Earlier researchers have produced conceptual models of Mississippi River delta plain development which divide the deltaic plain into upper and lower reaches. The upper deltaic plain has been described as an area composed mainly of lacustrine, lacustrine delta, backswamp, and crevasse channels, with minimal distributary development. The lower deltaic plain is characterized by numerous distributaries forming distributary systems and lobes. Detailed geomorphic mapping and chronologic reconstruction within the Atchafalaya Backwater Area of the upper deltaic plain of the Mississippi River has led to the recognition of a complex network of distributary development related to three distinct distributary systems that formed in the upper deltaic plain over the past 2500 years. These systems do not fit previous models of upper deltaic plain development. The East Atchafalaya Basin Protection Levee blocked Atchafalaya River water and sediment from entering the study area and burying these older distributary systems, preserving their surface expression and allowing their identification. Results show that distributary systems can be a major contributor to upper deltaic plain development and that these systems are not always related to the lower delta plain delta switching process. A stable Mississippi River position and a favorable gradient in the study area over the past 4,000 years appear to be responsible for the geomorphic development of the study area.

The Wax Lake Delta (WLD) is a sandy, modern river delta prograding rapidly into Atchafalaya Bay. This dissertation uses field data to improve the understanding of channel kinematics that dictate river delta geometry and stratigraphy, while providing a framework for coastal restoration efforts. The studies presented here show that the distributary channel network of the WLD is erosional. In the first study, analyses of the feeder channel to the WLD and the channel network within the sub-aerially emergent delta show that the channel bed has incised into the consolidated muds that act as bedrock. The large (>62%) fraction of bedrock exposure found in multi-beam surveys is related to the under-saturation of suspended sand measured during the flood of 2009. The second study concerns the delta front beyond the emergent delta Distributary channels extend 2 – 6 km into the delta front. Four bathymetric surveys of one bifurcating distributary channel – Gadwall Pass – show that the majority of bed aggradation occurs during floods, but the majority of channel extension of each bifurcate channel occurs during low river discharge. In the third study, field measurements of fluid flow during a tidal cycle indicate that tidal augmentation of during periods of low river discharge is responsible for channel extension during low river discharges. Flow direction measured from streaklines present in aerial photomosaics is combined with bathymetric evolution data to quantify spatial velocity changes on the delta front. These data show that flow spreading is insufficient to prevent acceleration at channel margins, providing an explanation for observed erosion. Flow divergence is limited on the delta front by the proximity of neighboring channels, even though they are separated by 10-30 channel widths. The associated convergence of flow in inter-distributary bays occurs along “drainage troughs”. These channel-forms collect flow that has been dispensed from distributary channel network. Finally, ambient currents in Atchafalaya Bay (0.06 – 0.2 m/s) caused by tides and the proximity to the neighboring Atchafalaya Delta appear to alter flow patterns on the delta foreset, and are responsible for channel curvature on the delta front. / text

A Formação Tacuarembó (Jurássico Superior – Cretáceo Inferior), subdividida em Membro Batoví e Membro Rivera, aflora na região norte do Uruguai, nos departamentos de Rivera e Tacuarembó. O objetivo principal deste trabalho é a análise sedimentológica e estratigráfi-ca da Formação Tacuarembó, através da caracterização faciológica, a reconstrução dos modelos deposicionais e a definição das relações de contato entre os membros Batoví e Rivera. Para alcançar tal objetivo, foi realizado o levantamento, na escala 1:50, de um tes-temunho e de quarenta e uma seções colunares, estas divididas em sete transectas com base em sua distribuição espacial. Como resultado, foram detalhadas litofácies posterior-mente agrupadas em diferentes associações de fácies. O Membro Batoví é constituído por associações de fácies de (1) dunas eólicas, (2) lençóis de areia eólicos, (3) canais fluviais efêmeros, (4) canais fluviais perenes entrelaçados e (5) deltas. O Membro Rivera, por sua vez, é constituído essencialmente por associações de fácies de dunas eólicas. A intercala-ção entre depósitos fluviais, eólicos e deltaicos, com predominância de associações fluviais sugere que o Membro Batoví representa o modelo deposicional de porção distal de um sis-tema fluvial distributário Já o Membro Rivera caracteriza-se pelo sucessivo cavalgamento de dunas eólicas, sem a ocorrência de depósitos de interdunas úmidas ou encharcadas, definindo um sistema eólico seco. A mudança abrupta de sistemas deposicionais, marcada por uma superfície plana, por vezes com concentração de clastos, indica a existência de uma discordância entre os membros Batoví e Rivera. Aliado a isto, a mudança no modelo deposicional sugere uma alteração climática, passando de um clima arido a semi-árido du-rante a deposição do Membro Batoví, para um clima hiperárido ao longo da deposição do Membro Rivera. / The Tacuarembó Formation (Upper Jurassic - Lower Cretaceous), subdivided into Batoví Member and Rivera Member, crops in the northern region of Uruguay, in the Rivera and Tacuarembó departments. The main objective of the present work is the sedimentological and estratigraphic analysis of the Tacuarembó Formation, through the faciological charac-terization, reconstruction of the depositional models and definition of contact relations be-tween the Batoví and Rivera members. To reach such objective, a well-log and forty-one columnar sections were surveyed in a scale 1:50, and later the columnar sections were di-vided into seven transects, based on their spatial position. As a result, lithofacies were de-tailed and later grouped in different facies associations.The Batoví Member consists of associations of facies of (1) eolian dunes, (2) eolian sand sheets, (3) ephemeral fluvial channels, (4) perennial braided fluvial channels and (5) deltaic. On the other hand, the Ri-vera Member, is essentially constituted by facies associations eolian dunes. The intercala-tion between fluvial, eolian and deltaic deposits, with predominance of fluvial associations, suggests that the Batoví Member represents the depositional model of the distal portion of a distributary fluvial system. Contrastingly, the Rivera Member is characterized by the suc-cessive eolian dunes climbing, without the occurrence of wet or damp interdunes deposits, defining a dry eolian system. The abrupt change of depositional systems, marked by a flat surface, sometimes with clasts concentration, indicates the existence of an unconformity between the members Batoví and Rivera. Allied to this, the change in the depositional model suggests a climatic change, going from arid to semi-arid climate during the deposi-tion of the Batoví Member, to a hyperarid climate during the deposition of the Rivera Mem-ber.

A Formação Tacuarembó (Jurássico Superior – Cretáceo Inferior), subdividida em Membro Batoví e Membro Rivera, aflora na região norte do Uruguai, nos departamentos de Rivera e Tacuarembó. O objetivo principal deste trabalho é a análise sedimentológica e estratigráfi-ca da Formação Tacuarembó, através da caracterização faciológica, a reconstrução dos modelos deposicionais e a definição das relações de contato entre os membros Batoví e Rivera. Para alcançar tal objetivo, foi realizado o levantamento, na escala 1:50, de um tes-temunho e de quarenta e uma seções colunares, estas divididas em sete transectas com base em sua distribuição espacial. Como resultado, foram detalhadas litofácies posterior-mente agrupadas em diferentes associações de fácies. O Membro Batoví é constituído por associações de fácies de (1) dunas eólicas, (2) lençóis de areia eólicos, (3) canais fluviais efêmeros, (4) canais fluviais perenes entrelaçados e (5) deltas. O Membro Rivera, por sua vez, é constituído essencialmente por associações de fácies de dunas eólicas. A intercala-ção entre depósitos fluviais, eólicos e deltaicos, com predominância de associações fluviais sugere que o Membro Batoví representa o modelo deposicional de porção distal de um sis-tema fluvial distributário Já o Membro Rivera caracteriza-se pelo sucessivo cavalgamento de dunas eólicas, sem a ocorrência de depósitos de interdunas úmidas ou encharcadas, definindo um sistema eólico seco. A mudança abrupta de sistemas deposicionais, marcada por uma superfície plana, por vezes com concentração de clastos, indica a existência de uma discordância entre os membros Batoví e Rivera. Aliado a isto, a mudança no modelo deposicional sugere uma alteração climática, passando de um clima arido a semi-árido du-rante a deposição do Membro Batoví, para um clima hiperárido ao longo da deposição do Membro Rivera. / The Tacuarembó Formation (Upper Jurassic - Lower Cretaceous), subdivided into Batoví Member and Rivera Member, crops in the northern region of Uruguay, in the Rivera and Tacuarembó departments. The main objective of the present work is the sedimentological and estratigraphic analysis of the Tacuarembó Formation, through the faciological charac-terization, reconstruction of the depositional models and definition of contact relations be-tween the Batoví and Rivera members. To reach such objective, a well-log and forty-one columnar sections were surveyed in a scale 1:50, and later the columnar sections were di-vided into seven transects, based on their spatial position. As a result, lithofacies were de-tailed and later grouped in different facies associations.The Batoví Member consists of associations of facies of (1) eolian dunes, (2) eolian sand sheets, (3) ephemeral fluvial channels, (4) perennial braided fluvial channels and (5) deltaic. On the other hand, the Ri-vera Member, is essentially constituted by facies associations eolian dunes. The intercala-tion between fluvial, eolian and deltaic deposits, with predominance of fluvial associations, suggests that the Batoví Member represents the depositional model of the distal portion of a distributary fluvial system. Contrastingly, the Rivera Member is characterized by the suc-cessive eolian dunes climbing, without the occurrence of wet or damp interdunes deposits, defining a dry eolian system. The abrupt change of depositional systems, marked by a flat surface, sometimes with clasts concentration, indicates the existence of an unconformity between the members Batoví and Rivera. Allied to this, the change in the depositional model suggests a climatic change, going from arid to semi-arid climate during the deposi-tion of the Batoví Member, to a hyperarid climate during the deposition of the Rivera Mem-ber.

