Ao modelar-se depósitos minerais é comum enfrentarmos o problema de estimar múltiplos atributos possivelmente correlacionados, onde algumas variáveis são amostradas menos densamente do que outras. A falta de dados impõe um problema que requer atenção antes de qualquer modelagem subsequente. Precisamos, ao final, de modelos que sejam estatisticamente representativos. A maioria dos conjuntos de dados de problemas práticos são amostrados de maneira heterotópica e, para obter resultados coerentes, é preciso entender os motivos pelos quais alguns dados faltam e quais são os mecanismos que influenciaram a ausência de informações. A teoria de dados faltantes relaciona as amostras ausentes com aquelas medidas através de três mecanismos distintos: Faltante Completamente Aleatório (Missing Completely At Random - MCAR), Faltante Aleatório (Missing At Random - MAR) e Faltante Não Aleatório (Missing Not At Random - MNAR). O último mecanismo é extremamente complexo e a literatura recomenda ser tratado inicialmente como um mecanismo MAR. E após uma transformação fixa deve ser aplicada aos valores complementados para que estes se transformem em valores MNAR Embora existam métodos estatísticos clássicos para lidar com dados faltantes, tais abordagens ignoram a correlação espacial, uma característica que ocorre naturalmente em dados geológicos. A metodologia adequada para tratar com a falta de dados geológicos é a atualização bayesiana, em que se inserem valores sob mecanismo MAR considerando a correlação espacial. No presente estudo, a atualização bayesiana foi combinada com transformações fixas para tratar o mecanismo de falta de dados MNAR em dados geológicos. A transformação fixa aqui empregada é baseada no erro de inserção gerado em um cenário MAR no conjunto de dados. Assim, com o conjunto completo resultante foi utilizado em uma simulação sequencial gaussiana dos teores de uma base de dados multivariada, apresentando resultados satisfatórios, superiores aos obtidos por meio da cossimulação sequencial gaussiana, não inserindo qualquer viés no modelo final. / When modeling mineral deposits, it is common to face the problem of estimating multiple attributes possibly correlated where some variables are more densely sampled then others. Missing data imposes a problem that requires attention prior to any subsequent modeling. The later requires estimation models statistically representative. Most practical data sets are often heterotopically sampled, and to obtain coherent results one must understand the reasons why there are missing data and what are the mechanisms that cause the absence of information. The theory of missing data relates the missing samples to those measured through three different mechanisms: Missing Completely At Random (MCAR), Missing At Random (MAR), and Missing Not At Random (MNAR). The last mechanism is quite complex to deal with, and the literature recommends being treated as a MAR mechanism and after a fixed transform should be applied to the imputed values so that these turn into MNAR imputed values. Even though there are classical statistical methods to deal with missing data, such approaches ignore spatial correlation, a feature that occurs naturally in geological data. The adequate methodology to deal with missing geologic data is Bayesian Updating, which approaches the MAR mechanism and accounts for spatial correlation. In the present study, bayesian updating was used combined with fixed transforms to treat MNAR missing data mechanism in geologic data. The fixed transform herein used is based on the error of MAR imputation on the data set. The resulting complete set was then used on a sequential gaussian simulation of the grades on a multivariate data set, presenting satisfactory results, superior to those obtained through sequential gaussian cossimulation, not inserting any biases on the final model.

