structuraux, lithologiques et vegetaux a ete realisee a partir de l'etude de terrain, de l'interpretation de photographies aeriennes et d'analyses de l'image tm landsat. L'ensemble de ces donnees a permis l'eboration des cartes de chacun de ces elements. Ce secteur se divise en quatre domaines morphologiques principaux : le plateau avec des couvertures pelitiques precambriennes et greseuses du cretace ; le massif avec des roches carbonatees precambriennes denudees ; le glacis avec les colluvions et les sols rouges et les fonds des vallees. Trois surfaces etagees qui janolent l'encaissement ont ete mises en evidence. Ces surfaces ont ete elaborees par de processus combinant erosion et epirognese, qui ont cause le degagement des couvertures du plateau, l'exhumation du massif, sa karstification et l'enfoncement du reseau du drainage. L'etude du remplissage d'un abri-sous-roche situe a l'interieur du canyon du morro furado, entaille dans la serra do ramalho, a mis en evidence trois unites stratigraphiques liees a ses etapes de formation. Des datations au carbone 14 ont permis de situer l'unite superieure du remplissage dans l'holocene, entre 8040 et 980 bp, avec l'occupation prehistorique. Les analyses physico-chimiques, mineralogiques et palynologiques des sediments ont permis de connaitre la nature, les sources et les conditions climatiques du remplissage : seches a tres seches au pleistocene superieur et moins seches pendant l'holocene
THIS INVESTIGATION PRESENTS A GEOMORPHOLOGICAL, SEDIMENTOLOGICAL AND PALAEOENVIRONMENTAL STUDY OF THE NORTHWESTERN PART OF SERRA DO RAMALHO. THIS CONSISTS OF A LIMESTONE MASSIF OF PRE-CAMBRIAN AGE ON WHICH IMPORTANT KARSTIC LANDFORMS ARE DEVELOPED. GEOMORPHOLOGICAL, STRUCTURAL, LITHOLOGICAL AND VEGETATIONAL CHARACTERISATION OF THE AREAS HAS BEEN ACHIEVED BY FIELD INVESTIGATION, AIR PHOTOGRAPHIC INTERPRETATION AND THE ANALYSIS ONF LANDSAT TM IMAGERY. THE RESULTS OF THIS INVESTIGATION HAVE ENABLED THE PRESENTATION OF MAPS OF EACH OF THESE ELEMENTS. THIS REGION IS DIVIDED INTO FOUR MORPHOLOGICAL AREAS: THE PLATEAU UNDERLAIN BY PRE-CAMBRIAN PELITES AND CRETACEOUS SANDSTONES; THE MASSIF OF EXPOSED PRE-CAMBRIAN LIMESTONES; THE GLACIS with COLLUVIAL DEPOSITS AND READ SOILS, AND THE VALLEY FLOORS. THREE EROSIONAL SURFACES HAVE BEEN IDENTIFIED. THESE SURFACES HAVE RESULTED FROM COMBINED EROSIONAL AND EPEIROGENIC PROCESSES WHICH HAVE CAUSED THE REMOVAL OF THE PELITIC AND ARENITIC ROCKS OVERLYING THE PRE-CAMBRIAN LIMESTONES, EXHUMATION OF THE MASSIF, ITS KARSTIFICATION AND INCISION OF THE DRAINAGE SYSTEM. THREE STRATIGRAPHICAL UNITS HAVE BEEN IDENTIFIED WITHIN INFILLING A ROCK SHELTER IN THE SUBSTANTIAL MORRO FURADO CANYON, INCISED INTO THE SERRA DO RAMALHO. THE FORMATION OF THESE SEDIMENTS IS DISCUSSED. RADIOCARBON DATING HAS SHOWN THAT THE UPPER UNIT, WHICH INCLUDES EVIDENCE FOR PREHISTORIC OCCUPATION, IS OF HOLOCENE AGE (8040-980 BP). THE PHYSICO-CHEMICAL, MINERALOGICAL AND PALYNOLOGICAL ANALYSES HAS ALLOWED THE IDENTIFICATION OF THE SEDIMENTARY CHARACTERICS AND PROVENANCE OF SEDIMENTS. IT HAS ALSO INDICATE THE CONTEMPORANEOUS CLIMATIC CONDITIONS : DRY TO VERY DRY TO PLEISTOCENE AND LESS DRY DURING THE HOLOCENE

Le Sahara Atlantique a pour cadre géographique l'ex Sahara Espagnol et l'extrême Nord Ouest de la Mauritanie. Notre zone d'étude s'étend ainsi sur une superficie de 300 000 km2, compris entre le 20ème et le 30ème parallèle. Ses frontières sont à la fois naturelles ; le bas Oued Draâ (au sud de la boutonnière d'Agadir) au Nord et l'Océan Atlantique à l'Ouest, et pollitiques ; l'Algérie au N-E, la Mauritanie à l'Est et au Sud. Le Sahara Atlantique, où les altitudes supérieures à 400 m sont exceptionnelles, est le domaine des plaines et des plateaux. Ce vaste territoire est traversé par de nombreux accidents structuraux dont le plus important est celui d'Agadir-Timiris-Dakar parallèle à la fracture médio-atlantique, situé à la limite de deux bassins sédimentaires de bordure océanique : le bassin sénégalo-mauritanien et le bassin de Tarfaya-Laâyoune-Dakhla. L'étonnante monotonie (apparente. . . ) de cet espace s'explique, en partie, par l'extension considérable de la dalle moghrébine calcaro-gréseuse (d'âge Villafranchien 2. 