The population genetics of species occupying formerly glaciated regions are not only impacted by glacial retreat but also agricultural land use that is typical of such regions. Areas which have experienced glaciation often display a lowered amount of genetic variability and minimal population structure, and these effects become more predominant with increasing distance from a potential refugial population. Meanwhile, agricultural land use over the recent past has also been demonstrated to disrupt population structure distribution through disturbance regimes. The purpose of this study was to assess potential post-glacial and agricultural effects on populations of creek chub (Semotilus atromaculatus) in two agricultural watersheds that differ in the glacial history. The Saint Joseph River (SJR) watershed, Indiana and Michigan, USA was entirely glaciated during the last glacial maxima, while the Little Miami River (LMR) watershed in Ohio, USA, is situated on the boundary of the glacier. The degree of agricultural land use also varies between and within the two watersheds. Using eight microsatellite loci, 312 individuals were genotyped from 13 sites in SJR and 2,318 individuals from 29 sites in LMR. Measures of genetic differentiation showed that there was strong differentiation between watersheds. Analyses within watersheds recovered additional but weaker differentiation that was mostly associated with the geography of sub-watersheds and isolation by distance. Proximity to the glacial boundary appeared to play a minimal role in genetic differentiation and genetic variation. Differentiation among localities was not directly associated with the glacial boundary within LMR, and localities in this watershed had lower allelic richness and heterozygosity than those in the fully glaciated SJR. After accounting for the positive correlation of stream distance in LMR using partial Mantel test, both glacial history and agricultural land use were positively correlated with genetic differentiation. However, these predictor variables were also strongly correlated with one another which prevented disentangling the two potential effects. Within SJR, no 10 relationship of genetic differentiation with agricultural land use was recovered. My study shows that there is not a simple relationship between glacial history, contemporary land use, and genetic differentiation in creek chub. Rather, it appears that the patterns of genetic variation observed may be more closely linked to the dispersal behavior of creek chub within and among watersheds, and the history of effective population size within watersheds.

Nuclear power generation is being regarded as a solution to ever increasing demand for electricity, and concerns over global warming and climate change due to the use of fossil fuels. Although nuclear power generation is considered to be reliable, economical, clean, and safe, the wastes produced from the nuclear fuel cycle are not, and can remain hazardous for hundreds of thousands of years. An international consensus has developed over the past several decades that deep geologic disposal of low, intermediate, and high level radioactive wastes is the best option to protect the biosphere. In this thesis, both regional scale and sub-regional scale models are created to simulate groundwater flow and transport for a representative Canadian Shield setting, honouring site-specific topography and surface water features. Sub-surface characteristics and properties are derived from numerous geoscience studies. In addition, a regional scale model is developed, centred on the Bruce Nuclear Power Development (BNPD) site near Tiverton, Ontario, and located within the Michigan Basin. Ontario Power Generation (OPG) has proposed a Deep Geologic Repository (DGR) for low & intermediate level waste (L&ILW) at the BNPD site. Paleoclimate simulations using various combinations of parameters are performed for both the Canadian Shield Sub-Regional model, and the Michigan Basin Regional model. Fracture zone permeability is a very important parameter when modelling crystalline rock settings. Migration of a unit tracer representing glacial recharge water can occur to depth in fractures of high permeability. Representative rock compressibility values are necessary as compressibilities are used to calculate storage coefficients, and the one-dimensional loading efficiency; these affect the subsurface propagation of elevated pore pressures due to glacial loading at surface. Coupled density-dependent flow and transport in paleoclimate simulations affects deep flow systems and provides a measure of flow stability, as well as increasing the mean life expectancy at depth. Finally, hydromechanical coupling is a very important mechanism for reducing vertical hydraulic gradients during a glaciation event when a hydraulic boundary condition equal to the pressure at the base of an ice-sheet is applied at ground surface. Pore water velocities are reduced, thereby retarding migration of surface waters into the subsurface environment.

