The Mesaverde Group, Uinta Basin, Utah, is the source of significant natural gas production and contains several trillion cubic feet of undiscovered natural gas resources. Tight-gas sandstone reservoirs within the Mesaverde Group require hydraulic fracture treatments in order to produce economic volumes of gas. The nature of the natural fracture network is examined here using scanline sampling, image-log, well-log, core, and microstructural analyses to evaluate and model the potential connectivity of hydraulically induced fractures to natural fractures in the subsurface. Regional fracture sets include subvertical sets with dominant orientations of: N-S (006° - 015°), NE (045° - 059°), NNW (326° - 342°) and a WNW (271° - 286°). Sedimentologic and diagenetic characteristics of seven sandstone lithofacies control the fracture development and distribution in the Mesaverde Group. Key sedimentologic and diagenetic influences on fracture distribution include bed thickness, stratigraphic architecture, the degree of cementation and the type of cement. From outcrop and core analysis, discontinuous, well-cemented sandstone have a higher fracture density when compared with continuous, tabular bedded sandstone units and friable sandstone units. Based on the sedimentologic and diagenetic controls on the character of natural fractures, lithofacies can be used to predict fracture distribution within the Mesaverde Group based on environments of deposition. Sandstones deposited in braided river environments appear to have lower fracture densities than sandstones deposited in meandering fluvial environments. Northwesterly trending, discontinuous sandstone reservoirs were deposited in meandering fluvial environments, are highly fractured by a pervasive WNW-striking fracture helps to explain fairways of prolific natural gas production within the Greater Natural Buttes field.

Στο πρώτο κεφάλαιο πραγματοποιείται η περιγραφή της περιοχής μελέτης με γενικά στοιχεία και δίνεται η εικόνα χρήσεων γης της περιοχής. Στο δεύτερο κεφάλαιο παρουσιάζονται τα γεωμορφολογικά στοιχεία, γίνεται ανάλυση του υδρογραφικού δικτύου και του αναγλύφου. Στο τρίτο κεφάλαιο αναλύεται η γενική γεωλογική δομή της περιοχής μελέτης. Πραγματοποιείται ανάλυση της στρωματογραφίας αλλά και της τεκτονικής. Στο τέταρτο κεφάλαιο περιλαμβάνονται οι αναλύσεις και τα συμπεράσματα από την περιοχή μελέτης. Σημειώνεται ότι η περιοχή μελέτης χωρίστηκε σε δύο τμήματα που αποτελούν χωριστές διπλωματικές εργασίες. Η παρούσα αναφέρεται στο κομμάτι του Αλφειού ποταμού μετά την ένωση με τον παραπόταμο του, Ερύμανθο. Η αναφορά που φαίνεται στους πίνακες και για τα στοιχεία των αναλύσεων για τον Ερύμανθο γίνεται για να μπορέσει να γίνει σύγκριση μεταξύ των δυο διπλωματικών. Τέλος, θα πρέπει να αναφέρω ότι οι εργασίες πεδίου έγιναν συγχρόνως και στα δύο τμήματα του Αλφειού όμως η παρουσίαση γίνεται χωριστά για να αναδειχτούν οι διαφορές μεταξύ των δύο τμημάτων. Στο τελευταίο κομμάτι της διπλωματικής υπάρχει ένα παράρτημα με φωτογραφικό υλικό. / The work is part of the sedimentological analysis of the Alpheus River and tributary Erimanthos results comparing particle size analysis of rocks, spherical, chemical composition etc.

