Located in the south of the Moroccan Sahara, the Adrar Souttouf Massif is the northern continuation of the Mauritanides at the western margin of the West African Craton. The massif itself exhibits a complex polyphase geologic history and contains four geologically different, SSW-NNE trending main units named from west to east: Oued Togba, Sebkha Gezmayet, Dayet Lawda, Sebkha Matallah. They are thrusted over each other in thin-skinned nappes with local windows of the discordantly overlain Archaean Reguibat basement. The eastern margin of the massif is bordered by the Tiris and Tasiast-Tijirit areas of the Reguibat Shield as well as its (par-) autochthonous Palaeozoic cover sequence, termed Dhloat Ensour unit. More than 5.500 U-Th-Pb age determinations and over 1.000 Hf isotopic measurements on single zircon grains from igneous, metamorphic, and sedimentary rocks of all the massifs units and its vicinity have yet been obtained. Most of the zircons were studied with respect to their morphological features. This method improves the accuracy of provenance studies by detecting varying zircon morphologies in space and time. These data are accompanied by U-Th-Pb age determinations on apatite as well as rutile. Together, they allow proposing a model of the geologic evolution of this poorly mapped area for the last 635 Ma. A combination of the obtained data with extensive zircon age databases of the surrounding cratons and terranes facilitates continental-scaled palaeogeographic reconstructions. Regarding the geologic evolution of the Adrar Souttouf Massif, the assembly of the first units began prior to 635 Ma. Although containing all the major zircon age and Hf-isotope populations of the West African Craton as well as some Mesoproterozoic grains, the Sebkha Gezmayet unit lies to the west of the Dayet Lawda unit of oceanic island arc composition. Hence, the Sebkha Gezmayet unit must have been rifted away from the craton prior to the formation of the oceanic unit within the West African Neoproterozoic Ocean at about 635 Ma. Recently published Hf and zircon age data of this unit suggest that the island arc was derived from a juvenile mantle source. Subsequently, the accretion of precursors of the Oued Togba and Sebkha Gezmayet units as well as a partial obduction of the oceanic Dayet Lawda unit and the Neoproterozoic sediments of a foreland basin (Sebkha Matallah unit) onto the Reguibat Shield took place. Peak metamorphism in the obducted oceanic rocks was reached at about 605 Ma. Magmatism in the western units between 610 and 570 Ma suggests on-going tectonic activity. The Early and Middle Cambrian is characterised by the erosion of the Ediacaran orogen and deposition of thick sedimentary sequences at the Sebkha Matallah unit, which acted as foreland basin. These sediments show a mostly West African zircon record with only some Mesoproterozoic grains provided by the westernmost parts of the massif. Initial rifting of the Oued Togba and Sebkha Gezmayet units from the remaining areas presumably occurred during the Late Cambrian. Coeval granitoid intrusions occurred on both sides of the rift. The two rifted units were likely involved to the polyphased Appalachian orogenies, which is emphasised by Devonian magmatism. Thus, and with respect to the isotopic data, the Oued Togba unit is interpreted to be of Avalonia affinity, while the Sebkha Gezmayet unit can likely be linked to Meguma. The units which remained at the West African Craton underwent intense sediment recycling during the entire Ordovician to Devonian times. Final accretion of all units and formation of the current massif was achieved during the Variscan-Alleghanian orogeny. This was accompanied by magmatism in the Sebkha Gezmayet unit and intense metamorphism of the Reguibat basement, whose zircons often show lower discordia intercepts of Carboniferous or Permian age. The post-Variscan period is characterised by erosion of the orogen and subjacent alternating cycles of sedimentation and deflation. The Adrar Souttouf Massifs importance for palaeogeographic reconstructions is given by the striking differences in the zircon age and Hf-isotope record of its westernmost Oued Togba unit and the remaining area. The results obtained from the Oued Togba unit resemble the published data of the Avalonia type terranes including prominent Mesoproterozoic, Ediacaran-Early Cambrian, as well as Early Devonian age populations. Many Mesoproterozoic zircons, which are exotic for the West African Craton prior to 635 Ma, form a ca. 1.20 to 1.25 Ga age peak that is an excellent tracer for detrital provenance studies and source craton identification of the sedimentary rocks. This is also valid for some sedimentary samples that do not show ages younger than 700 Ma, but large quantities of Mesoproterozoic zircon. These rocks can be correlated to similar sediments in Mauritania and W-Avalonia and are thought to be of pre-pan-African", i.e. pre-Ediacaran or even pre-Cryogenian age. They may give direct insights to the source area in Early to Mid Neoproterozoic times. Accordingly, comparison with published data of Amazonia and Baltica, allows setting up new hypotheses for the pre-Ediacaran history of the Avalonian type terranes. Lacking of magmatism in Amazonia between ca. 1200 and ca. 1300 Ma favours Baltica as source craton for the Avalonian terranes and requires a new point of view for the Neoproterozoic palaeogeography.