Nuclear power generation is being regarded as a solution to ever increasing demand for electricity, and concerns over global warming and climate change due to the use of fossil fuels. Although nuclear power generation is considered to be reliable, economical, clean, and safe, the wastes produced from the nuclear fuel cycle are not, and can remain hazardous for hundreds of thousands of years. An international consensus has developed over the past several decades that deep geologic disposal of low, intermediate, and high level radioactive wastes is the best option to protect the biosphere. In this thesis, both regional scale and sub-regional scale models are created to simulate groundwater flow and transport for a representative Canadian Shield setting, honouring site-specific topography and surface water features. Sub-surface characteristics and properties are derived from numerous geoscience studies. In addition, a regional scale model is developed, centred on the Bruce Nuclear Power Development (BNPD) site near Tiverton, Ontario, and located within the Michigan Basin. Ontario Power Generation (OPG) has proposed a Deep Geologic Repository (DGR) for low & intermediate level waste (L&ILW) at the BNPD site. Paleoclimate simulations using various combinations of parameters are performed for both the Canadian Shield Sub-Regional model, and the Michigan Basin Regional model. Fracture zone permeability is a very important parameter when modelling crystalline rock settings. Migration of a unit tracer representing glacial recharge water can occur to depth in fractures of high permeability. Representative rock compressibility values are necessary as compressibilities are used to calculate storage coefficients, and the one-dimensional loading efficiency; these affect the subsurface propagation of elevated pore pressures due to glacial loading at surface. Coupled density-dependent flow and transport in paleoclimate simulations affects deep flow systems and provides a measure of flow stability, as well as increasing the mean life expectancy at depth. Finally, hydromechanical coupling is a very important mechanism for reducing vertical hydraulic gradients during a glaciation event when a hydraulic boundary condition equal to the pressure at the base of an ice-sheet is applied at ground surface. Pore water velocities are reduced, thereby retarding migration of surface waters into the subsurface environment.

The aim of this research was to study the relationship between rock slope stability and glacial processes. An in-depth analysis of our current understanding of how glaciated rock slopes develop instability and movement during deglaciation is presented; this shows that understanding is incomplete without an appreciation of the variable mechanical behaviour of glacier ice. In this thesis, I argue that: (1) The ductile behaviour of ice at low strain rates allows movement of rock slopes buttressed by ice. Field evidence and simple force models are used to explore rate of movement of ice-contact slopes and the conditions under which they evolve. The results indicate that large rockslides can move and deform glacial ice at rates of 10-2 to 102 m-yr. This implies that ice-contact slope movement may be important for slope evolution and the erosion and entrainment processes of glaciers; and (2) the elastic strength of glacier ice at the high strain rates associated with seismic shaking enables ice to modify the response of the surrounding rock to seismic shaking. To explore this, numerical analyses of the interaction between glacial erosion, glacier mass, topography, and earthquake shaking intensity are undertaken. Shaking of mountains of variable shape and with different levels of ice inundation is simulated using FLAC 6.0. The results suggest that complete inundation by ice can significantly reduce shaking intensity. This, in combination with glacial steepening of slopes, may make recently deglaciated slopes more prone to coseismic failure. In the final chapter of the thesis, I present a conceptual model of the evolution of slope stability during stages of glaciation and deglaciation. The model incorporates the ideas presented in the thesis. I then offer recommendations for how our understanding of these processes can be further advanced.

The submarine geomorphology of Goletas Channel - Hardy Bay - Shusharti Bay is a record of environmental change, defined by sediment deposition since the late Pleistocene draped over glacially sculpted physiography. Sea level change, contiguous with waning ice extent at the termination of the Fraser Glaciation, triggered an oceanographic transition within Goletas Channel from a low energy closed embayment to a higher energy open channel environment. Morphologic evidence of lower sea level position is observed from sequence stratigraphy in Hardy Bay and suggests regression to 74 m below present. Stratigraphy also shows a correlation between sea level transgression and turbidity current flows in northwest Goletas Channel, and although triggering mechanisms remain elusive, they are likely related to reworking of glacial sediments concomitant to initial open channel conditions. Holocene sediment accumulation has been highest in southeast Goletas Channel, represented by mud with interstitial gas, and has been reworked by tidal currents into contourite structures. A combination of high-resolution multibeam bathymetry, seismic and core samples are used to study the geomorphology of the region.