Recent carbonate sediments from (133-236m) on the northern Jamaican island slope are significantly different from shallower reef zones (l-70m) in grain constituents, textural parameters, and foraminiferal assemblages. The island slope sediment is dominated by coral fragments, calcareous algae, Halimeda plates, and foraminiferal tests. The sediment is characteristically poorly-sorted, nearly-symmetrically skewed, and mesokurtic, with a mean grain size in the fine sand range. Mineralogically, the sediment is predominantly aragonite (66%) and high-Mg calcite (22%), with some calcite (8%), and minor amounts of clays and other insoluble minerals (4%). Q-mode cluster analyses of sediment constituents, textural parameters, and foraminiferal species and larger group abundances were utilized in the delineation of shelf and island slope depositional environments. ineffective for such use. Mineralogy proves No significant differences are observed in sedimentological parameters (textures, constituents, and sedimentation rates) between an island slope traverse located below an area with prominant sill reefs and a traverse below an area lacking well-developed sill reefs. It is suggested that the sill reefs have less effect on off-reef transport than was previously believed. Based on the abundance trends of certain sediment grains and the similarity of sediment grains in island slope and deep fore reef/fore reef slope sediment, it is suggested that the deeper reef zones (>30m) are the source of most sediment transported seaward. Foraminiferal abundances show lateral differences between traverses related to input of shallow water (

Η παρούσα διπλωματική διατριβή με τίτλο «Ιζηματολογική και Γεωχημική ανάλυση - Δυναμικό γένεσης υδρογονανθράκων στο νότιο τμήμα της κεντρικής Κρήτης», εκπονήθηκε στα πλαίσια μεταπτυχιακού προγράμματος με τίτλο «Γεωλογικές Διεργασίες στη Λιθόσφαιρα και Γεωπεριβάλλον», του τμήματος Γεωλογίας της σχολής Θετικών Επιστημών του Πανεπιστημίου Πατρών.Σκοπός της παρούσας διατριβής είναι η μελέτη τόσο κλαστικών όσο και ανθρακικών ιζημάτων, από διαφορετικά τεκτονικά καλύμματα, κεντρικά και νότια του νήσου Κρήτης. Η παρούσα διατριβή βασίστηκε στην σύνθεση δεδομένων πεδίου αλλά και σε μια σειρά εργαστηριακών αναλύσεων η οποία περιλάμβανε, ιζηματολογική και γεωχημική ανάλυση. Για την εργαστηριακή ανάλυση συλλέχθηκαν 72 δείγματα, εκ των οποίων τα περισσότερα ήταν κλαστικά ενώ κάποια εξ’ αυτών ήταν ανθρακικά. Κοκκομετρική ανάλυση έγινε σε 32 δείγματα ενώ τα υπόλοιπα ήταν ισχυρά διαγενημένα και περιγραφή τους έγινε μακροσκοπικά. Γεωχημική ανάλυση πραγματοποιήθηκε στο σύνολο των δειγμάτων.Πιο συγκεκριμένα, έγιναν κοκκομετρικές αναλύσεις των ιζημάτων, επεξεργασία των στατιστικών παραμέτρων, ποσοτικός προσδιορισμός του Οργανικού Άνθρακα (Corg) και του Ανθρακικού Ασβεστίου (CaCO3). Μελετήθηκαν τα αποθετικά περιβάλλοντα των ιζημάτων, οι συνθήκες σχηματισμού τους που σε συνδυασμό με τη γεωδυναμική εξέλιξη της περιοχής μελέτηςμας έδωσε τη δυνατότητα εκτίμησης της πιθανότητας ύπαρξης πεδίων μητρικών πετρωμάτων υδρογονανθράκων. / The present diploma thesis entitled "Sedimentological and Geochemical analysis - hydrocarbon generation potential in the southern part of central Crete," worked out during the postgraduate program entitled "Geological Processes in Lithosphere and Geoenvironment" of Geology of the Faculty of Sciences of the University of Patras.The purpose of this thesis is to study both clastic and carbonate sediments from different tectonic covers, center and south of the island of Crete. This thesis was based on field data composition but also in a series of laboratory analyzes that included, sedimentological and geochemical analysis. For laboratory analysis were collected 72 samples, of which most were clastic and some of them were carbonates. Particle size analysis was performed on 32 samples while the rest were strong diagenimena and their description became macroscopically. Geochemical analysis was performed on all deigmaton.Pio specifically made granulometric analyzes of sediments, processing of statistical parameters, quantification of organic carbon (Corg) and Calcium Carbonate (CaCO3). They studied the depositional environments sediment their forming conditions in combination with the development of geodynamic region meletismas enabled assessment of fields existence probability hydrocarbon parent rock.