5 (?) à 4Ma) à lumachelles et à pectens à l'Ouest et du Socle granitique archéen à l'Est. Cette monotonie localement voilée par des champs de barkhane, est rompue, dans certaines régions, par des reliefs qui, quel que soit leurs volumes, induisent des contrastes saisissants. Cependant, le Sahara Atlantique tout comme l'ensemble de l'Afrique saharienne, a connu les effets des glaciations et des interglaciaires et vraisemblablement des événements (néo)tectoniques plus ou moins importants comme nous le laisse supposer les structures et les rejets observées. Après l'élaboration de l'encroûtement terminal durant le Pliocène moyen /supérieur, sont survenues des crises morphogéniques d'origine tectonique, climatique et marine qui détruisit définitivement l'équilibre des reliefs néogènes. La plus importante des crises se place à la charnière entre le Miocène et le Quaternaire ancien (plio-quaternaire) et constitue un véritable tournant dans l'évolution morphologique du Sahara Atlantique. En effet, de notables modifications des facteurs de la morphogenèse marquent les débuts des temps Quaternaires où des retouches ont été apportées au paysage, et ce dans un contexte d'alternance d'humide et d'aride qu nous connaissons, plus ou moins. Soumis aux conditions d’érosion en climat aride au moins depuis l’Ogolien (15 000-10 000 BP) et post-holocène (5 000-3 000 BP), les terrains anciens, du Précambrien au Cénozoïque, sont masqués par des débris de cette destruction. Ils ne subsistent souvent que des dépôts détritiques Quaternaire de cailloutis générés par l’action combinée de l’érosion fluviatile, éolienne, marine et des processus de la météorisation. Les modelés de glacis, de terrasses et les dépressions atteignent des dimensions supérieures vers l’Ouest. Ainsi, depuis la fin de l’Holocène (3000 BP) date de l’aridification du Sahara, le vent a pris une place de plus en plus importante dans l’édification du paysage actuel, effaçant ou fossilisant progressivement la paléo-topographie et certains dépôts superficiels. Pour le secteur margino-littoral, la morphologie du triptyque désert, falaise, mer est intimement liée à l’évolution des dynamiques hydro-climatiques récentes et à la compétence lithologique des affleurements face aux vents très puissants et dans une moindre mesure aux ruissellements. Par conséquent les alizés, vent de secteur Nord, sont probablement depuis l’Ogolien l’agent fondamental de la morphogenèse du plateau littoral (dénommé « Aguerguer ») comme en témoignent les modelés aérodynamiques que constituent les dunes fossiles, les « fleuves de sables » et les « Yardang »
The Atlantic Sahara is located between the ex-Spanish Sahara and the far North/West part of Mauritania. Our study area is 300 000 km2 big, and lies between the 20th and 30th parallel. Its boundaries are natural (the low Oued Draâ and the Atlantic Ocean on the West side) but also administrative (Algeria on the N-E side and Mauritania on the East and South). With very few points over 400 m over the sea level, the Atlantic Sahara is a plateau and plains area. This huge territory is crossed by several structural accidents whose most important one is the Agadir-Timiris-Dakar accident. This accident is parallel to the medio-atlantic fracture, located just at the boundaries of two sedimentary basins reaching the Ocean (the senegalo-mauritanian basin and the Tarfaya-Laâyoune-Dakhla basin). The surprising (and seeming) monotony of this area can be