A Formação Tacuarembó (Jurássico Superior – Cretáceo Inferior), subdividida em Membro Batoví e Membro Rivera, aflora na região norte do Uruguai, nos departamentos de Rivera e Tacuarembó. O objetivo principal deste trabalho é a análise sedimentológica e estratigráfi-ca da Formação Tacuarembó, através da caracterização faciológica, a reconstrução dos modelos deposicionais e a definição das relações de contato entre os membros Batoví e Rivera. Para alcançar tal objetivo, foi realizado o levantamento, na escala 1:50, de um tes-temunho e de quarenta e uma seções colunares, estas divididas em sete transectas com base em sua distribuição espacial. Como resultado, foram detalhadas litofácies posterior-mente agrupadas em diferentes associações de fácies. O Membro Batoví é constituído por associações de fácies de (1) dunas eólicas, (2) lençóis de areia eólicos, (3) canais fluviais efêmeros, (4) canais fluviais perenes entrelaçados e (5) deltas. O Membro Rivera, por sua vez, é constituído essencialmente por associações de fácies de dunas eólicas. A intercala-ção entre depósitos fluviais, eólicos e deltaicos, com predominância de associações fluviais sugere que o Membro Batoví representa o modelo deposicional de porção distal de um sis-tema fluvial distributário Já o Membro Rivera caracteriza-se pelo sucessivo cavalgamento de dunas eólicas, sem a ocorrência de depósitos de interdunas úmidas ou encharcadas, definindo um sistema eólico seco. A mudança abrupta de sistemas deposicionais, marcada por uma superfície plana, por vezes com concentração de clastos, indica a existência de uma discordância entre os membros Batoví e Rivera. Aliado a isto, a mudança no modelo deposicional sugere uma alteração climática, passando de um clima arido a semi-árido du-rante a deposição do Membro Batoví, para um clima hiperárido ao longo da deposição do Membro Rivera. / The Tacuarembó Formation (Upper Jurassic - Lower Cretaceous), subdivided into Batoví Member and Rivera Member, crops in the northern region of Uruguay, in the Rivera and Tacuarembó departments. The main objective of the present work is the sedimentological and estratigraphic analysis of the Tacuarembó Formation, through the faciological charac-terization, reconstruction of the depositional models and definition of contact relations be-tween the Batoví and Rivera members. To reach such objective, a well-log and forty-one columnar sections were surveyed in a scale 1:50, and later the columnar sections were di-vided into seven transects, based on their spatial position. As a result, lithofacies were de-tailed and later grouped in different facies associations.The Batoví Member consists of associations of facies of (1) eolian dunes, (2) eolian sand sheets, (3) ephemeral fluvial channels, (4) perennial braided fluvial channels and (5) deltaic. On the other hand, the Ri-vera Member, is essentially constituted by facies associations eolian dunes. The intercala-tion between fluvial, eolian and deltaic deposits, with predominance of fluvial associations, suggests that the Batoví Member represents the depositional model of the distal portion of a distributary fluvial system. Contrastingly, the Rivera Member is characterized by the suc-cessive eolian dunes climbing, without the occurrence of wet or damp interdunes deposits, defining a dry eolian system. The abrupt change of depositional systems, marked by a flat surface, sometimes with clasts concentration, indicates the existence of an unconformity between the members Batoví and Rivera. Allied to this, the change in the depositional model suggests a climatic change, going from arid to semi-arid climate during the deposi-tion of the Batoví Member, to a hyperarid climate during the deposition of the Rivera Mem-ber.