Στην παρούσα εργασία πραγματοποιήθηκε ιζηματολογική και γεωχημική ανάλυση των Μέσο-Μειοκαινικών ιζημάτων της Τομής Ποταμός (Kατ. Τορτόνιο) στο ΒΔ τμήμα της νήσου Γαύδου, με απώτερο σκοπό να μελετηθούν τα αποθετικά τους περιβάλλοντα, οι συνθήκες σχηματισμού τους και η γεωδυναμική εξέλιξη της περιοχής στην κατεύθυνση ύπαρξης πεδίων υδρογονανθράκων. Από τις κοκκομετρικές αναλύσεις προέκυψε ότι τα ιζήματα βαθειάς θάλασσας της μελετηθείσας τομής ανήκουν στο μέγεθος του πηλού, η μεταφορά τους έχει γίνει κυρίως ως ομογενές αιώρημα ενώ η απόθεσή τους στο σύνολό τους, σύμφωνα με το C-M διάγραμμα (Passega,1957,1964), έγινε με τουρβιδιτικά ρεύματα. Επίσης από την ανάλυση του Ανθρακικού ασβεστίου η οποία βασίστηκε στην διάσπαση (CaCO3) με τη χρήση (CH3COOH) προέκυψε πως τα δείγματα στο σύνολό τους είναι φτωχά. Aπό τα αποτελέσματα της έρευνας της οργανικής γεωχημείας του περιεχόμενου Οργανικού Άνθρακα τα οποία βασίστηκαν στην μέθοδο της Tιτλοδότησης (Gaudette at al.1974), αλλά και κατά δεύτερο λόγο από τα αποτελέσματα των δεικτών (για συγκριτικούς σκοπούς) με την μέθοδο της πυρόλησης (Rock-Eval 2), προέκυψε πως τα δείγματα παρουσιάζουν φτωχή δυνατότητα γένεσης υδρογονανθράκων. Αντιθέτως η ιζηματογενής ακολουθία του σχηματισμού Ποταμός κρίθηκε ιδανική να λειτουργήσει ως ρεζερβουάρ αποθήκευσης υδρογοναναθράκων αλλά και ως μονωτήριο πέτρωμα σύμφωνα με τον τρόπο ανάπτυξής της. Από τον συνδυασμό αναλύσεων στην περιοχή μελέτης με αυτές στην υπολεκάνη της Μεσσαράς (Νότια Κρήτη), ίδιας ηλικίας (Κάτω Τορτόνιο) και λαμβάνοντας υπόψιν πως η Μεσσαρά αποτελεί το βόρειο τμήμα της βυθιζόμενης τάφρου, μεταξύ Κρήτης και Γαύδου (μια από τις backstop λεκάνες), και σύμφωνα με τη δράση κανονικών ρηγμάτων πίσω από τη Μεσογειακή ράχη που δημιουργούν αυτή τη λεκάνη, μπορούμε να υποθέσουμε πως υπάρχει πλούσιο οργανικό υλικό στο βόρειο τμήμα της και η τροφοδοσία της λεκάνης προέρχεται από ένα δελταϊκό σύστημα. Η κύρια τάφρος δομείται από υποθαλάσια ριπίδια – τουρβιδιτικές αποθέσεις και η παρουσία έστω και ολιγάριθμων δειγμάτων πλούσιων σε οργανικό υλικό στις μελετηθείσες τομές δείχνει ότι πιθανά στο κέντρο της τάφρου οι συνθήκες να είναι ιδανικότερες για τη γένεση υδρογονανθράκων. Η τάφρος φαίνεται να συγκεντρώνει το μεγαλύτερο ποσοστό ιζημάτων στο κεντρικό της τμήμα εξασφαλίζοντας τη συνεχή ταφή τους, οδηγώντας τα σε ωρίμανση και παραγωγή υδρογονανθράκων, με πιθανούς ταμιευτήρες τους ψαμμίτες που έχουν αναγνωριστεί στην περιοχή. / In the present thesis, sedimentological and geochemichal analysis of the Middle-Miocene sediments of the Lower Tortonian Potamos section in the northwestern part of the island of Gavdos was conducted, aiming to study the depositional environments, the conditions of the formation and the geodynamic evolution of the region towards presence of hydrocarbon fields. Grain size analysis revealed that deep sea sediments of the studied section belong to the size of clay, the transfer has taken place mainly as a homogeneous suspension whereas the deposit, as a whole, according to the C-M diagram (Passega,1957,1964), was made by turbitity currents. In addition, the analysis of calcium carbonate which was based on decomposition (CaCO3) using (CH3COOH) revealed that the samples in their entirety, are poor. From the results of the research in the organic geochemistry Organic Carbon content, which was based on the method of tritation (Gaudette et al., 1974), and secondly on the results of indicators (for comparative purposes) with the method of pyrolysis (Rock-Eval 2), emerged that the studied rocks represent poor oil source. In contrast, the sedimentary succession of Potamos was ideal to function as a reservoir as well as a cap rock (seal) according to the manner of its development. From the compined analysis in the study area to those in Messara basin (Southern Crete), which have the same age (Lower Tortonian) and taking into account that the Messara basin (is at the northern part of the sink trench), between Crete and Gavdos (one of the backstop basins), and under the action of normal faults behind the Mediterranean ridge that creates this basin, it can be assumed that there is a rich organic material in the northern part and the feed of the basin originates from a delta system. The main trench is constructed by submarine fans –turbitity deposits and the presence of even a restricted number of samples rich in organic material in the studied sections indicates that probably in the center of the trench the conditions are ideal for the genesis of hydrocarbons. The trench appears to concentrate the highest percentage of sediments in the central part of the trench providing their continued burial, leading to the maturation and production of hydrocarbons, with the prospective sandstone reservoirs which have been recognized in the region.

