The Late Neogene sedimentary sequence of the Murray Basin provides an excellent opportunity to examine paleoenvironmental change across southeastern Australia. A detailed stratigraphic analysis of sediments deposited within the basin in the last 10 Ma was undertaken to assess the influence of tectonic and eustatic processes on deposition. / Stratigraphic observations and radiogenic isotope analysis reveals the onset of deposition by 7.2 Ma with a transgressive episode that deposited the marine marls of the Bookpurnong Beds. Deposition was restricted to the central and eastern parts of the basin due to the Hamley Fault. In the west, subsurface elevation contours indicate the presence of incised paleodrainage channels above Miocene limestones, which facilitated the formation of a large estuary system at 5.3 Ma. The sediments of the Norwest Bend Formation were deposited within this western region, while further east, the Loxton-Parilla Sands strandplain deposited over 214 coastal ridges. The basal parts of this unit occur as lateral equivalents to the sediments of the Lower Norwest Bend Formation (in the west). Topographic and magnetic data reveal that tectonism was active during this period and resulted in the erosion and truncation of strandlines. / Tectonic evidence and an estimated minimum 28,037 year cyclicity between strandline sets, suggests that the Loxton-Parilla Sands strandlines do not represent an unbroken record of glacioeustatic change. The subaerial exposure of these sediments at approximately 3.0 Ma caused the formation of a calcareous karst above the Norwest Bend Formation and a ferruginous and/or silicious cap (the Karoonda Surface) above the Loxton-Parilla Sands. The stratigraphic position of these surfaces are indicative of a regional widespread unconformity. / The Douglas-Blackburn paleodrainage system in western Victoria was dammed during the Mid-Late Pliocene by uplift associated with the Padthaway High, which caused the formation of a 400,000 km2 lacustrine system, known as Lake Bungunnia. Topographic analysis indicates that Lake Bungunnia comprised at least four distinct sub-basins with water depths of up to 30 metres, with lake shorelines indicating that active tectonism occurred during this period. The resulting lack of sediment input to the coast caused the formation of the Kanawinka Escarpment, a large erosional scarp along the southern margin of the Padthaway High. / The geomorphology of the modern Murray Basin can be directly attributed to the demise of the Lake Bungunnia system. Movement along the Morgan Fault in the west at approximately 700 Ka, resulted in the draining and progressive drying of Lake Bungunnia as a breach was created along the Padthaway High. The Murray River gorge as observed today was incised following this episode. The modern Murray River (and playa lakes such as Lake Tyrell) occupy the lowest elevations along the former sub-basins of Lake Bungunnia. / The Late Neogene sedimentary sequence across the Murray Basin illustrates a complex interaction of eustatic and tectonic processes on deposition. Sedimentation within strandline, estuarine and lacustrine systems, particularly in the western Murray Basin, display evidence of significant tectonic control. This highlights the important role that neotectonic processes have played in shaping southeastern Australia.

<p>Denna avhandling behandlar den småskaliga rumsliga variationen av löst organiskt kol (DOC, engelsk term: dissolved organic carbon), dess koncentration, masstransport och karaktär, i bäckar inom två barrskogsbeklädda avrinningsområden (delavrinningsområden 0,01-78 km²). Provtagningen gjordes uppströms och nedströms varje bäckförgrening under sommarbasflöde. Koncentrationen av DOC varierade inom en tiopotens (4-66 mg/l), liksom flera andra kemiska parametrar. Vid riksinventeringen av vattendrag för 2000 i norra Sverige noterades en snarlik spännvidd. Enligt Naturvårdverkets bedömningsgrunder för sjöar och vattendrag återfanns alla tillståndsklasser för DOC och pH, samt mänsklig påverkansgrad till försurningen inom de två studerade områdena. Den specifika avrinningen (flöde per areaenhet) varierade kraftigt i källflödena och inverkade på deras bidrag till kemin nedströms. Vattenkemin och specifika avrinningen var stabila i delavrinningsområden större än 15 km². Det kan vara nödvändigt att provta så stora områden om generella värden för landskapet önskas, men källflödenas kemi kommer då inte att kunna karakteriseras, ehuru källflödena utgör den största delen av bäcksträckan och det akvatiska ekosystemet.