Dissertations / Theses on the topic 'Submarine geology'

Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, June 2005.
Thesis Advisor(s): D. Benjamin Reeder, Mary Batteen. Includes bibliographical references (p. 119-121). Also available online.

The southwestern margin of the Iberian Peninsula, which includes the Gulf of Cadiz, is characterized by a present-day active deformation mainly driven by the NW-SE trending convergence between the African and Eurasia plates. In addition, this area hosts some of the largest earthquakes occurred in Western Europe. For this reason, in this PhD Thesis, tectonic and sedimentary processes in the Cape of São Vicente area are identified, important faults of the SW Iberian margin are analysed with high-resolution data, and 3D fault-plane models of the main active structures in the study area, to carry on tsunami simulations, are done. Related to the first issue, in the Cape of São Vicente area the largest submarine canyon in the external part of the Gulf of Cadiz is developed, the São Vicente Canyon. Their dynamics are highly conditioned by the convergence between the Eurasian and African plates and it is controlled by three current-active thrust faults: the Marquês de Pombal Fault, the São Vicente Fault and the Horseshoe Fault. The origin of the canyon is fully tectonic, as it shows a strong structural control. The main sediment source of the canyon is related to the disintegration of canyon flanks and the Mediterranean Outflow Water sedimentary deposits. Due to the canyon retrogressive erosion, submarine slides and scars are the main seafloor morphologies. The São Vicente Canyon is a clear example of a diachronic and segmented canyon developed since the Late Miocene in an area of active plate tectonics. Linked to the second issue, high-resolution data (autonomous underwater vehicle bathymetry and high-resolution 2D multichannel seismic profiles) allow to characterize, in detail, the Lineament South and the Marquês de Pombal faults. The Lineament South strike-slip fault is the longest active structure in the study area that may generate one of the most powerful earthquakes in the SW Iberian margin. Both ends of the Lineament South fault raise the seafloor demonstrating its current activity. The main motion component of the fault is right-lateral, as the dislocated structures in both extremes of the fault suggest. Although, a vertical component cannot be excluded. The Marquês de Pombal fault is an active left-lateral reverse fault. As isochore maps and the distribution of the vertical slip evidenced, this structure was especially active from the Middle-Miocene until nowadays where its uplift control the incision and the activity of the São Vicente Canyon. Finally, to identify the most vulnerable areas to be affected by a tsunami in SW Iberia and NW Morocco, realistic tsunami models have been built modelling in detail the main active faults in the region, including: the Gorringe Bank, Marquês de Pombal, Horseshoe, North Coral Patch and South Coral Patch thrust faults, and the Lineament South strike-slip fault. Based on a large dataset of 2D multi-channel seismic profiles, 3D sub-surface models that involves dimensional complexities of the fault planes have been generated. Additionally, with the aim to know the influence of the slip distribution along the fault plane in tsunami simulations, various heterogeneous slip-distributions have been considered in the Horseshoe fault tsunami scenario. The results show that using more complex fault geometries and slip distributions, the peak wave height (about the mean sea level) at the coastline can double compared to simpler tsunami source scenarios from planar fault geometries. Therefore, complex fault geometries and non-uniform slip distribution should be considered in future tsunami hazard updates. Tsunami simulations also show that the presence of submarine canyons attenuates the wave heights that reach the coastline, while the submarine ridges and the shallow shelf increase it. The tsunami simulations done, reveal that the most dangerous faults for the Moroccan coast are the Horseshoe, Gorringe Bank and South Coral Patch; for the Spanish and the Algarve coasts is the Lineament South fault, while the Gorringe Bank is the fault that most affects the west coast of Portugal.
Aquesta tesis doctoral s’enfoca en caracteritzar les estructures actives del Golf de Cadis, la relació d’aquestes amb els processos sedimentaris de la zona i el seu potencial tsunamigènic. En el Golf de Cadis es desenvolupa un dels canyons més importants del marge atlàntic, el canyó de São Vicente (SVC). Aquest canyó i la seva activitat estan fortament condicionats per tres falles actives: la falla de Marquês de Pombal (MPF), la falla de Horseshoe (HF) i la falla de São Vicente. El SVC presenta un origen tectònic i un fort control estructural. La principal font de sediment, que alimenten el canyó, està relacionada amb la desintegració dels seus flancs i els dipòsits sedimentaris de les corrents submarines de la zona. El SVC és un clar exemple de canyó diacrònic i segmentat desenvolupat des de finals del Miocè fins l’actualitat en una zona de tectònica activa de plaques. Per fer un estudi detallat de la perillositat tsunamigènica de les falles de MPF, HF, NCPF (Falla de North Coral Patch), SCPF (Falla de South Coral Patch), GBF (Falla de Gorringe Bank) i LSF (Falla del Lineament South) s’ha avaluat la sensibilitat dels escenaris de tsunamis a la geometria dels plans de falla i la distribució del lliscament. Primer, s’han considerant plans de falla simples amb lliscament uniforme per a totes les falles. Seguidament, s’han realitzat models complexos en 3D dels plans de falla de MPF, NCPF, SCPF i HF en base a un gran conjunt de dades de perfils de sísmica multicanal 2D. Finalment, s’utilitzen diverses distribucions de lliscament heterogeni pel cas de HF. Els models de tsunami desenvolupats suggereixen que utilitzant geometries de falla complexes i distribucions de lliscament heterogènies, l'alçada màxima de l'ona a la costa es pot duplicar en comparació amb escenaris simples, on el tsunami és generat per una falla amb geometria planar. Les simulacions de tsunami realitzades revelen que les falles més perilloses per a la costa marroquina són HF, GBF i SCPF, mentre que per a les costes espanyoles i de l'Algarve és el LSF. GBF és la falla que més afecta la costa oest de Portugal.