Bryant and Eastern Canyon systems are located on the northwest Gulf of Mexico, and they are characterized by a very complex sedimentological history related to glacioeustatic cycles, river discharges, and interactions of depositional and halokinetic processes. Both canyon systems were active during the low sea-level stand of Oxygen Isotope Stage 6, and provided the pathways for the transport of enormous amounts of sediments on the continental slope and abyssal plain of the northwest Gulf of Mexico. Right after their abandonment, at the beginning of Stage 5, salt diapirs encroached into the canyons, and resulted in their transformation into a network of intraslope basins. The transformation of the canyons resulted in the generation of massive sediment failures. The mid-shelf (Stages 4 and 3) to shelf edge (Stage 2) lowering of the sea-level during the last glacial episode resulted in: 1) extensive river-sourced deposits on the outer shelf and/or upper continental slope that contributed in a seaward mobilization of the underlying salt masses, and 2) the generation of numerous gravity flows and turbidity currents on the outer shelf/upper continental slope. The seaward mobilization of the salt masses resulted in the oversteepening of the flanks of the basins, and consequently in the generation of numerous and massive sediment failures. The turbidity currents were confined on the intraslope basins of the upper continental slope, depositing their coarsest material. However, their most diluted upper and end members were able to continue their downslope propagation depositing characteristic fine-grained turbidites. The frequency of the turbidity currents was highly increased during the last glacial maximum (Stage 2), and three short melt-water pulses centered at 30.5, 36, and 52 ky B.P. The last deglaciation event is characterized by the development of a major melt water event that resulted in the deposition of distinct organic rich sediments, similar to the sapropels of the Eastern Mediterranean. At about 11 ky B.P. the melt water discharges of the North America switched from Mississippi River to St Lawrence Seaway, causing the domination of hemipelagic sedimentation on the continental slope of the northwest Gulf of Mexico.