Orientador: Ticiano Jose Saraiva dos Santos / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociencias / Made available in DSpace on 2018-08-09T21:14:51Z (GMT). No. of bitstreams: 1 Amaral_WagnerdaSilva_M.pdf: 44117000 bytes, checksum: fc74c3c06d9f515fb8c5571bbc187c3b (MD5) Previous issue date: 2007 / Resumo: O avanço das tecnologias de processamento de dados aerogeofísicos e integração com dados geológicos permitem recuperar informações úteis e valiosas contidas em levantamentos geofísicos com uma tecnologia mais antiga. Essas informações representam uma ferramenta essencial ao mapeamento geológico-estrutural de terrenos Pré-Cambrianos, onde as relações estratigráficas e estruturais são difíceis de serem delineadas em trabalhos de campo. Dados aerogeofísicos adquiridos nos Projetos Rio Acaraú (1975) e Itatira (1977), realizados respectivamente nas regiões noroeste e central do Ceará, foram processados e integrados com a finalidade de gerar produtos que possam ser utilizados como ferramenta indireta na identificação de feições geológicas regionais. A verificação e aplicabilidade do método foram postas em prática com a definição de uma área piloto compreendida pelas folhas topográfica 1.100.000 Umirim e Canindé. A integração dos dados aerogeofísicos e geológicos de campo, dando suporte ao mapeamento geológico em escala 1:100.000, permitiu reconhecer duas principais unidades de mapeamento: o Arco Magmático de Santa Quitéria ¿ AMSQ e as seqüências supracrustais para e ortoderivadas que o bordejam. Do arco, foram identificados quatro tipos litológicos representados por Np1: Núcleos anatéticos; Np2: Migmatitos ortoderivados; Np3: Granitos gnáissicos porfiríticos; Np4: Gnaisses granodioríticos. Da supracrustal têm-se: a seqüência paraderivada (Ccp) constituída por seis subunidades de mapeamento, onde se destacam paragnaisses, migmatitos, micaxistos, quartzitos, cálcio silicáticas e metacalcários; e a seqüência ortoderivada (Cco) formada por oito subunidades compostas por granodioritos, leucogranitóides, migmatitos (diatexitos e metatexitos), anfibolitos, dioritos e granulitos máficos. A análise dos lineamentos estruturais da área de estudo, foi realizada com o processamento e interpretação dos produtos aeromagnéticos e do modelo digital do terreno-SRTM para a extração das grandes estruturas regionais. Os maiores lineamentos da região correspondem a zonas de cisalhamentos transcorrentes destrais representadas pelo do sistema de falhas de Paramoti (ZCP) de direção NE-SW, e as zonas de cisalhamento de baixo ângulo com vergência para E-SE no setor noroeste, e para W-NW no setor sudeste. Em termos deformacionais, o principal regime atuante na área é de natureza compressiva, responsável pela geração de foliações, lineações, dobras e zonas de cisalhamento, contendo três fases deformacionais denominadas Fn, Fn+1, Fn+2. A fase Fn é representada por empurrões com vergência aproximada para E-SE no setor NW e para W-NW no setor SE. A fase Fn+1, de natureza transpressional, marca o desenvolvimento de zonas de cisalhamento de direção aproximada NE-SW. E por fim, a fase Fn+2 relaciona-se à exumação e conseqüente tectônica frágil das rochas supracrustais. As rochas do arco magmático de Santa Quitéria foram caracterizadas por apresentarem altas contagens no canal de K em quase toda região de abrangência e contagens intermediárias e baixas de Th e U. De modo geral, a seqüência supracrustal foi caracterizada por apresentar alta contribuição dos canais de U e Th e baixa de K. As subunidades Migmatitos anfibolíticos e Metaultramáficas (Cco3) e Hornblenda gnaisses migmatíticos, granulitos máficos (Cco4), compostas por rochas máficas/metaultramáficas e anfibolíticas, onde se destaca a ocorrência faixas de retro-eclogitos e granulitos máficos encaixados como lentes em gnaisses e migmatitos apresentam fortes anomalias negativas, com baixas contagens nos três canais K-Th-U. A anomalia mais proeminente com esses registros encontra-se na região central da área, a sul do município de Pentecoste. Na magnetometria essas rochas têm anomalias positivas com altos valores de susceptibilidade magnética / Abstract: Advances in airborne geophysical data processing techniques and their integration with geologic data allow recovering valuable information from both geophysical surveys and, the older technology. These information represent an essential tool for geologic-structural mapping of Pre-Cambrian terrains, where the stratigraphic and structural relations are difficult to be delineated in field works. The airborne geophysical data from Rio Acaraú (1975) and Itatira (1977) projects were carried out through respectively, in the northwest and central regions of the State of the Ceará. Their processing produced products useful to indirectly identify regional geologic features. The verification and applicability of this approach was tested in an pilot-area whose limits are within the Umirim and Canindé topographic sheets, at 1: 100,000 scale. The integration between the airborne geophysical and the geologic field data supported to the geologic mapping at the same cited scale. Two main units were recognized: the Santa Quitéria Magmatic Arc - AMSQ and the para-and-orthoderivative supracrustal sequences that surround the arc. The AMSQ has four major lithologies: Np1 with anatetic granites; Np2: orthoderivated migmatites; Np3: porfiritic gneissic granites; Np4: granodioritic gneisses. The paraderivative supracrustal sequence (Ccp) consists of six