abstract: The Kinsley Mountain gold deposit of northeastern Nevada, located ~70 km south of Wendover, Nevada, contains seven sediment-hosted, disseminated-gold deposits, in Cambrian limestones and shales. Mining ceased in 1999, with 138,000 ounces of gold mined at an average grade between 1.5-2.0 g/t. Resource estimates vary between 15,000 and 150,000 ounces of gold remaining in several mineralized pods. Although exploration programs have been completed within the study area, the structural history and timing of precious-metal mineralization are still poorly understood. This study aims to better understand the relation between stratigraphy, structural setting, and style of gold mineralization. In order to accomplish these goals, geological mapping at a scale of 1:5,000 was conducted over the property as well as analysis of soil and rock chip samples for multi-element geochemistry. Using cross-cutting relationships, the structural history of Kinsley Mountain has been determined. The deformation can broadly be categorized as an early stage of compressional tectonics including folding, attenuation of the stratigraphy, and thrust faulting. This early stage was followed by a series of extensional deformation events, the youngest of which is an ongoing process. The structural history determined from this study fits well into a regional context and when viewed in conjunction with the mineralization event, can be used to bracket the timing of gold mineralization. The northwest oriented structure responsible for concentrating decalcification, silicification, and mineralization has two generations of cave fill breccias that both pre- and post-date the gold event. The statistical analysis of multi-element geochemistry for rock chip and soil samples has determined that Au is most strongly associated with Te, while weaker correlations exist between Au and Ag, As, Hg, Mo, Sb, Tl, and W. This suite of elements is associated with an intrusion driven system and is atypical of Carlin-type gold systems. From these elemental associations the gold mineralization event is thought to be controlled by the emplacement of a felsic intrusion. The responsible intrusion may be an exposed quartz monzonite to the south of the study area, as suggested by possible zonation of Cu, Pb, and Zn, which decrease in concentration with increasing distance from the outcropping stock. Alternatively, an unexposed intrusion at depth cannot be ruled out as the driver of the mineralizing system. / Dissertation/Thesis / M.S. Geological Sciences 2012

Este estudo visa à obtenção de um maior detalhamento da seção carbonática do Albiano Inferior / Médio da Bacia de Santos, suportado na Estratigrafia Química e nos princípios da Estratigrafia de Seqüências. Esta seção carbonática, por ter sido depositada em condições ambientais muito estressantes (altas salinidades), possui um conteúdo fossilífero bastante restrito, que tem limitado seu refinamento cronoestratigráfico com o uso apenas da bioestratigrafia. Visando obter esse detalhamento e, também, um maior entendimento da história deposicional dessa seção, ferramentas convencionais (perfis de poços, dados litológicos e bioestratigráficos tanto de amostras de calha como de testemunhos e dados sísmicos) e não convencionais (construção da curva de isótopos de carbono e oxigênio; teores de elementos maiores, menores e traços; carbono orgânico total; enxofre e análise de ciclos sedimentares) usadas na indústria do petróleo, foram integradas no presente trabalho. Para a avaliação da metodologia proposta, uma área, com 16.000 Km, no sul da bacia foi selecionada, onde a seção equivalente ao Meso Eoalbiano (cerca de 7 milhões de anos) encontra se bem desenvolvida. Somente o Andar Albiano engloba cerca de 12 milhões de anos (ICS, 2006) e sua seção sedimentar chega a atingir quase 1500 metros de espessura, sendo que aproximadamente 90% desta pertence ao Albiano Inferior / Médio e permanece indivisa pela bioestratigrafia. Por outro lado, o Neo Albiano (cerca de 5 milhões de anos) e o Cenomaniano (cerca de 6 milhões de anos) possuem isópacas bem mais modestas na área de estudo. O primeiro está representado por uma seção condensada de águas mais profundas, resultante da grande transgressão marinha que afogou completamente a plataforma carbonática ao final do Meso Albiano. Já a seção cenomaniana é composta por sedimentos pelíticos remanescentes à discordância do Turoniano. Na parte sul da Bacia de Santos, a seção turoniana é bem marcada pela presença de um folhelho radioativo, correspondente ao evento anóxico global, responsável pela maior parte do