FARIAS, Teresa Raquel Lima. Estradas rurais não pavimentadas como fonte de sedimentos em bacia hidrográfica do semiárido. 2016. 97 f. : Tese (doutorado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Engenharia Agrícola, Programa de Pós-Graduação em Engenharia Agrícola, Fortaleza-CE, 2016. / Submitted by guaracy araujo (guaraa3355@gmail.com) on 2016-08-05T17:12:33Z No. of bitstreams: 1 2016_tese_trlfarias.pdf: 2470558 bytes, checksum: 30335a2cc35e4a28efe3e35816823a1e (MD5) / Approved for entry into archive by guaracy araujo (guaraa3355@gmail.com) on 2016-08-05T17:15:47Z (GMT) No. of bitstreams: 1 2016_tese_trlfarias.pdf: 2470558 bytes, checksum: 30335a2cc35e4a28efe3e35816823a1e (MD5) / Made available in DSpace on 2016-08-05T17:15:47Z (GMT). No. of bitstreams: 1 2016_tese_trlfarias.pdf: 2470558 bytes, checksum: 30335a2cc35e4a28efe3e35816823a1e (MD5) Previous issue date: 2016 / Approximately 80% of the road network in Brazil is unpaved. Studies have reported high erosion rates and runoff produced by the road infrastructure in various parts of the world and report that unpaved roads are significant sources of sediment in river basins. For two years (2013-2014), monitoring in the field under natural rainfall conditions was conducted to characterize runoff and sediment yield of unpaved rural road segments and the respective slopes in semiarid area of the Caatinga biome of northeastern Brazil, vulnerable to desertification. It was assessed the application of modelling in the yield of sediments from road surface. The sediment yield values measured in the years 2013-2014 ranged from 0.30 Mg.ha-1.year-1 to 0.92 Mg.ha-1.year-1, higher than those recorded in the preserved area, but generally lower than those reported in the literature for unpaved roads. However, it is a semiarid area with low rainfall and characterized by low runoff coefficients, which limits the sediment yield and the hydrological connectivity in the area, additionally the two monitoring years coincided with drought in the region. In the monitored road slope segments, sediment yield from the non-vegetated slope was about ten times that of the slope with vegetation. On the road surfaces, the annual sediment yield (normalized by the slope) in a segment with traffic was three times higher than that without traffic, in addition, events occurring after maintenance activities generated sediment concentration peaks as high as 5,000 mg.L-1 in these areas. In the road segment scale, among the models tested for the predicting of sediment yield, the USLE associated with the Maner equation, proved to be a suitable approach, the best results being obtained for the road without traffic due to no interference from external factors, such as traffic and maintenance activities, which are not explained by the model. In the scale of the Benguê catchment (933 km²), where the roads occupy only 0.7% of the surface, the modelling indicated that these areas contributed with approximately 7% of the total soil loss. The results of this study suggest that the sediment yield from roads and slopes with bare surface is at least one order of magnitude higher than those recorded in the preserved areas of the basin. Maintenance activities on roads and traffic of vehicles contribute to the increased availability of sediments and impacting the sediment concentrations, but produce lower impact on the sediment loads, which depend on runoff and the its occurrence after reprofiling of roads. It was also found that the natural vegetation of the semiarid region has potential in capturing sediments in road slopes, with an important role in breaking down connectivity between sediment flows from unpaved roads and the natural drainage system of the catchment. / Aproximadamente 80% da malha viária no Brasil não possui pavimentação. Estudos têm registrado elevadas taxas de erosão e escoamento superficial produzidas pela infraestrutura viária em várias partes do mundo e reportam que estradas não pavimentadas são fontes significativas de sedimentos em bacias hidrográficas. Durante dois anos (2013-2014) foi conduzido monitoramento em campo sob condições de chuva natural para caracterizar escoamento e produção de sedimentos de segmentos de superfície de estradas rurais não pavimentadas e talude viário, em área semiárida do bioma Caatinga do nordeste do Brasil, vulnerável à desertificação. Também avaliou-se a aplicação de modelagem na predição da produção de sedimentos de superfície de estradas. Os valores de produção de sedimentos medidos nos anos de 2013-2014, variaram de 0,30 Mg.ha-1.ano-1 a 0,92 Mg.ha-1.ano-1, superiores aos registrados na área em condição preservada, porém em geral inferiores aos reportados na literatura para estradas não pavimentadas. Entretanto, trata-se de uma área semiárida com baixa pluviometria e caracterizada por baixos valores de coeficiente de escoamento superficial, o que limita a produção de sedimentos e a conectividade hidrológica da área, além de os dois anos de monitoramento terem coincidido com período de seca na região. Nos segmentos de talude rodoviário monitorados, a produção de sedimentos do talude sem vegetação foi cerca de dez vezes superior à do segmento com vegetação. Na superfície de estradas, a produção de sedimentos anual (normalizada pela declividade) em um segmento com trânsito foi três vezes mais elevada que da estrada sem trânsito, além disso, eventos que ocorreram após atividades de manutenção das vias geraram picos de concentração de sedimentos superiores a 5.000 mg.L-1 nessas superfícies. Na escala de segmento de estrada, entre os modelos avaliados para predição da produção de sedimentos, a USLE associada a equação de Maner, mostrou-se uma abordagem adequada, em que os melhores resultados foram obtidos para a estrada sem trânsito, devido a não interferência neste segmento, de fatores externos como trânsito e atividades de manutenção, não explicados pelo modelo. Já na escala da Bacia do Benguê (933 km²), onde as estradas ocupam apenas 0,7% da superfície, a aplicação de modelagem mostrou que estas contribuíram com aproximadamente 7% do total de perdas de solo na área. Os resultados deste estudo sugerem que a produção de sedimentos em estradas e taludes com superfície desnuda é pelo menos uma ordem de magnitude superior àquelas registrada nas áreas preservadas da bacia. Atividades de manutenção nas estradas e o trânsito de veículos contribuem para o aumento da disponibilidade de sedimentos com impacto nos valores de concentração de sedimentos, mas impactando menos as cargas de sedimentos que dependem do escoamento superficial e da ocorrência de eventos após manutenção das vias. Constatou-se que a vegetação natural do semiárido tem potencial na captura de sedimentos em taludes rodoviários, com papel importante na quebra de conectividade entre fluxos de sedimentos provenientes de estradas não pavimentadas e o sistema de drenagem natural da bacia.

