No description available.

Corophium volutator (Pallas) fit the criteria of ‘ecosystem engineers' as defined by Jones and colleagues (1994, 1997): they are widely distributed within and across North Atlantic estuaries, are often present in intertidal soft sediment in vast numbers, and build semi-permanent burrows in the sediment matrix, which they irrigate continuously. Previous studies have demonstrated that C. volutator burrowing and feeding not only modifies the sediment biogeochemistry but can also modify the overlying water biogeochemistry (during immersion). C. volutator activities have also been shown to be detrimental to microphytobenthic (MPB) biofilms in the immediate vicinity of the burrows. As MPB are the stabilizing force in the estuary, the decimation of biofilm destabilizes the habitat for all the organisms colonising it. However, several aspects of C. volutator ecology remain unclear. First, previous studies on the effect of C. volutator on local (within burrow proximity) MPB diversity have not presented a clear signal as to whether they increase or decrease biodiversity or established whether there is preferential survival amongst MPB taxa with certain cell shapes and sizes or lifestyles. Second, as it has been established that C. volutator have the potential to change the water column, it is possible for them to effect MPB populations remotely (outwith burrow proximity). It is therefore of interest to determine the effects they have, whether such an effect can be achieved within a tidal period, and whether these effects can change MPB biomass, behaviour or diversity over time. A series of controlled mesocosm experiments were carried out to quantify those effects of C. volutator on the water column which were likely to impact MPB survival, to determine whether those effects were specific to C. volutator or common to deposit‐feeding bioturbators, to determine to what degree they could be achieved within a single immersion period, and to separate the effects of C. volutator on MPB bulk (chlorophyll-a in top 5 mm) and photosynthesizing (fluorescing) biomass and diversity both ‘locally' and ‘remotely'. The results of the first 3 experiments consistently showed that C. volutator substantially increased the resuspension of sediment to the overlying water column and that the resulting turbidity could reduce lightpenetration to the sediment by as much as 50% within one immersion period. Results of nutrient fluxes were less consistent and clear within and between experiments but there was some suggestion that increased bioirrigation increased inorganic nitrogen flux to the overlying water column in accordance with previous studies. The effects of C. volutator on local and remote MPB biomass (bulk and surface) and diversity varied between experiments but, broadly speaking: (1) bulk biomass was unaffected, reduced locally, or increased remotely; (2) surface biomass was reduced both locally and remotely; and (3) community diversity (Simpson's diversity index) was consistently unaffected, both locally and remotely. Because increased water column turbidity is the most distinctive calling card of C. volutator but is only likely to affect the photosynthetically active (surface) MPB biomass during immersion, a controlled laboratory experiment was designed to examine the extent to which turbidity could influence MPB migratory behaviour and photosynthetic activity. MPB bulk migration was shown to be driven by sitespecific, entrained rhythms of light availability and spatial variation in light availability only drove micro‐cycling in the photic zone during the immersion period. So, in the absence of C. volutator, or any other turbidity producing phenomenon (deep water columns, high flow rates, physical disturbance, etc.), MPB will remain at the surface to photosynthesize during immersion and the productivity during this period is determined by total light intensity and exposure hours (or ‘light dose'). Therefore, the proximity and size of C. volutator populations to a site is likely to be influential in determining local productivity patterns of MPB. In addition, differences in MPB assemblage composition were shown to influence the biofilm productivity but what drives changes in MPB assemblage composition is still unclear and requires further investigation.

No description available.

Η εργασία αυτή αποσκοπεί στην προσπάθεια ανασύνθεσης του παλαιοπεριβάλλοντος της περιοχής της Αρχαίας Ελίκης μέσω της ιζηματολογικής ανάλυσης των δειγμάτων του πυρήνα της δειγματοληπτικής γεώτρησης που πραγματοποιήθηκε σε συγκεκριμένη θέση. / The purpose of this paper is to attempt to reconstruct the palaeoenvironment of the area of Ancient Helike through Sedimentological analysis of samples from the core sample drilling held in a specific position.

Η παρούσα διπλωματική διατριβή με τίτλο << Συνθήκες ιζηματογένεσης και παλαιογεωγραφική εξέλιξη των ιζημάτων της τομής «Φανερωμένη» σε σχέση με άλλες τομές της περιοχής στη λεκάνη της Σητείας στην Κρήτη >>, εκπονήθηκε στα πλαίσια του Προπτυχιακού Προγράμματος Σπουδών του τμήματος Γεωλογίας της σχολής Θετικών Επιστημών του Πανεπιστημίου Πατρών. Στόχος της εργασίας αυτής ήταν η ιζηματολογική και γεωχημική ανάλυση της τομής «Φανερωμένη» της νήσου Κρήτης με σκοπό να μελετηθούν όσο το δυνατό καλύτερα τα αποθετικά τους περιβάλλοντα, οι συνθήκες σχηματισμού τους, η γεωδυναμική εξέλιξη της περιοχής καθώς και ο εντοπισμός και η αξιολόγηση πιθανών μητρικών πετρωμάτων υδρογονανθράκων. / This thesis is entitled "Treaties sedimentary and palaeogeographic evolution of the sediment section "Phaneromene" compared with other sections of the basin area of Sitia in Crete >> , produced as part of the curriculum of the Geology Department of the Faculty of Sciences University of Patras. The aim of this work was the sedimentological and geochemical analysis of the intersection " Phaneromene " the island of Crete in order to study the best possible way the depositional environments , the conditions of their formation , the geodynamic evolution of the region and the identification and evaluation of potential parent rocks for hydrocarbons .