volume de petróleo já descoberto no mundo. Para o presente trabalho, foram selecionados 12 poços, que melhor representam o intervalo cronoestratigráfico estudado, além de seções sísmicas passando por eles. O uso da Estratigrafia Química foi concentrado em 2 poços, denominados aqui de X e Y, que apresentam a seção do Albiano Inferior / Médio mais completa da área, chegando a atingir a seção evaporítica aptiana mais profunda. Neles amostras para análise química foram coletadas a partir das amostras de calha existentes e de testemunhos. Através da integração dos resultados das análises químicas com os perfis dos poços e com os conceitos fundamentais da Estratigrafia de Seqüências, obteve se uma subdivisão da seção albocenomaniana em 6 seqüências deposicionais. Estas seqüências, por envolverem um intervalo de tempo suficientemente grande, podem ser classificadas como de 3a ordem, desde que apresentem uma boa correspondência no dado sísmico existente A correlação com dados sísmicos, via sismogramas sintéticos, mostrou que as superfícies chaves (limites de seqüência) identificadas nos poços X e Y têm uma boa representatividade sísmica, o que permitiu o rastreamento destes eventos para os demais poços selecionados e confirmou a classificação proposta. Os dados obtidos das análises de elementos químicos, feitas somente nas amostras do poço X, além de corroborarem as interpretações feitas, foram particularmente importantes para uma melhor caracterização paleoambiental de cada seqüência identificada. Isso mostra que o método proposto é particularmente indicado em áreas onde u ma avaliação adequada do risco exploratório requer um maior detalhamento das condições vigentes durante a deposição de uma determinada seção sedimentar. Os resultados extremamente positivos vêm resgatar, também, as vantagens do uso de amostras de calha, disponíveis em todos os poços de petróleo, e que possibilitam, quando devidamente trabalhadas, a geração de uma quantidade muito grande de informações analíticas que poderão nortear pesquisas exploratórias a custos muito baixos. / The main goal of this work is to detail the lower / middle Albian carbonatic section of Santos Basin based on the principles of Chemostratigraphy and Sequence Stratigraphy. Because this section was deposited under intense stress conditio ns (high salinity), its fossil content is very poor . It has limited the chronostratigraphic subdivision based only on biostratigraphic data. In order to get this detailing and also a better understanding of the depositional history of this section, conventional (well log data, lithological and biostratigraphic data from drill cuttings, cores and cuttings and seismic data) and non conventional (carbon and oxigen isotopes curves; total organic carbon; sulfur; major, minor and trace elements det erminations and analysis of sedimentary cycles) data used in the petroleum industry were integrated in the current study. An area with 16.000 km, where the equivalent section of Lower / Middle Albian (about 7 million years) is well developed, located in the southern part of Santos Basin, was selected to evaluate the proposed methodology. The Albian Andar itself extends to approximately 12 million years (ICS, 2006) and its sedimentary section reaches almost 1500 meters of t hickness, of which ninety percent belong to the lower / middle Albian section that remains without a proper biostratigraphic subdivision. On the other hand, the Upper Albian (about 5 million years) and the Cenomanian (about 6 million years) are represented by very thin equivalent sections in the study area. The first one is represented by a condensed section, typically deposited in deep waters, resulting from a marine transgression that completely drawn the carbonatic platform during the end of the Middle Albian. Fine grained siliciclastics sediments remaining from the well known Turonian unconformity characterize the Cenomanian section. In the southern part of Santos Basin, the Turonian section is represented by a radioactive shale related to the well known and wor ld wide anoxic event, which is the source rock for most of the petroleum already found in the world. For this work, well log, core and drill cuttings data from 12 wells, where the studied chronostratigraphic interval is better represented, were selected, as well as seismic data connecting these wells. The chemostratigraphic studies were concentrated in 2 wells, named well X and Y, which sampled the most complete lower / middle Albian section in the study area, including the top of the deeper Aptian evaporitic section. Samples for chemical analysis