En raison de son importance comme source de sédiments et de sa capacité à modifier l'eau et la connectivité des sédiments lors de pluies intenses, en particulier dans les terres cultivées, le ravinement a besoin d'être mieux compris afin de pouvoir le gérer et atténuer ses effets. Le Pays de Thelle et l'Artois sont les deux régions du Bassin parisien qui concentrent le plus grand nombre de ravins, or les études sur les processus de ravinement ainsi que les tentatives de modélisation restent rares. En utilisant l'analyse morphométrique et l'étude des dépôts conservés à l'aval des incisions, la recherche vise à déterminer quelles sont les variables du système contrôlant de telles incisions, et à reconstituer les étapes de la morphogenèse de ces incisions et les risques qu'elles représentent aujourd'hui. Les ravins se développent là où l'aire drainée et la pente sont suffisantes pour que l'écoulement concentré puisse éroder, on les trouve souvent au niveau de rupture de pente. La mesure des volumes érodés et accumulés montre que l'érosion l'emporte largement sur le dépôt.Les ravins ont enregistré plusieurs phases d'incision dont l'importance s'explique par la conjonction de précipitations exceptionnelles, de fortes pressions anthropiques (défrichements et mise en culture) et de phénomènes tectoniques (soulèvement lent des axes anticlinaux du Bray et de l'Artois). Ces ravins sont des formes fluviatiles, mais la néotectonique joue un rôle essentiel dans le Pays de Thelle, alors qu'en Artois ce sont plutôt les phénomènes karstiques qui l'emportent. Le boisement récent des ravins freine l'incision, mais n'empêche pas l'érosion régressive de faire reculer les têtes de ravins et les risques d'inondations et de coulées boueuses menacent toujours les villages situés à l'aval immédiat de ces ravins / Because of its importance as a source of sediment and its capacity to change the water and the connectivity of sediments during intense rainfall, particularly in the cultivated lands, the gullies have need to be better understood for being able to manage them and mitigate its effects. The Pays de Thelle and Artois are the two regions of the Parisian Basin in which the largest number of ravines is concentrated ; however the studies about the processes of gullies and the attempts of modeling remain rare. Using the morphometric analysis and the study of the preserved deposits in the downstream of the incisions, the research aims to determine which are the variables of the controlling system such incisions, and to reconstruct the morphogenesis stages of these incisions and the risks they represent today. Ravines are occurring where the area draining and the slope are sufficient to make concentrated flow that can erode, they are often found at the level of slope's breakdown. The measurement of the volumes which have been eroded and accumulated shows that the erosion wins largely on the depot. The ravines have recorded several phases of incision in which the importance is explained by the conjunction of exceptional rainfall, strong anthropogenic pressures (land clearing and cultivation) and tectonic phenomena (uprising slow anticlinal axes of Bray and Artois). These ravines are fluvial forms, but the Neotectonic plays an essential role in the Pays de Thelle, whereas it is rather the karst phenomena which prevail in Artois. The recent afforestation of ravines slows the incision, but does not prevent the regressive erosion to roll back the heads of gullies and the risks of floods and mudslides muddy still threaten the villages located immediately downstream of these ravines

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Aproximadamente 80% da malha viÃria no Brasil nÃo possui pavimentaÃÃo. Estudos tÃm registrado elevadas taxas de erosÃo e escoamento superficial produzidas pela infraestrutura viÃria em vÃrias partes do mundo e reportam que estradas nÃo pavimentadas sÃo fontes significativas de sedimentos em bacias hidrogrÃficas. Durante dois anos (2013-2014) foi conduzido monitoramento em campo sob condiÃÃes de chuva natural para caracterizar escoamento e produÃÃo de sedimentos de segmentos de superfÃcie de estradas rurais nÃo pavimentadas e talude viÃrio, em Ãrea semiÃrida do bioma Caatinga do nordeste