mapped subunits, the paragneisses, marbles migmatites, mica-schists, quartzites and, calk-silicated rocks. The ortoderivative sequence (Cco) is formed by eight subunits, the granodiorites, leucogranitoids, mafic migmatites (diatexites and, metatexites), amphibolites, diorites and, granulites. The structural lineaments analysis at regional scale was done after the processing and interpretation of the airborne magnetic products and, the digital elevation model derived from the Shuttle Radar Topographic Mission-SRTM. The major lineaments correspond to the dextral transcurrent Paramoti Shear Zone (ZCP) of NE-SW direction and, to low angle shear zones with E-SE thrustdirection at the Northwestern sector and, another shear zone facing to W-NW direction at the Southeastern sector. About the deformation history, the main operating regime was compressive and, responsible for foliation, lineation, folds and shear zones.This history comprises three deformational phases called Fn, Fn+1, Fn+2. The Fn phase is represented by thrust toward E-SE in the Northwestern sector and towards W-NW direction at the Southeastern sector. The Fn+1 phase, of transpressional nature, marks the development of shear zones with NE-SW direction. Finally, the Fn+2 phase is related to the exhumation and consequently ruptile tectonics of the supracrustal rocks. The rocks from Santa Quitéria magmatic arc are characterized by high counting on the K-channel in its almost entire region and intermediate and low counting of Th and U. Generally, the supracrustal sequences are characterized by high values on the U-and-Th-channels and low on K-channel. The subunit Metaultramafics (Cco3) and Hornblendgnaisses and, mafics granulites (Cco4), are remarkable by the occurrence retro-eclogites bands and mafic granulites as lenses within gneisses and migmatites. These subunits present strong negative anomalies, with low counting on the three K, Th and, U channels. The best example for this negative anomalies are in the central region of the area, at south of Pentecostes city. That area also has positive magnetic anomalies, with high values of magnetic susceptibility / Mestrado / Geologia e Recursos Naturais / Mestre em Geociências

A distribuição espacial e o volume dos domínios litológicos são freqüentemente as maiores fontes de incerteza na modelagem geológica. Geralmente, a interpretação destas características é baseada em critérios subjetivos de observações, sem levar em consideração a incerteza inerente a este processo. Existem métodos de simulação geoestatísticos capazes de quantificar esta incerteza tipológica das unidades geológicas. A maioria desses métodos utiliza como medida de continuidade geológica os modelos de covariância. Entretanto, estas ferramentas de estatística de dois-pontos, raramente, conseguem capturar os padrões de geometrias complexas. Uma alternativa para esta limitação é utilizar métodos de estatística de múltiplos pontos para reproduzir os padrões espaciais de heterogeneidade que são informados por uma imagem de treinamento. Nessa dissertação, será aplicada a geoestatística de múltiplos pontos (SNESIM) para simular os litotipos de um depósito de minério de ferro. A imagem de treinamento foi baseada em seções interpretadas. Os furos de sondagem são utilizados como amostras primárias. As informações geológicas são acessadas por mapas de probabilidade utilizados como informações secundárias. A metodologia é testada na simulação de um depósito de ferro brasileiro com três diferentes litotipos. Os resultados das simulações são comparados contra um modelo de referência e novos furos de sondagens. As geometrias e distribuição espacial das tipologias foram reproduzidas de forma consistente. A incerteza das distribuições e dos volumes dos domínios tipológicos foi quantificada. O algoritmo de múltiplos pontos e a metodologia proposta mostraram grande potencial de aplicação na simulação de depósitos minerais. / The spatial distribution and volumes of lithological domains are often the biggest sources of uncertainty in geological modeling. Usually, the interpretation of these characteristics is based on subjective criteria of observations, without taking into account the uncertainty inherent in this process. There geostatistical simulation methods capable of quantifying this uncertainty typological geological units. Most of these methods uses as a measure of continuity in geological models covariance. However, these two-point statistical is rarely sufficient to capture the patterns of complex geometries. An alternative to this limitation is to use statistical methods of multiple points to reproduce the spatial patterns of heterogeneity that are informed by a training image. In this dissertation, will be applied to multi-point geostatistics (SNESIM) to simulate lithotypes a deposit of iron ore. The training image was based on sections interpreted. The drillholes are used as primary samples. Geologic information is accessed by probability maps used as secondary information. The methodology is tested in the simulation of a deposit of Brazilian iron with three different rock types. The simulation results are compared against a reference model and new drillholes. The geometries and spatial typologies were reproduced consistently. The uncertainty distributions and volumes of typological domains were quantified. The algorithm of multiple points and the proposed methodology showed great potential for application in the simulation of mineral deposits.

