@phdthesis{Schimpf2020,
  author    = {Schimpf, Stefan},
  title     = {Herkunft und Ablagerungsmilieu quart{\"a}rer Sedimente im Einzugsgebiet des Heihe, NW China},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xi, 186},
  year      = {2020},
  abstract  = {Der zentralasiatische Naturraum, wie er sich uns heute pr{\"a}sentiert, ist das Ergebnis eines Zusammenwirkens vieler verschiedener Faktoren {\"u}ber Jahrmillionen hinweg. Im aktuellen Kontext des Klimawandels zeigt sich jedoch, wie stark sich Stofffl{\"u}sse auch kurzfristig {\"a}ndern und dabei das Gesicht der Landschaft verwandeln k{\"o}nnen. Die Gobi-W{\"u}ste in der Inneren Mongolei (China), als Teil der gleichnamigen Trockenregionen Nordwestchinas, ist aufgrund der Ausgestaltung ihrer landschaftspr{\"a}genden Elemente sowie ihrer Landschaftsdynamik, im Zusammenhang mit der Lage zum Tibet-Plateau, in den Fokus der klimageschichtlichen Grundlagenforschung ger{\"u}ckt. Als großes Langzeitarchiv unterschiedlichster fluvialer, lakustriner und {\"a}olischer Sedimente stellt sie eine bedeutende Lokalit{\"a}t zur Rekonstruktion von lokalen und regionalen Stofffl{\"u}ssen dar.. Andererseits ist die Gobi-W{\"u}ste zugleich auch eine bedeutende Quelle f{\"u}r den {\"u}berregionalen Staubtransport, da sie aufgrund der klimatischen Bedingungen insbesondere der Erosion durch Ausblasung preisgegeben wird. Vor diesem Hintergrund erfolgten zwischen 2011 und 2014, im Rahmen des BMBF-Verbundprogramms WTZ Zentralasien - Monsundynamik \& Geo{\"o}kosysteme (F{\"o}rderkennzeichen 03G0814), mehrere deutsch-chinesische Expeditionen in das Ejina-Becken (Innere Mongolei) und das Qilian Shan-Vorland. Im Zuge dieser Expeditionen wurden f{\"u}r eine Bestimmung potenzieller Sedimentquellen erstmals zahlreiche Oberfl{\"a}chenproben aus dem gesamten Einzugsgebiet des Heihe (schwarzer Fluss) gesammelt. Zudem wurden mit zwei Bohrungen im inneren des Ejina-Beckens, erg{\"a}nzende Sedimentbohrkerne zum bestehenden Bohrkern D100 (siehe W{\"u}nnemann (2005)) abgeteuft, um weit reichende, erg{\"a}nzende Informationen zur Landschaftsgeschichte und zum {\"u}berregionalen Sedimenttransfer zu erhalten. Gegenstand und Ziel der vorliegenden Doktorarbeit ist die sedimentologisch-mineralogische Charakterisierung des Untersuchungsgebietes in Bezug auf potenzielle Sedimentquellen und Stofffl{\"u}sse des Ejina-Beckens sowie die Rekonstruktion der Ablagerungsgeschichte eines dort erbohrten, 19m langen Sedimentbohrkerns (GN100). Schwerpunkt ist hierbei die Kl{\"a}rung der Sedimentherkunft innerhalb des Bohrkerns sowie die Ausweisung von Herkunftssignalen und m{\"o}glichen Sedimentquellen bzw. Sedimenttransportpfaden. Die methodische Herangehensweise basiert auf einem Multi-Proxy-Ansatz zur Charakterisierung der klastischen Sedimentfazies anhand von Gel{\"a}ndebeobachtungen, lithologisch-granulometrischen und mineralogisch-geochemischen Analysen sowie statistischen Verfahren. F{\"u}r die mineralogischen Untersuchungen der Sedimente wurde eine neue, rasterelektronenmikroskopische Methode zur automatisierten Partikelanalyse genutzt und den traditionellen Methoden gegen{\"u}bergestellt. Die synoptische Betrachtung der granulometrischen, geochemischen und mineralogischen Befunde der Oberfl{\"a}chensedimente ergibt f{\"u}r das Untersuchungsgebiet ein logisches Kaskadenmodell mit immer wiederkehrenden Prozessbereichen und {\"a}hnlichen Prozesssignalen. Die umfangreichen granulometrischen Analysen deuten dabei auf abnehmende Korngr{\"o}ßen mit zunehmender Entfernung vom Qilian Shan hin und erm{\"o}glichen die Identifizierung von vier texturellen Signalen: den fluvialen Sanden, den D{\"u}nensanden, den Stillwassersedimenten und St{\"a}uben. Diese Ergebnisse k{\"o}nnen als Interpretationsgrundlage f{\"u}r die Korngr{\"o}ßenanalysen des Bohrkerns genutzt werden. Somit ist es m{\"o}glich, die Ablagerungsgeschichte der Bohrkernsedimente zu rekonstruieren und in Verbindung mit eigenen und literaturbasierten Datierungen in einen Gesamtkontext einzuh{\"a}ngen. F{\"u}r das Untersuchungsgebiet werden somit vier Ablagerungsphasen ausgewiesen, die bis in die Zeit des letzten glazialen Maximums (LGM) zur{\"u}ckreichen. W{\"a}hrend dieser Ablagerungsphasen kam es im Zuge unterschiedlicher Aktivit{\"a}ts- und Stabilit{\"a}tsphasen zu einer kontinuierlichen Progradation und {\"U}berpr{\"a}gung des Schwemmf{\"a}chers. Eine besonders