do Brasil, vulnerÃvel à desertificaÃÃo. TambÃm avaliou-se a aplicaÃÃo de modelagem na prediÃÃo da produÃÃo de sedimentos de superfÃcie de estradas. Os valores de produÃÃo de sedimentos medidos nos anos de 2013-2014, variaram de 0,30 Mg.ha-1.ano-1 a 0,92 Mg.ha-1.ano-1, superiores aos registrados na Ãrea em condiÃÃo preservada, porÃm em geral inferiores aos reportados na literatura para estradas nÃo pavimentadas. Entretanto, trata-se de uma Ãrea semiÃrida com baixa pluviometria e caracterizada por baixos valores de coeficiente de escoamento superficial, o que limita a produÃÃo de sedimentos e a conectividade hidrolÃgica da Ãrea, alÃm de os dois anos de monitoramento terem coincidido com perÃodo de seca na regiÃo. Nos segmentos de talude rodoviÃrio monitorados, a produÃÃo de sedimentos do talude sem vegetaÃÃo foi cerca de dez vezes superior à do segmento com vegetaÃÃo. Na superfÃcie de estradas, a produÃÃo de sedimentos anual (normalizada pela declividade) em um segmento com trÃnsito foi trÃs vezes mais elevada que da estrada sem trÃnsito, alÃm disso, eventos que ocorreram apÃs atividades de manutenÃÃo das vias geraram picos de concentraÃÃo de sedimentos superiores a 5.000 mg.L-1 nessas superfÃcies. Na escala de segmento de estrada, entre os modelos avaliados para prediÃÃo da produÃÃo de sedimentos, a USLE associada a equaÃÃo de Maner, mostrou-se uma abordagem adequada, em que os melhores resultados foram obtidos para a estrada sem trÃnsito, devido a nÃo interferÃncia neste segmento, de fatores externos como trÃnsito e atividades de manutenÃÃo, nÃo explicados pelo modelo. Jà na escala da Bacia do Benguà (933 kmÂ), onde as estradas ocupam apenas 0,7% da superfÃcie, a aplicaÃÃo de modelagem mostrou que estas contribuÃram com aproximadamente 7% do total de perdas de solo na Ãrea. Os resultados deste estudo sugerem que a produÃÃo de sedimentos em estradas e taludes com superfÃcie desnuda à pelo menos uma ordem de magnitude superior Ãquelas registrada nas Ãreas preservadas da bacia. Atividades de manutenÃÃo nas estradas e o trÃnsito de veÃculos contribuem para o aumento da disponibilidade de sedimentos com impacto nos valores de concentraÃÃo de sedimentos, mas impactando menos as cargas de sedimentos que dependem do escoamento superficial e da ocorrÃncia de eventos apÃs manutenÃÃo das vias. Constatou-se que a vegetaÃÃo natural do semiÃrido tem potencial na captura de sedimentos em taludes rodoviÃrios, com papel importante na quebra de conectividade entre fluxos de sedimentos provenientes de estradas nÃo pavimentadas e o sistema de drenagem natural da bacia. / Approximately 80% of the road network in Brazil is unpaved. Studies have reported high erosion rates and runoff produced by the road infrastructure in various parts of the world and report that unpaved roads are significant sources of sediment in river basins. For two years (2013-2014), monitoring in the field under natural rainfall conditions was conducted to characterize runoff and sediment yield of unpaved rural road segments and the respective slopes in semiarid area of the Caatinga biome of northeastern Brazil, vulnerable to desertification. It was assessed the application of modelling in the yield of sediments from road surface. The sediment yield values measured in the years 2013-2014 ranged from 0.30 Mg.ha-1.year-1 to 0.92 Mg.ha-1.year-1, higher than those recorded in the preserved area, but generally lower than those reported in the literature for unpaved roads. However, it is a semiarid area with low rainfall and characterized by low runoff coefficients, which limits the sediment yield and the hydrological connectivity in the area, additionally the two monitoring years coincided with drought in the region. In the monitored road slope segments, sediment yield from the non-vegetated slope was about ten times that of the slope with vegetation. On the road surfaces, the annual sediment yield (normalized by the slope) in a segment with traffic was three times higher than that without traffic, in addition, events occurring after maintenance activities generated sediment concentration peaks as high as 5,000 mg.L-1 in these areas. In the road segment scale, among the models tested for the predicting of sediment yield, the USLE