were collected from drill cuttings and cores in both wells. As a result of the present work, a subdividion of the Albian Cenomanian section into 6 depositional sequences was obtained through the int egration of chemical analysis data with well log data, based on the basic concepts of sequence stratigraphy. As these sequences represent a geological time relatively long, they can be classified as third orders sequences, since they have correspondence on seismic data. Correlation of the identified sequence boundaries in the wells X and Y, via synthetic seismograms, showed that these boundaries have a good seismic representation, which allowed the picking of these events towards the others selected wells and confirmed the proposal classification.The additional data obtained by the chemical elements analysis, besides to corroborate previous interpretation, were particularly important for the paleo environmental characterization of t he identified sequences. This shows that the proposed method is particularly appropriated for areas where the exploratory risk assessment requires a better understanding of the environmental onditions present durin the deposition of a given sedimentary section. The encouraging results obtained by this work also point to the strong potential of drill cuttings samples, which are always available in all wells drilled by the oil industry and which can bring a great amount of analytical information to the exploration process at low additional cost.

Magister Scientiae - MSc (Earth Science) / The complexity of the Platreef stratigraphy and the generic position of the Ni-Cu-PGE mineralisation is a challenge to prospecting and mining companies in the Northern Limb of the Bushveld Complex, partially, as a result of various floor rock interactions with the reef. Therefore, this study evaluated the effects of contact metasomatic fluids on the nature and style of PGE mineralisation as the main event leading to the complexity of the Platreef stratigraphy from the contact zone near the floor rock. Fifty samples from boreholes MO009 and MO019 drilled at Moordkopje 813 LR farm for Akanani Project by Lonmin Plc were used for this study. The mineralogy and geochemistry of the Platreef samples were studied and associated with their mineralisation occurrences. Major, minor and trace element contents were analysed by XRF analysis using fused beads, and PGE contents (Pt, Pd) in 11 samples were determined by Fire Assay.

This thesis investigates the utility of sequence stratigraphy on a regional scale and the control of eustacy on basin infill in unprecedented detail. To achieve this, the thesis utilises a wealth of data, including a continuous 3D seismic MegaSurvey dataset covering 55,000 sq. km, combined with state of the art seismic interpretation software to interpret the basin infill of the Late Cenozoic southern North Sea. The prograding shelf-prism clinoforms of the Late Cenozoic are calibrated to high density borehole penetrations, high resolution chronostratigraphy and climate proxies. The chronostratigraphic control enables a correlation of geomorphology, seismic architectures and seismic facies with full 3D control to the global sea level curve, which enables an evaluation of the impact of eustatic change on sequence development. The control of eustacy and the limitations of sequence stratigraphy are highlighted by: 1) Investigating the regional expression of chronostratigraphically calibrated seismic units, which are linked to the global sea level curve. This was carried out by mapping across the region, the dominance of oblique or sigmoidal clinoform types and seismic features such as iceberg scours, terrestrial channels and submarine fans in order to evaluate the lateral variation of depositional systems and accommodation. 2) Investigating sediment partitioning basinwards of the shelf edge and how deposition basinwards can be predicted via observations of seismic facies and architecture. This was achieved by focusing on specific seismic architectures of forced regressive slope clinoforms and deep water sedimentary systems and the link updip to the shelf within the highly constrained chronostratigraphic framework. The thesis results suggest that sequence stratigraphic models do not represent lateral variation well or integrate other allocyclic forcings on sequence development. A holistic and observation based approach to understanding basin infill and recognising the importance of sediment supply, pre-existing geomorphology, process type of the feeder system, differential subsidence, as well as eustacy, is imperative.

