Age-model derived sediment mass accumulation rates (MARs) are consistently higher than 230Th-normalized MARs in the Equatorial Pacific Ocean during the past 25 ka. The offset, being highest in the Panama Basin, suggests sediment redistribution in this region is prominent. I test the hypothesis that downslope transport of sediments from topographically highs that surround the Panama Basin is the cause of higher-than-expected xs230Th inventories in the deeper parts of the basin. There is little difference in xs230Th inventories between the highest and lowest reaches of the basin suggesting that the topographic highs did not serve as a source of xs230Th. A spatial analysis suggests that there may be an enhanced scavenging of xs230Th closest to the equator in productive waters. To examine whether lateral mixing of productive equatorial waters with adjacent waters delivers xs230Th to the Panama Basin, I measured dissolved 230Th in eight deep-water casts within the Guatemala, Panama, and Peru Basins along a meridional transect at ~86°W. Below 1000 m, the Panama Basin shows the highest deficit (~50%) of 230Th in deep waters assuming a reversible exchange of 230Th between dissolved and sinking particulate matter. Peru Basin waters have a larger range of dissolved 230Th concentrations (7.9-16.5 fg/kg) than that within Panama Basin waters (5.7-7.1 fg/kg). There is a progressive decrease, suggesting advection, in average dissolved deep-water (>1000 m) 230Th concentrations from the southernmost sites in the Peru Basin toward the Panama Basin. My calculations suggest that advected 230Th is between 15-30% of the total 230Th being produced within waters of the Panama Basin itself. In the Panama Basin, the averaged biogenic barium and opal MARs suggest that productivity was greater during the Holocene (0-13000 years) than that during the last glacial (13000-25000 years) suggesting higher productivity during the Holocene. Uauth, however, is higher in sediments deposited during the last glacial than in those deposited during the Holocene, suggesting that low bottom water oxygen contents rather than respiration of organic matter drives Uauth enrichment. This oxygen depletion during the last glacial suggests that bottom waters were enriched in respired carbon, which, in turn, could be a driver of lower glacial atmosphere pCO2 values.

In contrast to early work establishing the importance of earthquake-induced liquefaction in producing soft-sediment deformation (SSD) of the Navajo Sandstone, this report advances the use of SSD analysis to: characterize wet climatic conditions and flood events during the depositional history of ancient eolianites; discriminate the signatures of multiple deformation events from those of complex deformation features formed in a single event; and to document the occurrence of liquefaction features unrepresented in modern Earth analogues. The diversity of deformation styles, presented here, is very unusual in a report from a single formation; yet the high resolution of interpreted time relationships between various processes of deposition, erosion, water table fluctuation, and deformation is even more notable. These exceptional features derive from the extraordinary outcrops of the Colorado Plateau, which expose many large-scale (tens of meters) features throughout their entire extent and reveal an extended history of episodic deformation through thick (hundreds of meters) sections of cross-bedded units, which frequently continue along several kilometers of cliff face. Prior studies of fluid escape from unconsolidated sand that support the present work are outlined in Chapter II. These include laboratory simulations of liquefaction and fluidization as well as analyses of analogous deposits, both ancient and modern. Chapter III provides an overview of outcrop evidence, gathered during the course of this study, for dramatic alterations in the topography and sedimentation patterns of the Navajo erg. Interpreted perturbations include: the foundering of active dunes; sediment eruptions; and the subsidence of interdune surfaces. Chapter IV constitutes an example of the detailed analyses that support the overview of Chapter III. Outcrop features from a site in West Canyon, Arizona provide the basis for interpreting the subsidence of a dry interdune surface to a position several meters below the contemporary water table, followed by the filling of this depression with a succession of mass flow, lacustrine, and eolian deposits. Chapter V outlines the implications of various outcrop features for the prevailing model of soft-sediment deformation in the Navajo Sandstone. Proposed modifications of this model accommodate a broader range of deformation dynamics and specifically incorporate the impact of wet climates.