</p><p>Nedströms är DOC-koncentrationen, och många andra kemiska parametrar, lika med summan av bidragen från källflödena och nedströms utspädning av inflödande vatten. Tillkommer gör processer inom bäcken och vattnets utbyte med botten/grundvatten (den hyporheiska zonen), men även DOC-förluster/transformationer vid vissa bäckförgreningar och sjöar. Ovanstående resonemang förklarade bäckvattenkemins minskande variation och vanligen lägre DOC-koncentrationer nedströms i ett landskapsperspektiv. Längs bäcksträckorna observerades ingen generell minskning av DOC-koncentration eller ändring av dess karaktär. Skillnaden i DOC-koncentration och relaterade parametrar mellan källflöden och nedströms styrdes i hög grad av vilka landskapselement (myrar, sjöar och skogsmark) som vattnet hade passerat innan det hamnade i bäckarna, samt samspelseffekter med den specifik avrinningen och platserna med DOC-förlust. Prognoser med multivariata modeller baserade på kartinformation testades men kunde inte förutsäga det rumsliga mönstret eller DOC-koncentrationen med erforderlig precision.</p><p>Lämpliga rutiner inom miljöövervakningen för att övervaka den rumsliga variationen av kemin i ytvatten saknas alltjämt. Vid planering av terrestra och akvatiska skötselåtgärder bör man beakta bäckvattnets naturliga kemiska variation.</p> / <p>This thesis quantifies the small-scale spatial variation of dissolved organic carbon (DOC) concentrations, fluxes and character in two boreal catchments (subcatchments 0.01-78 km²) using ”snapshots” of summer base flow where samples were taken upstream and downstream from every node in the stream network. An order of magnitude variation was found in DOC-concentrations, and many other chemical parameters. The range was similar to that found in all of northern Sweden by the national stream survey in 2000. According to the official assessment tools used in Sweden, the entire range of environmental status for DOC, pH and human acidification influence existed within these two study catchments. A large variability in specific discharge had a major impact on the contribution of headwaters to downstream chemistry. The water chemistry parameters were relatively stable at catchment areas greater than 15 km². Sampling at that scale may be adequate if generalised values for the landscape are desired. However the chemistry of headwaters, where much of the stream length and aquatic ecosystem is found would not be characterized.</p><p>Downstream DOC-concentrations, as well as many other chemical parameters, are the sum of headwater inputs, in combination with progressive downstream dilution by inflowing water with its own DOC-concentration and character. Superimposed upon this are in-stream and hyporheic processes, as well as discrete loci of DOC loss/transformation at lakes and stream junctions. At the landscape scale, this results in a decreased downstream variation in stream water chemistry and often, but not necessarily, lower average DOC-concentrations. Along stream reaches there was not a loss of DOC-concentration or a consistent change in character. While the importance of in-stream/hyporheic processes that consistently alter DOC-concentrations along the channel network cannot be ruled out, the differences between headwater and downstream DOC-concentrations and related parameters depend largely on the mosaic of landscape elements (mires, lakes and forest soil) contributing water to the channel network, combined with patterns of specific discharge and discrete loci of DOC loss. Assessment would be facilitated by map information that could predict spatial patterns. Multivariate models using maps, however, did not give satisfactory predictions.</p><p>Appropriate procedures for dealing with spatial variation in the environmental assessment of surface waters are not yet established. An awareness of stream water chemistry’s natural spatial variability should be considered when planning aquatic and terrestrial management.</p>

Thesis (M.Sc.)--Memorial University of Newfoundland, 2005. / The CD-ROM includes Appendix A. Bibliography: leaves 205-214. Also available online.