explained by the important moghrebine limestone-sandy (Villafranchian from 2,5 to 4 Ma) composed by lumachel and pectens shell extension on the West side and the granitic archean layer on the East side. This monotony partly hidden by the barkhane fields disappears din some parts with relieves which induce (whatever its volume) very strong contrasts. However, as the rest of the Saharan Africa, the Atlantic Sahara suffered from glaciations and interglacial effects as well as neotectonic events more or less important (as the present observed structures and rejects let us suppose). After the elaboration of the terminal encrusting during the middle/ upper Pliocene, it occurred some morphogenetic crisis (from tectonic, climatic and oceanic origin) which destroyed definitely the neogenic relives balance. The most important crisis took place between the Miocene and the old Quaternary. It has been a major turning point in the morphologic evolution of the Atlantic Sahara. Indeed some significant modifications of morphogenetic factors put in relief the beginning of the Quaternary era, while the landscape was modified by a wet/arid alternation that we know, more or less at this time. Because of erosion conditions in arid climate since - at least - Ogolian (15 000 - 10 000 BP) and post-Holocene (5 000 - 3 000 BP), old fields from Precambrian and Cenozoic are hidden by the debris of that destruction. Most of time there are only quaternary clastic deposits broken stone left, which are generated by the combined action of fluviatile, wind and marine erosion and the weathering processes. Glacis and terraces’ models such as depressions have larger dimensions in the West. Since the end of the Holocene era (3 000 BP) -Sahara’s aridification beginning - the wind took a more and more important role in the current landscape erection, gradually erasing or fossilizing the paleo-topography and some superficial deposits. On the margino-littoral area, the desert – cliff - sea triptych morphology is closely linked to the evolution of the recent hydro-climatic dynamics and to the lithologic competence of the outcrops that face very powerful winds, and of lesser importance, of run-off. As a result, the trade winds (from North) are probably the fundamental agent of morphogenesis of the littoral shells (named “Aguerguer”) and this since Ogalian era, as proved by the aerodynamic models that form the Barkhanes (fossils), the sand river and the “Yardangs”. Nonetheless, the Atlantic Sahara littoral geosystem is currently in a landscape mutation, following its development. Moreover the Atlantic Sahara geopolitical strakes that process and embrittle the regional development politics in this hostile area and the relief of its ecosystem facing the filling with sand, erosion and land implosion risks to the margino-littoral dynamics

Dans l'espace méditerranéen,le soulèvement vertical d'une dorsale néotectonique est toujours difficile à montrer et à mesurer,en raison même de l'intense dissection qui en découle. Tel est le cas de la dorsale de l'Apennin ombrien qui se superpose,à partir du Pliocène supérieur,aux structures complexes du plissement apennique. Deux styles de déformations quaternaires peuvent être observés : le revers tyrrhénien est haché par un système de grandes failles normales à regard occidental,tandis que le front adriatique est soumis à un soulèvement en masse associé à un basculement à grand rayon de courbure. Cette analyse montre que l'importante multiplication d'étagements continentaux peut être utilisée comme critère de surrection verticale comme cela se fait couramment dans l'analyse des bourrelets littoraux,grâce au repère des plages soulevées
In the mediterranean peninsulas,the general disposition of the main bulks of relief,on a regional scale,takes often the shape of swells or broad ridges. .

