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dc.contributor.author
Krawielicki, Julia
dc.contributor.supervisor
Willett, Sean
dc.contributor.supervisor
Eglinton, Timothy I.
dc.contributor.supervisor
Magill, Clayton
dc.contributor.supervisor
Levin, Naomi
dc.date.accessioned
2020-03-16T08:58:07Z
dc.date.available
2020-03-16T07:38:38Z
dc.date.available
2020-03-16T08:58:07Z
dc.date.issued
2019
dc.identifier.uri
http://hdl.handle.net/20.500.11850/405004
dc.identifier.doi
10.3929/ethz-b-000405004
dc.description.abstract
Earth’s landscapes are dynamic systems shaped by the interplay of geology, biosphere and atmosphere. The focus of this thesis is to reconstruct ecosystems of the Oligo-Miocene using lipids and their stable isotopic composition. Organic compounds from plant leaves and microbes provide information on the climate, hydrology and vegetation of this period. Here, plant wax n-alkanes and their hydrogen (δDwax) and carbon isotopic values (δ13Cwax) are used to reconstruct changes and diversity of vegetation and precipitation. In addition, microbial lipids (brGDGTs) are applied to reconstruct temperature and soil pH in order to trace climatic changes. These proxies are paired with lithology observations and the mineralogical composition of the sediment. In summary, these proxies allow investigation of different ecological and tectonic settings from dramatic landscape changes in the Messinian Mediterranean, to environmental changes in the Miocene Arabian Sea, and mountain uplift in Oligo-Miocene northeast Africa. First, a survey of modern stable isotopic signals of precipitation and plants in northeast Africa provides insight into modern isotopic patterns and mechanisms. Plant leaf (n = 77) and surface water (n = 181) samples have been collected from the Ethiopian plateau to measure plant δ13Cwax & δDwax and water δ18OH2O & δDH2O. Additionally, analysis of data from the global GNIP database supports previous studies highlighting the contrasting isotopic values in precipitation from the Gulf of Guinea and Indian Ocean. The analysis of modern samples in Chapter 2 are in agreement with previous findings that analyzed the impact of Ethiopian topography on rainout and stable isotope pattern. Chapters 3 and 4 focus on the paleo-environmental changes in northeast Africa during the Oligo-Miocene. In the Oligocene, northern and central Africa moved through the equatorial zone, thus the climate changed towards higher humidity, supporting large forests and woodlands where deserts and open habitats dominate today. In the mid-Miocene, grasslands spread across the lower latitudes and C4 grasses started to dominate east African vegetation. Paleontologists have observed changes in the biogeographical configuration during the late Oligocene, which were attributed to the increasing topography of the Ethiopian highlands. To test this hypothesis, fluvio-lacustrine sediment samples (n = 197) from outcrops on the Ethiopian plateau were targeted. The results show that Ethiopia’s Oligocene vegetation was dominated by open and closed woodlands that fostered the earliest African C4 plants. Their emergence is evident in high carbon isotopic values of plant wax n-alkanes and supports a phylogenetic hypothesis that they emerged as highly specialized plants long before the expansion of C4 grasslands. Later in the early Miocene, these open habitats are replaced by denser forests that stand in contrast to the woodlands and early grasslands of other African regions on the same latitude. A short-term appearance of C4 plants is also seen in another record from the lower latitudes in the Kerala-Konkan basin (Arabian Sea, offshore western India). Here, marine sediments from a core integrate organic matter from the Indian Deccan plateau. The results paint a different picture of continuous C3 vegetation in the Oligocene-early Miocene and a short emergence of C4 plants during the mid-Miocene climatic optimum. Although high temperatures of this period were a large advantage for C4 plants, no such rise can be seen in mid-Miocene sediments of Ethiopia. This comparison shows that neither temperature nor other global factors such as pCO2 are exclusively responsible for the emergence of C4 plants. Instead, more complex localized factors need to be taken into consideration which are discussed in detail in Chapter 4. The focus of Chapter 5 is an extreme event of desiccation in the Mediterranean Sea caused by limited exchange of seawater with the Atlantic Ocean in the late Miocene. This ‘Messinian salinity crisis’ (MSC) had significant effects on the landscapes of the Mediterranean region and re-organized hydrological conditions through dramatic effects on evaporation and freshwater input. To reconstruct environmental and landscape changes during this event, sediment samples have been collected from marine sedimentary outcrops of the Idice section in the northern Apennines (n = 74) and the Maccarone section in the central Apennines (n = 17). Based on the assumption that the hydrogen isotopic signature of plant waxes is mostly influenced by altitude in this region, the comparison of data in both sections shows that the Apennines experienced localized uplift to ca. 2 km elevation. Furthermore, the combination of marine and terrestrial biomarkers shows that climate played a minor role as an additional desiccation agent in the early stage of the MSC, but became more important towards the end of the event. The last MSC stage is characterized by abrupt climate and vegetation shifts reflected in terrestrial markers. Before reflooding the Mediterranean with Atlantic Ocean water, the data shows extreme shifts in marine and terrestrial proxies, indicating that climate had a strong impact on ending this event.
en_US
dc.format
application/pdf
en_US
dc.language.iso
en
en_US
dc.publisher
ETH Zurich
en_US
dc.subject
Organic geochemistry
en_US
dc.subject
geology
en_US
dc.subject
ETHIOPIAN HIGHLANDS
en_US
dc.subject
Isotope fractionation
en_US
dc.subject
C4 grasses
en_US
dc.title
Coupled climate, ecosystem and landscape development in the Afro-Mediterranean region since the Oligocene
en_US
dc.type
Doctoral Thesis
dc.date.published
2020-03-16
ethz.size
272 p.
en_US
ethz.code.ddc
DDC - DDC::5 - Science::550 - Earth sciences
en_US
ethz.identifier.diss
26318
en_US
ethz.publication.place
Zurich
en_US
ethz.publication.status
published
en_US
ethz.leitzahl
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02330 - Dep. Erdwissenschaften / Dep. of Earth Sciences::02704 - Geologisches Institut / Geological Institute::03754 - Willett, Sean / Willett, Sean
en_US
ethz.leitzahl.certified
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02330 - Dep. Erdwissenschaften / Dep. of Earth Sciences::02704 - Geologisches Institut / Geological Institute::03754 - Willett, Sean / Willett, Sean
en_US
ethz.date.deposited
2020-03-16T07:38:48Z
ethz.source
FORM
ethz.eth
yes
en_US
ethz.availability
Embargoed
en_US
ethz.date.embargoend
2022-03-16
ethz.rosetta.installDate
2020-03-16T08:58:20Z
ethz.rosetta.lastUpdated
2021-02-15T08:46:47Z
ethz.rosetta.versionExported
true
ethz.COinS
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