Este estudo visa à obtenção de um maior detalhamento da seção carbonática do Albiano Inferior / Médio da Bacia de Santos, suportado na Estratigrafia Química e nos princípios da Estratigrafia de Seqüências. Esta seção carbonática, por ter sido depositada em condições ambientais muito estressantes (altas salinidades), possui um conteúdo fossilífero bastante restrito, que tem limitado seu refinamento cronoestratigráfico com o uso apenas da bioestratigrafia. Visando obter esse detalhamento e, também, um maior entendimento da história deposicional dessa seção, ferramentas convencionais (perfis de poços, dados litológicos e bioestratigráficos tanto de amostras de calha como de testemunhos e dados sísmicos) e não convencionais (construção da curva de isótopos de carbono e oxigênio; teores de elementos maiores, menores e traços; carbono orgânico total; enxofre e análise de ciclos sedimentares) usadas na indústria do petróleo, foram integradas no presente trabalho. Para a avaliação da metodologia proposta, uma área, com 16.000 Km, no sul da bacia foi selecionada, onde a seção equivalente ao Meso Eoalbiano (cerca de 7 milhões de anos) encontra se bem desenvolvida. Somente o Andar Albiano engloba cerca de 12 milhões de anos (ICS, 2006) e sua seção sedimentar chega a atingir quase 1500 metros de espessura, sendo que aproximadamente 90% desta pertence ao Albiano Inferior / Médio e permanece indivisa pela bioestratigrafia. Por outro lado, o Neo Albiano (cerca de 5 milhões de anos) e o Cenomaniano (cerca de 6 milhões de anos) possuem isópacas bem mais modestas na área de estudo. O primeiro está representado por uma seção condensada de águas mais profundas, resultante da grande transgressão marinha que afogou completamente a plataforma carbonática ao final do Meso Albiano. Já a seção cenomaniana é composta por sedimentos pelíticos remanescentes à discordância do Turoniano. Na parte sul da Bacia de Santos, a seção turoniana é bem marcada pela presença de um folhelho radioativo, correspondente ao evento anóxico global, responsável pela maior parte do volume de petróleo já descoberto no mundo. Para o presente trabalho, foram selecionados 12 poços, que melhor representam o intervalo cronoestratigráfico estudado, além de seções sísmicas passando por eles. O uso da Estratigrafia Química foi concentrado em 2 poços, denominados aqui de X e Y, que apresentam a seção do Albiano Inferior / Médio mais completa da área, chegando a atingir a seção evaporítica aptiana mais profunda. Neles amostras para análise química foram coletadas a partir das amostras de calha existentes e de testemunhos. Através da integração dos resultados das análises químicas com os perfis dos poços e com os conceitos fundamentais da Estratigrafia de Seqüências, obteve se uma subdivisão da seção albocenomaniana em 6 seqüências deposicionais. Estas seqüências, por envolverem um intervalo de tempo suficientemente grande, podem ser classificadas como de 3a ordem, desde que apresentem uma boa correspondência no dado sísmico existente A correlação com dados sísmicos, via sismogramas sintéticos, mostrou que as superfícies chaves (limites de seqüência) identificadas nos poços X e Y têm uma boa representatividade sísmica, o que permitiu o rastreamento destes eventos para os demais poços selecionados e confirmou a classificação proposta. Os dados obtidos das análises de elementos químicos, feitas somente nas amostras do poço X, além de corroborarem as interpretações feitas, foram particularmente importantes para uma melhor caracterização paleoambiental de cada seqüência identificada. Isso mostra que o método proposto é particularmente indicado em áreas onde u ma avaliação adequada do risco exploratório requer um maior detalhamento das condições vigentes durante a deposição de uma determinada seção sedimentar. Os resultados extremamente positivos vêm resgatar, também, as vantagens do uso de amostras de calha, disponíveis em todos os poços de petróleo, e que possibilitam, quando devidamente trabalhadas, a geração de uma quantidade muito grande de informações analíticas que poderão