Le but de cette thèse est d'étudier le rôle de la tectonique et du climat dans l'élaboration des reliefs de grande et de moyenne échelle. L'approche pluridisciplinaire y constitue le cadre méthodologique. Il est montré que le sillon de Boudenib se situe au croisement de trois unités géotectoniques majeures : planafricaine, hercynienne et atlasique. Cette structuration transparait dans la dissymétrie des formes de relief. Le remplissage sédimentaire a enregistré la totalité des phénomènes qui se sont succédés à l'interieur du bassin et sur ses bordures. L'évolution préturonienne est marquée par le contrôle des facteurs tectoniques, climatiques et eustatiques. À partir du crétacé supérieur, seuls les facteurs tectoniques ou climatiques rythment l'évolution. L'étude du Piémont hamadien de Boudenib apporte des faits nouveaux sur la tectonique atlasique, la nature des dépôts et les alterations associées dont les silicifications y font l'originalité. Deux grands types de silicification ont été distingués : silicification pédogénétique associée à La Hamada de Boudenib I (eocene inférieur) et silicification de nappe affectant la Hamada du Guir (néogene). Enfin, la morphogeneèse tertiaire est marquee par la juxtaposition d'un Piémont d'accumulation à un Piémont d'érosion. La phase fini-pliocène ? met en place les unités de relief majeurs, mais les conditions morphogeniques quaternaires sont plutôt placées sous le contrôle du climat, évoluant vers l'aride, et ce malgré une néotectonique active jusqu'au. .
The purpose of this research is to study the role of tectonic and climat in the elaboration of reliefs of high and middle scale. The pluridisciplinary approch constitues the methodologic frame. It is shown that boudenib grooc is situated in the intersection of three major geotectonic units : panafrican, hercynian and atlasic. The dissymetry of topographical features reflects this structure. The sedimentation recorded the total phenomenon which succeeded inside the basin as well as on the borders. Therefore, dissymetry between eastern and western parts of the boudenib groov has been constant in the evolution. The preturonian evolution was caracterized by the control of tectonic factors, climat and eustatic ones. However, from the upper cretaceous only tectonic and climatic factors predominated. The study of hamadas deposits on the piedmont of boudenib brings new factors about the atlasic tectonic, the kind of deposits and associeted paleoweathering in which silicification makes the originaly. Two types of silicification were difined : pedogenetic silicification in the lower part of "hamada de boudenib" (lower eocene) and ground water silicification in the "hamada de guir" (neogene). Eventually, the tertiary morphogenisis is caracterized by the juxtaposition of two piedmonts : accumulation and erosion. .

Made available in DSpace on 2017-05-12T14:42:07Z (GMT). No. of bitstreams: 1 Andressa_Fachin.pdf: 7147263 bytes, checksum: c3f02dba66f39392f3087baf7f763360 (MD5) Previous issue date: 2013-12-16
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
This thesis presents the paleovalley head evolution in the Chopinzinho drainage basin inside Araucária Plateau (Planation Surface 2), aiming to understand the landscape evolution in the South Brazil during the Upper Quaternary. The stratigraphic record was characterized using the combined criteria of pedo-, litho-, allo-, and cronostratigraphic, for which chronology was establish by 14C (AMS) and thermoluminescence. As base these criteria was utilized following technical: field survey, laboratory analyses (textural, ten major oxides more zirconium oxide, clay mineralogy, and dating) and office work (cluster statistical analysis and organization of date). It has been done the reconstitution spatial distribution of the paleosol and paleogullies by drilling. The field survey showed stratigraphic section in the cutting rural road. Therein was identified paleosol with Ab horizon (27.36 + 0.14 Kyr BP 44.13 Kyr cal. BP), paleogullies field of colluvium (15 beds), colluvium-alluvial (4 beds) and alluvial (1 bed). The colluvium beds was divided into clogging faces and ramp faces. The paleogullies were generated in Last Glacial Maximum (< 24 Kyr to > 17 Kyr BP.) and in Medium Holocene (< 7 Kyr to > 4 Kyr BP). This last moment were generated two paleogullies generations promoting the larger erosion phenomenon in the paleovalley head. The paleovalley head happens to be clogging in the Upper Holocene (< 4 Kyr BP) and change of the morphology becoming colluvium ramp. The palleovalley head was eroded by spot drainage and becoming one convex mound in the end of period. This moment there was one inversion of the relief.