This thesis presents a novel technique for the quantitative characterisation of bathymetric data sets. The technique integrates three main geomorphometric methods: morphometric attributes and their statistical analyses, feature-based quantitative representation, and automated topographic classification. These methods allow useful morphological information to be extracted from bathymetric data and can significantly enhance submarine geomorphological investigations. The methods are applied to bathymetric data from the Storegga Slide, one of the largest known submarine landslides, to investigate three aspects of submarine mass movements: spreading, fractal statistics and morphology and slide development. The morphological signature of spreading, in the form of a repetitive pattern of ridges and troughs, covers at least 25% of the Storegga Slide scar. Two modes of failure can be identified for submarine spreading. The first involves retrogressive slide development via the unloading of the headwall. The second entails the extension of a thin coherent slab of semi-consolidated material downslope by gravity. Both modes of failure involve the break up of surface sediment units into coherent blocks and their displacement along planar slip surfaces. The block movement pattern entails an exponential increase of displacement, and thinning of the failing sediment, with distance downslope. Loss of support and seismic loading are the main potential triggering mechanisms of submarine spreading. Analysis of headwall morphologies within the Storegga Slide reveals the occurrence of spatial scale invariance. One explanation for this scale invariance is that the Storegga Slide is a geomorphological system that may exhibit self-organised criticality. Spatial scale invariance may also be linked to the retrogressive nature of the Storegga Slide. The shape and fractal dimension of headwalls, on the other hand, can be used as a proxy for the type and number of the formative mass movements. A detailed reconstruction of the development of the north-eastern Storegga Slide shows that after the initial evacuation of the surface sediment as turbidity currents, the area failed as an extensive spread. The spreading blocks subsequently underwent higher displacement and remoulding, and were partly removed by debris flows and turbidity currents. The renewed instability within the spreading areas may have been related to gas hydrate dissociation and pore pressure increases due in response to the changing overburden, and the distribution of contourite drift deposits within underlying palaeoslide scars.

“El present és la clau del passat”. James Hutton (1788), amb aquesta prou coneguda asserció uniformista, posà els fonaments pel desenvolupament de la investigació geològica moderna des de la perspectiva actualista. L’estratigrafia es val d’aquest principi per interpretar l’origen de les formacions geològiques a partir de l’observació de processos i geometries actuals i subactuals. Alhora, la geomorfologia estudia els processos afaiçonadors del relleu per conèixer l’origen i l’evolució del paisatge actual. Conceptualment, aquesta Tesi se situa a cavall entre l’estratigrafia i la geomorfologia amb l’objectiu general de reconèixer el per què i el com de la variabilitat morfosedimentària dels marges continentals passius silicoclàstics a llarg termini. Per atènyer aquest objectiu adoptem la hipòtesi de partida següent: la variabilitat morfològica dels marges continentals silicoclàstics passius pot ésser classificada per categories de forma objectiva i sistemàtica. Les diferències morfològiques observades responen principalment a l’acció d’uns pocs processos sedimentaris claus. Els mètodes i conceptes emprats en aquesta Tesi són propis de la hidrodinàmica i la sedimentologia. L’observació detallada de la morfologia i l’estratigrafia dels marges continentals, junt amb l’estudi dels processos hidrodinàmics que les han generades i l’anàlisi de la variabilitat espaciotemporal de les condicions ambientals en què s’han format, permet establir lleis de transport geomòrfic, altrament dites lleis de la morfodinàmica. En els successius capítols d’aquesta Tesi abordem aquests aspectes mitjançant l’anàlisi de dades geofísiques de reconeixement del fons i del subsòl marins, amb un especial èmfasi en les xarxes de drenatge del talús continental i la conca profunda. Els resultats d’aquesta anàlisi se sintetitzen en el plantejament d’un model morfodinàmic predictiu sobre la forma del perfil longitudinal dels canyons submarins. Aquest model dóna peu a discutir sobre transitorietat i equilibri en les formes de drenatge observades a les dades geofísiques considerades. Així doncs, en aquest treball advoquem per la complementarietat i interdependència de les anàlisis observacionals i la modelització basada en la formulació teòrica de processos. Els principals resultats obtinguts en aquest treball demostren la possibilitat d’extreure informació sobre l’evolució de les conques sedimentàries a partir de l’estudi de les seves morfologies, tan modernes com relictes i fòssils, i indiquen la necessitat d’entendre els canyons submarins com a sistemes capaços d’evolucionar a partir de mecanismes netament deposicionals, a més dels mecanismes erosius ja prou coneguts. Aquests resultats es poden traduir en una millora de les prediccions estratigràfiques al talús continental, en un millor coneixement de la distribució de reservoris sedimentaris d’hidrocarburs o aigua en aquests ambients, i a replantejar els models establerts sobre el desenvolupament dels canyons submarins a escala global. La Tesi està formada per un compendi de quatre articles publicats en revistes pertanyents al Journal Citation Report de l’Institute for Scientific Information (JCR-ISI), i l’hem estructurada en set capítols. El Capítol 1 consisteix en una introducció general destinada a centrar el lector en el marc conceptual, geogràfic i metodològic en què s’ha elaborat l’estudi. Els capítols 2 a 5 corresponen als quatre articles publicats. El capítol 6 correspon a la síntesi i discussió general dels principals resultats presentats als quatre capítols anteriors. Al capítol 7 hi incloem un sumari de les conclusions més rellevants conjuntament amb algunes perspectives de futur sorgides arran d’aquest treball. Finalment, a l'Annex, hi incloem un treball de síntesi bibliogràfica on descrivim les principals característiques fisiogràfiques dels fons marins mediterranis.
Sedimentary morphodynamics of siliciclastic passive continental margins "The present is the key to the past". James Hutton (1788), with this well-known principle of uniformitarianism, established the basis of the modern geology by following the assumption of actualism. Stratigraphy makes use of this principle to interpret the origin of geological formations according to observations of modern and submodern processes and geometries. Geomorphology studies the processes that sculpt the Earth’s surface to understand the origin and evolution of present landscapes. The main objective of this Thesis, which is conceptually halfway between stratigraphy and geomorphology, is to understand the long-term morphosedimentary variability of siliciclastic passive continental margins. Our initial hypothesis is that the morphology differences among modern siliciclastic passive margins can be objectively and systematically categorized, and that these differences are mainly related to the action of a few key sedimentary processes. The methods and concepts we use in this study are based on hydrodynamics and sedimentology. The detailed observation of continental margin morphology and stratigraphy, the study of the hydrodynamic processes that control their evolution, and the analysis of changing environmental conditions through time and space facilitate the development of geomorphic transport laws (also known as morphodynamic flux laws) for predicting landscape forms and dynamics. In the following chapters we discuss these topics while analysing seafloor and subseafloor geophysical data, with a particular focus on submarine drainage networks. An important result of this analysis is a morphodynamic model that can explain the long-profile shape of submarine canyons. The model stimulates our discussion about the equilibrium and transience of drainage morphologies observed in the geophysical data set we present. In this work we advocate for the complementariness and interdependence of observational analyses and modeling of sedimentary processes. This Thesis demonstrates that much can be learned about the sedimentary evolution of submarine basins from the study of seascape morphologies, both modern and ancient, and that submarine canyons can evolve while remaining net depositional, beyond the broadened view of these features as purely erosive. These results can be translated to improved stratigraphic prediction in slope strata, a better knowledge of hydrocarbon and water resource distribution in these settings, and a broadened view of submarine canyon development.