aktive Phase kann zwischen 8 ka und 4 ka BP festgestellt werden, w{\"a}hrend der es aufgrund zunehmender fluvialer Aktivit{\"a}ten zu einer deutlich verst{\"a}rkten Schwemmf{\"a}cherdynamik gekommen zu sein scheint. In den Abschnitten davor und danach waren es vor allem {\"a}olische Prozesse, die zu einer {\"U}berpr{\"a}gung des Schwemmf{\"a}chers gef{\"u}hrt haben. Hinsichtlich der mineralogischen Herkunftssignale gibt es eine große Variabilit{\"a}t. Dies spiegelt die enorme Heterogenit{\"a}t der Geologie des Untersuchungsgebietes wider, wodurch die r{\"a}umlichen Signale nicht sehr stark ausgepr{\"a}gt sind. Dennoch, k{\"o}nnen f{\"u}r das Einzugsgebiet drei gr{\"o}ßere Bereiche deklariert werden, die als Herkunftsgebiet in Frage kommen. Das {\"o}stliche Qilian Shan Vorland zeichnet sich dabei durch deutlich h{\"o}here Chloritgehalte als prim{\"a}re Quelle f{\"u}r die Sedimente im Ejina-Becken aus. Sie unterscheiden sich insbesondere durch stark divergierende Chloritgehalte in der Tonmineral- und Gesamtmineralfraktion, was das {\"o}stliche Qilian Shan Vorland als prim{\"a}re Quelle f{\"u}r die Sedimente im Ejina-Becken auszeichnet. Dies steht in Zusammenhang mit den Gr{\"u}nschiefern, Ophioliten und Serpentiniten in diesem Bereich. Geochemisch deutet vor allem das Cr/Rb-Verh{\"a}ltnis eine große Variabilit{\"a}t innerhalb des Einzugsgebietes an. Auch hier ist es das {\"o}stliche Vorland, welches aufgrund seines hohen Anteils an mafischen Gesteinen reich an Chromiten und Spinellen ist und sich somit vom restlichen Untersuchungsgebiet abhebt. Die zeitliche aber auch die generelle Variabilit{\"a}t der Sedimentherkunft l{\"a}sst sich in den Bohrkernsedimenten nicht so deutlich nachzeichnen. Die mineralogisch-sedimentologischen Eigenschaften der erbohrten klastischen Sedimente zeugen zwar von zwischenzeitlichen {\"A}nderungen bei der Sedimentherkunft, diese sind jedoch nicht so deutlich ausgepr{\"a}gt, wie es die Quellsignale in den Oberfl{\"a}chensedimenten vermuten lassen. Ein Grund daf{\"u}r scheint die starke Vermischung unterschiedlichster Sedimente w{\"a}hrend des Transportes zu sein. Die Kombination der Korngr{\"o}ßenergebnisse mit den Befunden der Gesamt- und Schwermineralogie deuten darauf hin, dass es zwischenzeitlich eine Phase mit {\"u}berwiegend {\"a}olischen Prozessen gegeben hat, die mit einem Sedimenteintrag aus dem westlichen Bei Shan in Verbindung stehen. Neben der Zunahme ultrastabiler Schwerminerale wie Zirkon und Granat und der Abnahme opaker Schwerminerale, weisen vor allem die heutigen Verh{\"a}ltnisse darauf hin. Der Vergleich der traditionellen Schwermineralanalyse mit der Computer-Controlled-Scanning-Electron-Microscopy (kurz: CCSEM), die eine automatisierte Partikelauswertung der Proben erm{\"o}glicht, zeigt den deutlichen Vorteil der modernen Analysemethode. Neben einem zeitlichen Vorteil, den man durch die automatisierte Abarbeitung der vorbereiteten Proben erlangen kann, steht vor allem die deutlich gr{\"o}ßere statistische Signifikanz des Ergebnisses im Vordergrund. Zudem k{\"o}nnen mit dieser Methode auch chemische Variet{\"a}ten einiger Schwerminerale bestimmt werden, die eine noch feinere Klassifizierung und sicherere Aussagen zu einer m{\"o}glichen Sedimentherkunft erm{\"o}glichen. Damit ergeben sich außerdem verbesserte Aussagen zu Zusammensetzungen und Entstehungsprozessen der abgelagerten Sedimente. Die Studie verdeutlicht, dass die Sedimentherkunft innerhalb des Untersuchungsgebietes sowie die ablaufenden Prozesse zum Teil stark von lokalen Gegebenheiten abh{\"a}ngen. Die Heterogenit{\"a}t der Geologie und die Gr{\"o}ße des Einzugsgebietes sowie die daraus resultierende Komplexit{\"a}t der Sedimentgenese, machen exakte Zuordnungen zu klar definierten Sedimentquellen sehr schwer. Dennoch zeigen die Ergebnisse, dass die Sedimentzufuhr in das Ejina-Becken in erster Linie durch fluviale klastische Sedimente des Heihe aus dem Qilian Shan erfolgt sein muss. Die Untersuchungsergebnisse zeigen jedoch ebenso die Notwendigkeit einer erg{\"a}nzenden Bearbeitung angrenzender Untersuchungsgebiete, wie beispielsweise den Gobi-Altai im Norden oder den Beishan im Westen, sowie die Verdichtung der Oberfl{\"a}chenbeprobung zur feineren Aufl{\"o}sung von lokalen Sedimentquellen.},
  language  = {de}
}
@article{TofeldeBufeTurowski2022,
  author    = {Tofelde, Stefanie and Bufe, Aaron and Turowski, Jens M.},