Detta kandidatarbete har haft som mål att ta fram en exkursionsguide för naturvetenskapsstudenter som är i ett tidigt stadie i deras utbildning och för den intresserade allmänheten. Syftet har varit att exkursionsguiden ska ge en översiktlig version av Uppsala läns kvartärgeologiska landskapsutvecklingsom är lätt för potentiella läsare att ta till sig. Kandidatarbetet är uppdelat i två delar, med en första del som introducerar läsarna till de geologiska och hydrologiska processer som ägt rum under perioden kvartär. Dessa är nödvändiga för att förstå den andra delen, som består av själva exkursionsguiden. Eftersom exkursionsguidens fokusär geologiska strukturer som bildats under och efter den senaste istiden, så består den första delen huvudsakligen av inlandsisens mekanismer och processer, olika typer av jordavlagringar samt hur de strukturer som inlandsisen bildat kan identifieras i fält. I första delen ingår även en tidslinje över landskapsutvecklingen i Uppsala län med början i inlandsisens tillbakadragande. Den andra delen av arbetet består som nämnt ovan av exkursionsguiden. Denna innehåller 10 lokaler som visar på de mest vanligt förekommande strukturer från kvartär. Fotografier har använts för att visa de mest intressanta strukturerna från varje lokal, dessa har även tillhörande informationsrutor som ger läsarna nödvändig information om den specifika landformen eller strukturen. Båda delar av arbetet innehåller kartor gjorda i programmet ArcGIS. Dessa kartor har tagits framför att visa istäckets utbredning vid olika tidpunkter och jordarter vid och omkring lokalerna. Vägbeskrivningskartor finns även för varje lokal samt en virtuell guide i Google Earth, passande för tider med pandemi-restriktioner. Detta kandidatarbete har inte kommit fram till traditionella resultat, utan exkursionsguiden utgör resultatet. Arbetet med detta projekt visade sig vara mer utmanande än förväntat. Det stora perspektivet var isynnerhet en aspekt som var hindrande. För att ta fram en mer detaljerad exkursionsguide skulle någotav följande behövts: en begränsning av ämnesområdet, mer tid, alternativt mer kunskap om ämnet av författarna. / This bachelor’s thesis has been about creating an excursion guide for natural sciences students in theearly stages of their education, as well as for the interested public. The aim has been to give the students a condensed, easy to grasp version of the quaternary landscape development in Uppsala län, Sweden. The thesis is made up of two parts, where the first part introduces the students to quaternary processes and terms necessary to understand the second part, which is the excursion itself. Since the excursion is centered around the geological structures left by the last glaciation, the first part contains information mostly about the glacier's mechanisms and processes, different types of soil and how the structures left by the glacier is recognizable in the field. Featured in part one is also a timeline of the landscape development in Sweden since the last glaciations regression. The second part features 10 localities that show off landforms and geological structures of interest from the quaternary period. Photographs are used to illustrate what parts are important for each locality and infographics have been used to give students easy access to the most crucial knowledge for that specific landform, structure or mechanism. Both parts of this thesis contain maps made in ArcGIS. These maps show off a few different things, like the ice-sheets extent at different points in time, the types of soil in and around each locality aswell as an overview map that shows the localities whereabouts. In addition to the maps, a virtual guide was created in Google Earth suitable for a time with travel restrictions. Because of the nature of this thesis, no results of the traditional kind were arrived at. The result is the excursion guide itself. This project proved to be more difficult than anticipated, the scope of it in particular made it challenging. In order to make a detailed excursion guide, one would need to either be more knowledgeable within the field, have more time or need to restrict the scope of the project.