This thesis examines the interaction of pre-existing and evolving salt-related topography on the temporal and spatial evolution of depositional systems in deepwater. To achieve this, the thesis integrates stratigraphic and structural analysis of 3D seismic data from the Miocene record of the salt-influenced Lower Congo Basin, Offshore Angola. Observations at multiple scales ranging from the semi-regional (&gt; 50 km) to local, kilometre-scale and covering timescales ranging from the entire Miocene (~ 18 Myr) to &gt; 2 Myr are presented. At the semi-regional scale, results from this study shows that the progressive along-strike linkage of short (&lt;10 km) fault segments and salt diapirs into through-going large scale (&gt; 30 km) faults and elongated saltwalls results in long lived diversion and/or confinement of depositional system fairways. Axial confinement of fairways occurs where structural strike is parallel to sediment input, contrasting with ponding or diversion of deposits oriented at a high angle to structural strike. The orientation of the structures remains relatively static, which in combination with the fixed sediment entry points of the fairways results in recurrence of the major styles of interaction, and long term pinning of fairways throughout the Miocene. The development of large (10's of km) "sediment shadow" zones devoid of coarse clastics downdip of diverted and or confined sediment gravity flows is also observed through the Miocene. At the intraslope basin (10's of km) and sub-basin scale ( < 10 km), the role of confinement by salt-related structures on the temporal evolution and dip-and-strike variability of Late Miocene channelised-lobe complexes in an elongate intraslope basin was also investigated. At both of these scales, the morphology of the recieving basin geometry significantly influences the dimensions, planform morphology and vertical stacking patterns of channelised-lobe complexes. A transition from thick, radial shaped lobe-complexes which are aggradationally stacked and deposited via 'fill-and-spill' of sub-basins within an intraslope basin to thinner, elongate, laterally offset and compensationally stacked channelised-lobe complexes in the intraslope basin is observed. This transition occurs as the salt-related structural template evolves and confinement changes from the sub-basin scale to the intraslope basin scale. At the depositional element scale ( < 5 km), results from this study further shed light on the critical and hitherto neglected role of salt-related topography in controlling the location of channel to lobe transition zones in deepwater depositional systems. The location of the transition zones are documented from four case studies, with the transitions spatially controlled by salt-related reduction in gradient e.g. a break in slope downflow of monoclinal structures, and/or a reduction in lateral confinement of depositional fairways downflow of segment boundaries. Overall, the result of this thesis show the significant influence which evolving saltrelated topography exerts on the stratigraphic development, geometry and sediment routing patterns on salt-influenced continental margins. In particular the study highlights how variable the interaction between evolving salt-related topography and deepwater sedimentation is at a range of temporal and spatial scales.

ABSTRACT The Eocene Roda Formation in northern Spain documents the deposits from a range of coastal depositional environments. These include alluvial plains, distributary channels, mouth bars, upper to lower-shorefaces, and tidal shelf ridges. Eighteen progradational sand tongues that are interpreted as parasequences compose two third-order sequences. Sequence 1 accumulated in an environment with strong tidal currents and high rates of progradation, while Sequence 2 was deposited under relatively weaker currents and higher rates of aggradation, which produced a higher mudstone:sandstone ratio. The stratigraphy highlights the transgressive origin of six tidal shelf ridges, three in each sequence, that overlie regressive deltaic tongues. Sequence 1 shelf ridges are composed almost entirely of cross-bedded sandstones, whereas Sequence 2 ridges are composed of a mixture of cross-bedded and ripple-laminated deposits. Ridges in both sequences contain bioturbation that is typical of the Cruziana Ichnofacies, and that indicates a marine origin. The tidal ridges are stratigraphically located at or near the point of maximum third-order regression, and are not found within early highstand or late transgressive deposits― times of high relative sea level when the deltaic shoreline did not protrude significantly. Tidal currents were accentuated at the coast when the delta complex had prograded several kilometres into the basin, while during times of high relative sea level, the basin was wider and tidal currents were weaker, consequently leading to a lack of tidal deposits. The tidal ridges are, thus, interpreted as being headland-associated deposits. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2011-04-29 17:10:10.008