Ademas de identificar y describir las formas del relieve, la geomorfologia tambien intenta descifrar los procesos y mecanismos causantes. Esto, que es válido para la geomorfología en general, lo es también para la geomorfología submarina. La mayoría de procesos geológicos que tienen lugar en el fondo del mar, en sus proximidades, y en su subsuelo, dejan una huella en el lecho marino que se puede observar medir e interpretar. Pero también es cierto, que además de los procesos geológicos, hay otros tipos de procesos físicos, químicos, biológicos y antropogénicos que también modelan el lecho de los océanos. Por otro lado, el mismo relieve submarino afecta a dichos procesos, confor- mando así un bucle de acción reacción. Lo ilustran las interacciones entre las corrientes de contorno y el fondo, o entre el substrato y las comunidades bentónicas. La ecosonda de multihaz es la herramienta más valiosa para el estudio de la geomorfología sub- marina y, en consecuencia, también lo ha sido para esta tesis. Los modelos de elevación digitales obtenidos a partir de datos de multihaz son el primer paso para el estudio integrado de la geomor- fologia de una regi6n o lugar, y la base para planificar actividades de muestreo. En esta tesis, la lo- calización precisa y la interpretación de los elementos del relieve han permitido situar los puntos de mayor interes para una inspecci6n detallada, ademas de guiar las tareas de muestreo y verificaci6n de lo observado e interpretado en los fondos marinos de las islas Canarias. El archipiélago canario está situado en el margen pasivo del África nor-occidental. Pero lejos de res- ponder a un modelo estructural sencillo y fácilmente interpretable, el contexto geológico regional del archipiélago es notablemente complejo y su origen objeto de debate. Además, el conjunto de edificios volcanicos de que forma parte el archipielago consta de mucho mas que de las siete islas principales, puesto que también lo integran un número considerable de montes y cerros submari- nos, que en conjunto configuran la provincia de montes submarinos de las islas Canarias, termino bastante más adecuado para referirse al enclave geológico en que se inscribe esta tesis. Los nuevos datos batimétricos de alta resolución recogidos en este trabajo, junto con otros datos complementarios, su analisis y la discusi6n de su significado, representan una contribuci6n original para una mejor comprensión del rompecabezas geológico de la provincia de montes submarinos de las islas Canarias. Se trata de una contribución que creemos que incluye elementos clave. Por un lado, hemos podido documentar la más reciente erupción submarina ocurrida en aguas del archipiélago, mar adentro de su isla más joven; El Hierro, cosa que ha permitido conocer mejor la contribución de este tipo de eventos a la formaci6n de los edificios volcanicos insulares. Por otro lado, hemos puesto de manifiesto la evoluci6n tardia de una antigua isla de extensi6n mas que notable, el actual banco de Concepción, actualmente sumergido por completo. La aplicación de técnicas como el álgebra de mapas o la geomorfometria, asi como la verificaci6n de interpretaciones mediante la observaci6n in situ y el muestreo, aportan objetividad y solidez cientifica a los resultados alcanzados. Uno de los resultados más relevantes del presente trabajo es la constatación de la sutil frontera que separa lo viejo de lo joven en la provincia de montes submarinos de las islas Canarias. Esto lo ilustra el surgimiento del volcán más joven de Canarias, en 2011, en el lecho marino al sur de El Hierro, al lado de un edificio volcanico de 132 millones de anos de edad: el rift o dorsal sur de El Hierro. Tam- bién nos parece particularmente relevante el papel de procesos geológicos y estructuras antiguas como substrato moderno de hábitats de especial interés, como arrecifes de corales de aguas frías y comunidades quimiosintèticas de aguas profundas, tales como las encontradas en el banco de Concepción.
A mes d'identificar i descriure les formes del relleu, la geomorfologia també mira d'escatir els processos i mecanismes causants. Això, que val per a la geomorfologia en general, també val per la geomorfologia submarina. La majoria de processos geològics que es donen al subsòl marí, al mateix fons i prop del fons, deixen una empremta observable, mesurable i interpretable en el fons marí. És cert, però, que a més dels processos geològics, hi ha altres tipus de processos físics, químics, biològics i antropogènics que també afaiçonen el fons dels oceans. Per altra banda, el mateix relleu submarí influencia aquests processos, tancant-se aixi una mena de circuit. Ho il•lustren les interaccions entre corrents de contorn i el fons, o entre el substrat i les comunitats bentòniques. L’ecosonda de multifeix és l’eina més valuosa per a l’estudi de la geomorfologia submarina i, en conseqüència, també ha estat l’eina principal d’aquesta tesi. Els models d’elevació digitals obtinguts a partir de dades de multifeix són el primer pas per a l’estudi integrat de la geomorfologia d'una regió o indret, i la base per planificar activitats de mostratge. En aquesta tesi, la localitzaci6 precisa i la interpretació dels elements del relleu han permès situar els punts de més interès per a una inspecci6 detallada, a més de guiar les tasques de mostratge i verificació d'allò observat i interpretat en els fons marins de les illes Canàries. L’arxipèlag canari està situat al marge passiu d’Àfrica nord-occidental. Però lluny d’obeir a un model estructural senzill i fàcilment interpretable, el context geològic regional de l’arxipèlag és força complex i el seu origen objecte de debat. A més, el conjunt d'edificis volcànics de que forma part l’arxipèlag consta de molt més que les set illes principals, doncs també l’integren un nombre molt alt de monts i turons submarins, el conjunt dels quals forma la província de monts submarins de les illes Canàries, un terme força més adequat per a referir-se a l’entorn geològic en que s’inscriu aquesta tesi. Les noves dades batimètriques d’alta resolució recollides en aquest treball, juntament amb altres dades complementàries, el seu anàlisi i la discussió del seu significat, representen una contribució original per a una millor comprensió del trencaclosques geològic de la província de monts submarins de les illes Canàries. Es tracta, però, d’una contribució que creiem que inclou elements clau. Per un costat, hem pogut documentar l’erupció submarina més recent ocorreguda en aigües de l’arxipèlag, enfora de la seva illa més jove, El Hierro, cosa que ha permès conèixer millor la contribuci6 d'aquests tipus d'esdeveniments a la formaci6 dels edificis volcànics insulars. Per un altre costat, hem fet palesa l’evolució tardana d’una antiga illa d’extensió més que notable, l’actual banc de Concepción, ara sota l’aigua. L’aplicació de tècniques de l’àlgebra de mapes i de la geomorfometria, aixi com la verificaci6 d'interpretacions mitjan;ant l'observaci6 in situ i el mostratge, donen objectivitat i solidesa científica als resultat assolits. Un dels resultats més rellevants del present treball és la constatació de la subtil frontera que se- para el que és vell del que és jove a la província de monts submarins de les illes Canàries, com ho il•lustra la formaci6 del volcà mes jove, l'any 2011 als fons del sud de El Hierro, al costat d'un edifici volcànic de 132 milions d'anys d'edat: el rift o dorsal sud d'El Hierro. També ens sembla particularment rellevant el paper de processos geològics i estructures antigues com a substrat modern d’hàbitats d’especial interès, com ara esculls de coralls d’aigües fredes i comunitats qui- miosintètiques d'aigües profundes, tal i com il•lustra el cas del banc de Concepción.
Beyond identifying and describing landforms, geomorphology aims at unveiling their causative processes and mechanisms. This, which applies to geomorphology in the broadest sense, is also valid for submarine geomorphology. Most of the geological processes that occur below, at and close to the seafloor leave an observable, measurable and interpretable imprint on it. However, it is also true that processes other than geological do shape the seabed as well. These include a ran- ge of physical, chemical, biological and anthropogenic processes. Moreover, the submarine lands- cape influences those processes in an action/reaction loop. This is illustrated by the interactions between contour currents and the bottom, or between the substratum and benthic communities. The multibeam echo sounder is the most valuable tool to investigate the geomorphology of the marine environment and, therefore, has been the main tool for this thesis. The Digital Elevation Models (DEMs) resulting from multibeam data are the first step for the comprehensive study of a region or site geomorphology, and the main reference for the planning of sampling activities. In this thesis, the precise location and interpretation of landforms, has allowed to pinpoint the ‘hot spots’ deserving detailed inspection, to guide sampling and to groundtruth the observations and interpretations made across the seafloor of the Canary Islands. The Canary archipelago is located on the passive continental margin of Northwest Africa. But far from responding to a simple and easy to interpret structural model, the geological setting of the archipelago is quite complex and its origin still debated. Furthermore, the cluster of volcanic edifices to which the archipelago belongs is much more than the main seven islands, as it also consists of a large number of seamounts and submarine knolls, altogether forming the Canary Is- lands Seamount Province, a more appropriate term to refer to the geological setting of this thesis. The new high-resolution bathymetric datasets gathered in this work, and other complementary data, together with the analysis and discussion of their meaning, represent a novel contribution for an improved understanding of the Canary Island Seamount Province geological puzzle. We think this contribution includes key elements. On one hand, we have been able to document the most recent submarine eruption around the archipelago, offshore its youngest island, El Hierro, which has resulted in a better knowledge of the contribution of this kind of events to the outbuil- ding of the volcanic edifices forming the islands. On the other hand, we have evidenced the late evolution of a rather large old island, Concepcion bank, now under water. The application of map algebra and geomorphometry techniques, jointly with the groundtruthing of interpretations by means of in situ observations and sampling provide scientific objectivity and robustness to the results achieved. One of the most noticeable outcomes of the present work is the finding of the narrow separation between the old and the young in the Canary Island Seamount Province, as illustrated by the eruption of the youngest submarine volcano in 2011 south of El Hierro besides to a 132 Ma old volcanic edifice off the south rift of El Hierro. The role of ancient geological processes and struc- tures as substratum for modern habitats of special interest also looks highly relevant, as illustrated by the cold-water coral reefs and deep-water chemosynthetic communities found in Concepcion Bank.