Dans lhémisphère Sud, les reconstitutions paléoclimatiques à haute résolution sont encore relativement rares. Cette partie du monde joue pourtant un rôle essentiel dans la compréhension des changements climatiques terrestres. Le Sud du Chili étant suffisamment éloigné des calottes glaciaires de lhémisphère Nord et de linfluence de la circulation thermohaline, il constitue une région idéale en vue détudier les changements paléoclimatiques de lhémisphère Sud. Dans ce travail, le remplissage sédimentaire de deux lacs chiliens dorigine glaciaire a été étudié par une analyse multi-paramètres de carottes prélevées lors de lété austral 2002 dans le cadre du projet SSTC ENSO-Chili. Dans le lac Puyehue (164 km², 40°S, altitude 185 m), la carotte la plus prometteuse a été prélevée au site PU-II, localisé sur un cordon morainique sous-aquatique, dominé par les courants intermédiaires du Rio Golgol. Les sédiments de ce site sont finement laminés et faiblement perturbés par les activités volcanique et sismique. Premièrement, une carotte courte du site PU-II a été étudiée de manière détaillée en vue de (1) tester différentes techniques de mesure de la densité et du contenu sédimentaire en matière organique et en silice biogénique, et (2) reconstituer les changements climatiques régionaux au cours des 600 dernières années. Plusieurs traceurs ont été utilisés : la granulométrie, la susceptibilité magnétique, la géochimie des éléments majeurs, les concentrations en silice biogénique ainsi que les concentrations et les propriétés géochimiques de la matière organique (C/N, d13C). Ces analyses sont utilisées pour reconstituer les variations de paléoproductivité et de paléoprécipitations aux alentours de 40°S. Les résultats démontrent que, durant les 600 dernières années, les plus forts taux daccumulation massique en particules terrigènes sont enregistrés dans lintervalle 1490 1700 AD. Ce résultat est interprété comme une période humide associée à la mise en place du Petit Age Glaciaire européen (LIA). Les fortes précipitations caractérisant cette période pourraient être la signature locale du LIA. Le LIA serait donc un évènement global qui nest pas restreint à lhémisphère Nord. Les traceurs sélectionnés ont ensuite été appliqués à une carotte de 11 m de longueur prélevée au site PU-II. Le modèle dâge de cette carotte a été élaboré à partir de 9 datations radiocarbone et prouve que cette séquence sédimentaire couvre la dernière déglaciation et lHolocène. Les résultats démontrent que la granulométrie est hautement corrélée avec le contenu biogénique du sédiment et peut ainsi être utilisée comme traceur de paléoproductivité lacustre. La susceptibilité magnétique quant à elle est fortement corrélée avec les concentrations en aluminium et en titane et constitue un indicateur des apports terrigènes. Les variations temporelles de la composition du sédiment démontrent que, depuis le Dernier Maximum Glaciaire, la Région des Lacs chilienne a été soumise à trois changements climatiques abrupts survenus lors dune évolution climatique à plus long terme. Ces changements climatiques rapides sont : (1) la fin du Dernier Maximum Glaciaire à 17.300 cal. yr. BP ; (2) un évènement froid entre 13.100 et 12.300 cal. yr. BP, caractérisé par une terminaison abrupte et interprété comme léquivalent local de la période froide caractéristique du Dryas Récent et (3) une instabilité climatique à 3400 2900 cal. yr. BP probablement à mettre en relation avec une faible activité solaire. Lâge de lévènement froid à 13.100 12.300 cal. yr. BP est comparé aux datations obtenues sur des enregistrements similaires dans les deux hémisphères. Cette comparaison démontre que lévènement enregistré à Puyehue précède denviron 500 à 1000 ans lévènement froid caractéristique de la période du Dryas Récent dans lhémisphère Nord. Lenregistrement sédimentaire du lac Icalma (11,65 km², 38°S, altitude 1140 m) est fortement perturbé par les évènements sismiques et volcaniques. Lexistence de particules sédimentaires grossières nous a amenés à développer une méthode de mesure granulométrique combinant diffraction laser et tamisage par voie sèche. Les descriptions macroscopiques, les analyses granulométriques, les profils de susceptibilité magnétique et les résultats minéralogiques ont permis de décrire quatre types de dépôts évènementiels probablement engendrés par des séismes (homogénites, turbidites, slumps et dépôts chaotiques). Ces analyses démontrent également que les turbidites et les homogénites sont engendrées par un mécanisme similaire et que des dépôts texturalement intermédiaires existent. Ils peuvent être regroupés sous le terme turbidite s.l. et, dans ce cas, une homogénite serait léquivalent dune turbidite déposée sous linfluence dun effet de seiche. La séismite la plus récente décrite dans les sédiments du lac Icalma est un dépôt de slump ubiquiste de 6 cm dépaisseur daté à 1100 AD. Bien que la région ait été affectée par de nombreux séismes de magnitude importante au cours de la période historique (1500 2000 AD), il semble quaucun dentre eux nait engendré une séismite dans le lac Icalma. Daprès les résultats obtenus sur deux carottes longues (8 m), la région dIcalma a été soumise à une importante activité sismo-tectonique entre 3000 et 2200 cal. yr. BP.