Located in the south of the Moroccan Sahara, the Adrar Souttouf Massif is the northern continuation of the Mauritanides at the western margin of the West African Craton. The massif itself exhibits a complex polyphase geologic history and contains four geologically different, SSW-NNE trending main units named from west to east: Oued Togba, Sebkha Gezmayet, Dayet Lawda, Sebkha Matallah. They are thrusted over each other in thin-skinned nappes with local windows of the discordantly overlain Archaean Reguibat basement. The eastern margin of the massif is bordered by the Tiris and Tasiast-Tijirit areas of the Reguibat Shield as well as its (par-) autochthonous Palaeozoic cover sequence, termed Dhloat Ensour unit. More than 5.500 U-Th-Pb age determinations and over 1.000 Hf isotopic measurements on single zircon grains from igneous, metamorphic, and sedimentary rocks of all the massifs units and its vicinity have yet been obtained. Most of the zircons were studied with respect to their morphological features. This method improves the accuracy of provenance studies by detecting varying zircon morphologies in space and time. These data are accompanied by U-Th-Pb age determinations on apatite as well as rutile. Together, they allow proposing a model of the geologic evolution of this poorly mapped area for the last 635 Ma. A combination of the obtained data with extensive zircon age databases of the surrounding cratons and terranes facilitates continental-scaled palaeogeographic reconstructions. Regarding the geologic evolution of the Adrar Souttouf Massif, the assembly of the first units began prior to 635 Ma. Although containing all the major zircon age and Hf-isotope populations of the West African Craton as well as some Mesoproterozoic grains, the Sebkha Gezmayet unit lies to the west of the Dayet Lawda unit of oceanic island arc composition. Hence, the Sebkha Gezmayet unit must have been rifted away from the craton prior to the formation of the oceanic unit within the West African Neoproterozoic Ocean at about 635 Ma. Recently published Hf and zircon age data of this unit suggest that the island arc was derived from a juvenile mantle source. Subsequently, the accretion of precursors of the Oued Togba and Sebkha Gezmayet units as well as a partial obduction of the oceanic Dayet Lawda unit and the Neoproterozoic sediments of a foreland basin (Sebkha Matallah unit) onto the Reguibat Shield took place. Peak metamorphism in the obducted oceanic rocks was reached at about 605 Ma. Magmatism in the western units between 610 and 570 Ma suggests on-going tectonic activity. The Early and Middle Cambrian is characterised by the erosion of the Ediacaran orogen and deposition of thick sedimentary sequences at the Sebkha Matallah unit, which acted as foreland basin. These sediments show a mostly West African zircon record with only some Mesoproterozoic grains provided by the westernmost parts of the massif. Initial rifting of the Oued Togba and Sebkha Gezmayet units from the remaining areas presumably occurred during the Late Cambrian. Coeval granitoid intrusions occurred on both sides of the rift. The two rifted units were likely involved to the polyphased Appalachian orogenies, which is emphasised by Devonian magmatism. Thus, and with respect to the isotopic data, the Oued Togba unit is interpreted to be of Avalonia affinity, while the Sebkha Gezmayet unit can likely be linked to Meguma. The units which remained at the West African Craton underwent intense sediment recycling during the entire Ordovician to Devonian times. Final accretion of all units and formation of the current massif was achieved during the Variscan-Alleghanian orogeny. This was accompanied by magmatism in the Sebkha Gezmayet unit and intense metamorphism of the Reguibat basement, whose zircons often show lower discordia intercepts of Carboniferous or Permian age. The post-Variscan period is characterised by erosion of the orogen and subjacent alternating cycles of sedimentation and deflation. The Adrar Souttouf Massifs importance for palaeogeographic reconstructions is given by the striking differences in the zircon age and Hf-isotope record of its westernmost Oued Togba unit and the remaining area. The results obtained from the Oued Togba unit resemble the published data of the Avalonia type terranes including prominent Mesoproterozoic, Ediacaran-Early Cambrian, as well as Early Devonian age populations. Many Mesoproterozoic zircons, which are exotic for the West African Craton prior to 635 Ma, form a ca. 1.20 to 1.25 Ga age peak that is an excellent tracer for detrital provenance studies and source craton identification of the sedimentary rocks. This is also valid for some sedimentary samples that do not show ages younger than 700 Ma, but large quantities of Mesoproterozoic zircon. These rocks can be correlated to similar sediments in Mauritania and W-Avalonia and are thought to be of pre-pan-African", i.e. pre-Ediacaran or even pre-Cryogenian age. They may give direct insights to the source area in Early to Mid Neoproterozoic times. Accordingly, comparison with published data of Amazonia and Baltica, allows setting up new hypotheses for the pre-Ediacaran history of the Avalonian type terranes. Lacking of magmatism in Amazonia between ca. 1200 and ca. 1300 Ma favours Baltica as source craton for the Avalonian terranes and requires a new point of view for the Neoproterozoic palaeogeography.