Extreme heterogeneity in oil saturation between closely adjacent sandstone beds reflects different timing and degree of diagenesis. Understanding the distribution and origin of such heterogeneity is critical to effectively exploiting intercalated sandstone deposits within fine-grained unconventional reservoirs and in unraveling subtleties of stratigraphic traps. Sea cliff exposures at Point Fermin, California, expose a submarine channel facies within the largely hemipelagic facies. Separated by only meters, Point Fermin Sandstone is oil-saturated, whereas Altamira Shale sandstone is not. Samples were analyzed for porosity, permeability and fluid saturation in conjunction with thinsection petrographic analysis. Sandstones are primarily schist- bearing lithic arenites and the grains are cemented mostly by rhombic dolomite. Data show that both units have the same provenance but differ in the timing and type of diagenesis with shale-hosted sandstones generally showing earlier cementation. The degree and type of cementation occluded pore spaces to prevent hydrocarbon charging in the non-saturated sandstone.

Hydrothermal systems may have been more widespread in the Hadean due to a greater heat flux. To investigate this possibility, and unravel the mechanism(s) by which the pH of high-temperature vent fluids become acidic and what produces their distinctive black colour, reactions between model seawater and mafic/ultramafic rock were conducted. Results indicated that ancient, medium to high temperature (150-300°C), alkaline hydrothermal fluids would have precipitated carbonates, brucite, and calcite upon re-mixing with cold, slightly alkaline seawater and may have predominated in the Hadean. Acid pH was effected by the loss of magnesium from seawater and calcium loss from mafic rock. Black-smokers were unlikely in the Hadean as the ocean was probably acidic due to high levels of CO2. Water-rock reaction models were constructed to test the possibility that simple amino acids could have been generated in early hydrothermal fluids, and to see how pH and redox conditions affect their distribution (cf. Amend and Shock, 1998). Though concentrations of amino acids produced were negligible, amino acids were stable in low-temperature, alkaline, and reduced hydrothermal fluids and may have concentrated in the colloidal sieve comprising a hydrothermal mound. An extension of the experiment to determine if glycine could be condensed to higher carbon number amino acids (alanine, valine, leucine) under hydrothermal conditions, indicated that condensation may be 'pulled' by a decrease of H2O activity of the fluid. In conclusion, this study improved on previous environmental and reactant constraints by simulating the generation of inorganic prebiotic reactants from the local geochemical hydrothermal environment. Consequently, the quantity of chemical species such as hydrogen and sulfide available for organic synthesis were limited by the local geochemical settings in the model, whereas others have, often admittedly, used reactants in higher concentrations than were probably available when Life emerged.