nortear pesquisas exploratórias a custos muito baixos. / The main goal of this work is to detail the lower / middle Albian carbonatic section of Santos Basin based on the principles of Chemostratigraphy and Sequence Stratigraphy. Because this section was deposited under intense stress conditio ns (high salinity), its fossil content is very poor . It has limited the chronostratigraphic subdivision based only on biostratigraphic data. In order to get this detailing and also a better understanding of the depositional history of this section, conventional (well log data, lithological and biostratigraphic data from drill cuttings, cores and cuttings and seismic data) and non conventional (carbon and oxigen isotopes curves; total organic carbon; sulfur; major, minor and trace elements det erminations and analysis of sedimentary cycles) data used in the petroleum industry were integrated in the current study. An area with 16.000 km, where the equivalent section of Lower / Middle Albian (about 7 million years) is well developed, located in the southern part of Santos Basin, was selected to evaluate the proposed methodology. The Albian Andar itself extends to approximately 12 million years (ICS, 2006) and its sedimentary section reaches almost 1500 meters of t hickness, of which ninety percent belong to the lower / middle Albian section that remains without a proper biostratigraphic subdivision. On the other hand, the Upper Albian (about 5 million years) and the Cenomanian (about 6 million years) are represented by very thin equivalent sections in the study area. The first one is represented by a condensed section, typically deposited in deep waters, resulting from a marine transgression that completely drawn the carbonatic platform during the end of the Middle Albian. Fine grained siliciclastics sediments remaining from the well known Turonian unconformity characterize the Cenomanian section. In the southern part of Santos Basin, the Turonian section is represented by a radioactive shale related to the well known and wor ld wide anoxic event, which is the source rock for most of the petroleum already found in the world. For this work, well log, core and drill cuttings data from 12 wells, where the studied chronostratigraphic interval is better represented, were selected, as well as seismic data connecting these wells. The chemostratigraphic studies were concentrated in 2 wells, named well X and Y, which sampled the most complete lower / middle Albian section in the study area, including the top of the deeper Aptian evaporitic section. Samples for chemical analysis were collected from drill cuttings and cores in both wells. As a result of the present work, a subdividion of the Albian Cenomanian section into 6 depositional sequences was obtained through the int egration of chemical analysis data with well log data, based on the basic concepts of sequence stratigraphy. As these sequences represent a geological time relatively long, they can be classified as third orders sequences, since they have correspondence on seismic data. Correlation of the identified sequence boundaries in the wells X and Y, via synthetic seismograms, showed that these boundaries have a good seismic representation, which allowed the picking of these events towards the others selected wells and confirmed the proposal classification.The additional data obtained by the chemical elements analysis, besides to corroborate previous interpretation, were particularly important for the paleo environmental characterization of t he identified sequences. This shows that the proposed method is particularly appropriated for areas where the exploratory risk assessment requires a better understanding of the environmental onditions present durin the deposition of a given sedimentary section. The encouraging results obtained by this work also point to the strong potential of drill cuttings samples, which are always available in all wells drilled by the oil industry and which can bring a great amount of analytical information to the exploration process at low additional cost.