In the analysis of environmental samples for uranium and thorium pollutants and at natural levels for the dating of geological samples there was felt a need to develop better uranium and thorium separation procedures to replace the established anion exchange method used at AEA Technology plc. This was the first aim of the PhD research. Separation of uranium from thorium prior to measurement of the isotopes by alpha spectrometry was necessary due to the similar alpha energies of234U and 230Th. TRU and UTEVA extraction chromatography resins (EIChroM Industries) were investigated as potential replacements to the anion exchange separation method. The resins are claimed by EIChroM to offer the advantage of providing an actinide specific separation while reducing the separation time from 2 to 0.5 days; the volume of acidic waste produced by a factor of 3, therefore, the cost of analysis was reduced. A uranium and thorium separation procedure using the UTEVA extraction chromatography resin was developed. The uranium and thorium were sorbed by the UTEVA resin from 2M nitric acid. The thorium was then eluted from the resin with 5M hydrochloric acid and the uranium with 0.02M hydrochloric acid. The separation procedure was then evaluated using uraninite ore, coral, granite and lake sediment reference materials. The uranium and thorium concentrations and the 234U/238U and 23oTh/234U activity ratio values determined for the reference material were in good agreement with certified values. The presence of plutonium was found to interfere with the measurement of uranium and thorium by alpha spectrometry. This was due to the similar alpha energies of uranium, thorium and plutonium. The co-elution of plutonium with uranium and thorium from the UTEVA resin was prevented by the inclusion of a reduction step using iron (Il) sulphamate. The resulting plutonium (Ill) was not retained by the UTEVA column. The chemical recoveries for the procedure were similar to those for anion-exchange, but the extraction chromatography procedure provided a more rapid separation using less reagents.

The purpose of the study was to examine the distributional patterns of diatoms in the surface sediments of ten southern British Columbia inlets with respect to oceanographic and hydrographic setting, and phytoplankton distribution and productivity. The study area was divided on the basis of inlet type (high, medium, and low runoff), within-inlet gradients, and zones (northern, central, and southern). A small group of species dominated the 95 sediment assemblages. There was a fairly good correlation between the biocoenoses and the thanatocoenoses in the sense that most of those species reported as dominants in the phytoplankton were also dominants in the sediment assemblages. However, there were discrepancies and these could not be explained on the basis of the relative silicification of the diatom valves. Skeletonema costatum, usually considered a weakly-silicified, dissolution-sensitive species, was abundant in British Columbia sediments. Both the pacifica and the aestivalis forms of Thalassiosira aestivalis were abundant in the phytoplankton, but only the pacifica form was preserved well in the sediments. Thalassiosira nordenskioeldii, which is found in other sediment assemblages, was rare in most British Columbia sediments. The distributional patterns of freshwater and marine littoral species appeared to be indicative of river sources entering the estuarine system. The absolute abundance of diatoms in the sediment assemblages increased from the northern to the southern zone. Within the inlets, both absolute abundance and primary productivity increased toward the mouth. Estuarine circulation did not appear to alter substantially the spatial relationship between the biocoenoses and the thanatocoenoses. In general, individual species and species-groups often exhibited distinct distributional patterns which could be related to inlet type, zonal, and within-inlet patterns. In particular, the principal coordinate analysis showed a zonal correlation between the dominant species in the sediment assemblages, and primary productivity, salinity, and temperature in the surface waters. / Science, Faculty of / Botany, Department of / Graduate

The aim of the San Andreas Fault Observatory at Depth (SAFOD) project, a component of the NSF Earthscope Initiative, is to directly observe active fault processes at seismogenic depths through the drilling of a 3 km deep (true vertical depth) inclined borehole across San Andreas fault. Preliminary subsurface models based on surface mapping and geophysical data predicted different lithologies than were actually encountered. At 1920 meters measured depth (mmd), a sequence of well-indurated, interbedded arkosic conglomerates, sandstones, and siltstones was encountered. We present a detailed lithologic and structural characterization as a step toward understanding the complex geologic history of this fault-bounded block of arkosic sedimentary rocks. We divide the arkosic section into three lithologic units with different compositional, structural, and sedimentary features: the upper arkose, 1920-2530 mmd, the clay-rich zone, 2530-2680 Illtlld, and the lower arkose, 2680-3150 mmd. We interpret the section to have been deposited in a Salinian transtensional basin, in either a subaqueous or subaerial fan setting. We suggest four different possibly equivalent sedimentary units to the SAFOD arkoses, the locations of which are dependent on how the San Andreas fault system has evolved over time in the vicinity of the SAFOD site. Detailed analysis of three subsidiary faults encountered in the arkosic section at 1920 mmd, 2530 mmd, and 3060 mmd, shows that subsurface faults have similar microstructures and composition as exhumed faults at the surface, with less evidence of alteration from extensive fluid flow.