Orientador : Rodolfo José Angulo / Co-orientadores : Sidnei Pires Rostirolla e Eduardo Marone / Dissertaçao (mestrado) - Universidade Federal do Paraná / Resumo: A manutenção dos canais de navegação que acessam os portos organizados de Paranaguá e Antonina, através das operações de dragagens e despejo de material dragado, constituem uma atividade onerosa para os portos e impactante para o meio ambiente. Este estudo procurou oferecer uma contribuição ao conhecimento da dinâmica sedimentar e batimetrica da Baia de Antonina e porção ocidental da Baia de Paranaguá, correlacionando levantamentos históricos de batimetria e de sedimentos de fundo com dados mais recentes. O resultado desta comparação evidenciou de modo gerai uma tendência ao aumento do diâmetro médio dos sedimentos de fundo em toda a área estudada, passando de silte médio em 1966 para areia muito fina em 1995. Do ponto de vista batimetrico, ficou caracterizado intenso assoreamento da Baia de Antonina, principalmente na porção superior e nas margens, onde se constatou progradacao das planícies de maré. O volume de sedimento depositado no período entre 1901 e 1979 foi cerca de 60 x 106 m3, caracterizando uma taxa de sedimentação de aproximadamente 2,6 cm/ano. A influencia antropica exercida através da interligação das bacias de drenagem dos rios Capivari e Cachoeira para a construção de uma usina hidroelétrica, do desmatamento da Serra do Mar na região das cabeceiras dos rios e das atividades de dragagens e despejo de material dragado, parece ter tido uma contribuição significativa na aceleração do processo de colmatação deste setor do Complexo Estuarino de Paranaguá. / Abstract: The maritime channel that provides access to Paranagua and Antonina harbors requires periodic maintenance of its security maritime depth. The maintenance requires dredging and disposal, a study of the bottom sediment distribution, and a study of the bathymetrical behavior of the area under the Paranagua Harbor influence. This study aims to increase our knowledge of the sedimentary and bathymetric dynamics of Antonina Bay and the western portion of Paranagua Bay by correlating historical survey data with actual data. The results of this comparison show an increase in the average diameter of the bottom sediments all over the study area, passing the medium grain size from medium silt in 1966 to very fine sand of 1995. Regarding the bathymetrical concern, it was characterized by an intense shoaling on Antonina Bay, mainly on the upper portion and on the margins, where extensive tidal flats have developed. The total sediment volume deposited in the period between 1901 and 1979 was around 60 x 106 m3, reflecting a sedimentation rate of approximately 2,6 cm/year. Anthropic influence such as the connection of the rivers Capivari and Cachoeira for hydroelectric purposes, deforestation on river catchment areas at Serra do Mar, and activities of dredging and disposal, suggest a significant acceleration of the silting process of this portion of the Paranagua Bay Estuarine Complex.

