Zugl.: Diss.

The Afar region of Ethiopia is slowly being torn apart by the Red Sea, Gulf of Aden and Main Ethiopian rifts which all meet at this remote, barren corner of Africa. Prior to rifting, volcanism probably started here some 30 million years ago, marked by the arrival of the Afar mantle plume and subsequent eruption of kilometres thick flood basalts. To the north and east the Red Sea and Gulf of Aden rifts have already progressed to become sea-floor spreading centres where new oceanic crust is produced. Active spreading on the Red Sea rift takes a landward step west into Eritrean Afar at approximately 15oN, after which divergence between the Nubian and Arabian tectonic plates is localised into 60 km long, 20 km wide magmatic segments that undergo periodic rifting cycles. This part of Afar is a unique natural laboratory where the process of transition from continental rifting to sea floor spreading can be studied. In September 2005 a dramatic rifting episode began on one such segment of the Red Sea rift in Afar (the Dabbahu magmatic segment), whereby a 60 km long dyke containing an estimated 2.5 km3 magma was intruded in just two weeks, allowing opening of up to 8 m. Since then a further 13 smaller dykes have been intruded, some with fissural eruptions of basaltic lava. Subsidence observed via geodetic observations can only account for a small fraction of the magma supply required to in ate the dykes, suggesting a deep crustal or upper mantle source must exist. The magnetotelluric (MT) method is a passive geophysical technique, used to probe the Earth to reveal subsurface conductivity. The presence of fluids can dramatically increase conductivity by orders of magnitude making the MT method ideally suited to detecting them. MT data collected from 22 sites on profiles near to and crossing the active rift are analysed and interpreted in conjunction with seismic and petrological constraints. They reveal for the first time, the existence of both a mid to lower-crustal magma chamber directly below the rift, and an o -axis zone of partial melt well within the mantle. The volume of melt contained within the crust and upper mantle below the Dabbahu segment is estimated to be at least 350 km3; enough to supply the rift at current spreading rates for almost 30 thousand years, assuming that both melt containing regions supply the rift. Vast amounts of highly conductive material, suggesting the existence of pure melt in places, are also required in the shallow crust close to Dabbahu volcano which lies at the northern end of the segment. Further data collected on the currently inactive Hararo segment which is the next one to the south of Dabbahu, show a smaller zone of partial melt that appears to be pooling at the Moho, inferred seismically to be at about 22 km, but little or no melt is required within the mid-crust. The minimum amount of melt estimated to be contained here is just 21 km3; an order of magnitude less than on the Dabbahu segment, but similar to estimates for melt within the crust found below the rift axis in the continental Main Ethiopian rift. This, along with other morphological evidence, suggests that this rift segment is less mature than the Dabbahu segment to the north, rather than it simply being at a different stage of a rifting cycle. A wide spread layer of highly conductive sediments up to 2 km thick has been imaged at most locations. This was unexpected on the Dabbahu segment where the surface of the Earth is dominated by heavily faulted basalts erupted from fissures, which are seen as a resistive uppermost layer several hundred metres thick. The high conductivity of the sediments is attributed to high heat flow and the presence of brines.

Zugl.: Berlin, Humboldt-University, 2008.