This thesis results from a pilot study which, driven by repeatedly surprising results, opens up a reliable method of geochronology for Quaternary research. There have been repeated attempts to expand the limits of normal use of U-Pb dating. Geologists typically use U-Pb dating on detrital zircons (DZ) for dating and provenance studies on rocks older than the Cenozoic era. We tested several tephra layers in Utah and New Mexico, USA, with published 40 Ar/ 39 Ar ages between 1.3 and 1.6 Ma and found that the ages derived from clustered U-Pb dating are reliable, even though they were discordant. We used one of these tephra layers in the La Sal Mountains, Utah, to assign a minimum age to slope deposit layers (cover beds) underlying the tephra bed. In doing so, we discovered that we could not only identify unconformities between layers by means of palaeopedology. But that - although they were similar to one another regarding physical and chemical properties - they were not the same at all in terms of the provenance of their aeolian matter as derived from U-Pb analysis of detrital zircons, as one could actually assume. The source of aeolian matter mixed to these layers has changed decisively from layer to layer. The findings also allowed tentatively assigning palpable source areas for each layer. Since this had demonstrated the feasibility of a provenance approach, we then extended our study regionally to cover beds of the central Great Basin (GB) and the northern Colorado Plateau (CP). Using a published sequence-stratigraphic approach based upon stratigraphically consistent phases of soil development, we attempted to study cover beds from the same two Upper Quaternary time slices. We expanded our range of methods by end-member modelling analyzes (EMMA) and the analysis of surface and shape of detrital zircons. We used statistical methods such as multidimensional scaling (MDS) and density functions (probability density functions and kernel density estimations) to visualize similarities and distances of age distributions. The MDS and the density functions showed very clearly that the patterns of ages between the GB and the CP can be divided into two groups that differ from one another. This is probably due to different transport cascades of the zircons to and within both areas. Due to the lack of databases on the morphology of in-situ zirconia, it is not yet possible to draw precise conclusions about transport routes from them, although we have probably been able to identify traces of several stages of aeolian transport on many zircons. Conclusions can also be drawn about detrital zircons that were transported to the sampling point purely by the kinetic energy of volcanic eruptions during the Cretaceous (Cordilleran magmatic arc) and the Paleogene (strong volcanism within the study area). Moreover, we can show main similarities of the layers across the CP. Although they are separated spatially and temporally, they have a similar age distribution. The only exception here is the upper La Sal Mountains profile, for which I have several assumptions as to why this is so. We did not have enough conclusions for the reconstruction of the palaeoenvironmental conditions during the layer and soil formation phases; further investigations will have to follow. However, we show that a provenance study on Quaternary layers and further conclusions from the results are possible and would like to condense this approach for the study area in the future, but also try to transfer it to other study areas.:Abstract .......................................................................................................................3 Kurzfassung ................................................................................................................5 Contents ......................................................................................................................7 List of figures ............................................................................................................ 11 List of tables ............................................................................................................. 13 List of abbreviations and units .................................................................................. 14 1 Introduction ........................................................................................................... 16 1.1 Research questions ........................................................................................... 16 1.2 Cover beds ......................................................................................................... 17 1.3 Palaeosols .......................................................................................................... 17 1.4 Study area .......................................................................................................... 18 1.5 Zircons ............................................................................................................... 21 1.6 Thesis format ...................................................................................................... 