[pt] Zonas de falha são estruturas geológicas usualmente presentes em subsuperfície. Na indústria de óleo e gás, tais estruturas podem trazer diferentes impactos, tanto no comportamento geomecânico dos campos quanto na produção nos reservatórios. Em geral, as zonas de falha são compostas pelo núcleo e pela zona de dano. O núcleo é responsável pela compartimentalização de reservatórios atuando como barreira para a passagem de fluidos. A zona de dano, região de rocha deformada adjacente ao núcleo, pode ter um impacto direto na produção, criando caminhos de fluxo preferencial ou barreiras, dependendo das feições geológicas formadas no processo de deformação. Enquanto o núcleo pode ser caracterizado com larguras da ordem de centímetros a alguns metros, as larguras das zonas de dano são uma grande incerteza. Este trabalho apresenta uma metodologia para a modelagem numérica da geração de zonas de dano. A metodologia é baseada no método de elementos finitos, em modelos constitutivos elastoplásticos representativos do comportamento geomecânico de rochas, e na aplicação de deslocamentos prescritos (rejeito) para simular o processo de formação da falha. Diversos cenários são analisados considerando o impacto dos parâmetros geomecânicos das rochas e as distâncias relativas entre duas falhas na definição das zonas de dano. Em seguida, a metodologia é utilizada para a análise de regiões favoráveis à trajetória de um poço de produção localizado entre três falhas geológicas. Os resultados obtidos demonstram que a metodologia proposta pode servir como base para caracterizar as zonas de dano em falhas geológicas. / [en] Fault zones are geological structures usually present in subsurface. In the oil and gas industry, such structures can have different impacts on geomechanical behavior and on reservoir production. In general, fault zones are composed by a core and a damage zone. The core is responsible for the compartmentalization of reservoirs, acting usually as a barrier for fluid flow. The damage zone is the region of rock deformed adjacent to the core that may directly impact on production, creating preferential flow paths or barriers, depending on the geological features triggered in the deformation process. While the core width can be in the order of centimeters to a few meters, the damage zone width is uncertain. This work presents a methodology for numerical modeling of the generation of damage zones. The methodology is based on finite element method, elastoplastic constitutive models representative of the geomechanical behavior of rocks, and on the application of prescribed displacements to simulate the fault formation process. Several scenarios are analyzed considering the impact of the geomechanical parameters of rocks and the relative distances between two faults to characterize the damage zones. Then, the methodology is used to analyze regions favorable to the trajectory of a production well located between three geological faults. The obtained results demonstrate that the proposed methodology can serve as a basis for characterizing damage zones in geological faults.

The Starkville Quadrangle is a hotspot for geological research. The Late Cretaceous is represented by the Demopolis Formation in the northeast corner of the quadrangle, followed by the Ripley Formation, and the Prairie Bluff Formation. The K-Pg boundary is exposed in the quadrangle, and the remarkable paleontology is of global importance. The Clayton Formation is the first Paleocene unit. Where the Clayton Formation channel sands are in contact with the underlying Prairie Bluff Formation, springs occur. Springs were a rare source of water in the Black Prairie and spurred the settlement of the area over 10,000 years ago. The Paleocene Porters Creek Formation occurs in the southwest corner of the Quadrangle. Quaternary streams left Holocene to Pleistocene alluvium and terraces overlying the subcrop. This project provides a modern geologic map and stratigraphic framework as a background for future research in the Starkville Quadrangle.