Cette description grammaticale de l’afar s’appuie essentiellement sur des données recueillies sur le terrain auprès de très nombreux locuteurs afarophones, vivant à Djibouti, en Erythrée et en Ethiopie. La richesse des données a permis de prendre en compte les variantes dialectales tout au long de la description. Celle-ci s’organise autour de plusieurs parties : système phonologique et phonétique, système nominal, système verbal, et syntaxe de l’énoncé. Cette étude a permis de mieux évaluer l’originalité de certains traits connus mais aussi de mettre en valeur des traits peu connus voire ignorés jusqu’à présent. Citons entre autres : redéfinition du statut de la rétroflexe ; approfondissement des valeurs sémantiques et syntaxiques attachées aux différents procédés de dérivation nominale et verbale ; illustration du rôle primordial de la relative dans une langue où il n’y a pas de catégorie « adjectif » ; étude détaillée de la polarité de genre et de l’accord du verbe en genre non en nombre (accord au singulier avec un nom marqué comme pluriel) ; distinction entre noms adverbiaux et adverbes sur des critères syntaxiques; mise en valeur de la portée syntaxique et sémantique des quatre postpositions; meilleure définition de la catégorie des idéophones sur le plan morphophonologique, syntaxique et sémantique ; mise en lumière des procédés de topicalisation. En apportant un nouvel éclairage sur l’afar, à l’intérieur du couchitique et de la famille afro-asiatique, cette thèse se veut aussi une contribution à la typologie des langues. / This grammatical description of Afar is mostly based on fieldwork data collected from a great number of Afar speakers living in Djibouti, Eritrea and Ethiopia. The wealth of data has allowed us to embrace dialectal variations in the description. This description has been built around several components: the phonological and phonetic system, the nominal system, the verbal system, and the syntax.This study leads us to better assess the originality of some features that are already known, and also to bring out other features that were not well known or unknown until now: redefinition of the status of retroflex consonants ; enhanced understanding of semantic and syntactic values of different processes of nominal and verbal derivation ; illustration of the crucial role of the relative clause in a language without adjectives ; detailed study of gender polarity and verb agreement in gender – and not in number – (agreement in the singular with a name marked in the plural) ; differentiation between adverbial names and adverbs on the basis of syntactic criteria ; highlight of the syntactic and semantic significance of four postpositions ; better definition of ideophones from the morphophonological, syntactic and semantic aspects ; highlight of topicalization processes. By shedding new light on Afar within the Cushitic and Afro-Asian family, this thesis aims also to contribute to language typolog*y.

Cette description grammaticale de l’afar s’appuie essentiellement sur des données recueillies sur le terrain auprès de très nombreux locuteurs afarophones, vivant à Djibouti, en Erythrée et en Ethiopie. La richesse des données a permis de prendre en compte les variantes dialectales tout au long de la description. Celle-ci s’organise autour de plusieurs parties : système phonologique et phonétique, système nominal, système verbal, et syntaxe de l’énoncé. Cette étude a permis de mieux évaluer l’originalité de certains traits connus mais aussi de mettre en valeur des traits peu connus voire ignorés jusqu’à présent. Citons entre autres : redéfinition du statut de la rétroflexe ; approfondissement des valeurs sémantiques et syntaxiques attachées aux différents procédés de dérivation nominale et verbale ; illustration du rôle primordial de la relative dans une langue où il n’y a pas de catégorie « adjectif » ; étude détaillée de la polarité de genre et de l’accord du verbe en genre non en nombre (accord au singulier avec un nom marqué comme pluriel) ; distinction entre noms adverbiaux et adverbes sur des critères syntaxiques; mise en valeur de la portée syntaxique et sémantique des quatre postpositions; meilleure définition de la catégorie des idéophones sur le plan morphophonologique, syntaxique et sémantique ; mise en lumière des procédés de topicalisation. En apportant un nouvel éclairage sur l’afar, à l’intérieur du couchitique et de la famille afro-asiatique, cette thèse se veut aussi une contribution à la typologie des langues. / This grammatical description of Afar is mostly based on fieldwork data collected from a great number of Afar speakers living in Djibouti, Eritrea and Ethiopia. The wealth of data has allowed us to embrace dialectal variations in the description. This description has been built around several components: the phonological and phonetic system, the nominal system, the verbal system, and the syntax.This study leads us to better assess the originality of some features that are already known, and also to bring out other features that were not well known or unknown until now: redefinition of the status of retroflex consonants ; enhanced understanding of semantic and syntactic values of different processes of nominal and verbal derivation ; illustration of the crucial role of the relative clause in a language without adjectives ; detailed study of gender polarity and verb agreement in gender – and not in number – (agreement in the singular with a name marked in the plural) ; differentiation between adverbial names and adverbs on the basis of syntactic criteria ; highlight of the syntactic and semantic significance of four postpositions ; better definition of ideophones from the morphophonological, syntactic and semantic aspects ; highlight of topicalization processes. By shedding new light on Afar within the Cushitic and Afro-Asian family, this thesis aims also to contribute to language typolog*y.

