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A tilting bed flume study was made to examine the relationships between velocity, suspended sediment and infiltration rate in alluvial channels for velocities from 2 to 5 feet per second and suspended sediment up to 0.6 percent. Preliminary experiments using samples from Rhllito Creek near Tucson, Arizona to define limits for the flume study included mechanical analyses of bed sediments, permeability and infiltration tests, and analyses of suspended sediment in flood waters. Flume experiments using bed materials from Rillito Creek were made with constant velocity and variable suspended sediment content, then with constant suspended sediment and variable velocity. Considerable variability was found in the mechanical analyses, permeability and infiltration tests, and suspended sediment content for samples from different locations. The flume studies indicated a direct relationship between velocity and infiltration rate and an inverse relationship between the suspended sediment content and infiltration rate in the ranges tested. Very poor correlation was found between the preliminary permeability and infiltration tests and the flume infiltration rates, but good correlation was obtained for the flume results with the flow losses and natural recharge occurring in the river channels in the Tucson area.

The question posed in this study is why alluvial soil on a floodplain is finer than the bed material of the river that supplied the sediments deposited to form the floodplain. A schematic, simplified river/floodplain system is used in an approximate analysis to find the size distribution of the floodplain soil. It is assumed that the stable limiting condition is a suspended load in the floodplain flow of the same concentration and composition as the sediment load in that portion of the river channel flow above the level of the floodplain. It was found that floodplain soil should be finer than the channel bed material; how much finer depending on the bank height, and to a lesser degree the width of the floodplain.

In order to better understand the relationship of tidally dominated depositional environments and their palynological assemblages, the Middle Jurassic sediments of the Lajas Formation, Neuquén Basin were examined. The ambition was to present models and trends which can be used for studies of other such deposits. In order to integrate the palynoassemblages with the environment of deposition, additional granulometric data and nutrient data from XRF analysis were used in combination with the palynology. A new method using correspondence analysis was used for understanding the palaeoecology and floral dynamics. An updated, dynamic model for the Middle Jurassic floral palaeoecology of the Neuquén Basin has been presented and the drivers of floral succession are interpreted as disturbance tolerance and substrate water content. Taphonomic expressions of seral groupings show that later seral stage community palynomorphs are preferentially deposited within or close to distributary systems, whereas earlier seral stage palynomorphs are preferentially deposited in environments of greater accommodation space, such as bayfills. Taphonomic signatures, using palaeoecological groupings provide trends in low (4th/5th) order cycles and lateral variations relating to tidal channels and surrounding bayfill mudstones. A model for 4th/5th order boundaries is also presented using new interpretations of the distribution of pinaceous pollen and microforaminiferal test linings. Using Canonical Correspondence Ananlysis (CCA), a model is presented of depositional environments incorporating palynological data and granulometric proxies for grain size and grain sorting. The relationship between sediment processes in a tidal flat dominated palaeoenvironment and the hydrodynamic properties of some palynomorphs is investigated and presented. The weathering and nutrient status of the substrates throughout the Lajas Formation is presented using XRF proxy data. The proxies are also used with CCA to create nutrient related floral groupings. When plotted stratigraphically, these show cycles of eutrophication and subsequent weathering of the substrates.

M.Sc. / High-grade hematite ores at the Thabazimbi Mine, Limpopo Province, occur as stratabound bodies in the Early Paleoproterozoic Penge Iron Formation of the Transvaal Supergroup. Iron ores occur at three distinct positions in the Penge Iron Formation (i) basal ore bodies located immediately above a thin oxidised shale unit that marks the base of the Penge Iron Formation in the Thabazimbi area and that may be interpreted as a structural contact towards the underlying dolostones of the Malmani Subgroup; (ii) ore bodies developed immediately above a prominent mafic sill in the Penge Iron Formation; (iii) small, lenticular ore bodies developed in the iron-formation without apparent structural control. Ore bodies in all three stratigraphic positions formed on the expense of the Penge Iron Formation protore, they share very similar mineralogical and textural attributes and can be subdivided into three major ore types with respect to their mineralogy and physical characteristics, namely, (a) carbonate-hematite ore; (b) hard hematite ore; (c) supergene modified ore. Further subdivision into subtypes is possible based on textural attributes. The first stage of iron ore formation at the Thabazimbi deposit is marked by oxidation of ferrous minerals (carbonates and grunerite) and their replacement by hematite. Efficient leaching and replacement of chert in the iron-formation to produce high-grade hematite ores characterizes the second stage of alteration. Stable isotope and fluid inclusion evidence point to a hydrothermal origin of the iron ores. Two hydrothermal fluids were identified, namely a highly saline Ca-Mg-rich brine (S = 27 wt% NaClequiv, TH = 160ºC) and a Nadominated fluid of intermediate salinity (S = 10 wt% NaClequiv, TH = 130ºC) that is possibly of meteoric origin. The results obtained in this study are used to propose the following sequence of mineralising events for the Thabazimbi iron ore deposit: (i) Deposition of iron-formation and diagenesis; (ii) contact metamorphic alteration related to the intrusion of the Bushveld igneous complex; (iii) metasomatic oxidation, leaching and residual upgrading that is tentatively linked to structurallycontrolled hydrothermal fluid flow; (iv) supergene modification of existing high-grade ore bodies in post-Gondwana times along the old African land surface.