There exist various glacial units in the Neoproterozoic strata of southern Namibia (Kalahari Craton). They were recognised and discussed in the scientific literature for at nearly 100 years (e.g. Coleman, 1926; Gevers, 1931; Schwellnuss, 1941; Martin, 1965). The Snowball Earth theory (Hoffman et al., 1998) had an huge impact on Neoproterozoic geosciences and especially outcrops of the Otavi Group in northern Namibia helped to strengthen and support this idea. Nevertheless, the Neoproterozoic glacial horizons in southern Namibia were difficult to interpret and even more difficult to correlate, due to their tectonic overprint and their scarce outcrops. In order to correlate and differentiate the various Neoproterozoic glacial units of southern Namibia (western rim of Kalahari Craton) a multi‐method approach based on isotopic analyses on zircon grains, whole rock geochemistry, grain size measurements combined with extensive field work, mapping and sampling was applied. In total, ten sections were mapped and measured from which 33 samples were chosen for further analyses. Two of these samples represent local basement rocks, 19 the siliciclastic Neoproterozoic sedimentary cover including glacial diamictites, and twelve carbonate samples. 3474 single zircon grains were picked and measured for their dimensions (width and length). Of those, 2404 zircons were analysed with LA‐ICP‐MS techniques for their U‐Pb and Th‐U ratios in order to calculate detrital zircon ages and to obtain information about the source magma. 1535 of those gave concordant ages (90‐110 % of concordance). Further, selected zircon grains (in total 346) with concordant U‐Pb ages were analyses for their εHf(t) values. To gather more information and to be able to provide absolute ages for the Neoproterozoic glacial units the new technique of LAICP‐MS U‐Pb dating on carbonate samples was tested and gave reliable results for ten out of twelve samples (representing seven different sample locations). Field work revealed two sections containing the Sturtian as well as the Marinoan glacial diamictites in relatively undisturbed succession that qualified as reference profiles for Neoproterozoic strata in southern Namibia: the Dreigratberg and the Namuskluft section in the Gariep Belt close to the Orange River. All analysed samples contain a very similar detrital zircon isotopic record and the whole rock geochemical analyses confirm this interpretation. All siliciclastic samples show a general felsic provenance, with zircon ages mainly divided into two age groups (Mesoproterozoic 1.0 – 105 Ga and Palaeoproterozoic 1.7 – 2.1 Ga), reflecting four different growth and recycling events of Mesoproterozoic to Archaean crustal units. The samples have a geochemical signature of continental island arc and the zircon grain dimensions (width vs. length) are also very similar for all samples. Direct age dating of the samples based on detrital zircons was not possible caused by the lack of ages reflecting deposition times. Nevertheless, the most important differences between the various glacial horizons were found in petrographic features (diamictite pebble contents) and the age peak shift of detrital zircon U‐Pb ages (P/M ratio). Based on these and the two reference profiles correlations to other sections were achievable and the differentiation of four distinct Neoproterozoic glacial horizons for southern Namibia was possible. Furthermore, these new results provide new insights into the Neoproterozoic Gariep Belt formation comprising Tonian rifting events, Cryogenian formation of the Arachania Terrane and final Ediacaran collision of the Rio de la Plata and Kalahari cratons. The combination of all results reflects a continuous sedimentary recycling on the western Kalahari Craton. Comparison and statistical similarity tests based on zircon age data bases for possible source areas defined the Namaqua Natal and Gariep belts as the most likely sedimentary source areas, providing the rock material that got recycled for at least 200 Ma from Kaigas glaciation at ca. 750 Ma to Vingerbreek glaciation at ca. 550 Ma. In addition, the lack of exotic detrital zircon ages within the two Snowball Earth events of this study suggests the interpretation of none or only very minor glacial movement confirming the idea of a completely ice‐covered Earth. The assumed Sturtian and Marinoan ages of Numees Fm and Namaskluft Mbr diamictites were confirmed by the results of U‐Pb cap carbonate dating. Based on these, a minimum duration of ca. 8 Ma for the Sturtian and of ca. 14 Ma for the Marinoan glaciation can be assumed.:Abstract Kurzfassung Contents List of Figures List of Tables List of abbreviations Scientific question and thesis structure 1 Introduction 1.1 The Neoproterozoic era: Supercontinent dispersal and global glaciations 1.1.1 Rodinia supercontinent: Formation, dispersal, and location of Kalahari Craton 1.1.2 Glacial events during the Neoproterozoic era 1.1.2.1 A brief history on the discovery of Snowball Earth events 1.1.2.2 Formation and termination of a Snowball Earth event: The Snowball Earth flow chart 1.1.2.3 Hypotheses for cap carbonate formation 1.1.2.4 Survival of life during a Snowball Earth event 1.2 The Kalahari Craton 1.2.1 Evolution of the Kalahari Craton 1.3 Overview over the Geology of Namibia under special consideration of southern Namibia (Kalahari Craton) 2 Characteristics of southern Namibian Neoproterozoic glacial samples and sides 3 The problematic correlations of Neoproterozoic glacial deposits of the