23 2 Capability of U-Pb dating of zircons from Quaternary tephra: Jemez Mountains, NM, and La Sal Mountains, UT, USA ....................................................................... 24 2.1 Abstract .............................................................................................................. 25 2.2 Kurzfassung ....................................................................................................... 25 2.3 Introduction ........................................................................................................ 26 2.4 Geological setting ............................................................................................... 27 2.4.1 Jemez Mountains, New Mexico ...................................................................... 27 2.4.2 La Sal Mountains, Utah ................................................................................... 30 2.5 Methods ............................................................................................................. 30 2.6 Results and discussion ..................................................................................... 33 2.6 Conclusions ........................................................................................................ 38 Data availability ........................................................................................................ 38 Competing interests.................................................................................................. 38 Acknowledgements .................................................................................................. 38 2.7 References ......................................................................................................... 39 3 Cover beds older than the mid-Pleistocene revolution and the provenance of their aeolian components, La Sal Mountains, Utah, USA ........................................ 42 3.1 Abstract .............................................................................................................. 43 3.2 Introduction ........................................................................................................ 43 3.3 Material and methods ........................................................................................ 44 3.3.1 The La Sal Mountains tephra layer ................................................................. 44 3.3.2 Cover beds and palaeosols............................................................................. 45 3.3.3 Samples and analyses .................................................................................... 46 3.4 Results and discussion ...................................................................................... 49 3.5 Conclusions ....................................................................................................... 56 Acknowledgments ................................................................................................... 58 Summary information A. Supplementary data ......................................................... 58 3.6 References ........................................................................................................ 58 4 Zircon provenance of Quaternary cover beds using U-Pb dating: regional differences in the south-western USA ...................................................................... 63 4.1 Abstract .............................................................................................................. 64 4.2 Introduction ........................................................................................................ 65 4.3 Materials ............................................................................................................. 66 4.3.1 Study areas ..................................................................................................... 66 4.3.2 Stratigraphy and sampling sites ...................................................................... 68 4.3.3 Palaeolake deposits ........................................................................................ 71 4.3.4 Potential sources of detrital zircons ................................................................ 71 4.4 Methods ............................................................................................................. 75 4.4.1 End-member modelling of grainsize composition ........................................... 75 4.4.2 U-Pb dating ..................................................................................................... 75 4.4.3 Zircon dimensions and surfaces ..................................................................... 77 4.4.4 Statistical and graphical representations ........................................................ 78 4.5 Results and discussion ...................................................................................... 79 4.5.1 Aeolian contribution to cover beds .................................................................. 79 4.5.2 Zircon morphology .......................................................................................... 82 4.5.3 Age distributions of detrital zircons ................................................................. 88 4.5.4 Multidimensional scaling (MDS) ..................................................................... 