The purpose of this study was to investigate multiple methods used to locate and identify sources of submarine groundwater discharge (SGD) along the coastline of Santa Catalina Island (Catalina) in Los Angeles, California. The driving hypothesis is that SGD may be identified by higher temperature/lower salinity plumes. To test this hypothesis, temperature and conductivity measurements were made along the shoreline of Catalina and compared with previously collected airborne thermal infrared images. In some locations where potential zones of SGD were identified, samples were collected from the surface water within the plume and analyzed for the presence of radon. Radon in ocean water can be used as a tracer to identify the presence of terrestrial groundwater. The analysis was complicated by dynamic variables including tides, weather, and sample collection. In spite of this uncertainty, one potential zone of SGD was identified using sea surface temperature, electrical conductivity, and radon at Toyon Bay. This zone of SGD is consistent with the location of warm water shown in airborne infrared imagery. These results suggest that high-resolution thermal imagery may be useful for identifying diffuse SGD in southern California, but further field tests will be necessary to confirm this conclusion.

Hydrogeologically, Rapa Nui (Easter Island, Chile) is one of the least understood islands in Polynesia. There are no surface streams, the soils are poor in productivity and highly permeable, and the water table sits far below the surface of the island. One of the many mysteries of Rapa Nui is how the ancient inhabitants survived with so few sources of freshwater.

Fieldwork was conducted to identify terrestrial sources of freshwater and to evaluate the occurrence of submarine groundwater discharge (SGD). We documented observable surface water features located in the interior and coast of the island and made field measurements of water temperature and salinity to identify areas of SGD along the coast. The limited number of interior surface water features, periods of drought, permeable aquifers, and existence of puna (dug wells) along the coast of Rapa Nui lead us to conclude that coastal seeps were an important prehistoric source of freshwater.

Submarine flows can transport huge volumes of sediment across the large submarine fans that dominate many parts of the deep ocean floor. Active flow events are notoriously difficult to monitor directly, and therefore our understanding of such flows still strongly relies on the analysis of the deposits they leave behind. This thesis aims to investigate the transport and depositional processes, the stacking patterns and the time frequency distribution of turbidites and debrites deposited in the Miocene Marnoso Arenacea Formation (Italian Apennines). This location is unique because deposits from individual flow events (beds) can be traced for long distances, allowing the lateral and down flow evolution of single flow events to be analyzed in detail. Lateral changes in individual flow deposits are documented through extensive correlation of beds deposited in a stratigraphic interval below the most prominent Contessa Marker bed. The observed transitions in facies, and the external shape of different types of deposit, are used as an independent test of models that capture our understanding of submarine flow processes. This work highlights how deposits of submarine density flows can be complex, even in relatively simple basin plain settings. A single event can comprise different flow types, and transformations can occur between these flow types. The initial volume, sediment concentration and grain size (including the proportion of fine cohesive mud) control the external shape of the deposits. Low density turbidity currents deposit clean sandstone beds with an exponentially tapering shape, while coarser grained high density turbidity currents produce massive or parallel laminated layers that maintain their thickness for longer (10’s of kilometers) distances. Cohesive debris flows form istinctive ungraded mud-rich sandstone that can either pinch-out abruptly or gradually taper. Liquefied debris flows with elevated pore pressures can deposit clean (mud-poor) sand over large areas (up to 30 km) of the Marnoso Arenacea basin plain. This is suggested by the distinctive swirly, patchy fabric of a particular type of clean sandstone, that records pervasive liquefaction during the late stages of the flow, and confirmed by the rapid pinch-out geometry of flow deposits at their margins. Such debris flows most likely form through transformation from an initial high density turbidity current. A similar flow process may characterize the distal, rapid pinch out of sandstone lobes in Fan 4 of the Skoorsteenberg Formation (Karoo basin, South Africa). The observed stacking pattern of turbidite beds in a 530 meters thick stratigraphic section indicates a long-term clustering. Debrite intervals however occur randomly, and bed correlation suggest that almost every large volume flow deposited clean or muddy debrite (or both) intervals in different positions of the basin. Hemipelagic marl thickness is used as a proxy for time between flow events. The distribution of time between events is exponential, therefore related to a Poisson Process. This indicates that flow events (most likely triggered by submarine slope failures) occur independently one from the other through time.

Submarine-fan deposits form the largest sediment accumulations on Earth and host significant reservoirs for hydrocarbons. While many studies of ancient fan deposits qualitatively describe lateral architectural variability (e.g., axis-to-fringe, proximal-to-distal), these relationships are rarely quantified. In order to enable comparison of key relationships that control the lateral architecture of submarine depositional environments, I digitized published bed-scale outcrop correlation panels from five different environments (channel, levee, lobe, channel-lobe-transition-zone, basin plain). Measured architectural parameters (bed thickness, bed thinning rates, lateral correlation distance, net-to-gross) provide a quantitative framework to compare facies architecture between environments. The results show that sandstone and/or mudstone bed thickness alone or net-to-gross do not reliably differentiate between environments. However, environments are distinguishable using a combination of thinning rate, bed thickness, and correlation distance. For example, channel deposits generally display thicker sandstone beds than mudstone beds whereas levees display the opposite trend. Lobe deposits display the most variability in all parameters, and thus would be the most difficult to identify in the subsurface. I sub-classified lobe deposits to provide a more detailed analysis into unconfined, semiconfined and confined settings. However, the results for semiconfined lobes indicate that the degree of lobe confinement and subenvironment is not easily interpretable at the outcrop scale. This uncertainty could be partially caused by subjectivity of qualitative interpretations of environment, which demonstrates the need for more quantitative studies of bed-scale heterogeneity. These results can be used to constrain forward stratigraphic models and reservoir models of submarine lobe deposits as well as other submarine depositional environments.