Cette description grammaticale de l’afar s’appuie essentiellement sur des données recueillies sur le terrain auprès de très nombreux locuteurs afarophones, vivant à Djibouti, en Erythrée et en Ethiopie. La richesse des données a permis de prendre en compte les variantes dialectales tout au long de la description. Celle-ci s’organise autour de plusieurs parties : système phonologique et phonétique, système nominal, système verbal, et syntaxe de l’énoncé. Cette étude a permis de mieux évaluer l’originalité de certains traits connus mais aussi de mettre en valeur des traits peu connus voire ignorés jusqu’à présent. Citons entre autres : redéfinition du statut de la rétroflexe ; approfondissement des valeurs sémantiques et syntaxiques attachées aux différents procédés de dérivation nominale et verbale ; illustration du rôle primordial de la relative dans une langue où il n’y a pas de catégorie « adjectif » ; étude détaillée de la polarité de genre et de l’accord du verbe en genre non en nombre (accord au singulier avec un nom marqué comme pluriel) ; distinction entre noms adverbiaux et adverbes sur des critères syntaxiques; mise en valeur de la portée syntaxique et sémantique des quatre postpositions; meilleure définition de la catégorie des idéophones sur le plan morphophonologique, syntaxique et sémantique ; mise en lumière des procédés de topicalisation. En apportant un nouvel éclairage sur l’afar, à l’intérieur du couchitique et de la famille afro-asiatique, cette thèse se veut aussi une contribution à la typologie des langues. / This grammatical description of Afar is mostly based on fieldwork data collected from a great number of Afar speakers living in Djibouti, Eritrea and Ethiopia. The wealth of data has allowed us to embrace dialectal variations in the description. This description has been built around several components: the phonological and phonetic system, the nominal system, the verbal system, and the syntax.This study leads us to better assess the originality of some features that are already known, and also to bring out other features that were not well known or unknown until now: redefinition of the status of retroflex consonants ; enhanced understanding of semantic and syntactic values of different processes of nominal and verbal derivation ; illustration of the crucial role of the relative clause in a language without adjectives ; detailed study of gender polarity and verb agreement in gender – and not in number – (agreement in the singular with a name marked in the plural) ; differentiation between adverbial names and adverbs on the basis of syntactic criteria ; highlight of the syntactic and semantic significance of four postpositions ; better definition of ideophones from the morphophonological, syntactic and semantic aspects ; highlight of topicalization processes. By shedding new light on Afar within the Cushitic and Afro-Asian family, this thesis aims also to contribute to language typolog*y.

Les marges passives volcaniques, qui représentent plus des trois-quarts des marges passives sur Terre, sont les témoins privilégiés des processus d'extension lithosphérique menant à l'ouverture de nouveaux bassins océaniques. Nous explorons les relations structurales et temporelles qui existent entre le développement des grandes structures qui accommodent l'extension et l'amincissement, et la production magmatique qui lui est associée pendant le développement d'une marge volcanique naissante, accessible à l'observation directe : le point triple Afar en Éthiopie. Nous produisons une nouvelle lecture de la province Afar en tant qu'analogue en devenir des marges volcaniques. L'approche combine (1) une étude de terrain et de datation du volcanisme pour caractériser le timing de la déformation crustale et le style structural du rift pendant les phases les plus précoces, (2) la détermination géochimique de l'évolution des régimes de fusion mantellique au cours de l'extension, (3) la construction d'un modèle régional qui traite de l'évolution des marges volcaniques en lien avec leur segmentation. Nous mettons en évidence un style structural de " magmatic wide rift " en Afar, associé au jeu de grands détachements. Des phases tectoniques ponctuelles alternent avec des périodes de magmatisme plus prolongées. La segmentation précoce syn-rift contrôle le style structural, la mise en place du magma et l'asymétrie des marges. Le break-up correspond à l'amincissement et le remplacement de la croûte initiale par du matériel mafique pour former la première croûte océanique. / Volcanic passive margins, that represent more than the three quarters of continental margins worldwide, are privileged witnesses of the lithospheric extension processes that form new oceanic basins. We explore the structural and temporal relationships that exist between the development of the major thinning and stretching structures and the magmatic production associated to them. To do so, we will focus our work on the Afar triple junction, Ethiopia, a nascent volcanic passive margin. The rationale of this work is threefold. First, we present fieldwork analysis with lavas geochronology to determine the timing and style of the rift formation, since the early syn-rift period to present days. Second, we determine how the melting regime evolved in response to the deformation of the crust, through a geochemical study of the pre- to syn-rift lavas. Third, we present a synthetic regional that describes the evolution of the volcanic margins in relationship with their segmentation. Central Afar deformed as a magmatic wide rift, associated with major detachment faults. Punctual tectonic phases alternate with protracted magmatic periods. Early syn-rift segmentation controls the structural style, magma emplacement and asymmetry of the margins. The break-up is reached when the initial crust is thinned and replaced by mafic material to form the first oceanic crust.