The topic of this thesis is the study of deposits from ancient submarine channel systems in the Miocene Maraş Basin (southern Turkey). The results show four independent systems in the form of slope channel complexes in the stratigraphic sequence of the basin. The present study focuses particularly on the reconstruction of the sedimentary architecture and palaeo-flow interpretation of the deposits of two of these systems: the Alikayası and the Karışık Systems. The approach followed was the architectural analysis scheme. The data from maps, sketches and logs was organized following a hierarchy of bounding surfaces as well as by the grouping of canyon/channel-fills according to key sedimentary attributes. The resultant sedimentary architecture of the Alikayası System suggests a fundamental control by the propagation of a submarine fold-and-thrust belt. The sedimentary architecture of the Alikayası System does not agree with generic hierarchical models proposed for the description of slope channel complexes. On the other hand, the Karışık System is interpreted as an intraslope system, which was dominated by submarine landslides and developed small channel systems, resulting in sequences of mass transport deposits and channel-fills. The propagation of a fold-and-thrust belt also controlled the sedimentary architecture of the Karışık System. All the systems identified in the Maraş Basin are interpreted to have been part of submarine channel systems connected to the shelf, transferring coarse-grained clastic sediments (e.g. gravel and sand) from the coast to the marine deepwater environment.

Orientador: Mario Luis Assine / Banca: Roberto Salvador Francisco D'Avila / Banca: Paulo César Fonseca Giannini / Resumo: Campos de dunas podem constituir importantes vestígios de variações paleoclimáticas no registro geológico. Aspectos paleogeográficos, paleoclimáticos e características de circulação atmosférica dos paleodesertos do Cretáceo no Brasil, ainda pouco estudados, apresentam grande potencial no entendimento da evolução de Gondwana. A Formação Três Barras é a unidade superior do Grupo Areado, Cretáceo da Bacia Sanfranciscana, e é constituída predominantemente por sedimentos eólicas depositados no oeste de Gondwana. A análise sedimentológica e estratigráfica revelou a presença de importante superfície de deflação regional limitando dois sistemas eólicos de características faciológicas, diagenéticas e paleoambientais distintas. O sistema inferior é interpretado como depositado em sistema eólico úmido, com campos de dunas, interdunas úmidas e alagadas, lençóis de areia e, ocasionalmente, rios efêmeros. As fácies deste sistema apresentam comumente cimentação em grau variável e a elas estão associados perfis de paleossolos. Pegadas de saurópodes são descritas pela primeira vez em depósitos da Bacia Sanfranciscana. O sistema eólico superior ultrapassou os limites iniciais da bacia e é interpretado como registro sedimentar de sistemas eólicos secos, com predomínio de dunas eólicas e, localmente, interdunas secas. No topo deste sistema existem fácies com deformações sinsedimentares, delimitada por camadas não deformadas, e com ocorrência de lapilis e bombas vulcânicas do Grup... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Aeolian dune fields are humidity-sensitive environments that represent vestiges of important regional palaeoclimatic variations in the geological record. Paleogeographic and atmospheric circulation patterns of palaeodeserts from the Brazilian Cretaceous period are of great potential for understanding the Gondwana evolution during its final rifting stages. The Early Cretaceous Três Barras Formation, Areado Group of the Sanfranciscana Basin, mainly consists of aeolian successions deposited in an ancient palaeodesert developed in the central portion of the western Gondwana. Detailed sedimentological and stratigraphic analysis revealed the presence of an important regional deflation surface limiting two aeolian systems with different faciological, diagenetic and paleoenvironmental signatures. The lower system is interpreted a wet aeolian system with sand dunes, wet and damp interdunes, sand sheets and rare, ephemeral rivers. The facies of this system commonly present cementation in variable degree and to them they are associated paleossolos profiles. Footprints of sauropods are described for the first time in deposits of the Sanfranciscana Basin. The upper aeolian system exceeds the basin's limits and is interpreted as a dry aeolian system, with predominance of dune deposits and dry interdunes. At the top of this system there are facies with sinsedimentary deformations, delimited by nondeformed layers, and with occurrence of lapilis and volcanic bombs of the Mata ... (Complete abstract click electronic access below) / Mestre

Fluvial systems and their associated deposits host globally important mineral deposits, water reserves and hydrocarbons. Crucial to the extraction of these resources is an understanding of heterogeneity distribution within deposits of fluvial systems. To constrain and predict heterogeneity distribution within fluvial deposits, outcrop data together with lidar and drone derived virtual outcrop models have been collected from the Salt Wash Distributive Fluvial System (DFS) in Utah and Colorado. The study records an analysis of sedimentary architecture, facies distribution and intra-channel heterogeneity of five study sites within the proximal, medial and distal reaches of the Salt Wash DFS. Specifically the fluvial style, lateral variability of fluvial architecture, intrachannel and overbank ratio, grainsize, channel body and storey width:thickness ratios and intrachannel heterolthics at outcrops considered representative of the proximal, medial and distal portions of a DFS have been documented. Data from the study sites have been used to generate 3D reservoir models. The models have been subject to flow simulation to better understand the significance of hetergenity variability within fluvial reservoirs at an 'inter-well' scale (approximatley 0.1 km2). An indepth workflow and methodology for measuring and describing DFS channel bodies and for the construction of a reservior flow simulation model from outcrop derived data are presented here. Data collection has involved mapping and measuring; palaeocurrents, barscale accretion surfaces, storey dimensions, channel body dimensions, facies and intrachannel heterolithics. Results show clear trends within channel channel bodies and associated deposits such as, intra channel heterogenity channel body percentage, channel body grain size, storey/channel body width thickness; which can be predicted within a distributive fluvial system context, ultimately leading to better subsurface interpretation with smaller datasets. This field based study of the Salt Wash DFS, coupled with virtual outcrop models has provided a quantitive analys's of channel body architectures and facies distributions. Additionally, field work conducted on point bar deposits now illustrates the limitations of 2D outcrops when attempting to describe meandering or braided fluvial deposits and why this may have resulted in gross underestimation of meanderbelt deposits in the fluvial rock record.

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