This study investigated the warm-temperate to tropical shallow-water Miocene carbonates of the Perfugas basin (Anglona area), northern Sardinia, Italy (Central Mediterranean). The aim of this study was to identify and document the existence and significance of early diagenesis in this carbonate system, especially the diagenetic history, which reflects the diagenetic potential in terms of skeletal mineralogy. The motivation behind the present study was to investigate the role that early cementation has over facies stabilization linked to differences in biotic associations in shallow-water settings. Principal to this was to unravel the amount, kind and distribution of early cements in this type of carbonates, in order to complement previous studies, and hence acquire a more global perspective on non-tropical carbonate settings. The shallow-buried Sedini Limestone Unit was investigated for variations on early diagenetic features, as well as for the type of biotic association, and oxygen and carbon stable isotope stratigraphy. Results showed, that particularly at the Perfugas basin (< 15 km2), which evolves in time from a ramp into a steep-flanked platform, shallow-water facies are characterized by a “transitional” type of biotic association. The biotic assemblages change gradually over time from a heterozoan-rich into a photozoan-rich depositional system. This transition implies a change in the depositional environmental control factors such as temperature. It is considered that sedimentation took place under warm-temperate waters, which shifted to more warmer or tropical waters through time. Moreover, it was noticed that along with these changes, marine early syn-depositional cements (high-Mg calcite), with particular fabrics (e.g. fibrous), gradually contributed to the early lithification of rocks, favoring a steepening of the platform relief. The major controls for the shift of the depositional geometry was triggered by the change of the type of biotic associations (carbonate factory), related with the shift towards warmer conditions, and the development of early marine cementation. The identification of the amount and distribution of different cement phases, porosities and early diagenetic features, within facies and stratigraphy, showed that diagenesis is differential along depth, and within the depositional setting. High-Mg calcite cements (micrite, fibrous and syntaxial inclusion-rich) are early syn-depositional, facies-related (shallow-water), predominant at the platform phase, and marine in origin. Low-Mg calcite cements (bladed, syntaxial inclusionpoor and blocky) are early to late post-depositional, non-facies related (shallow- to deep-water) and shallow-burial marine in origin. However, a particular difference exists when looking at the amount and distribution of low-Mg calcite bladed cements. They become richer in shallow-water facies at the platform phase, suggesting that the enrichment of bladed cementation is linked to the appearance of metastable grains (e.g. aragonite). In both depositional profiles, the development of secondary porosity is the product of fabric-selective dissolution of grains (aragonite, high-Mg calcite) and/or cements (syntaxial inclusion-rich). However, stratigraphy and stable isotopes (oxygen and carbon), indicate that the molds found at shallower facies located beneath, and close to stratigraphic boundaries, have been produced by the infiltration of meteoric-derived water, which caused recrystallization without calcite cementation. Away from these stratigraphic locations, shallow- and deep-water facies show molds, and recrystallization, as well as low-Mg calcite cementation, interpreted as occurring during burial of these sediments by marine waters. The main cement source is suggested to be aragonite. Our results indicate that the Sedini Limestone Unit was transformed in three different diagenetic environments (marine, meteoric and shallow-burial marine); however, the degree of transformation in each diagenetic environment differs in the heterozoan-dominated ramp from the photozoan-dominated platform. It is suggested that the sediments from the ramp follow a