94 4.6 Conclusions ....................................................................................................... 98 Appendix ................................................................................................................ 102 Acknowledgements ................................................................................................ 102 4.7 References ....................................................................................................... 103 5 Extended summary .............................................................................................. 118 5.1 Synthesis .......................................................................................................... 118 5.2 Regional differences and similarities ................................................................ 123 5.3 Outlook ............................................................................................................. 128 6 Supplementary Information ................................................................................. 130 6.1 Supplementary material chapter ‘Capability of U-Pb dating of zircons from Quaternary tephra: Jemez Mountains, NM, and La Sal Mountains, UT, USA’........ 130 6.1.1 Raw data electron microprobe analyses of glass shards from tephra layers .131 6.1.2 Raw data U-Pb ratios and calculated ages for all samples ............................137 6.2 Supplementary material chapter 3 ‘Cover beds older than the mid-Pleistocene revolution and the provenance of their eolian components, La Sal Mountains, Utah, USA’ .............................................................................................................. 160 6.3 Supplementary material chapter 4 ................................................................... 175 6.3.1 SI1 Raw U-Pb ratios and calculated ages ......................................................175 6.3.2 SI 3 Grainsize diagrams of samples of the present study (except for PL)......266 6.3.3 SI 4 Zircon morphology data .........................................................................269 6.3.3.1 Great Basin .................................................................................................269 6.3.3.2 Colorado Plateau ........................................................................................289 7 References (excluding chapters 2, 3 and 4) ....................................................... 308 8 Acknowledgements ............................................................................................. 312 / Diese Arbeit ist das Ergebnis einer Pilotstudie, die aufgrund immer wieder neuer, unerwarteter Ergebnisse eine zuverlässige geochronologische Methode für die Quartärforschung eröffnet. Es wurde mehrfach versucht, die üblichen Grenzen der Verwendung der U-Pb-Datierung zu erweitern. In der Geologie wird die U-Pb-Datierung an detritischen Zirkonen (DZ) normalerweise für Datierungs- und Provenienzstudien an Gesteinen, die älter als das Känozoikum sind, eingesetzt. Wir haben mehrere Tephra-Schichten in Utah und New Mexico, USA, mit veröffentlichten 40 Ar/ 39 Ar-Altern zwischen 1.3 und 1.6 Ma getestet und festgestellt, dass die Alter, die aus den Clustern der U-Pb-Datierungen abgeleitet wurden, zuverlässig sind, obwohl sie diskordant waren. Wir haben eine dieser Tephra-Schichten in den La Sal Mountains, Utah, verwendet, umlagernden Deckschichten ein Mindestalter zuzuweisen. Dabei stellten wir fest, dass wir nicht nur mittels Paläopädologie Schichtgrenzen zwischen Schichten ausweisen konnten. Sondern dass sie sich, obwohl sie sich in Bezug auf physikalische und chemische Eigenschaften ähneln, in Bezug auch auf die Herkunft ihres äolischen Materials (abgeleitet aus der U-Pb-Analyse der DZ) überhaupt nicht glichen, wie man eigentlich annehmen könnte. Die Herkunft des eingemischten äolischen Materials hat sich von Schicht zu Schicht entscheidend verändert. Die Ergebnisse ermöglichten es auch, jeder Schicht konkrete wahrscheinliche Liefergebiete zuzuweisen. Da dies die Möglichkeit einer Provenienz-Analyse belegt hatte, erweiterten wir unsere Studie regional auf Deckschichten des zentralen Great Basin (GB) und des nördlichen Colorado Plateaus (CP). Unter Verwendung eines publizierten sequenz-stratigraphischen Ansatzes, der auf stratigraphisch konsistenten Phasen der Bodenentwicklung basiert, haben wir versucht, Deckschichten aus denselben beiden oberen quartären Zeitscheiben zu untersuchen. Wir erweiterten unser Methodenspektrum um End Member-Modellierung (EMMA) und die Analyse der Oberfläche und Form von DZ. Wir verwendeten statistische Methoden wie mehrdimensionale Skalierung (MDS) und Dichtefunktionen (Wahrscheinlichkeitsdichtefunktionen und Kerndichteschätzungen), um Ähnlichkeiten und Abstände von Altersverteilungen zu visualisieren. MDS und Dichtefunktionen zeigten deutlich, dass GB und CP unterschiedliche Altersspektren aufweisen. Dies ist wahrscheinlich auf unterschiedliche Transportkaskaden der Zirkone in beide und innerhalb beider Gebiete zurückzuführen. Aufgrund des Fehlens von Datenbanken zur Morphologie von gesteinsbürtigen Zirkonen kann man daraus noch keine genauen Rückschlüsse über Transportwege ziehen, obwohl wir wahrscheinlich an vielen Zirkonen Spuren mehrerer Schritte des äolischen