The Kribi-Campo sub-basin is the northernmost of a series of Aptian basins along the coast of West Africa. These extensional basins developed as a result of the northward progressive rifting of South America from West Africa, initiated c. 130 Ma ago. Post-rift sediments of the Kribi-Campo sub -basin contain several regional unconformities and changes in basin-fill architecture that record regional tectonic events. The tectono-stratigraphic evolution and plumbing system has been investigated using a high-quality 3D seismic reflection dataset acquired to image the deep-water Cretaceous-to-Present-day post-rift sediments. The study area is located c. 40 km offshore Cameroon in 600 to 2000 m present-day water depth, with full 3D seismic coverage of 1500 km2, extending down to 6.5 seconds Two-Way Travel time. In the late Cretaceous the basin developed as a result of tectonism related to movement of the Kribi Fracture Zone (KFZ), which reactivated in the late Albian and early Senonian. This led to inversion of the early syn-rift section overlying the KFZ to the southeast. Two main fault-sets - N30 and N120 - developed in the center and south of the basin. These normal faults propagated from the syn-rift sequences: the N120 faults die out in the early post-rift sequence (Albian time) whilst N30 faults tend to be associated with the development of a number of fault-related folds in the late Cretaceous post-rift sequence, and have a significant control on later deposition. The basin is filled by Upper Cretaceous to Recent sediments that onlap the margin. Seismic facies analysis and correlation to analogue sections suggest the fill is predominantly fine-grained sediments. The interval also contains discrete large scale channels and fans whose location and geometry were controlled by the KFZ and fault-related folds. These are interpreted to contain coarser clastics. Subsequently, during the Cenozoic, the basin experienced several tectonic events caused by reactivation of the KFZ. During the Cenozoic, deposition was characterized by Mass Transport Complexes (MTCs), polygonal faulting, channels, fans and fan-lobes, and aggradational gullies. The main sediment feeder systems were, at various times, from the east, southeast and northeast. The plumbing system shows the effects of an interplay of stratigraphic and structural elements that control fluid flow in the subsurface. Evidence for effective fluid migration includes the occurrence of widespread gas-hydrate-related Bottom Simulating Reflections (BSRs) 104 - 250 m below the seabed (covering an area of c. 350 km2, in water depths of 940 m - 1750 m), pipes and pockmarks. Focused fluid flow pathways have been mapped and observed to root from two fan-lobe systems in the Mid-Miocene and Pliocene stratigraphic intervals. They terminate near, or on, the modern seafloor. It is interpreted that overpressure occurred following hydrocarbon generation, either sourced from biogenic degradation of shallow organic rich mudstone, or from effective migration from a thermally mature source rock at depth. This latter supports the possibility also of hydrocarbon charged reservoirs at depth. Theoretical thermal and pressure conditions for gas hydrate stability provide an opportunity to estimate the shallow geothermal gradient. Variations in the BSR indicate an active plumbing system and local thermal gradient anomalies are detected within gullies and along vertically stacked channels or pipes. The shallow subsurface thermal gradient is calculated to be 0.052 oC m-1. With future drilling planned in the basin, this study also documents potential drilling hazards in the form of shallow gas and possible remobilised sands linked with interconnected and steeply dipping sand bodies.

Abstract This thesis deals with the Holocene development of palsa mires in continental Europe, especially permafrost dynamics and its consequences on vegetation succession and peat accumulation. Peat deposits of four permafrost mires in boreal and subarctic northeastern European Russia and in northern oroboreal Finland have been studied using plant macrofossil analysis, (AMS) radiocarbon dating, dry bulk density and carbon content measurements. In addition, preliminary results are available from another palsa mire in northeastern European Russia. Modern vegetation has been investigated to support the interpretation of fossil plant assemblages. Earlier literature on vegetation, stratigraphy and dating of permafrost mires in Europe has been reviewed. The vegetation of palsa mires in general is well known. As a rule, palsas are dry ombrotrophic habitats, surrounded by wet flarks of variable trophic levels. There is a lack of information about vegetation in different small-scale habitats within palsa mires, which would have been useful when studying the permafrost-vegetation relationship. Although no functional indicator species of permafrost have been found, permafrost dynamics in peat stratigraphy can often be detected with high degree of probability based on changes in vegetation. Some plant assemblages and vegetation successions are typical on permafrost, while many species rarely grow on or near to permafrost. Relatively sudden changes between dry and wet mire environments and continuously dynamic conditions are good signs of permafrost impact. Also gradual changes towards drier conditions may be caused by permafrost; in these cases the timing of first permafrost aggradation is more difficult to ascertain and can usually be pronounced only in terms of maximum and minimum ages. Changes in peat accumulation rates and even hiatuses in stratigraphy are additional tools to support the interpretation