diagenetic pathway similar to their heterozoan counterparts (i.e. lack of marine cementation, and loss of primary porosity by compaction), and the sediments from the platform follow a diagenetic pathway similar to their photozoan counterparts (i.e. marine cementation occluding primary porosity). However, in this carbonate setting, cements are Mg-calcite, no meteoric cementation was produced, and secondary porosity at shallow-water facies of the platform phase is mostly open and preserved. Despite the temporal and transitional change in biotic associations, ramp and platform facies (shallow- to deep-water facies) showed an oxygen isotope record overprinted by diagenesis. Oxygen primary marine signatures were not found. It is believed that burial diagenesis (recrystallization and low-Mg calcite cementation) was the main reason. This was unexpected at the ramp, since heterozoan-rich carbonates can hold isotope values close to primary marine signals due to their low-Mg calcite original composition. Ramp and platform facies (shallow- to deep-water facies) showed a carbon isotope record that was less affected by diagenesis. However, only at deep-water facies, did the carbon record show positive values comparable with carbon primary marine signals. The positive carbon values were noticed with major frequency at the platform deep-water facies. Moreover, these values usually showed a covariant trend with the oxygen isotope record; even that the latter did not hold positive values. The main conclusion of this work is that carbonates, deposited under warm-temperate to tropical conditions, have a unique facies, diagenesis and chemostratigraphic expression, which is different from their cool-water heterozoan or warm-water photozoan counterparts, reflecting the “transitional” nature of biotic association. / Diese Arbeit befasst sich mit den warmen bis tropischen miozänen Flachwasserkarbonaten des Perfugas Beckens (Region Anglona) im nördlichen Sardinien, Italien. Ziel dieser Arbeit war es, die Existenz und Signifikanz der frühen Diagenese in diesem Karbonatsystem zu identifizieren und zu dokumentieren. Die Geschichte der Verfestigung reflektiert dabei das diagenetische Potential, welches von der Mineralogie der Grundgerüste ehemaliger Lebewesen abhängig ist. Die Motivation bestand darin, die frühe Zementation der Karbonate zu beschreiben, da sie eine wesentliche Rolle bei der Faziesstabilisierung spielt wenn diese durch unterschiedliche biotische Verbindungen im Flachwasser aufgebaut wurde. Der Fokus dieser Studie liegt bei der Trennung von Menge, Art und Verteilung der frühen Zemente in Karbonaten. Frühere Arbeiten wurden ergänzt und zusammen gefasst, um eine globale Übersicht bezüglich nicht tropischer karbonatischer Milieus zu erlangen. Die flach abgelagerte Einheit der Sedini Karbonate wurde unter multiplen Gesichtspunkten z.B. früher diagenetischer Strukturen, biotischer Gesellschaften sowie durch Messungen stabiler Isotope an Sauerstoff und Kohlenstoff untersucht. Die Ergebnisse zeigen, dass das Perfugas Becken (< 15 km2), welches sich von einer Rampe zu einem, von steilen Flanken begrenzten, Plateau entwickelte und sich durch eine Flachwasserfazies auszeichnet, die auf eine “Übergangsart” der biotischen Gemeinschaft hinweist. Diese Gemeinschaft veränderte sich allmählich von einem heterozoischen zu einem photozoischen Ablagerungssystem. Diese Verschiebung impliziert einen Wechsel der Faktoren, wie der Temperatur, die das Ablagerungsmilieu beeinflussen. Es wird angenommen, dass die Sedimentation in warmen Gewässern stattfand, welche sich bis hin zu tropischen Temperaturen kontinuiertlich erwärmten. Es ist bekannt, dass sich parallel zu diesen marinen Veränderungen frühe Mg- reiche kalzitische Zemente bildeten, die ein ausgeprägtes z.T. faseriges Gefüge zeigen. Diese unterstützen die frühe Verfestigung der Kalke und ermöglichen eine Versteilung des Reliefs der Plattform. Die hauptsächlichen Faktoren, die eine Verschiebung der Ablagerungsumgebung hervorriefen, wurden durch die Veränderung der biotischen Gesellschaft und durch die Entwicklung früher Zemente aufgezeichnet, die wiederum mit der Erwärmung des Habitats