This work is paired with a case study to refine the depositional environment of submarine lobe strata of the Upper Cretaceous Point Loma Formation at Cabrillo National Monument near San Diego, California. These fine-grained turbidites have been interpreted as distal submarine lobe deposits. The strike-oriented, laterally-extensive exposure offers a rare opportunity to observe bed-scale architecture and facies changes in turbidites over 1 km lateral distance. Beds show subtle compensation, likely related to evolving seafloor topography, while lobe elements show drastic compensation. This indicates more hierarchical method of compensational stacking as the degree of bed compensation is small compared to the degree of element compensation. Thinning rates and bed thicknesses are not statistically different between lobe elements. This signifies that the lateral exposure is necessary to distinguish lobe elements and it would be extremely difficult to accurately interpret elements in the subsurface using 1D data (e.g., core). The grain size, mudstone to sandstone bed thicknesses, element/bed compensation, and lack of erosion observed in the Cabrillo National Monument exposures of the Point Loma Formation are most similar to values of semiconfined lobe deposits; hence, I reinterpret that these exposures occupy a more medial position, perhaps with some degree of confinement.

Submarine channels are conduits that transfer sediment from continental shelves to the deep sea. They can form important hydrocarbon reservoirs when filled with sand-prone deposits and are, consequently, one of the most important hydrocarbon prospects on continental margins around the world. In this thesis, a 3D seismic volume from offshore Espírito Santo (SE Brazil) was used to analyse submarine channel systems near the modern sea floor. The aim of the thesis was to investigate the key controlling factors on variations in the morphology and architecture of submarine channel systems, at the same time, providing an analogue for modern and ancient depositional systems on continental slopes around the world. This work shows significant variations in morphology and architectures along the investigated submarine channel systems. The spatial variations in both channel and valley morphology documented here suggest an important role of local factors (e.g. mass-wasting events, tributaries, substrate lithology and salt tectonics) in the development of channel systems. It also records in great detail the nature of the interaction between mass-transport deposits and turbidity currents at the early stages of channel evolution. Basal scars created by mass-wasting events can capture turbidity currents and facilitate flow channelisation, which is a key process for submarine-channel initiation. In addition, the replacement of MTDs by channel-fill deposits has profound implications for reservoir volumes and net-to-gross ratios in channel systems. Spatial variations in channel sinuosity observed in this work are interpreted as reflecting substrate erodibility beneath the channel system. Submarine channels will show higher sinuosity when encountering resistant substrates, and lower sinuosity when the substrate is more erodible. Temporal changes in channel sinuosity resulted from enhanced sediment discharge from tributaries. This work stresses the role of lateral channel migration as an important mechanism responding to factors such as sediment supply and ultimately, controlling the evolution of submarine channel systems.