on permafrost history at the studied sites. Dry organic matter and carbon accumulation rates for different developmental stages are calculated for the five studied mires. From earlier studies this information is not available. Accumulation rates in the permafrost environment are very variable: from zero or negative rates in old palsas to as high as 100 gC/m2yr in incipient palsas. On moist plateau palsas, permafrost flarks and in unstable permafrost conditions, accumulation continues at low to moderate rates. Thermokarst processes result in decomposition of former peat deposits with important consequences for the ecosystem carbon balance, especially in plateau palsa mires. Radiocarbon datings are available from 27 permafrost mires in continental Europe; only 5 of these are situated in Russia. Many of the published dates cannot be considered reliable as dating permafrost aggradation. Based on limited material, permafrost started to develop at latest about 3000 BP in mires of northern Russia and 2500 BP in Fennoscandia. Older permafrost formation is suggested for a few sites, but the evidence is insufficient to confirm this interpretation. The oldest preserved palsas are ca. 2500–2000 14C years old. Most of the modern palsas are less than 600 14C years old. Permafrost aggradation follows the major climate development in the Holocene, with formation being most active during the coldest stages. Global warming is expected to greatly affect the Arctic in the near future, which would imply significant changes in ecosystem functioning and carbon balance of permafrost mires. This study contributes to the understanding of the possible impacts of climate change on these ecosystems using paleoecological techniques.

Lake basins contain depositional systems whose stratigraphy and sedimentology are highly influenced by allogenic and authigenic processes. Identifying the relative roles of these controls is complicated in settings where both tectonic and climate influences control sediment inputs and accommodation availability. In order to identify how these controls may interact in carbonate lake basins the lacustrine Mayrán Formation, northeast México was investigated. The Mayrán Formation is well exposed and the strata geometries are well preserved. The necessary data needed to unravel these complexities was obtained using field based techniques (geological and structural mapping, sedimentary logging and sampling), combined with optical and electron optical microscopy, mineralogical (XRD), and geochemical (oxygen and carbon stable isotopes, total organic carbon [TOC], organic carbon isotopes, and U-Pb carbonate dating) techniques, to characterise the lake basins. These data reveal that the Mayrán Formation was deposited in four, northerly, down-stepping, broadly coeval, hydrologically linked, carbonate-dominated lake subbasins (the Mayrán Basin system), that formed at different elevations spanning ~500 m. Subbasin geomorphology was controlled by the inherited topography of the exhumed and eroded Parras foreland fold-and-thrust belt, as a result, the subbasins are compartmentalized by prominent sandstone ridges that form sills between subbasins. Sedimentary infill of the subbasins consists of a fluvio-lacustrine succession (carbonate and clastic) that overly an angular unconformity truncating the folded and faulted Cretaceous bedrock. Clastic sediments were preferentially trapped in the most proximal subbasin in the south, adjacent to the mountain front. In more distal settings to the north, carbonate production resulted in deposition of horizontally bedded lacustrine limestones with subordinated siliciclastics and evaporite minerals. Carbonate deposition occurred during overfilled to balance filled conditions. Prominent aggradational to progradational tufa clinoforms form at the spillover points between the subbasins, and interfinger up- and down-dip with the horizontally bedded lacustrine limestones. The tufas consist of steeply dipping clinoforms that prograde northwards. They formed by inorganic and biogenically mediated calcite precipitation as waters from the topographically upper lake overflowed the sill. U-Pb dating of speleothem cements formed in the tufas yield a Pliocene age (3.06 ± 0.2 Ma). The horizontally bedded limestones that predominantly fill the subbasins are composed of nine lithofacies. These are: ostracode mudstone-wackestone, clotted boundstone, gastropod wackestone-packstone, oncoid wackestone-packstone, stromatolite, charophyte wackestone-packstone, marlstones, crystalline carbonate and evaporite minerals. These lithofacies contain variable proportions of production-derived components, with subordinated detrital and diagenetic components. They overall contain inorganic and organic calcite (average 91%), organic matter (average 12.6 % TOC) and subordinated detrital quartz, feldspar and clay. Stable isotope conditions from stromatolite laminations (δ13C -6.3‰ and δ18O -8.0‰), and micritic matrix from samples in all the subbasins (δ13C -5.7‰ and δ18O -8.4‰), indicate that overall calcite deposition occurred in freshwater lakes, under predominantly oxic conditions. Carbonate particles deposited mainly by in situ disaggregation and by settling. Significant preservation of the organic matter likely occurred because of the fine grained carbonate matrix, and because of moderate rates of both carbonate sediment and organic matter production. Stacking patterns in the lake successions show an overall shallowing upward cyclicity. It is considered, that the effects of inherited basin geomorphology and climate, ultimately controlled facies variability and strata geometries in these subbasins.