zusammenhängen. Die Identifizierung der Menge und Verteilung der verschiedenen Zementphasen, der Porosität und der frühen diagenetischen Elemente in Fazies und Stratigraphie zeigen, dass die Verfestigung mit zunehmender Tiefe und innerhalb des Ablagerungsareals variiert. Mg- reiche kalzitische Zemente (mikritisch, faserig, syntaxial einschlussreich) wurden im frühen, marinen Stadium während der Ablagerung gebildet. Mg- arme kalzitische Zemente (blättrig, syntaxial einschlussarm, blockig) entstanden nach der Ablagerung im flachen bis tiefen marinen Wasser z.T. unter überlagernden Einheiten. Ein offensichtlicher Unterschied existiert bei Menge und Verteilung von Mg-armen, blättrigen Zementen. Sie werden in der Flachwasserfazies innerhalb der Plattformphase häufiger, was mit dem Auftreten metastabiler aragonitischer Körner zusammen fällt. In beiden Ablagerungsprofilen ist die Entwicklung der Sekundärporosität das Produkt einer gefügeabhängigen Auflösung der Körner (aragonit, Mg-reiche Kalzite) und/oder der Zemente (syntaxial einschlussreich). Stratigraphie und stabile Isotope (Sauerstoff, Kohlenstoff) zeigen jedoch, dass sich Abdrücke in der Flachwasserfazies finden lassen, die sich zwischen und in der Nähe der stratigraphischen Grenze befinden. Die Abdrücke entstanden durch Infiltration von meteorischen Wässern, was zu Rekristallisation ohne kalzitische Verfestigung führte. Fernab dieser stratigraphischen Lokalitäten, zeigen Flach- und Tiefwasserfazien Abdrücke, Rekristallisationen und Mg-arme kalzitische Zemente die offensichtlich durch Überlagerung dieser Sedimente in marinen Gewässern entstanden sind. Als Hauptzementkomponent wird Aragonit angenommen. Unsere Ergebnisse zeigen, dass die Sedini Kalksteineinheit in drei verschiedene diagenetische Umgebungen umstrukturiert wurde (marin, meteorisch, flach überlagert). Der Grad der Umwandlung in den einzelnen diagenetischen Umgebungen unterscheidet sich von der heterozoisch dominierten Rampe zur photozoisch dominierten Plattform. Es wird angenommen, dass die Sedimente der Rampe einem diagenitischen Pfad folgen, der ähnlich des heterozoischen Gegenstücks verläuft (z.B. Fehlen der marinen Zementation, Verlust primärer Porosität durch Kompaktion). Die Plattformsedimente folgen einer diagenetischen Abfole ähnlich ihrer photozoischen Pendants (z.B. marine Zementation welche die primäre Porosität). In diesem Karbonatumfeld sind die Zemente Mg-reich und nicht meteorische verfestigt. Eine sekundäre Porosität der Flachwasserfazien in der Plattformphase ist offen und gut erhalten. Trotz der temporären und vorübergehenden Wechsel in den biotischen Vergesellschaftungen, in den Flachwasserfazien von Rampe und Plattform wie in den Tiefwasserfazien der Rampen, sind Signale in den Sauerstoffisotopen erkennbar, wenn diese auch durch von der Diagenese überdeckt. In diesen Fazien wurden keine primären, marinen Sauerstoffisotopien gefunden. Es wird angenomen, dass die erfolgte überdeckt Diagenese (rekristallisation, Mg-arme kalzitische Zementation) der Hauptgrund dieser fehlenden Isotopensignale darstellen. Dies war an der Rampe unerwartet, da heterozoen-reiche Karbonate primäre, marine Isotopenwerte speichern können, welches aufgrund ihrer Mg-armen Zusammensetzung ermöglicht wird. Das Kohlenstoffisotopensignal der unterscheidlichen Fazien von Rampe und Plattform, zeigten sich weniger von der Diagenese betroffen. Nur in den Tiefwasserfazien zeigte das Kohlenstoffsignal positive Werte, vergleichbar mit primären, marinen Signalen. Die positiven Kohlenstoffwerte wurden an den Plattformtiefenwasserfazien mit größter Häufighkeit registriert. Diese Werte zeigten in der Regel einen kovarianten Trend mit dem Sauerstoffisotopensignal, sogar wenn letzterer keine positiven Werte enthielt. Die Schlussfolgerung aus dieser Arbeit ist, dass Karbonate welche unter warmen bis tropischen Verhältnissen abgelagert wurden, eine einmalige Faziesgenese und chemische Stratigraphie aufweisen. Diese ist unterschiedlich zu ihren heterozoischen Kaltwasser oder ihren photozoischen Gegenstücken aus wärmeren Wässern. Dies wiederum reflektiert gut das “transitionale” Wesen einer biotischen Gesellschaft.