Amidst the global climate action movement, geologic carbon storage (GCS) has emerged as a pivotal strategy for mitigating atmospheric CO2 levels, offering environmental and economic opportunities. This thesis targets the Bunter Sandstone Formation within the Rødby structures in Denmark, focusing on seismic Profile 1. Profile 1 is chosen as it crosses over the existing domal structure, and this will enable to investigate the closure or the extension of the domal structure, and also to evaluate its capacity for CO2 sequestration. Utilizing 2D Reflection Seismic Imaging and collaborating with the Geological Survey of Denmark and Greenland (GEUS), the study employs advanced seismic techniques to analyse the Triassic period sandstone formation.  The seismic data for Profile 1 was acquired during June-July 2023 as part of GEUS's national GCS projects by Uppsala University’s Geophysics Program, utilizing the SeisMoveTM dual-element recording system. A total of 991 shots were recorded by 1030 wireless recorders in a fixed geometry, enhancing the signal-to-noise ratio through vertical stacking of repeated shot records. The data acquisition parameters were carefully selected based on similar projects involving pilot and upscaling work conducted in Denmark prior to the Rødby survey. These parameters were influenced by experiences gained during previous successful applications in Denmark and similar environments, ensuring the retrieval of high-resolution seismic reflection images across a wide depth range. The results reveal the presence of a potential new domal structure within the Rødby region, which could substantially influence the area's capacity for carbon storage. The new possible domal structure extend toward east of the survey area and this discovery suggests the need for further investigations to comprehensively assess the extent of this new structure. Therefore, this study enhances the understanding of the Rødby region's subsurface geology; and by advancing the application of carbon capture and storage technologies, this study aligns with Denmark's climate initiatives and contributes to global climate change mitigation efforts. / Mitt i den globala klimatrörelsen har geologisk kollagring (GCS) dykt upp som en viktig strategi för att minska atmosfärens CO2-nivåer, vilket erbjuder miljömässiga och ekonomiska möjligheter. Denna avhandling är inriktad på Bunter-sandstensformationen i Rødby-strukturerna i Danmark, med fokus på seismisk profil 1. Profil 1 valdes eftersom den korsar den befintliga konvexa strukturen, och detta gördet möjligt att undersöka formationens omfattning, och detta i sin tur gör det möjligt att undersöka stängningen eller utvidgningen av domalstrukturen och att utvärdera dess kapacitet för CO2-bindning. Att använda och Isamarbete med Danmarks och Grönlands geologiska undersökning (GEUS) använder studien avancerade seismiska tekniker för att analysera sandstensformationen från triasperioden.  Seismiska data för Profil 1 samlades in under juni-juli 2023 som en del av GEUSs nationella GCSprojekt av Uppsala universitets Geofysikprogram, med hjälp av SeisMoveTM inspelningssystem med dubbla element. Totalt 991 bilder spelades in av 1030 trådlösa inspelare i en bestämd geometri, vilket förbättrade signal-brusförhållandet genom vertikal stapling av upprepade tagningar. Datainsamlingsparametrarna valdes noggrant ut baserat på liknande projekt med pilot- och uppskalningsarbete som genomfördes i Danmark före Rødby-undersökningen. Dessa parametrar valdes baserat på erfarenheter från tidigare framgångsrika tillämpningar i Danmark och liknande miljöer, vilket säkerställde registreringen av högupplösta seismiska reflektionsbilder över ett brett djupområde. Resultaten visar att det finns en potentiell ny struktur i Rødbyregionen, vilket skulle kunna påverka områdets kapacitet för koldioxidlagring avsevärt. Den nya möjliga konvexa strukturen sträcker sig öster om undersökningsområdet och denna upptäckt tyder på behovet av ytterligare undersökningar för att göra en omfattande bedömning av kunna bedöma omfattningen av denna nya struktur. Därför ökar denna studie förståelsen för Rødbyregionens underjordiska geologi. Genom att främja tillämpningen av teknik för avskiljning och lagring av koldioxid är denna studie i linje med Danmarks klimatinitiativ och bidrar till de globala insatserna för att begränsa klimatförändringarna.