In contrast to early work establishing the importance of earthquake-induced liquefaction in producing soft-sediment deformation (SSD) of the Navajo Sandstone, this report advances the use of SSD analysis to: characterize wet climatic conditions and flood events during the depositional history of ancient eolianites; discriminate the signatures of multiple deformation events from those of complex deformation features formed in a single event; and to document the occurrence of liquefaction features unrepresented in modern Earth analogues. The diversity of deformation styles, presented here, is very unusual in a report from a single formation; yet the high resolution of interpreted time relationships between various processes of deposition, erosion, water table fluctuation, and deformation is even more notable. These exceptional features derive from the extraordinary outcrops of the Colorado Plateau, which expose many large-scale (tens of meters) features throughout their entire extent and reveal an extended history of episodic deformation through thick (hundreds of meters) sections of cross-bedded units, which frequently continue along several kilometers of cliff face. Prior studies of fluid escape from unconsolidated sand that support the present work are outlined in Chapter II. These include laboratory simulations of liquefaction and fluidization as well as analyses of analogous deposits, both ancient and modern. Chapter III provides an overview of outcrop evidence, gathered during the course of this study, for dramatic alterations in the topography and sedimentation patterns of the Navajo erg. Interpreted perturbations include: the foundering of active dunes; sediment eruptions; and the subsidence of interdune surfaces. Chapter IV constitutes an example of the detailed analyses that support the overview of Chapter III. Outcrop features from a site in West Canyon, Arizona provide the basis for interpreting the subsidence of a dry interdune surface to a position several meters below the contemporary water table, followed by the filling of this depression with a succession of mass flow, lacustrine, and eolian deposits. Chapter V outlines the implications of various outcrop features for the prevailing model of soft-sediment deformation in the Navajo Sandstone. Proposed modifications of this model accommodate a broader range of deformation dynamics and specifically incorporate the impact of wet climates.

An expansive panel of well exposed (periglacial) strata of the Upper Kaza Group permitted a detailed study of the stratal architecture of proximal basin floor deposits in the Neoproterozoic Windermere turbidite system. Detailed stratigraphic and petrographic analyses identified six lithofacies: poorly-sorted, clast-rich mudstone (F1), thin-bedded siltstone and mudstone (F2), thick-bedded, massive sandstone (F3), medium-scale, cross-stratified sandstone (F4), mudstone-clast breccia (F5), and medium-bedded turbidites (F6). The spatial distribution of these facies identify five architectural elements: heterolithic feeder channel deposits (FA1), thin-bedded intralobe turbidites (FA2), terminal splay deposits (FA3), distributary channel deposits (FA4), and isolated scours (FA5). FA 1-4 are genetically related and form the basic building blocks of large-scale basin floor depositional lobes. FA 5, which is isolated to the stratigraphic top of the study area, is interpreted to have formed in a base-of-slope setting, and its superposition on FA 1-4 suggests the long-term progradation of the Windermere turbidite system.

No description available.