An interdisciplinary study of the geomorphology, sedimentology, stratigraphy and physical oceanography of the deep-sea environments of the Alboran Sea (south-western Mediterranean Sea) has been carried out with the purpose of evidencing and understanding the role of bottom currents in the sedimentary evolution of the Spanish and Moroccan continental margins and adjacent basins during the Pliocene and Quaternary. This study was conducted using swath bathymetry data, more than 1900 profiles consisting of parametric, single- and multi-channel seismic records, scientific and commercial wells, sediment cores, and hydrographic data comprising: Conductivity, Temperature and Depth (CTD) profiles, Acoustic Doppler Current (ADCP) profiles, and EK60 echograms. Here, for the first time, a morphosedimentary scenario with a wide spectrum of depositional (plastered, sheeted, channel-related, mounded confined, elongated and separated drifts) and erosional (terraces, escarpments, moats, channels and furrows) contourite features are described in the Alboran Sea, from the shelf break to the basin floor. Hydrographic data offers new insights into the distribution of the Mediterranean water masses, and reveals that the bottom circulation of the Western Intermediate Water (WIW) and the Levantine Intermediate Water (LIW) interact with the Spanish slope, and the Western Mediterranean Deep Water (WMDW) with the Moroccan slope, Spanish base- of-slope and deep basins. The integration of distinct datasets and approaches allow a new sedimentary model to be proposed for the Alboran Sea that underlines the significance of bottom current processes in shaping deep-sea morphology. This model suggests that the bottom circulation of water masses governs physiography that the interface positions of water-masses with contrasting densities sculpt terraces at a regional scale, and that morphological obstacles play an essential role in the local control of processes and water- mass distribution. An analysis of the seismic stratigraphy from the Pliocene and Quaternary sequences has enabled to update and rename the stratigraphic boundaries and establish a new seismic stratigraphy for the Alboran Sea, after relocating the base of the Quaternary from 1.8 to 2.6Ma. Additionally, the seismic analysis involves the presentation and discussion for the first time of the evidence for contourite features reaching the scale of the Alboran Basin. Contourite drifts (plastered, sheeted, elongated separated and confined mounded drifts) and erosive features (terraces, escarpments, moats, channels, furrows) were developed under the continuous influence of Mediterranean water masses after the opening of the Strait of Gibraltar (-5.33Ma). At least two primary factors have controlled the contourite features in this sea: i) tectonics, which has governed the relocation of the main Mediterranean flow pathways and their circulation patterns; and ii) climate, which has influenced both water-mass conditions (depth and density contrast of the interfaces) and hinterland sediment sources, conditioning the morphoseismic expression and growth pattern of drifts and terrace formation (dimensions). The distribution of contourite features through time and space allows to propose three main scenarios for ocean circulation since the opening of the Strait of Gibraltar: i) Atlantic Zanclean flooding; ii) the Pliocene sea, with two different stages for the dense circulation and characterised by poorly-defined and unstable interfaces for the Atlantic Waters (AW), light and dense Mediterranean waters and the presence of a strong countercurrent in the Western Basin; and iii) the Quaternary sea, characterised by tabular Mediterranean water masses with multiple current dynamics, increasingly important density contrasts, and climate shifts causing major vertical and horizontal displacement of the interfaces. These stages reflect variability in the bottom current regimes and related alongslope efficiency in terms of transport, deposition and erosion. The detailed seismic analysis of the units making up the Pliocene and Quaternary sequences allows for the first time, to make an in-depth analysis of the contourite features, turbidite systems and mass-movement deposits, and map them through time. These maps are enormously helpful when it comes to understanding the sedimentary architecture of the Spanish and Moroccan continental margins and basins, as well as for decoding the palaeoceanographic processes from a geological perspective. Two main contourite depositional systems are defined: the Intermediate Mediterranean Contourite System (IMCS), formed under the action of the Light Mediterranean Waters (LMW) on the Spanish margin, and the Deep Mediterranean Contourite System (DMCS), formed under the action of the Dense Mediterranean Waters (DMW) mainly on the Moroccan margin and basins. The characterisation of the terraces as contourite features that form under the combination of two water masses, has also led to the definition of the Atlantic Contourite System (ACS). The occurrence of several contourite depositional systems has led to the suggestion of a new term, not heretofore considered in the literature: Multiple Contourite Depositional System (MCDS), which refers to the set of different CDSs that occurs in the same area and evolving under the action of multiple water masses. In addition, twenty turbidite systems have been characterised, revealing that they are responsible for the different sedimentary architecture of the Spanish margin, where they coexist with contourites, as on the Moroccan margin the turbidite systems are less well developed. The mass-movement deposits are mainly related to the reworking of the contourites draping the highs. Mainly contourites but also turbidites, allowed to define from a geological perspective the basic oceanographic processes and to determine their occurrence, relative magnitude and energy, and time of action. This PhD thesis also explains the uneven development of the turbidite systems in the Alboran Sea, which is interpreted to be conditioned by the interaction of alongslope with downslope processes. Several morphological and sedimentary signatures produced by the interaction between both processes have been identified in the Pliocene and Quaternary records, as well as on the present-day seafloor of the Alboran Sea. The interaction scenarios move between two-end-members: from bottom currents dominating gravity flows to gravity flows dominating contour currents. In between these extreme cases, the alternation and mutual influence of both processes can occur. Two different conceptual models of interaction are proposed for the Spanish and Moroccan margins. i) On the Spanish margin, the alongslope and downslope interaction is especially complex and varied, with both regional and local effects on the turbidite systems. This is because here the turbidite systems are influenced at different water depths by Atlantic and Mediterranean water masses and their interfaces, with current flows that change across- and downslope. ii) On the Moroccan margin, the vigorous action of the WMDW primarily inhibits the formation of canyons and associated deposits. The findings of this PhD thesis suggest that the relevance of bottom-water processes in deep sea must be reevaluated. It is concluded that understanding the influence of bottom currents is not only essential for reconstructing present and past water mass circulation, but also for recognising sea floor morphologies and decoding the sedimentary stacking pattern and evolution of deposits, as well as global climate and periods of eustatic variation.
En el presente trabajo se ha llevado a cabo un estudio multidisciplinar de la geomorfología, sedimentología, estratigrafía y oceanografía física de los ambientes profundos del Mar de Alborán (extremo sur-oeste del Mar Mediterráneo), con el propósito de comprender el papel que los procesos asociados a las corrientes de fondo juegan en la evolución sedimentaria de los márgenes continentales de España y Marruecos, así como de las cuencas adyacentes, durante el Plioceno y el Cuaternario. Este estudio se ha llevado a cabo empleando datos de batimetría multihaz, más de 1900 registros sísmicos de sonda paramétrica, mono- y multi-canal, sondeos científicos e industriales, testigos de sedimento, y varios tipos de datos hidrográficos que comprenden: perfiles de conductividad, temperatura y profundidad (CTD), perfiles obtenidos con un correntómetro acústico Doppler (ADCP), y ecogramas registrados con una ecosonda EK60. Por primera vez en el Mar de Alborán, se ha sido descrito un contexto morfosedimentario compuesto por un amplio espectro de rasgos contorníticos deposicionales (crestas adosadas, laminares, asociadas a canales, monticulares confinadas y elongadas separadas) y erosivos (terrazas, escarpes, fosas, canales y surcos erosivos), desde el borde de la plataforma continental hasta las cuencas. Los datos hidrográficos han ofrecido nueva informaci6n sobre la distribución de las masas de agua mediterráneas, y han revelado que la circulación de fondo del Agua Intermedia Occidental ("Winter Intermediate Water", WIW) y el Agua Intermedia Levantina ("Levantine Intermediate Water", LIW) interaccionan con el talud continental del margen español, mientras que el Agua Mediterránea Occidental Profunda ("Western Mediterranean Deep Water", WMDW) interactúa con el talud continental del margen marroquí, la base de talud del margen español y las cuencas profundas. La integraci6n de diversas bases de datos y de distintas disciplinas ha permitido proponer un nuevo modelo sedimentario para el Mar de Alborán el cual enfatiza la importancia de los procesos sedimentarios asociados a corrientes de fondo en el moldeado de los fondos marinos. Este modelo sugiere que la circulación de fondo de las masas de agua condiciona la fisiografía, que la posici6n de las interfaces de las masas agua con un importante contraste en sus densidades, es capaz de esculpir terrazas a escala regional, y que los altos morfológicos desempeñan un papel esencial en el control local de procesos y en la distribución de las masas de agua. El análisis de la estratigrafía sísmica de las secuencias Pliocena y Cuaternaria ha permitido actualizar y renombrar los límites estratigráficos del Mar de Alborán, tras la reubicación además de la base del Cuaternario de 1,8 a 2.6 Ma, así como establecer una aproximación cronológica a los mismos. Asimismo, este análisis sísmico ha permitido presentar y discutir evidencias de depósitos contorníticos a escala del Mar de Alborán. Los rasgos contorníticos de tipo deposicional (crestas adosadas, laminares, elongadas separadas y confinadas) y erosivo (terrazas, escarpes, fosas, canales y surcos) se desarrollaron bajo la influencia continua de las masas de agua mediterráneas tras la apertura del Estrecho de Gibraltar (-5.33 Ma). Al menos dos factores principales han controlado los rasgos contorníticos en esta cuenca: i) la tectónica, que rige la reubicación de los principales flujos mediterráneos y por tanto sus patrones de circulaci6n; y ii) el clima, que ha influido en las condiciones de las masas de agua (profundidad y contraste de densidad en las interfaces) y en las áreas fuentes de sedimento en tierra, condicionando la expresión morfo-sísmica y los patrones de crecimiento de los depósitos contorníticos así como la formación de terrazas (dimensiones). La distribución de los elementos contorníticos en el espacio y el tiempo, permite proponer tres escenarios principales para explicar la circulación de las masas de agua desde la apertura del Estrecho de Gibraltar: i) la inundación atlántica en el Zancliense; ii) el mar Plioceno, con dos etapas diferentes para la circulación profunda y que en general se caracteriza por la presencia de interfaces poco definidas e inestables entre las aguas atlánticas (AW), y las aguas mediterráneas ligeras y densas, así como por la presencia de una fuerte contracorriente en la cuenca occidental de Alborán; por último, iii) el mar Cuaternario, que se caracteriza por masas de agua mediterráneas con flujo mayormente tabular pero con múltiples dinámicas de flujo a nivel local, una creciente influencia de los contrastes de densidad, y grandes cambios climáticos que provocan desplazamientos verticales y horizontales de las interfaces. Estas tres grandes etapas reflejan la variabilidad en los regímenes de corrientes de fondo, y la eficiencia en el transporte de sedimento, sedimentación y erosión a lo largo del margen. El estudio sísmico detallado de las unidades que componen las secuencias Pliocena y Cuaternaria ha permitido por primera vez el análisis y la cartografía a lo largo del tiempo de los rasgos contorníticos, los sistemas turbidfticos y los depósitos de inestabilidad sedimentaria. Estos mapas han permitido comprender la arquitectura sedimentaria de los margenes continentales espanol y marroquí y de las cuencas, así como definir los procesos paleoceanograficos desde un enfoque geológico. Se han definido dos grandes sistemas deposicionales contorníticos: el Sistema Deposicional Contornítico Intermedio (SDCI), formado bajo la acci6n de las aguas mediterráneas de menor densidad en el margen español, y el Sistema Deposicional Contornítico Profundo (SDCP), formado bajo la acción de las aguas mediterráneas densas principalmente en el margen marroquf y en las cuencas. La caracterización de las terrazas como rasgos contorníticos formados bajo la acción combinada de dos masas de agua ha llevado tambien a definir el Sistema Deposicional Contornítico Atlántico (SDCA). El desarrollo de varios sistemas deposicionales contorníticos ha dado lugar a la definición de un nuevo termino no planteado previamente en la literatura: el Sistema Deposicional Contornftico Multiple (SDCM), referido a un conjunto de diferentes SDC que se forman en una misma zona bajo la acción de múltiples masas de agua. Asimismo, se han caracterizado veinte sistemas turbidítiicos que son la causa principal de las diferencias en la arquitectura sedimentaria que presentan el margen español, en el que coexisten con las contornitas, y el margen marroquí, donde están menos desarrollados. Con respecto a los depósiitos de inestabilidad sedimentaria, su formación esta relacionada principalmente con el retrabajamiento de las contornitas que recubren los altos. Las contornitas principalmente, pero tambien las turbiditas, han permitido definir desde una perspectiva geológica los principales procesos oceanográficos así como determinar su ocurrencia, magnitud y energía relativas, y su tiempo de acción. En esta Tesis se explica tambien el desarrollo desigual que presentan los sistemas turbidíticos en el mar de Alborán, y que ha sido interpretado como resultado de la interacción entre los procesos sedimentarios paralelos (asociados a las corrientes de fondo) y perpendiculares (asociados a los procesos de flujos gravitativos) al margen. En los registros Plioceno y Cuaternario, asf como en el fondo marino actual del mar de Alborán, se han identificado rasgos de tipo morfológico, sedimentario y sedimentológico producidas por la interacción entre ambos procesos. Los escenarios de interacción varfan entre dos situaciones extremas: las corrientes de fondo dominan sobre los flujos gravitativos, y los flujos gravitativos dominan sobre la acción de las corrientes de fondo. Entre ambos extremos puede producirse la alternancia y la influencia mutua de ambos procesos. Se han propuesto dos modelos de interacción conceptuales para los margenes español y marroquí. i) En el margen espanol la interacción es especialmente compleja y variada, con efectos regionales y locales sobre los sistemas turbidíticos. Esto ocurre debido a que los sistemas turbidíticos están influenciados a diferentes profundidades por las masas de agua atlánticas y mediterráneas y sus interfaces, con una dinámica además que varía longitudinal y perpendicularmente al margen. ii) En el margen marroquí, la acción intensa de la WMDW inhibe en gran parte la formación de canones y depósitos asociados. Los resultados de esta Tesis sugieren que la importancia de los procesos relacionados con corrientes de fondo en ambientes marinos profundos debería ser reevaluada. Se concluye que una mayor comprensión de su influencia es esencial no sólo para reconstruir los patrones de circulación recientes y pasados, sino también para identificar determinados rasgos morfosedimentarios, descifrar sus patrones de sedimentación y evolución, así como establecer tendencias en el clima y variaciones eustáticas a nivel global.