Transports identifizieren konnten. Es liegen auch DZ vor, die vermutlich ausschließlich durch die kinetische Energie von Vulkanausbrüchen während der Kreidezeit (Cordilleran Magmatic Arc) und des Paläogens (starker Vulkanismus innerhalb des Untersuchungsgebiets) zum Probenahmepunkt transportiert wurden. Darüber hinaus können wir Ähnlichkeiten zwischen den verschiedenen Schichten im CP zeigen. Obwohl sie räumlich und zeitlich getrennt sind, haben sie eine ähnliche Altersverteilung. Die einzige Ausnahme hiervon ist das Profil der höheren La Sal Mountains, wofür es mehrere mögliche Gründe gibt. Wir konnten nicht genügend Erkenntnisse für die Rekonstruktion der paläoökologischen Bedingungen während der Schicht- und Bodenbildungsphasen gewinnen; weitere Untersuchungen müssen folgen. Wir zeigen jedoch, dass eine Provenienzstudie an quartären Schichten und weiterreichende Schlussfolgerungen möglich sind, und möchten diesen Ansatz für das Untersuchungsgebiet in Zukunft verdichten, aber auch versuchen, ihn auf andere Untersuchungsgebiete zu übertragen.:Abstract .......................................................................................................................3 Kurzfassung ................................................................................................................5 Contents ......................................................................................................................7 List of figures ............................................................................................................ 11 List of tables ............................................................................................................. 13 List of abbreviations and units .................................................................................. 14 1 Introduction ........................................................................................................... 16 1.1 Research questions ........................................................................................... 16 1.2 Cover beds ......................................................................................................... 17 1.3 Palaeosols .......................................................................................................... 17 1.4 Study area .......................................................................................................... 18 1.5 Zircons ............................................................................................................... 21 1.6 Thesis format ...................................................................................................... 23 2 Capability of U-Pb dating of zircons from Quaternary tephra: Jemez Mountains, NM, and La Sal Mountains, UT, USA ....................................................................... 24 2.1 Abstract .............................................................................................................. 25 2.2 Kurzfassung ....................................................................................................... 25 2.3 Introduction ........................................................................................................ 26 2.4 Geological setting ............................................................................................... 27 2.4.1 Jemez Mountains, New Mexico ...................................................................... 27 2.4.2 La Sal Mountains, Utah ................................................................................... 30 2.5 Methods ............................................................................................................. 30 2.6 Results and discussion ..................................................................................... 33 2.6 Conclusions ........................................................................................................ 38 Data availability ........................................................................................................ 38 Competing interests.................................................................................................. 38 Acknowledgements .................................................................................................. 38 2.7 References ......................................................................................................... 39 3 Cover beds older than the mid-Pleistocene revolution and the provenance of their aeolian components, La Sal Mountains, Utah, USA ........................................ 42 3.1 Abstract .............................................................................................................. 43 3.2 Introduction ........................................................................................................ 43 3.3 Material and methods ........................................................................................ 44 3.3.1 The La Sal Mountains tephra layer ................................................................. 44 3.3.2 Cover beds and palaeosols............................................................................. 45 3.3.3 Samples and analyses .................................................................................... 