La producción de sedimentos en zonas de montaña es un motivo de preocupación no sólo por la pérdida de la fertilidad de la capa superficial de suelo, sino también debido a sus efectos aguas abajo, tales como la deposición de sedimentos en embalses. En este trabajo, la producción de sedimentos se estudio a dos escalas espaciales: una cuenca pequeña y una grande en el noreste de los Pirineos orientales. La cuenca pequeña es Cal Rodó (4,2 km2), y la grande es la cuenca Alta Llobregat del Río Llobregat (504 km2), donde a la salida se encuentra el embalse de La Baells, la primera cuenca está anidado dentro de la última. En Cal Rodó, el objetivo fue determinar y comparar los intervalos de confianza de la carga de sedimentos en suspensión a escala de evento y a escala anual. Los datos utilizados abarcan 10 años (1996-2005). Estos incluyen muestras discretas de agua recogidas por un muestreador automático de agua, lecturas de turbidez proporcionada por un sensor de infrarojo de turbidez, un sensor de ultrasonidos, y mediciones de la lámina de agua. Todo conectado a un registrador de datos. La incertidumbre de producción de sedimentos fueron evaluados por simulaciones de Monte Carlo usando la función de distribución de la carga de sedimentos y modelación de residuales. La producción total para el periodo estudiado y estimada a través de la calibración de sensores de turbidez fue 17,217.0 Mg (4,1 Mg/ha/año) y su intervalo de confianza al 90% está entre 16,311.4 Mg y 18,395.8 Mg. Por otra parte la producción de sedimentos a través de las curvas de transporte de sedimento a escala anual fue de 103,441.0 Mg (24,6 Mg/ha/año), y su intervalo de confianza oscila entre 49,107.0 Mg y 254,803.0 Mg. Las conclusiones generales son que la incertidumbre de la carga de sedimentos por las curvas de transporte de sedimentos son amplias (> 300%) y que la producción de sedimentos se sobreestimo en un orden de magnitud. Una buena distribución de las muestras en todo el hidrograma es necesaria, a fin de desarrollar las curvas de transporte más fiable. La segunda fase de este estudio fue realizada en la cuenca Alta del Río Llobregat donde la cubierta del suelo es principalmente bosque de coníferas y pastos, con presencia de algunas zonas intensamente erosionadas (badlands). El promedio anual de erosión de suelo se estimó cuantitativamente a través de RUSLE integrado en SIG. Los datos tratados provienen de las precipitaciones registradas en ocho estaciones meteorológicas que abarcan 14 años (1991-2004), las propiedades físicas del suelo, el inventario de cubierta vegetal, las características de gestión del suelo y un modelo digital de elevaciones. Todo ello se utilizó como entradas (inputs) para generar cada uno de los factores de RUSLE, las imágenes tienen una resolución de 20 m. La producción de sedimentos se calculó mediante la aplicación de una tasa de entrega de sedimentos (sediment delivery ratio SDR) a los resultados obtenidos por RUSLE. También se llevaron a cabo análisis de sensibilidad para cada uno de los factores de RUSLE y una evaluación de la incertidumbre global de erosión de suelo. Adicionalmente diversos escenarios de erosión de suelos debido al Cambio Global fueron desarrollados. La producción de sedimentos media anual fue de 3,35 Mg/ha/año y el intervalo de confianza al 90% fue entre 0,95 y 13,7 Mg/ha/año. Estos resultados son similares a los resultados de un estudio previo de batimetría del embalse el cual fue de 4.54 Mg/ha/año, y su intervalo de confianza al 90% fue entre 4,29 Mg/ha/año y 4,79 Mg/ha/año. El mapa de riesgos de erosión muestra que pequeñas áreas altamente erosionables (5%) producen el 50% de sedimento. / A better understanding of soil erosion and sediment yield in mountainous areas is needed, for management purposes and to envisage uncertainties when developing soil erosion models. In this thesis, sediment yield estimates and associated uncertainties were studied at two spatial scales: a small catchment (Cal Rodó 4.2 km2) and a relatively large basin (Upper Llobregat Basin 504 km2), the former is nested within the latter, in the SE Pyrenees, Spain. In Cal Rodó stream which is characterized by an event based regime, is assessed the uncertainty of suspended sediment load (SSL) at event and annual scales. SSL in streams are currently estimated using diverse types of sediment rating curves (SRC) that allow the interpolation and extrapolation of the discrete observations of sediment concentrations to the whole range of recorded discharges. However, the accuracy of outcomes using SRCs in mountain event based streams is still unknown. The parameters of the non-linear relationship are obtained by a log transformation and then a bias correction factor is applied, based on the residual analysis. The uncertainty of SSL can be assessed by using Monte-Carlo approaches based on the simulation of residuals. Nevertheless, when these methods are going to be applied in streams with a regime characterized by events, it is necessary to verify if different events have different discharge-concentration relationships; if this occurs, the role of events must be taken into account in the load analyses, as they modify the structure of the residuals. Results showed that when SRCs are used for interpolation between samples, paying attention to the role of events allows to avoid nonlinear bias overcorrection and to reduce the uncertainty associated with the sediment load estimates. The sediment yield from annual and seasonal rating curves were 6.0 and 5.1 times larger than the estimated by sensor calibrations. Therefore a good distribution of samples throughout the hydrograph needs to be ascertained in order to develop reliable SRCs. The second part of this research deals with soil erosion and sediment yield assessment and its associated uncertainties in the Upper Llobregat River Basin. Land cover is mainly coniferous forest and pastures with some intensely eroded areas (badlands). Annual average soil erosion was quantitatively estimated with an integration of GIS and the Revised Universal Soil Loss Equation (RUSLE). Maps for each of the factors involved where obtained with a 20 m resolution. Rainfall dataset from eight weather stations and spanning 14 years, soil properties, land cover inventory, land management features and digital elevation model were used as resource datasets to generate each of the RUSLE factor maps. Annual average sediment yield was computed by applying a sediment delivery ratio to the results obtained by RUSLE, and this result was compared with an existing bathymetric survey. Uncertainty and sensitivity analyses were undertaken for each of the RUSLE factors, in order to assess its magnitude and determine which of the factors influences the most the soil loss estimate. Results show that the annual average sediment yield was 3.35 Mg km-2 yr-1 and its confidence interval lied between 0.95 and 13.7 Mg km-2 yr-1 with 90% confidence. These results are in agreement with results from reservoir bathymetric survey. Additional comparisons of estimated sediment yield were done with empirical methods such as PSIAC and FSM. Erosion risk maps showed that about 5% of the area generated 50% of soil loss. These areas are located in steep slopes and coincide in many cases with badlands which are near the streams. Finally, sediment yield changes under climate conditions for the late 21st Century where not relevant, whilst spreading agricultural activity as in the 1950's had a relevant increase in sediment yield.