The Dabbahu-Manda Hararo rift segment is a ~25 x 60 km rift zone in Afar, Ethiopia, where a series of axial dyke intrusions has recently occurred. Basaltic eruptions associated with individual dyking events between 2007-2010 have been fed from fissures along the rift axis and been relatively short-lived events lasting less than 60 hours. The volume of melt delivered to the rift surface by these eruptions has been a minor component of the total melt volume supplied to the shallow crust since the onset of the active rifting phase in 2005 and the current intruded to erupted melt ratio for the 2005-2010 period is ~260:1. This is below typical values for magmatic rift zones and may suggest that further volcanism is likely to occur before this activity ceases. ⁴⁰Ar/³⁹Ar geochronology of basaltic lavas from the flank of the rift and from a region of off-axis volcanism to the west of the rift zone gives ages of 25 – 450 ka. These constrain the development of a prominent axial graben in the northern part of the rift to < 30 ka and based on the age-distribution of lavas across the rift flank suggests that volcanism has been focused to the present neo-volcanic zone for at least 200 ka. Geochemical and isotopic constraints on melt generation suggest ~4-6 % partial melting of fertile mantle beneath rift at depth of ~100-75 km. Lavas erupted at the rift axis and from off-axis volcanoes are derived from a common mantle source, however, axial lavas are shown to represent slightly greater extents of partial melting suggesting a focused mantle melting anomaly, such as those seen at ocean ridges, is forming beneath the rift zone.

L’activité du commerce électronique reçoit habituellement traduction dans un outil juridique classique mis à la disposition des acteurs économiques par le droit : le contrat. Celui-ci se conclue nécessairement à distance. Ainsi est-il dématérialisé. S’ajoutent le caractère éventuellement dépersonnalisé et le caractère éventuellement international grâce à la capacité procurée par les réseaux informatiques de s’affranchir des frontières. Ces caractéristiques du contrat du commerce électronique ont perturbé les paramètres du droit. Celui-ci étant essentiellement conçu pour encadrer une relation contractuelle dont les protagonistes sont des humains en faisant recours à des éléments tangibles. Dans une telle situation, un processus d’adaptation aux nouveaux paramètres du contrat du commerce électronique s’impose au droit sous peine d’un recul historique. Le droit français et le droit marocain se sont montrés réactifs dans la mesure où le droit des contrats ici et là connaît d’ores et déjà un processus d’adaptation aux nouveaux paramètres du contrat du commerce électronique. L’analyse d’un tel processus révèle; l’émergence des règles propres à un tel contrat; certaines règles y ont été déclarées inapplicables; certaines institutions ont été repensées en prenant en compte ces nouveaux paramètres et des définitions portant sur des notions déjà existantes ont été introduites dans le cadre d’un tel processus. La comparaison entre le droit des contrats français et le droit des contrats marocain en matière du contrat du commerce électronique nous a permis d’observer les lacunes . Ainsi, nous avons relevé à titre non exhaustif que : la règle de la capacité en l’état actuel du droit positif français ou marocain est défavorable à la conclusion du contrat par « les agents électroniques »; l’application du délai raisonnable à l’offre par voie électronique en droit français est incompatible avec le besoin de la veille concurrentielle qui se fait sentir dans le marché virtuel (cyberespace) plus qu’ailleurs; le législateur marocain s’est montré ferme à la reconnaissance de la qualité de l’offre par voie électronique en ignorant certaines techniques de la publicité qui permettent la mise en vente immédiate; etc. Toute initiative de nature à combler de telles lacunes doit être confiée à la jurisprudence, car la règle jurisprudentielle n’est pas obligatoire, elle est susceptible d’être rejetée ou modifiée à tout moment à l’occasion de l’examen d’une nouvelle espèce. Cette possibilité de revirement permet de marcher de pair avec le contrat du commerce électronique par nature mouvant. L’intervention du législateur en matière du contrat du commerce électronique dans la mesure où elle est nécessaire doit se limiter à adopter les cadres juridiques existants de façon à lever les blocages réels découlant d’une contrainte juridique. / The e-commerce business is usually embodied in a traditional legal tool made available to economic actors by the law: the contract. This one is usually signed from afar. Thus it is dematerialized. In addition, there is the possibility of depersonalization and internationalization thanks to the ability of computer networks to break free of borders. These characteristics of the e-commerce contract have disrupted the legal framework. The latter being essentially aimed at regulating a contractual relationship in which the parties involved are human beings by using tangible elements. In such a situation, an adjustment process due to the new parameters of the electronic commerce contract is required for the law to avoid a historical setback. French and Moroccan laws have proved to be reactive insofar as contract law here and there already witnesses a process of adaptation to the new parameters of the electronic commerce contract. The analysis of such a process reveals; the advent of rules specific to such a contract; certain rules have been declared inapplicable; some institutions have been rethought taking into account these new parameters and definitions of existing concepts have been introduced as part of such a process. The comparison between French contract law and Moroccan contract law in the field of electronic commerce contracts allowed us to observe the shortcomings. Thus, we noted, but not exhaustively, that: the capacity-rule in the current state of French or Moroccan positive law is detrimental to the signing of the contract by "electronic agents"; the application of the reasonable time limit to the offer by electronic means under French law is incompatible with the need for competitive intelligence which is felt in the virtual market (cyberspace) more than elsewhere; the Moroccan legislator has been quite firm in recognizing the quality of the offer through electronic means by ignoring certain advertising techniques which allow immediate sale; etc. Any initiative likely to fill such gaps must be entrusted to the case law, since the case-law is not mandatory, it is likely to be rejected or modified at any time when a new case is examined. This turnaround possibility makes it possible to work alongside the evolving nature of the e-commerce contract. The legislator's intervention in the field of electronic commerce contracts, insofar as it is necessary, must be limited to adopting existing legal frameworks in order to remove the real obstacles resulting from a legal constraint.

