1,720,971 research outputs found
Pleistocene terraced travertines and fluvial deposits, incision and uplift in Acquasanta Terme area (central Apennines, Italy)
No full textPlio-Quaternary evolution of the central Apennines: the case of the Medium-Upper Aniene River Valley (Latium, central Italy)
No full textRegional geology of the Dogu’a Tembien massif
No full textThe Dogu’a Tembien Massif is located on the western margin of the Mekelle Outlier, a nearly circular hilly area (8000 km2) with an average elevation of ~2000 m (Fig. 2.1) and elevations ranging between 1200 and 2850 m (Fig. 2.1a). The landscape, although deeply incised by rivers, is characterized by four planation surfaces (Palaeozoic, Triassic, Cretaceous, and Tertiary in age) that can be observed in the area northwest of Mekelle. They represent wide surfaces formed during long periods of tectonic quiescence when longstanding erosion shaped a gently rolling landscape down to almost sea level (see chapter 11). This chapter presents the regional geography of Dogu’a Tembien. Most geological formations, as well as planations and later dissection of the massif are detailed in the next chapters
The evolution of hydrography in the retro-wedge side of an orogen under extension: The case of the River Aniene in the central Apennines (Italy)
No full textIn the retro-wedge side of a mountain chain undergoing back-arc extension, the progressive development of the fluvial network is controlled by the interaction of the uplift of the orogen, the activity of tectonic structures, and the climate. Many studies have evidenced the continuous competition between the activity of the normal faults that generate intermontane basins and rivers that incise and erode headward. Less attention has been paid to the role of the extensional structures that border the basins at the foot of the orogen and close to the base level (the back-arc basin) in the development of the hydrography draining their footwall. Could these structures influence or even prevent the integration of the fluvial network into the retro-wedge side of an uplifting orogen? To answer to this question, we studied the Aniene R., a tributary of the Tiber R. that drains the western side of the central Apennines (Italy). Studying the geometry of the topography and hydrography of its basin, surveying some key areas, dating deposits, and inverting its longitudinal profile, we reconstructed the landscape evolution of the drainage basin. In particular, we provide new evidence on the involvement of the structures bordering the low-standing extensional basins in the drainage development. Indeed, the flexural uplift of their footwall can hamper their flow down to the base level closing temporary the upstream drainage basin and so influencing the alternating phases of erosion and deposition controlled by uplift and climate
The Uplift of an Early Stage Collisional Plateau Unraveled by Fluvial Network Analysis and River Longitudinal Profile Inversion: The Case of the Eastern Anatolian Plateau
Full text linkOrogenic plateaus of continental collision zones exhibit landforms and fluvial networks that retain first-order information on their topographic evolution and vertical growth. The inversion of river longitudinal profiles allows to reconstruct the base level fall history of plateaus, supporting the study of landscape evolution in the frame of geodynamic models. The Eastern Anatolian Plateau (EAP) of the Arabia-Eurasia collision zone is a plateau at an early stage of development. It stands at similar to 2,000 m, presents endorheic basins, and is drained by three main river networks. Seismic data indicate a thinned lithospheric mantle that explains the late Cenozoic volcanic activity. Despite the number of studies on the EAP uplift, its history is still debated. In this study we investigated the EAP hydrography and topography, and we inverted the longitudinal profile of one of the main rivers: the Arax River. The results describe a high-standing, low-relief plateau drained by a hydrography, controlled by active tectonics. Longitudinal profiles and ?-plots illustrate rivers in disequilibrium with channel steepness increasing downstream. The elevation of marine deposits indicates a surface uplift of similar to 2,000 m, similar to 500 m of which are of residual topography. This upheaval occurred by two increases: the first one at 10-11 Ma with the opening of a slab window and the arrival of a mantle flow from Arabia and the second one at similar to 5 Ma with the continued inflow coupled with isostasy. Our results describe the early stage of collisional plateau development, distinguishing the contribution of deep processes and isostasy to the topographic growth
Role of dynamic topography in sustaining the Nile River over 30 million years
No full textThe Nile is the longest river on Earth and has persisted for millions of years. It has been suggested that the Nile in its present path is ~6 million years old, whereas others argue that it may have formed much earlier in geological history. Here we present geological evidence and geodynamic model results that suggest that the Nile drainage has been stable for ~30 million years. We suggest that the Nile’s longevity in essentially the same path is sustained by the persistence of a stable topographic gradient, which in turn is controlled by deeper mantle processes. We propose that a large mantle convection cell beneath the Nile region has controlled topography over the last 30 million years, inducing uplift in the Ethiopian–Yemen Dome and subsidence in the Levant Sea and northern Egypt. We conclude that the drainage system of large rivers and their evolution over time can be sustained by a dynamic topographic gradient
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Formation and Persistence of Extensional Internally Drained Basins: The Case of the Fucino Basin (Central Apennines, Italy)
No full textThe interaction between sedimentation/erosion and faulting represents one of the most intriguing topics in landscape and tectonics evolution. Only few studies have been able to document the feedback between faulting and sedimentary loading from field observations. Here, we focus on how sediment loading/unloading influences the dynamics of fault systems in the Fucino basin, in the Central Apennines (Italy). The Fucino basin represents a remarkable case study with respect to the other main extensional basins in the Apennines because of its large dimension, square shape, significant sediment thickness, and its endorheic nature throughout its evolution. We present a detailed structural and geomorphologic analysis of the Fucino basin and its surroundings, investigating the kinematic and geometry of each main fault strand. The slickenlines analysis reveals multiple families of slip-vectors and timing of activity, suggesting a change in extension slip-direction from N240° to N200° during middle Pleistocene. Using a local isostatic model, we estimate that up to the 30% of the vertical geological displacement of the faults, which overall ranges from 0.5 to 2.5 km, is related to the sediment loading/unloading. We demonstrate a positive feedback between sedimentation and faulting which may also lead to a reorganization in fault kinematics related to a significant increase in vertical stress. We propose a conceptual model for the permanent endorheic configuration of the Fucino basin, which includes the effect of sediment loading
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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