Kalahari Craton (southern Namibia) 4 Methods 4.1 Field work 4.2 Whole Rock geochemical analyses 4.3 Heavy mineral separation and SEM analyses on zircon grains of siliciclastic samples 4.4 Zircon grain size analyses 4.5 LA‐ICP‐MS analyses on zircon grains 4.5.1 U‐Pb analyses with LA‐SF‐ICP‐MS 4.5.2 Th‐U ratio determination on zircon grains 4.5.3 Hf‐isotope measurements with LA‐MS‐ICP‐MS 4.6 LA‐ICP‐MS U‐Pb dating on carbonates 4.7 Provenance interpretations and likeness tests based on zircon U‐Pb age data bases 5 Study I: “The Namuskluft and Dreigratberg sections in southern Namibia (Kalahari Craton, Gariep Belt): a geological history of Neoproterozoic rifting and recycling of cratonic crust during the dispersal of Rodinia until the amalgamation of Gondwana” 5.1 Introduction and geological setting 5.2 Samples and methods 5.3 Results 5.4 Discussion and interpretation 5.5 Summary 6 Study II: “The four Neoproterozoic glaciations of southern Namibia and their detrital zircon record: The fingerprints of four crustal growth events during two supercontinent cycles” 6.1 Introduction 6.2 The samples 6.3 Methods 6.4 Results 6.5 Interpretation and discussion 6.6 Conclusion/Summary 7 Study III: “Correlation of Neoproterozoic diamictites in southern Namibia” 7.1 Introduction 7.2 Sample sites 7.2.1. The Kaigas and Sturtian Numees diamictites at the Orange River section 2.1.1. Outcrops of the Kaigas Fm diamictites 7.2.1.2 Outcrop of the Numees Fm diamictites (Sturtian) 7.2.2 The Sturtian diamcitite of the Blaubeker Fm (Witvlei Grp) at the farmgrounds Blaubeker and Tahiti 7.2.2.1 The Blaubeker diamictite at Blaubeker Farm (type locality) 7.2.2.2 The Blaubeker diamictite at Tahiti Farm (Gobabis‐syncline) 7.2.2.3 Correlation of Blaubeker diamictite at Blaubeker and Tahiti farms 7.2.3 The Sturtian diamictite at the Trekpoort Farm section 7.2.4 The Sturtian and Marinoan diamictites at Namuskluft section (reference profile) 7.2.5 The Sturtian and Marinoan diamictites at Dreigratberg section 7.2.6 Sturtian diamictite and Marinoan‐type cap carbonate at Dreigratberg North section 7.2.7 The Marinoan diamictite at the Witputs Farm section 7.2.8 The post‐Gaskiers Vingerbreek diamictite 7.2.8.1 The Vingerbreek diamictite along the Orange River 7.2.8.2 The Vingerbreek diamictite at Tierkloof Farm (Klein Karas Mountains) 7.3 Methods 7.4 Data and Results 7.4.1 Results of the U‐Pb detrital zircon data 7.4.2 Results of the U‐Pb carbonate dating 7.4.3 Results of zircon grain width and length measurements 7.4.4 Results of the Th‐U zircon ratios 7.4.5 Results of Lu‐Hf isotopic measurements 7.4.6 Geochemical results of the siliciclastic and basement samples 7.4.7 Geochemical results of the carbonate samples 7.5 Discussion and Conclusion 8 Sediment provenance and Snowball Earth ice dynamics 9 Implications on the evolution of the Gariep Belt 10 Conclusions and outlook 11 References Supplementary Material / Die neoproterozoischen Einheiten des südlichen Namibias (Kalahari Kraton) umfassen verschiedene glaziale Einheiten, die schon seit fast 100 Jahren bekannt sind und wissenschaftlich beschrieben wurden (z.B. Coleman, 1926; Gevers, 1931; Schwellnuss, 1941; Martin, 1965). Die Schneeball Erde Theorie (Hoffman et al., 1998) hatte einen enormen Einfluss auf die geologischen Studien des Neoproterozoikums, wobei besonders Aufschlüsse der Otavi Gruppe Nordnamibias die Theorie stärken und bestätigen. Im Gegensatz dazu sind neoproterozoische glaziale Horizonte Südnamibias aufgrund ihrer tektonischen Überprägung und der wenigen Aufschlüsse schwer zu interpretieren und zu korrelieren. Mit dem Ziel, die neoproterozoischen glazialen Einheiten Südnamibias zu unterscheiden und zu korrelieren, wurde ein Multimethodenansatz basierend auf Isotopenanalysen an Zirkonmineralen, Gesamtgesteinsgeochemie, Mineralkorngrößenmessungen und intensiver Feldarbeit angewandt. Insgesamt wurden zehn Profile kartiert und vermessen, von denen 33 Proben zur weiteren Analyse ausgewählt wurden. Zwei dieser Proben stammen vom lokalen Grundgebirge, 19 aus den sedimentären Einheiten darüber (inklusive der glazialen Ablagerungen) und zwölf repräsentieren Karbonatgesteinsproben. 3474 Einzelzirkone wurden hinsichtlich ihrer Breite und Länge vermessen, wovon 2404 Minerale mittels LA‐ICP‐MS nach ihren U‐Pb und Th‐U‐Gehalten analysiert wurden. 