Climate archives are of greatest significance when it comes to paleoclimate studies, since these types of archives in a natural way have registered and preserved the conditions of the past. There are several types of climate archives, one of the most commonly used are lake sediments, because lakes can reveal different types of information, for example weathering, vegetation and precipitation. Another reason why lakes are important in climate research is because they are widely spread over the world, and therefore they can be chosen depending on where the focus of the study will be. In this study, -the Lake Kuchi in the southern part of Taiwan, situated at the boundary between the Asian Mainland and the Western Pacific, was used. What makes this densely populated region of the world particularly interesting for climate research is because it is affected not only by monsoons, but also by typhoons and earthquakes. In this paleoclimate study, a total 16 core sections from three different coring points in the Kuchi Lake were analyzed. The main goal was to clarify if the lake could be used as a reliable climate archive, and also interpret the depositional environment of the sediment layers in the cores. All core sections were described and analyzed with the ITRAX XRF-scanner, which lead to the conclusion that the cores consist of a sedimentary sequence of alternating gray clay and dark gray gyttja clay layers, capped by peat, gyttja or clayey gyttja at topmost part.  By sieving samples from all different layers, it was observed that some dark gyttja clay layers contained terrestrial organic matter, and hard, angular clay clasts that suggest intense rain falls and flash floods as transportation mechanism. The uppermost part of the cores, from 310 cm to the top layers, consist of homogenous clay and in situ organic matter which indicate calmer depositional environments compared to the alternation between dark gyttja clay and homogenous gray clay. LOI-950 data indicate that the carbonate content of the Kuchi Lake is low, since the weight loss during this temperature is insignificant compared to LOI-550, which stood for the majority of the weight loss. Thus, the sediment sequence in the Kuchi Lake consist of alternation of clays deposited in a calm and relatively deep lake, mixed with layers apparently flushed in from land, possibly due to typhoons. This alternation is capped by organic rich layers, including peat, which indicating filling up of the basin, and shallower conditions.