Le comportement des rivières au cours du rifting joue un rôle important dans la sédimentation syn-rift et la distribution de la subsidence. Pendant la croissance des failles normales, les rivières répondent aux mouvements verticaux. En réponse au soulèvement tectonique, les rivières peuvent être déviées vers les zones en subsidence ou inversées. Les rivières peuvent aussi inciser les zones en soulèvement. L'évolution à long terme des rivières et leurs enregistrements stratigraphiques restent mal documentés pendant les processus de croissance et de migration des failles normales. Cette thèse analyse les interactions entre les rivières antécédentes et la croissance des réseaux de failles normales. Les implications en termes de distribution des faciès syn-rift sont étudiées à l'échelle du bassin et des blocs de failles. Les dépôts fluviatiles et deltaïques sont préservés dans plusieurs blocs de failles normales soulevés le long de la marge sud du rift de Corinthe (Grèce). Les logs sédimentaires et la cartographie des faciès syn-rift permettent le découpage lithostratigraphique de la zone d'étude. La série syn-rift est principalement conglomératique et difficile à dater. La magnétostratigraphie et quelques marqueurs biostratigraphiques sont utilisés pour dater et corréler les dépôts entre les différents blocs de faille. L'analyse des isotopes cosmogéniques 26Al et 10Be dans les dépôts a permis la détermination d'âge d'enfouissement. L'ensemble des âges obtenus par ces différentes méthodes permet de proposer un modèle de corrélation et de reconstruire l'évolution du rift précoce entre 3,6 et 1,8 Ma environ. (1) Le système fluviatile étudié évolue à travers plusieurs blocs de failles actives. (2) Le système de drainage antécédent hérité de la chaîne hellénique est caractérisé par un flux sédimentaire important depuis le début du rifting. (3) Le système fluviatile (au moins 30 km de long) remplit le paléorelief et le flux sédimentaire dépasse largement l'accommodation créée par les failles. L'enfouissement des failles par le système fluviatile limite la création de topographie et le développement d'un réseau de drainage conséquent. (4) L'axe fluviatile antécédent reste constant et contrôle la distribution des faciès. (5) Les changements de faciès et les architectures alluviales sont observés à l'échelle du bassin et ne sont pas directement contrôlés par les variations d'accommodation dans les blocs de failles. (6) Les zones d'accommodation maximale sont ici disposées parallèlement à l'axe fluviatile antécédent. La persistance des rivières et le flux sédimentaire pendant plusieurs centaines de milliers d'années ont permis la localisation de la déformation, induisant une rétroaction positive sur la croissance des failles. Le système distributaire se termine à l'est où des deltas progradent en milieu lacustre peu profond. Les systèmes de dépôts fluviatiles, deltaïques et turbiditiques actifs à l'initiation du rift de Corinthe enregistrent l'approfondissement diachrone du bassin. Le comportement des rivières antécédentes est aussi étudié à l'échelle d'une zone de relais entre deux failles bordières actuellement actives. Pendant le Pléistocène moyen et supérieur, la zone de relais a capturé la rivière antécédente de Krathis qui a construit une succession de deltas. La connexion entre les deux failles majeures est marquée par (1) des failles obliques dites "de transfert", (2) plusieurs familles de terrasses marines enregistrant le soulèvement diachrone de la rampe de relais, et (3) la migration progressive de l'accommodation vers le bassin. Cette étude permet pour la première fois de reconstruire les processus de connexion de failles sur une période 0,5 Ma. La rivière Krathis persiste au cours du développement de la zone de relais et met en évidence, une fois de plus, l'importance des rivières antécédentes dans la localisation des dépocentres majeurs dans les rifts / Rivers behaviour during early rifting can significantly impact on syn-rift sedimentation and the distribution of subsidence. During normal fault growth, existing rivers can be diverted toward subsiding zones. They can respond to footwall uplift either by reversing their flow or by incising into uplifting zones. Long-lived river systems and their stratigraphic record in rifts are poorly documented, not only during early fault propagation and linkage processes but also during successive migrating phases of fault activity. We investigate the interactions of major antecedent rivers with a growing normal fault system and the implications for facies distributions, both on a basin scale and at the scale of individual normal fault blocks. Along the southern margin of the western Corinth rift (Greece), the Plio-Pleistocene fluvial and deltaic successions are investigated. Syn-rift deposits are preserved in a series of uplifted normal fault blocks (10–20 km long, 3–7 km wide). Detailed sedimentary logging and high resolution mapping of the syn-rift deposits document variations of alluvial architecture across the basin and enable to define lithostratigraphic units. Magnetostratigraphy and rare biostratigraphic data are used to date and correlate the alluvial succession between fault blocks. Burial ages were tentatively determined using cosmogenic isotopes 10Be and 26Al produced in situ in quartz grains. Based on the correlation model, we reconstruct the evolution of the early western Corinth rift between about 3.6 and 1.8 Ma. (1) The transverse and antecedent Kalavryta river system flowed and deposited across a series of active normal fault blocks. (2) This river system was inherited from the Hellenide mountain belt and supplied high volumes of coarse sediments from the onset of extension. (3) As depocentres enlarged through time, the fluvial deposits progressively filled palaeorelief. A continuous braided plain developed above active buried faults and no significant consequent drainage system developed between the narrow fault blocks. (4) The main fluvial axis of the antecedent drainage persists through time and controlled facies distribution. (5) The length scale of facies transitions is greater than, and therefore not related to fault spacing. Here, along-strike subsidence variations in individual fault blocks represent a secondary contributor to the alluvial architecture. (6) The zones of maximum subsidence on individual faults are aligned across strike, parallel to the persistent fluvial axis. This implies that long-term sediment supply and loading influenced normal fault growth. Sediment supply largely outpaced local hangingwall subsidence and overfilled the early rift basin. The river system terminated eastward where small deltas are built into a shallow lake that occupied the central Corinth rift. During this time, another river system built fan deltas along the southern margin, recording diachronous deepening of the basin. The behaviour of antecedent rivers is also studied at the scale of a relay zone, that developed later in the rift history between two growing fault segments. During the Middle to Late Pleistocene, the relay zone captured the antecedent Krathis River, which deposited prograding Gilbert-type deltas. Transfer faults record progressive linkage and basinward migration of accommodation along the ramp axis, while marine terraces record diachronous uplift in their footwalls. Although early linkage occurred, the main normal faults continued to propagate until final connexion. For the first time a reconstruction of the linkage phase is presented over a period of ca. 0.5 Myr. Throughout this linkage history, the Krathis River continued to flow across the relay zone. Again, this emphasizes the role of antecedent rivers in supplying sediments and controlling the location of the major depocentres along the rift margins