1535 dieser Minerale ergaben konkordante Alter (90 – 110% Konkordanz). Darüber hinaus wurden von 346 ausgewählten konkordanten Zirkonen die εHf(t) Werte bestimmt. Um das Datenset zu vervollständigen wurden LA‐ICP‐MS U‐Pb Analysen an Karbonatgesteinen an zehn von zwölf Proben erfolgreich getestet. Im Zuge der Feldarbeiten kristallisierten sich zwei Profile nahe des Oranje heraus, welche die Sturtian und die Marinoan Vereisung in nahezu ungestörter Lagerung enthalten und sich deshalb als Referenzprofile qualifizieren. Alle analysierten Proben zeichnen sich durch sehr ähnliche Zirkonisotopenwerte aus, was durch die Gesamtgesteinsgeochemieanalysen weiterhin bestätigt wird. Alle siliziklastischen Proben zeigen eine generelle felsische Provenienz mit Zirkonaltern welche sich hauptsächlich in zwei Altersgruppen unterteilen lassen (mesoproterozoisch 1.0 – 1.5 Mrd Jahre, paläoproterozoisch 1.7 – 2.1 Mrd Jahre). Diese reflektieren vier verschiedene krustale Entwicklungsstadien vom Mesoproterozoikum bis Archaikum. Die geochemische Signatur aller Proben deutet auf einen kontinentalen Inselbogen hin und auch die Zirkonmineralgrößen sind für alle Proben ähnlich. Eine direkte Altersdatierung auf Grundlage der detritischen Zirkone war aufgrund fehlender junger Alter nicht möglich. Dennoch ist eine Unterscheidung der glazialen Schichten Südnamibias basierend auf den petrographischen Eigenschaften und dem sich verschiebenden Alterstrend der detritischen Zirkone möglich (P/M Verhältnis). In Kombination mit den zwei Referenzprofilen ist eine umfassende Korrelation aller untersuchten Profile möglich und die Unterscheidung von vier Neoproterozoischen glazialen Schichten in Namibia gelungen. Die Ergebnisse geben weitere Einblicke in die neoproterozoische Entwicklung des Gariep Gürtels, welcher durch Riftvorgänge im Tonium, die Bildung des Arachania Terranes während des Cryogeniums und die ediakarische finale Kollision zwischen den Rio de la Plata und Kalahari Kratonen geprägt ist. Die Kombination aller Ergebnisse zeigt ein kontinuierliches Sedimentrecycling auf dem westlichen Kalahari Kraton. Vergleiche und statistische Ähnlichkeitsanalysen basierend auf U‐Pb Zirkonalterdatenbanken ergaben, dass der Namaqua Natal und der Gariep Gürtel die wahrscheinlichsten Liefergebiete sind. Das Recycling fand für mindestens 200 Millionen Jahre zwischen der Kaigas Vereisung (etwa vor 750 Millionen Jahren) und der Vingerbreek Vereisung (etwa vor 550 Millionen Jahren) statt. Darüber hinaus zeigt das Fehlen fremder Zirkonalter für die Schneeball Erde Proben, dass sich die Eispanzer kaum oder nur sehr wenig bewegt haben können, was die Theorie einer komplett zugefrorenen Erde unterstützt. Die Ergebnisse der U‐Pb Karbonatgesteinsdatierungen bestätigen des angenommene Sturtian und Marinoan Alter der Numees Fm und des Namaskluft Mbr. Basierend auf diesen Analysen kann eine Mindestlänge von etwa 8 Millionen Jahren für das Sturtian und etwa 14 Millionen Jahren für das Marinoan Schneeball Erde Ereignis angenommen werden.:Abstract Kurzfassung Contents List of Figures List of Tables List of abbreviations Scientific question and thesis structure 1 Introduction 1.1 The Neoproterozoic era: Supercontinent dispersal and global glaciations 1.1.1 Rodinia supercontinent: Formation, dispersal, and location of Kalahari Craton 1.1.2 Glacial events during the Neoproterozoic era 1.1.2.1 A brief history on the discovery of Snowball Earth events 1.1.2.2 Formation and termination of a Snowball Earth event: The Snowball Earth flow chart 1.1.2.3 Hypotheses for cap carbonate formation 1.1.2.4 Survival of life during a Snowball Earth event 1.2 The Kalahari Craton 1.2.1 Evolution of the Kalahari Craton 1.3 Overview over the Geology of Namibia under special consideration of southern Namibia (Kalahari Craton) 2 Characteristics of southern Namibian Neoproterozoic glacial samples and sides 3 The problematic correlations of Neoproterozoic glacial deposits of the Kalahari Craton (southern Namibia) 4 Methods 4.1 Field work 4.2 Whole Rock geochemical analyses 4.3 Heavy mineral separation and SEM analyses on zircon grains of siliciclastic samples 4.4 Zircon grain size analyses 4.5 LA‐ICP‐MS analyses on zircon grains 4.5.1 U‐Pb analyses with LA‐SF‐ICP‐MS 4.5.2 Th‐U ratio determination on zircon grains 4.5.3 Hf‐isotope measurements with LA‐MS‐ICP‐MS 4.6 LA‐ICP‐MS U‐Pb dating on carbonates 4.7 Provenance interpretations and likeness tests based on zircon U‐Pb age data bases 5 Study I: “The Namuskluft and Dreigratberg sections in southern Namibia (Kalahari Craton, Gariep Belt): a geological history of Neoproterozoic rifting and recycling of cratonic crust during the dispersal of Rodinia until the amalgamation of Gondwana” 5.1 Introduction and geological setting 5.2 Samples and methods 5.3 Results 5.4 Discussion and interpretation 5.5 Summary 6 Study II: “The four Neoproterozoic glaciations of southern Namibia and their detrital zircon record: The fingerprints of four crustal growth events during two supercontinent cycles” 6.1 Introduction 6.2 The samples 6.3 Methods 6.4 Results 6.5 Interpretation and discussion 6.6 Conclusion/Summary 7 Study III: “Correlation of Neoproterozoic diamictites in southern Namibia” 7.1 Introduction 7.2 Sample sites 7.2.1. The Kaigas and Sturtian Numees diamictites at the Orange River section 2.1.1. Outcrops of the Kaigas Fm diamictites 7.2.1.2 Outcrop of the Numees Fm