Submarine landslides are one of the most important processes for moving sediment across our planet. Landslides that are fast enough to disintegrate can generate potentially hazardous tsunamis, and produce long run-out turbidity currents that break strategically important cable networks. It is therefore important to understand their frequency and triggers. This thesis aims to do so using extensive datasets (N>100) suitable for statistical analysis. The influence of temporally non-random variables on landslide and turbidity current frequency is assessed statistically. In light of predicted future global and sea level rises this is a timely study. Analysis of large volume turbidites (>0.1 km3) reveals two distinct frequency distribution forms for submarine landslide recurrence. A Poisson (time-independent) form is observed in three basins which may indicate similar controls on landslide frequency and triggers occur in disparate areas. A log-normal (time-dependent) distribution is seen in the Iberia Abyssal Plain over much longer timescales (20 Myr). Physiographic and palaeoclimatic effects are thought to explain the two different distribution forms. The influence of sea level is either shown to be statistically insignificant (Poisson form) or has a significantly delayed (~1.2 Myr) influence (log-normal form) on landslide and turbidite recurrence. Two sequences that cross the Initial Eocene Thermal Maximum (IETM) hyperthermal, show a reduction in turbidity current and landslide activity, rather than the increase hypothesised by many studies. Therefore, predicted future sea level rise and global warming may not necessarily result in significantly increased submarine landslide or turbidity current frequency on human timescales. Finally, a unique direct monitoring dataset from the Squamish Prodelta, British Columbia provides new insights into the links between rivers and offshore deltas on very short (