<p>The tropics are a significant source of heat and moisture export, which drive global circulation patterns, thus it is vital to systematically understand the land, ocean and sedimentological interactions within the tropics. The Brazilian continental margin is an ideal region to characterize the tropics due to its unique local oceanography and proximity to the atmospheric engine that is the Amazon Basin. A combination of: 1) terrestrial organics and hydrology; 2) oceanographic temperature, isotopic composition, and salinity and 3) early diagenesis and geochemistry of sedimentary interstitial water and methane hydrate, provide a detailed understanding of the primary constituents that influence the South American tropics.</p><p>Sedimentological, organic and paleoceanographic reconstructions of the Amazon Basin, Brazilian Nordeste, and western equatorial Atlantic have been undertaken on two sediment cores located on the Brazilian continental slope representing 30 and 110 ka, respectively. High-resolution XRF analyses of Fe, Ti, K and Ca are used to define the sedimentological history of the Amazon Basin and northern Nordeste. Here we present elemental ratios of Ti/Ca and Fe/K, in addition to magnetic susceptibility, to determine variability in Amazon Basin and Nordeste hydrology. Bulk organic proxies d13C and d15N of sedimentary organic carbon are used to define the organic history of the Amazon Basin. Peaks in Ti/Ca and Fe/K ratios largely correlate in both the Amazon Basin and in the Nordeste Record. These excursions correlate with commonly modeled global slowdown of the Atlantic meridional overturning circulation (AMOC) during increased northern hemisphere glaciation. Differences in the Fe/K and Ti/Ca records suggest periods of increased chemical weathering independent of precipitation driven sediment discharge in the Brazilian Nordeste. Bulk organic geochemistry indicates the vegetative history of the Amazon Basin has been relatively stable during the late Quaternary.</p><p>High-­resolution stable oxygen isotopic analysis and Mg/Ca paleothermometry undertaken on the near-­surface-dwelling planktic foraminiferal species Globierinoides ruber provide a picture of paleoceanographic forcings in the western equatorial Atlantic. The Nordeste core exhibits a rapid warming of ~3.5ºC between the last glacial maximum and the early Holocene. Furthermore, in almost all cases during the last glacial stage, there was a 0.5 to 2ºC warming of the western equatorial Atlantic during the periods of high Ti/Ca ratios that correlate with slowdown of AMOC. Thus, as observed in some previous studies, the western equatorial Atlantic was warm and the adjacent southern tropical continent was wet coincident with increased glaciation in the high latitude northern hemisphere.</p><p>Interstitial pore waters were analyzed from the Amazon Fan and Brazilian continental slope to determine early diagenesis, methane hydrate potential and its geographic variability. Interstitial waters were measured for total Mg, Ca, SO4, alkalinity, Cl, and d18O, combined with seismic bottom simulating reflectors (BSRs) to investigate early diagenesis. Interpolated maps of sulfate reduction, sedimentation rate and maximum alkalinity were produced to examine geographic variability in early diagenesis and methane hydrates. Inorganic precipitation of calcium and magnesium, likely via dolomite and siderite, correlates with a decrease in alkalinity through inorganic carbonate precipitation and methanogenesis, but alternatively increases through redox pathways, specifically sulfate reduction.</p><p>Through multiple lines of evidence it is likely that there is extensive methane hydrate occurrence on the Amazon continental shelf. A combination of: 1) A rapid linear decline in sulfate at an unusually shallow depth; 2) Uncommonly high sedimentation rates and terrestrial organic carbon input; 3) Significant variability in what should be conservative chloride concentrations; 4) Large variability in interstitial oxygen isotopes; 5) Widespread occurrence of BSRs provide substantial support for the presence of methane hydrates. Sulfate reduction rates are lowest along the main Amazon channel, with highest values distal of the main channel. Sedimentation rates are relatively low on the continental shelf and surrounding the main channel and highest toward the distal end of the main channel. Sulfate reduction rates provide key insights to the potential geographic variability of methanogenesis and methane hydrate formation. Given the tremendous influx of sediment from the Amazon River, this region is prone to massive sediment failures, subsequent release of methane hydrates, as well as significant potential for natural gas hydrates.</p> / Dissertation

The storm surge from Hurricane Ike inundated Bolivar Peninsula as well as pooled up (~4 meters above sea level) in the Galveston Bay System behind Bolivar. After the hurricane passed, this water flowed back over the peninsula for about 19 hours, causing a great deal of coastal destruction. Analysis of post-Hurricane Ike aerial photography and Lidar data revealed the development of dramatically different scour and backflow features in the beach and dune environments along Bolivar Peninsula, Texas. Using Ward's cluster analysis, the 454 identified features were grouped according to shape and size characteristics generated by an object-oriented shape analysis program. Five distinct groups of features emerged from the cluster analysis. Group 1 features were small and compact, distributed mostly in the west; Group 2 features were large and dendritic in nature, distributed where the peninsula was narrow. Group 3 features had a longshore orientation with many of them resembling piano keys, distributed in the east. Group 4 features were oriented longshore and ornate in shape. Many of them were similar in shape to Group 2 or 3 features though statistically different enough to be grouped alone; they were distributed mostly in the eastern half of the study area. Group 5 features tended to be elongated, oriented cross-shore, nonbranching, and distributed mostly in the east. At least four flow environments caused characteristic forms. The first flow environment is typified by seaward flowing water encountering a road parallel with the coastline. The water flowing over the road scours deeply on the leeward side (seaward side), denuding beach sediments down to the resistant mud layer (Groups 3 and 4). The second flow environment was caused by a geotube, which breached during the storm and channelized flow through the breaches (Groups 2 and 5). The third flow environment had a comparatively high elevation, high development, and shore-perpendicular roads (Group 2). The fourth flow environment was typified by wide beaches backed by dunes (lost in the storm) as well as flat vegetated areas. Water flowing seaward over the vegetation scoured deeply into troughs after it came off the vegetation (Groups 1, 3, and 4).