diamictites (Sturtian) 7.2.2 The Sturtian diamcitite of the Blaubeker Fm (Witvlei Grp) at the farmgrounds Blaubeker and Tahiti 7.2.2.1 The Blaubeker diamictite at Blaubeker Farm (type locality) 7.2.2.2 The Blaubeker diamictite at Tahiti Farm (Gobabis‐syncline) 7.2.2.3 Correlation of Blaubeker diamictite at Blaubeker and Tahiti farms 7.2.3 The Sturtian diamictite at the Trekpoort Farm section 7.2.4 The Sturtian and Marinoan diamictites at Namuskluft section (reference profile) 7.2.5 The Sturtian and Marinoan diamictites at Dreigratberg section 7.2.6 Sturtian diamictite and Marinoan‐type cap carbonate at Dreigratberg North section 7.2.7 The Marinoan diamictite at the Witputs Farm section 7.2.8 The post‐Gaskiers Vingerbreek diamictite 7.2.8.1 The Vingerbreek diamictite along the Orange River 7.2.8.2 The Vingerbreek diamictite at Tierkloof Farm (Klein Karas Mountains) 7.3 Methods 7.4 Data and Results 7.4.1 Results of the U‐Pb detrital zircon data 7.4.2 Results of the U‐Pb carbonate dating 7.4.3 Results of zircon grain width and length measurements 7.4.4 Results of the Th‐U zircon ratios 7.4.5 Results of Lu‐Hf isotopic measurements 7.4.6 Geochemical results of the siliciclastic and basement samples 7.4.7 Geochemical results of the carbonate samples 7.5 Discussion and Conclusion 8 Sediment provenance and Snowball Earth ice dynamics 9 Implications on the evolution of the Gariep Belt 10 Conclusions and outlook 11 References Supplementary Material

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The transition from the Neoproterozoic to the early Cambrian world was a critical time in the co-evolution of life and the environment, when dramatic changes in the environment, including global glaciations and rising atmospheric oxygen levels precipitated the conditions in which variety of complex life emerged, diversified, and proliferated. However, questions persist regarding the timing and duration of those environmental events, and thus the extent of their direct effect on the evolution of life. These changing environmental conditions also produced unique taphonomic conditions that preserved a wide variety of organisms, and also produced unusual early diagenetic features that can be difficult to distinguish from fossilized organisms. In order to better resolve the link between life and the environment during the Neoproterozoic to Cambrian transition I present three chapters. The first chapter of this dissertation examines the carbonate clasts from a glacial diamictite deposited at the end of the Cryogenian Period in South China. By determining the source locality of those carbonate clasts using stable carbon and oxygen isotope compositions, we can better understand the extent of the Marinoan Glaciation and the intensity of its impact on the Earth's surface. In the second chapter of this dissertation, I investigate the changing chemical conditions of ocean waters following both the Marinoan glaciation and potentially one of the most intense disruptions to the carbon cycle in Earth History, the Ediacaran Shuram carbon isotope anomaly. I use Hg concentrations and stable isotope compositions to determine changes in sediment sourcing along with changes in marine redox, such as the development of photic zone euxinia. In the third chapter, I investigate the identity of Brooksella alternata, a purportedly cnidarian fossil that was later suggested to be a hexactinellid sponge fossil. My morphological and compositional analysis reveals B. alternata to be a concretion and thus a pseudofossil. / Doctor of Philosophy / The Earth experienced major changes between 635 and ~514 million years ago; the last global scale glaciation in the history of Earth ended, early animals arose, primary producers such as algae grew larger and more complex, and the first animals that were mobile and with hard skeletal parts evolved and diversified tremendously. Concomitantly, the environment on the Earth changed dramatically: the carbon cycle experienced one of the greatest disruptions in all of Earth history and the oceans and atmosphere gradually became more oxygen-rich, though areas with low levels of dissolved molecular oxygen and high concentrations of dissolved iron or hydrogen sulfide persisted, which may have impeded the diversification of complex animals. The exact timing and intensity of these changes are not fully resolved, and by investigating this time interval in the geologic record, we can better understand how the world changed and how life at the time responded. These changing environments also produced unique conditions which led to fossils being preserved in unique ways, though these conditions also produced non-biological structures that superficially resemble fossils. The first chapter of this dissertation investigates the source of clasts made of carbonate rock from a glacial diamictite (the poorly sorted