abstract: Sedimentary basins in the Afar Depression, Ethiopia archive the progression of continental breakup, record regional changes in east African climate and volcanism, and host what are arguably the most important fossiliferous strata for studying early human evolution and innovation. Significant changes in rift tectonics, climate, and faunal assemblages occur between 3-2.5 million years ago (Ma), but sediments spanning this time period are sparse. In this dissertation, I present the results of a geologic investigation targeting sediments between 3-2.5 Ma in the central and eastern Ledi Geraru (CLG and ELG) field areas in the lower Awash Valley, using a combination of geologic mapping, stratigraphy, and tephra chemistry and dating. At Gulfaytu in CLG, I mapped the northern-most outcrops of the hominin-bearing Hadar Formation (3.8-2.9 Ma), a 20 m-thick section of flat-lying lacustrine sediments containing 8 new tephras that directly overlie the widespread BKT-2 marker beds (2.95 Ma). Paleolake Hadar persisted after 2.95 Ma, and the presence and characteristics of the Busidima Formation (2.7-0.016 Ma) indicates Gulfaytu was affected by a reversal in depositional basin polarity. Combined with regional and geophysical data, I show the Hadar Formation underlying CLG is >300 m thick, supporting the hypothesis that it was the lower Awash Pliocene depocenter. At ELG, I mapped >300 m of sediments spanning 3.0-2.45 Ma. These sediments coarsen upward and show a progression from fluctuating lake conditions to fluvial landscapes and widespread soil development. This is consistent with the temporal change in depositional environments observed elsewhere in the lower Awash Valley, and suggests that these strata are correlative with the Hadar Formation. Furthermore, the strata and basalts at ELG are highly faulted, and overprinted by shifting extension directions attributed to the northern migration of the Afar triple junction. The presence of fossiliferous beds and stone tools makes ELG a high-priority target for anthropological and archaeological research. This study provides a new temporally-calibrated and high-resolution record of deposition, volcanism, and faulting patterns during a period of significant change in the Afar. / Dissertation/Thesis / Ph.D. Geological Sciences 2013