In karst areas relationships between activities occurring on the surface and the overall health of the subsurface environment are often highly interconnected. However, the complex nature of karst flow systems can often make identification of these connections difficult. Carroll Cave, a large stream cave system located in the central Missouri Ozarks, is known for its biological and speleological significance. A dye tracing project to delineate a Carroll Cave recharge area through dye tracing has identified an area of 18.5 km2 which contributes water to the cave. The water from Thunder River within Carroll Cave was positively traced to eight springs of the thirteen springs at a distributary spring system known as Toronto Springs. Through examination of the geochemistry of the individual springs, differences in water chemistry between the various outlets has become evident. Additional work with YSI Sonde dataloggers and consideration of carbonate chemistry relationships has sought to further define the variations in hydrochemical behavior, thus aiding in the discrimination potential spring sources. Primary sources thought to contribute water to the spring system include Carroll Cave and Wet Glaize Creek, with some minor influence from other losing streams in the vicinity. Seepage runs along Wet Glaize Creek have also identified major losing reaches, in close proximity to structural features, which may contribute water to Toronto Springs. Examination of the measured parameters and derived have identified that Carroll Cave and Wet Glaize Creek are the primary end members for Ca2+, Mg2+, HCO3-, specific conductance, and temperature. Using these parameters a two end member mixing model has been developed which describes the mixing zone setting at Toronto Springs and calculates the average proportions of flow contributions by the end members. By using a multi-proxy approach of dye tracing, seepage runs, and geochemistry for the individual springs, the source waters and pathways for the springs at Toronto Springs have been identified.

The fault-bounded Cianzo basin represents a Cenozoic intermontane depocenter between the Puna plateau and Eastern Cordillera of the central Andean fold-thrust belt in northern Argentina. New characterizations of fold-thrust structure, nonmarine sedimentation, and sediment provenance for the shortening-induced Cianzo basin at 23°S help constrain the origin, interconnectedness, and subsequent uplift and exhumation of the basin, which may serve as an analogue for other intermontane hinterland basins in the Andes. Structural mapping of the Cianzo basin reveals SW and NE-plunging synclines within the >6000 m-thick, upsection coarsening Cenozoic clastic succession in the shared footwall of the N-striking, E-directed Cianzo thrust fault and transverse, NE-striking Hornocal fault. Growth stratal relationships within upper Miocene levels of the succession indicate syncontractional sedimentation directly adjacent to the Hornocal fault. Measured stratigraphic sections and clastic sedimentary lithofacies of Cenozoic basin-fill deposits show upsection changes from (1) a distal fluvial system recorded by vi fine-grained, paleosol-rich, heavily bioturbated sandstones and mudstones (Paleocene‒Eocene Santa Bárbara Subgroup, ~400 m), to (2) a braided fluvial system represented by cross-stratified sandstones and interbedded mudstones with 0.3 to 8 m upsection-fining sequences (Upper Eocene–Oligocene Casa Grande Formation, ~1400 m), to (3) a distributary fluvial system in the distal sectors of a distributary fluvial megafan represented by structureless sheetflood sandstones, stratified pebble conglomerates and sandstones, and interbedded overbank mudstones (Miocene Río Grande Formation, ~3300 m), to (4) a proximal alluvial fan system with thick conglomerates interbedded with thin discontinuous sandstone lenses (upper Miocene Pisungo Formation, ~1600 m). New 40Ar/39Ar geochronological results for five interbedded volcanic tuffs indicate distributary fluvial deposition of the uppermost Río Grande Formation from 16.31 ± 0.6 Ma to 9.69 ± 0.05 Ma. Sandstone petrographic results show distinct upsection trends in lithic and feldspar content in the Casa Grande, Río Grande, and Pisungo formations, potentially distinguishing western magmatic arc (Western Cordillera) sediment sources from evolving eastern thrust-belt sources (Puna‒Eastern Cordillera). In addition to growth stratal relationships and 40Ar/39Ar constraints, conglomerate clast compositions reflect distinct lithologic differences, constraining the activation of the Cianzo thrust and coeval movement on the reactivated Hornocal fault. Finally, U-Pb geochronological analyses of sandstone detrital zircon populations in conjunction with paleocurrent data and depositional facies patterns help distinguish localized sources from more distal sources west of the basin, revealing a systematic eastward advance of Eocene to Miocene fold-thrust deformation in the central Andes of northern Argentina. / text