mixture of the fine-grained and coarse-grained deposits left behind as glaciers recede) in South China deposited at the end of the last global scale glaciation about 635 million years ago. By determining the source, we can evaluate how far glacial activity transported sediments. I found that the previously suggested source of these clasts does not match the geochemical fingerprint of the carbonate clasts. I propose that these carbonate clasts may have come from a source that has since become "extinct" because of glacial erosion, or they may have come from another continent (for example, India). These scenarios highlight the magnitude of the global glaciation. In the second chapter, I investigated the mercury concentrations and stable isotope compositions from organic rich shales deposited ~550 million years ago. Mercury is an emerging tool for evaluating the level of dissolved molecular oxygen in ancient oceans. In this study, I found evidence of locally complex marine oxygen levels, including evidence for photic zone euxinia, meaning waters where oxygen was absent and hydrogen sulfide was present. Such conditions are toxic to animals and may have delayed the diversification of complex animal life. In the final chapter, I analyzed the ~503 million-year-old fossil Brooksella alternata. It was first described more than 100 years ago as a jelly-fish fossil. More recently it was suggested to be a sponge fossil (though it has been ascribed many other identities). Based on morphological analysis of a large collection, I determined that Brooksella alternata is not a fossil but rather a concretion with unusual shape.

Les régions polaires sont particulièrement touchées par le changement climatique actuel, en raison des mécanismes d'amplification qui y opèrent. Les forages de glace en Antarctique et au Groenland sont des témoins précieux des variations paléoclimatiques locales et donnent aussi accès à des informations sur les modifications environnementales des latitudes plus basses. Ce travail de thèse repose sur l'obtention d'informations délivrées par l'air progressivement emprisonné sous forme de bulle lors du processus de transformation de la neige en glace : la composition élémentaire et isotopique de l'air (N2, O2, Ar et Kr) et la concentration en méthane. Nos résultats permettent de progresser sur trois aspects différents mais intimement liés : (i) L'évolution passée de la structure des névés en Antarctique. La mesure des isotopes du krypton sur le forage profond de Dome C (EDC pour EPICA Dome C) nous permet de mettre en évidence qu'une zone convective de l'ordre de 20-50 m a pu se développer dans le névé en période glaciaire. L'étude conjointe des profils isotopiques de l'azote ("15N) mesurés sur les forages EPICA Dronning Maud Land (EDML) et TALDICE suggèrent que l'évolution de la structure du névé des deux sites ne répond plus de manière simple aux changements du taux d'accumulation en surface lorsque celui-ci dépasse un seuil de 5 ±1.5 cm eq. glace an- 1. (ii) La datation des forages glaciologiques. Nous avons exploité le premier enregistrement de "O2/N2 produit entre 300 000 et 800 000 ans sur l'air piégé dans la glace de EDC. Alors qu'il semble délicat d'utiliser ce signal pour construire une nouvelle datation par calage orbital de ce forage, en particulier pour les périodes de faible excentricité, le "O2/N2 se révèle être un outil pertinent pour tester les limites et les incertitudes de la datation actuelle du forage (EDC3). L'utilisation conjointe des isotopes de l'oxygène atmosphérique et du méthane nous permet d'établir une synchronisation des forages de EDML (Antarctique) et de NorthGRIP (Groenland) couvrant le début de la dernière période glaciaire (75 000-123 000 ans) avec une incertitude inférieure à 400 ans. (iii) Cette datation relative nous permet de décrire les variations climatiques rapides au début de la dernière période glaciaire au Groenland et en Antarctique. Nous mettons en évidence une variabilité climatique sub-millénaire superposée à la succession classique des évènements de Dansgaard Oeschger, i.e. des évènements précurseurs aux évènements rapides, des rebonds climatiques en fin d'interstade. Nous démontrons que le mécanisme de bascule bipolaire entre le Groenland et l'Antarctique est également opérationnel à l'échelle sub- millénaire. Une étude multiparamétrique sur le premier événement abrupt enregistré dans la glace de NorthGRIP (DO25) montre que cet événement caractérise la transition entre la dernière période interglaciaire et la mise en place d'une variabilité abrupte couplant les hautes et les basses latitudes. L'ensemble de nos résultats établit un lien étroit entre la dynamique climatique rapide à l'échelle millénaire et les composantes à évolution lente qui imposent l'état de base du système climatique (configuration orbitale, volume des glaces).