The Montian Kartal Formation lies in the south-west of Ankara region and overlies the Upper Cretaceous Beyobasi Formation and is overlain by Thanetian Kirkkavak Formation conformably in the studied region (Kayabasi village, NW of town of Haymana). A 283 m stratigraphic section, which is mainly composed of an alternation siliciclastic and carbonate rocks has been measured in the Kartal Formation within the Haymana-Polatli basin. The aim of this study is to carry out the sedimentological and cyclostratigraphical analyses of the upper part of the Kartal Formation within Haymana-Polatli basin which represents a well developed cyclic pattern. In this study, detailed lithofacies analyses were performed and four different facies were recognized along the measured section: sandstones, limestones, mudrocks and conglomerates. Sedimentological analyses, such as modal, provenance, palaeocurrent, grain-size and grain parameters were also performed and their relation with the depositional environment and change in depositional conditions were discussed. Interpretations of the depositional environment revealed that the deposition occurred by low sinuosity rivers and waves. Additional environmental interpretations suggested that the sediments were deposited in shallow marine and/or coastal (beach) environments. High resolution cyclostratigraphy studies based on meter scale cyclic and rhytmic occurrences of lithofacies along the measured section were performed. The whole section, which is 283 m thick, was divided into large-scale hierarchy-cycles which comprise smaller-scale fining upward and deepening upward cyclic and rhythmic beds.

Not available / text

The Central Cordillera and Eastern Cordillera of the northern Andes form the western and eastern flanks of the north-trending Middle Magdalena Valley basin. Previous estimates for the timing of initial exhumation of the two cordilleras range from ~100 to ~10 Ma. Accurately constraining the spatial and temporal distribution of deformation in Colombia has implications for the shortening history of the Andean convergent margin and the prediction of rapid lateral facies changes in sedimentary basins in close proximity to sediment sources. This study applies sandstone petrographic point counts, field sedimentological analyses of basin fill, and paleocurrent measurements of trough cross-stratification, clast imbrication, and flute casts to provide new insights into the tectonic history of the flanks of the Middle Magdalena Valley basin. Between the lower and upper Paleocene strata of the Lisama Formation, paleocurrent orientations show a shift from northward to eastward transport. This change in sediment dispersal coincides with a shift from a cratonic (Amazonian) to orogenic (Andean) sediment source, as recorded by published U-Pb detrital zircon geochronological results (Nie et al. 2010), suggesting initial uplift of the Central Cordillera by mid-Paleocene time. Later in the basin’s history, establishment of an alluvial-plain system with meandering-channel deposits is recorded in lower–middle Eocene strata of the lower La Paz Formation. Consistent eastward paleocurrents characterize mid-Paleocene through uppermost Eocene strata, indicating a continuous influence of western sediment source areas. However, within the upper middle Eocene succession (~40 Ma), at the boundary between the lower and upper La Paz Formation, sandstone compositions show a dramatic decrease in lithic content. This compositional change is accompanied by a facies shift to amalgamated fluvial channels, reflecting changes in both the composition and proximity of the western sediment source. We attribute these changes to the growing influence of the exhumed La Cira/Infantas paleohighs off the western flank of the present-day Nuevo Mundo syncline. In the uppermost Eocene strata of the Esmeraldas Formation, paleocurrents show a switch to dominantly westward transport that persisted through the Neogene. In addition, deposits show a contemporaneous decrease in the amount of coarse-grained channel deposits. These changes are interpreted to reflect the onset of exhumation in the Eastern Cordillera. The lack of a significant change in sandstone compositions at this boundary suggests a compositional similarity between strata uplifted by the Lisama structure and the Eastern Cordillera. These data support and further refine previous thermochronologic and provenance studies which suggest that uplift-induced exhumation of the Central Cordillera and Eastern Cordillera commenced by mid-Paleocene and late Eocene–early Miocene time, respectively. / text