46 3.4 Results and discussion ...................................................................................... 49 3.5 Conclusions ....................................................................................................... 56 Acknowledgments ................................................................................................... 58 Summary information A. Supplementary data ......................................................... 58 3.6 References ........................................................................................................ 58 4 Zircon provenance of Quaternary cover beds using U-Pb dating: regional differences in the south-western USA ...................................................................... 63 4.1 Abstract .............................................................................................................. 64 4.2 Introduction ........................................................................................................ 65 4.3 Materials ............................................................................................................. 66 4.3.1 Study areas ..................................................................................................... 66 4.3.2 Stratigraphy and sampling sites ...................................................................... 68 4.3.3 Palaeolake deposits ........................................................................................ 71 4.3.4 Potential sources of detrital zircons ................................................................ 71 4.4 Methods ............................................................................................................. 75 4.4.1 End-member modelling of grainsize composition ........................................... 75 4.4.2 U-Pb dating ..................................................................................................... 75 4.4.3 Zircon dimensions and surfaces ..................................................................... 77 4.4.4 Statistical and graphical representations ........................................................ 78 4.5 Results and discussion ...................................................................................... 79 4.5.1 Aeolian contribution to cover beds .................................................................. 79 4.5.2 Zircon morphology .......................................................................................... 82 4.5.3 Age distributions of detrital zircons ................................................................. 88 4.5.4 Multidimensional scaling (MDS) ..................................................................... 94 4.6 Conclusions ....................................................................................................... 98 Appendix ................................................................................................................ 102 Acknowledgements ................................................................................................ 102 4.7 References ....................................................................................................... 103 5 Extended summary .............................................................................................. 118 5.1 Synthesis .......................................................................................................... 118 5.2 Regional differences and similarities ................................................................ 123 5.3 Outlook ............................................................................................................. 128 6 Supplementary Information ................................................................................. 130 6.1 Supplementary material chapter ‘Capability of U-Pb dating of zircons from Quaternary tephra: Jemez Mountains, NM, and La Sal Mountains, UT, USA’........ 130 6.1.1 Raw data electron microprobe analyses of glass shards from tephra layers .131 6.1.2 Raw data U-Pb ratios and calculated ages for all samples ............................137 6.2 Supplementary material chapter 3 ‘Cover beds older than the mid-Pleistocene revolution and the provenance of their eolian components, La Sal Mountains, Utah, USA’ .............................................................................................................. 160 6.3 Supplementary material chapter 4 ................................................................... 175 6.3.1 SI1 Raw U-Pb ratios and calculated ages ......................................................175 6.3.2 SI 3 Grainsize diagrams of samples of the present study (except for PL)......266 6.3.3 SI 4 Zircon morphology data .........................................................................269 6.3.3.1 Great Basin .................................................................................................269 6.3.3.2 Colorado Plateau ........................................................................................289 7 References (excluding chapters 2, 3 and 4) ....................................................... 308 8 Acknowledgements ............................................................................................. 312