associated with the Maner equation, proved to be a suitable approach, the best results being obtained for the road without traffic due to no interference from external factors, such as traffic and maintenance activities, which are not explained by the model. In the scale of the Benguà catchment (933 kmÂ), where the roads occupy only 0.7% of the surface, the modelling indicated that these areas contributed with approximately 7% of the total soil loss. The results of this study suggest that the sediment yield from roads and slopes with bare surface is at least one order of magnitude higher than those recorded in the preserved areas of the basin. Maintenance activities on roads and traffic of vehicles contribute to the increased availability of sediments and impacting the sediment concentrations, but produce lower impact on the sediment loads, which depend on runoff and the its occurrence after reprofiling of roads. It was also found that the natural vegetation of the semiarid region has potential in capturing sediments in road slopes, with an important role in breaking down connectivity between sediment flows from unpaved roads and the natural drainage system of the catchment.

Dans le but de mieux comprendre les facteurs agissant sur le milieu fluvial à l’échelle plurimillénaire, ainsi que les effets de la dynamique alluviale sur la préservation de l’information archéologique, une étude géoarchéologique a été menée sur quatre fenêtres des vallées de la Loire, de la Saône et du Doubs en Bourgogne (France). À partir de sites de franchissement romains et d’un pont médiéval, retrouvés dans le chenal actuel, puis en étendant les recherches à d’autres secteurs, l’évolution des lits mineur et majeur au cours de l’Holocène a été reconstituée. Des informations de natures diverses, datées et spatialisées, ont été croisées : pour les deux derniers siècles, principalement les plans et vues aériennes contemporains, tandis que les périodes plus anciennes sont abordées grâce aux indices archéologiques, à l’analyse géomorphologique du lit majeur et, principalement, aux archives sédimentaires. Ces dernières ont été analysées du point de vue de la sédimentologie de faciès afin d’identifier les processus à l’origine des dépôts. Les grandes étapes de l’évolution des trois grands cours d’eau étudiés, une fois identifiées et datées, ont été confrontées aux données existantes afin d’interroger l’influence qu’ont pu avoir les fluctuations climatiques et les activités humaines sur la dynamique alluviale. La reconstitution de l’évolution du milieu au cours de l’Holocène permet enfin d’aborder la question de la conservation des données archéologiques en domaine alluvial, propice à l’implantation humaine, mais où l’information est la plupart du temps masquée par une succession de processus taphonomiques. / A geoarchaeological study was led on four sections of the valleys of the Loire, Saône and Doubs rivers (Burgundy, France) in order to point out the factors influencing the alluvial dynamics on a multimillennial scale, and their effects on the preservation of archaeological information. Investigations started by roman and medieval remains of bridges discovered in active channels, were then carried out on larger parts of alluvial plains, and altogether allowed the evolutions of the channels during the Holocene period to be deducted. Various types of information on alluvial characteristics were crossed through time and space: ancient maps and XXth century or aerial photographs for centennial scale, archaeological data, geomorphological analysis, but mostly alluvial deposits for older periods. Facies analyses on fluvial sediments led to the identification and the reconstitution of successive sedimentary environments through time. The main steps of the evolution of the three rivers, after being identified and dated, were compared to previous studies in order to estimate the respective roles of climatic changes and anthropic influence on alluvial dynamics, on this regional scale, during the Holocene. Preservation of archaeological information in fluvial deposits is therefore discussed here, to reach a better understanding of taphonomic issues in such environmennts, which are potentially rich in archaeological remains.