Esta dissertação apresenta a evolução de uma paleocabeceira de drenagem no Planalto das Araucárias (Superfície 2),buscando contribuir para o entendimento do Quaternário Tardio do Sul do Brasil. O registro estratigráfico foi caracterizado utilizando-se dos critérios conjugados da pedo-, lito-, alo- e cronoestratigrafia, cuja cronologia foi estabelecida pelo 14C (AMS) e termoluminescência (TL). Com base nesses critérios foram utilizadas as seguintes técnicas: levantamento de campo, análises laboratoriais (granulométrica, análise química dos 10 principais óxidos + Zircônio,mineralogia da fração argila e ainda datações por 14C e luminescência) e trabalho de gabinete (análise estatística por similaridade Cluster e organização dos dados). Foi feita a reconstituição da distribuição espacial do paleossolo e das paleovoçorocas por meio de sondagens. O levantamento de campo revelou seção estratigráfica exposta em corte de estrada. Nela identificou-se: paleossolo com horizonte A húmico (27.360 + 140 anos AP. 44.130 cal. AP.), paleovoçorocas colmatadas por colúvios (15 camadas), colúvio-alúvio (4 camadas) e alúvios (1 camada). As camadas colúviais foram subdivididas em fácies de colmatação e fácies de rampa.As paleovoçorocas foram geradas no Último Máximo Glacial (< 24.000 a> 17.000 anos AP) e no Holocêno Médio (< 7.000 anos a > 4.000 anos AP). Neste último período foram geradas duas gerações de paleovoçorocas, promovendo o maior fenômeno erosivo na cabeceira de drenagem. A paleocabeceira de drenagem passa a ser colmatada no Holoceno Superior (< 4.000 anos AP) e muda de morfologia para rampa de colúvio. No final desse período, a rampa de colúvio é dissecada pela drenagem local e torna-se uma colina convexa. Nessafasehouveumainversão de relevo.

Suess (1900) provided the first scientific treatment of the South American coast from a tectonic perspective when he distinguished between the Atlantic and Pacific structural styles on opposite sides of the continent. Inman and Nordstrom (1971) later complemented this approach by relating these styles to the concepts of plate tectonics that had emerged during the 1960s. Useful keys to understanding South American coastal processes and sediment supplies were then offered by Davies (1977) and Potter (1994), respectively, while regional accounts of South American coastal landforms were made by specialists in books edited by Bird and Schwartz (1985) and Schwartz (2005). Clapperton (1993) reviewed Quaternary coastal morphogenesis. Coastal sites of scientific importance and historical coastline changes were discussed by Bird and Koike (1981) and Bird (1985). This chapter focuses on the principal factors involved in coastal evolution and morphogenesis, describes key regional landforms, and proposes a new analytical perspective for South America’s coasts by introducing a hierarchical system within coastal groups. The main coastline of South America is approximately 31,100 km long, of which 10,400 km face the Pacific Ocean, 16,700 the open Atlantic Ocean, and the remaining 4,000 km the more sheltered Caribbean Sea. Of the total length, approximately two-thirds lie within the tropics, ensuring that physical and ecological responses to ocean-atmosphere circulation systems involving the Intertropical Convergence Zone dominate these coasts. The remaining one third of the coast beyond the tropics is dominated during part or all of the year by temperate westerly conditions, which become increasingly cool and stormy toward the continent’s southern tip. The origins of the present coast reflect the tectonic forces that have affected the South American plate over the past 200 million years, augmented by relative sea-level changes associated with changing global (eustatic) ocean volume and regional (isostatic) crustal adjustments. The Atlantic coast of South America owes its broad outline to the separation of the continent from neighboring parts of Gondwana that began more than 200 Ma (million years ago). The Pacific and Caribbean coasts have a more complex history, related to the progressive interaction of the westwardmoving South American plate with four oceanic plates with which it has come into contact).