No description available.

Diese Dissertation befasst sich mit der Entwicklung von “Fastebenen”, die im Weiteren einheitlich als “Peneplains” bezeichnet werden, sowie dem Zerfall dieses markanten geomorphologischen Erscheinungsbildes im südlichsten Teil des tibetischen Plateau dem sogenannten Lhasa Block. Im Zuge dieser Arbeit konnten neue Erkenntnisse über die Hebungsgeschichte und der Sedimentverteilung in diesem Untersuchungsgebiet gewonnen werden. Diese Ergebnisse tragen zu einem besseren Verständnis der geodynamischen Entwicklung Asiens bei, die bis heute viele Fragen aufwirft. Ende des 19. Jahrhunderts wurden Peneplains als metastabile geomorphologische Formen angesehen, die im Zuge großflächiger Erosion entstehen. Die Bezeichnung Peneplain und das dahinter stehende Konzept werden seitdem von der geomorphologischen Gemeinschaft jedoch kontrovers diskutiert. Bis heute gibt es keine standardisierte bzw. repräsentative Definition für das nicht zu übersehende landschaftsbildende Phänomen der Peneplains. Dementsprechend gibt es auch nur wenige Ansätze zu Modellierungen oder Berechnungen mit Geoinformationssystemen. Hier, in dieser Dissertation, werden idealisierte Peneplains als erhöhte, gleichmäßige und großflächige Ebenen mit abfallenden Hängen verstanden, auch wenn sich landschaftsbildende Peneplains oft gekippt darstellen und durch tektonische Prozesse gestört bzw. bereits durch fortschreitende Erosionsprozesse angegriffen sind. Gut erhaltene Peneplains sind speziell für das Gebiet um den höchstgelegenen See der Welt, dem Nam Co, im nördlichen Teil des Lhasa Blocks im Hochland von Tibet charakteristisch. Die Peneplains zerschneiden das dort vorkommende viel ältere und vorwiegend granitische Gestein sowie die angrenzenden Metasedimente. Zur Bestimmung der Abkühl- und Hebungsalter der Granite wurden geo- und thermochronologische Methoden wie Zirkon U-Pb, Zirkon (U-Th)/He, Apatit (U-Th)/He und Apatit-SpaltspurenDatierung angewendet. Neben der Hebungsrate konnte auch die Freilegung des granitischen Gesteines ermittelt werden. Mit der Methode zur Bestimmung des U-Pb-Zirkonalters konnten zwei Intrusionsgruppen, um 118 Ma und 85 Ma, festgestellt werden. Ebenso wurden vulkanische Aktivitäten nachgewiesen und auf einen Zeitraum zwischen 63 Ma und 58 Ma datiert. Thermische Modelle, aufbauend auf Zirkon- und Apatit-(U-Th)/He-Datierungen sowie auf ApatitSpaltspuren-Daten der untersuchten Granitoide, ergeben einen Hebungs- und Abkühlungszeitraum von 75 Ma bis 55 Ma mit einer Hebungsrate von 300 m/Ma, welche im Zeitfenster zwischen 55 Ma und 45 Ma stark abfällt auf 10 m/Ma. Die Auswertung der Messdaten unserer Kooperationspartner an der Universität Münster zu kosmogenen Nukliden zeigen sehr niedrigen Erosionsraten von 6-11 m/Ma und 11-16 m/Ma, in den letzten 10.000 Jahren die in den einzelnen Einzugsgebieten ermittelt wurden. Diese Daten zeugen von einer noch immer andauernden Periode der Stabilität und tragen zur Erhaltung der Peneplains bei. Während der anhaltenden Phase der Erosion und Einebnung sind vor ungefähr 45 Ma in der untersuchten Region zwischen 3 km und 6 km Gestein abgetragen und weg transportiert worden. Es ist naheliegend, dass das abgetragene Material als Sediment über das vorhandene Flusssystem fast vollständig in die heute bestehenden Ozenane transportiert wurde. Im Lhasa Block können nur verhältnismäßig wenig Sedimente aus dieser Zeit nachgewiesen werden. Alle bisherigen Untersuchungsergebnisse sowie die durchgeführte Sediment-Herkunftsanalyse untermauern die Theorie, dass die Peneplainbildung und ihre Erosionsprozesse in niedriger Höhe - höchstwahrscheinlich auf Meeresniveau - stattgefunden haben muss. Dieser Prozess wurde durch die Kollision des indischen Kontinents mit Asien gestoppt. Die resultierende Krustenverdickung führte zu einer Hebung der Landschaft mit den Peneplains, von Meeresniveau auf 5.000 bis 7.000 Höhenmeter. Die auf dem “das Dach der Welt” vorherrschenden idealen Klimabedingungen haben anschließend für die fast vollständige Erhaltung der Peneplains gesorgt. Der zweite Teil der Dissertation befasst sich mit der Entwicklung einer robusten Methode Peneplains anhand digitale Höhenmodelle (DEM) zu berechnen bzw. zu kartieren. Frei zugängliche DEMs machen es möglich, Erdoberflächen repräsentativ mathematisch und statistisch zu analysieren und zu charakterisieren. Diese Analysemethode stellt eine ausgezeichnete Möglichkeit dar, die Peneplains mittels aussagekräftiger Algorithmen zu charakterisieren und digital zu kartieren. Um Peneplains algorithmisch von der Umgebung klar abgrenzen zu können, wurde ein komplett neuer Ansatz der Fuzzylogik angewandt. Als DEM-Basis wurde ein 90 arcsec-DEM der Shuttle Radar Topography Mission (SRTM) verwendet. Mithilfe eines Geoinformationssystems (GIS) wurden Algorithmen geschrieben, die vier verschiedene kritische Parameter zur Beschreibung von Peneplains berücksichtigen: (I) Gefälle, (II) Kurvigkeit, (III) Geländerauhigkeit und (IV) Relative Höhe. Um die Eignung der Methode zu prüfen, wurde auf Basis der SRTM-DEM weltweit kartiert und mit schon in der Literatur beschriebenen Peneplains verglichen. Die dabei erhaltenen Ergebnisse von den Appalachen, den Anden, dem Zentralmassif und Neuseeland bestätigen dass ein Einsatz des Modells, weltweit und unabhängig von der Höhenlage möglich ist.