Natural climate variability over the past hundreds of thousands of years provides a uniquewindow into the drivers and processes that connect different parts of our climate system. This thesis investigates interactions between Earth’s mantle, its oceans, and ice sheets over the Quaternary. The dominant process that connects these spheres is glacial isostatic adjustment (GIA), which is the deformation of Earth’s mantle (and consequently its surface, gravity field, and sea level) in response to changes in ice and ocean mass loading. This dissertation focuses on time periods during which surface temperatures were warming or warmer than today to understand how these warm intervals affected ice sheets, permafrost, and sea level. I put my results in the context of current and future warming to improve predictions of future change and compare natural to anthropogenic variability. The thesis opens with an investigation of relative (i.e., local) sea level around Norway overthe last 16 thousand years (ka). Postglacial Norwegian sea level, though dominated by postglacial rebound and associated sea-level fall, is punctuated by two periods of sea-level rise. The causes of these episodes, named the ‘Tapes’ and ‘Younger Dryas’ transgressions, remain debated despite more than a century of study. I produce the first standardized and quality-controlled compilation of Norwegian sea-level data, then employ an ensemble of empirical Bayesian hierarchical statis- tical models to estimate relative sea level along the Norwegian coastline. The resulting model enables an examination of the relative contributions of isostatic rebound and global mean sea-level (GMSL) rise to the Tapes transgression, and lays the foundation for future applications such as in- version of sea-level data for Fennoscandian ice-sheet volume and the comparison of modern rates of Norwegian sea-level rise to pre-industrial rates. Chapter Two aims to better understand sea-level and Antarctic ice-sheet variability during the Holocene, which is the last time global temperatures may have exceeded early industrial (1850 CE) values. Both the Greenland and Antarctic ice sheets likely retreated inland of their present- day extents during the Holocene, yet previous GMSL reconstructions suggest that Holocene GMSL never surpassed early industrial levels. I use relative sea-level observations, GIA predictions, and new estimates of postglacial thermosteric sea-level and mountain glacier evolution to show that the available evidence is consistent with GMSL that exceeded early industrial levels in the mid- Holocene (8-4 ka) and an Antarctic Ice Sheet that was smaller than present at some time in the last 6000 years. I also demonstrate that Antarctic ice retreat lags Antarctic temperature by 250 years, which highlights the vulnerability of the future Antarctic ice sheet to 20th and 21st century warming. Comparing our reconstruction to projections for the future indicates that GMSL rise in the next 125 years will very likely (?>0.9) be faster than at any time in the last 5000 years, and that by 2080 GMSL will more likely than not be the highest of any time in the past 115,000 years. In Chapter Three, I explore the effect of GIA on subsea permafrost. Subsea permafrost forms when sea-level rise submerges terrestrial permafrost. Subsea permafrost underlies ∼1.8 million km² of Arctic continental shelf, with thicknesses in places exceeding 700 m. Sea-level variations over glacial–interglacial cycles control subsea permafrost distribution and thickness, yet no permafrost model has accounted for GIA, which leads to deviations of local sea level from the global mean. I incorporate GIA into a pan-Arctic model of subsea permafrost over the last 400,000 years. Including GIA significantly reduces estimates of present-day subsea permafrost thickness, chiefly because of hydro-isostatic effects and deformation related to Northern Hemisphere ice sheets. Additionally, I extend the simulation 1000 years into the future for emissions scenarios outlined in the Intergovernmental Panel on Climate Change’s sixth assessment report. I find that subsea permafrost is preserved under a low-emissions scenario but mostly disappears under a high-emissions scenario. In the final chapter, I turn to the Last Interglacial (LIG, 129–116 ka), a time interval considered a partial analogue for future warming due to its elevated temperatures. Observations of oscillations in LIG local sea level, combined with an assumption that the Laurentide Ice Sheet collapsed prior to the LIG, have been used to infer Antarctic and Greenland ice-sheet melt histories as well as oscillations in LIG global mean sea level. However, evidence of a Laurentide Ice Sheet outburst flood at ∼125 ka suggests that Laurentide Ice Sheet remnants may have persisted longer into the LIG than typically thought. Here we explore the effect on LIG sea level of a Laurentide collapse that occurred during rather than prior to the LIG and a West Antarctic Ice Sheet that collapsed in the early LIG. We find that due to GIA, this asynchronous ice-sheet evolution produces a global pattern of sea-level oscillations that is similar to field observations. We demonstrate that the oscillation pattern can be produced by the combination of ongoing GIA from the penultimate deglaciation with the fingerprint of West Antarctic collapse. By showing that LIG Laurentide persistence would lead to an RSL oscillation that accords with field evidence, we highlight the need for LIG climate simulations to consider Laurentide ice-sheet dynamics and for more constraints on the LIG history of the Laurentide Ice Sheet.