The majority of the Middle Cambrian Wheeler Formation in the Drum Mountains was deposited during a single 3rd order sequence. Superimposed onto this sequence are three indistinct 4th order cycles and twenty distinct 5th order cycles. These higher other cycles were likely deposited within short intervals of geologic time (204 to 405 ky). The lower sequence boundary zone occurs within the Swasey Formation. The Transgressive Surface is the contact between the Swaset and Wheeler Formations. The Maximum Flooding Surface is located near the top of the lower Wheeler Formation, which also approximates the base of the Ptychagnostus atavus range zone. The upper sequence boundary is marked by stromatolites, which occur near the top of the upper member of the Wheeler Formation in the Drum Mountains. Deposition of the Wheeler Formation in the Drum Mountains was controlled by eustacy and tectonics. Local normal faulting associated with Middle Cambrian postrifting thermal subsidence may have caused some of the 5th order cycles. The cycles and surfaces defined in this stratigraphic analysis, and the base of the Ptychagnostus atavus and P. gibbus range-zones, can be used to correlate strata occurring in other localities in the eastern Great Basin. In addition, this study enables the evaluation of the effect of tectonics (faulting) versus global eustacy on the sedimentary regime occurring within the Middle Cambrian House Range Embayment. (95 pages)

A brief account of the location and physical aspects of the region is followed by descriptions of mapping and laboratory techniques employed. Recent ideas on regional stratigraphical correlation in South West Africa are critically reviewed. Strata lying southeast of the farm Losberg 105 have, on the basis of lithology and copper mineralisation, been correlated with the Tsumis Formation. The Hasib Formation, of predominantly marine character, has on structural grounds been excluded from the Damara System. The latter here has a greater thickness than elsewhere in South West Africa, unless isoclinal folding is much more prevalent than has been assumed. The occurrence on Eintracht 118 of a pebble conglomerate, tentatively equated with the Chuos Tillite, makes possible a subdivision of the Damara strata into the various series established in the literature. It has been found possible to differentiate between Kamtsas and Damara quartzites on petrological grounds. Further, it is concluded that the bulk of Hakos carbonate rocks originated as dolomites and have subsequently been dedolomitized to a greater or lesser extent. The area contains both ortho- and para-amphibolites, as well as one occurrence of intrusive granite. Evidence is given for at least three periods of deformation. It is oonsidered that, if the Hosib Formation was involved in a pre-Damara orogenic episode, later folding must have been co-axial with this. Sedimentation and metamorphism are treated in broad outline. There appears to have been a deepening of the basin of deposition from Hasib to Damara times. Cyclicity in sedimentation is evidenced by lithological associations in the Damara strata. The entire area falls into the greenschist facies of regional metamorphism. Superficial deposits include river gravel and, silt, quartzite- and vein quartz-rubble, calcrete and Kalahari sand. The economic geology is described with special reference to the widespread copper mineralisation.