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
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:75890 |
| Date | 07 September 2021 |
| Creators | Richter-Krautz, Jana |
| Contributors | Kleber, Arno, Zöller, Ludwig, Veit, Heinz, Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | 10.5194/egqsj-67-7-2018, 10.1016/j.quascirev.2018.01.012, 10.1002/esp.5073 |
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