Headwater streams provide diverse habitat for aquatic organisms, drinking water for downstream communities and abundant recreational activities. The addition of in-stream wood to headwater channels can influence the hydrology, morphology and ecology of the system. The recruitment of wood to the channel and the export mechanisms determine the wood load and structure types formed in-stream, thus altering the channel’s morphological response. This research examined the effects of in stream wood on channel morphology in two headwater streams along the eastern slopes of the Canadian Rocky Mountains; Lyons East (LE) and Corolla Creek (CC). Lyons East has natural and anthropogenic disturbance (burned and salvage-logged) in the watershed, while Corolla Creek has anthropogenic (grazing and recreation) disturbances in the watershed. An assessment of the longitudinal spatial distribution and a reach-scale geomorphic classification were conducted to investigate the impacts of in-stream wood on channel morphology, pool formation and sediment storage. The spatial distribution of in-stream wood was 1.49 sites/100m for both watersheds, results that are comparable to previously conducted studies in similar geographic watersheds. The types of structures found in both watersheds were predominately jam formations (LE - 43%, CC - 47%), which is consistent with the wood loading and spatial distribution conceptual model previously developed by Whol and Jaeger (2009) for in-stream wood accumulations in mountain streams. At the reach-scale level of analysis, in-stream wood was found to impact channel morphology and pool forming processes. The addition of wood to the stream caused half of the studied reaches to have forced pool-riffle morphology. For all six selected study reaches, there was a decrease in expected pool spacing and an increase in the diversity of pool types. The relationship between wood-affected pools and sediment storage was examined and the results show that more sediment was stored in the burned/salvage logged reaches. Cohesive sediment was stored only in pools influenced by wood structures for half of the studied reaches. V* was generally higher in wood-affected pools for five of the six study reaches. The weighted average (V*w), which provides information regarding the storage of cohesive at the reach scale, was greater in Lyons East than in Corolla Creek. The presence of both exposed bedrock in the channel as well as the amount of vegetation are possible reasons for the smaller amounts of sediment observed in Corolla Creek. The observations from this reach scale investigation led to the development of a conceptual model, which can be used to predict the location of cohesive sediment storage in headwater streams of the Oldman River Basin. This model highlights the relationship between simultaneous recruitment of in-stream wood and sediment from local sources as a mechanism for protecting and storing cohesive sediment deposits. This research examined channel responses to in-stream wood within the context of land-use planning and Alberta’s Water for Life Strategy. There was evidence of lateral channel migration in the floodplain of both watersheds. At some sites, the channel shifted up to 30 metres while in other sections of the watershed, the channel was confined within a narrow valley. Accordingly, it is recommended that the current salvage logging guidelines be changed to include a flexible riparian buffer that would more appropriately reflect the diversity in riparian widths throughout the watersheds. In addition the best management practice is to allow natural in-stream wood processes to evolve and not to remove in-stream wood from the channel. The in-stream wood provides diverse aquatic habitat and the cycle of wood being recruited and being in the stream is part of the natural ecosystem in forested environments.

No description available.

Abstract This study investigated the distributions of polyclic aromatic hydrocarbons (PAHs) in the sediment cores collected from continental shelf of Gaoping submarine canyon. The sediment cores were analyzed for PAHs to reconstruct historical contamination record of these compounds and to find out the possible sources, trends and fluxes. The average concentrations of £U50 and £U16 PAHs ranged from 568 to 816 ng/g and from 169 to 256 ng/g, respectively. Except for sediment cores L10 and L26, the high molecular weight PAHs (4-6 ring PAHs) were found dominant in 1960s-2006, while the low molecular weight PAHs (2-3 ring PAHs) were found dominant before 1960s. Results from diagnostic ratios and hierarchical cluster analysis (HCA) both suggested that sources of PAHs in the cores of southern continental shelf were primarily from petrogenic, while those in the cores of northern continental shelf were from pyrogenic and petroleum combustion. There is a significant increasing of total PAH concentrations between 1930-1950, suggesting that might be an evident during the World War II. Due to increase of importing fossil fuel and the growth of heavy industrials in Gaoping area, the total concentrations of PAHs showed an increasing trend again since 1950s in the core from continental shelf of Gaoping submarine canyon. In addition, during 1990-2006, the total concentrations of PAHs showed a decreasing trend might result from the environmental protection laws. It is noteworthy that in L28 and L29 sediment cores, the increase of total PAH concentrations recorded during 1990-2006 may be due to the dumping of the sludge from dredged Kaohsiung harbor sediments. Comparing with the sediment quality guidelines (SQG), the PAH concentrations in the northern continental shelf sediment samples were higher than the Threshold Effect Level (TEL) value, suggesting there might be an adverse biological effects caused by PAHs. Keywords¡GPolycyclic aromatic hydrocarbons (PAHs), Kaohsiung harbor, Sediment quality guidelines (SQG)