  title     = {Hillslope Sediment Supply Limits Alluvial Valley Width},
  series = {AGU Advances},
  journal   = {AGU Advances},
  publisher = {American Geophysical Union (AGU); Wiley},
  address   = {Hoboken, New Jersey, USA},
  issn      = {2576-604X},
  doi       = {10.1029/2021AV000641},
  pages     = {20},
  year      = {2022},
  abstract  = {River-valley morphology preserves information on tectonic and climatic conditions that shape landscapes. Observations suggest that river discharge and valley-wall lithology are the main controls on valley width. Yet, current models based on these observations fail to explain the full range of cross-sectional valley shapes in nature, suggesting hitherto unquantified controls on valley width. In particular, current models cannot explain the existence of paired terrace sequences that form under cyclic climate forcing. Paired river terraces are staircases of abandoned floodplains on both valley sides, and hence preserve past valley widths. Their formation requires alternating phases of predominantly river incision and predominantly lateral planation, plus progressive valley narrowing. While cyclic Quaternary climate changes can explain shifts between incision and lateral erosion, the driving mechanism of valley narrowing is unknown. Here, we extract valley geometries from climatically formed, alluvial river-terrace sequences and show that across our dataset, the total cumulative terrace height (here: total valley height) explains 90\%-99\% of the variance in valley width at the terrace sites. This finding suggests that valley height, or a parameter that scales linearly with valley height, controls valley width in addition to river discharge and lithology. To explain this valley-width-height relationship, we reformulate existing valley-width models and suggest that, when adjusting to new boundary conditions, alluvial valleys evolve to a width at which sediment removal from valley walls matches lateral sediment supply from hillslope erosion. Such a hillslope-channel coupling is not captured in current valley-evolution models. Our model can explain the existence of paired terrace sequences under cyclic climate forcing and relates valley width to measurable field parameters. Therefore, it facilitates the reconstruction of past climatic and tectonic conditions from valley topography.},
  language  = {en}
}
@phdthesis{Lenz2016,
  author    = {Lenz, Josefine},
  title     = {Thermokarst dynamics in central-eastern Beringia},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-101364},
  school      = {Universit{\"a}t Potsdam},
  pages     = {XII, 128, A-47},
  year      = {2016},
  abstract  = {Widespread landscape changes are presently observed in the Arctic and are most likely to accelerate in the future, in particular in permafrost regions which are sensitive to climate warming. To assess current and future developments, it is crucial to understand past environmental dynamics in these landscapes. Causes and interactions of environmental variability can hardly be resolved by instrumental records covering modern time scales. However, long-term environmental variability is recorded in paleoenvironmental archives. Lake sediments are important archives that allow reconstruction of local limnogeological processes as well as past environmental changes driven directly or indirectly by climate dynamics. This study aims at reconstructing Late Quaternary permafrost and thermokarst dynamics in central-eastern Beringia, the terrestrial land mass connecting Eurasia and North America during glacial sea-level low stands. In order to investigate development, processes and influence of thermokarst dynamics, several sediment cores from extant lakes and drained lake basins were analyzed to answer the following research questions: 1. When did permafrost degradation and thermokarst lake development take place and what were enhancing and inhibiting environmental factors? 2. What are the dominant processes during thermokarst lake development and how are they reflected in proxy records? 3. How did, and still do, thermokarst dynamics contribute to the inventory and properties of organic matter in sediments and the carbon cycle? Methods applied in this study are based upon a multi-proxy approach combining sedimentological, geochemical, geochronological, and micropaleontological analyses, as well as analyses of stable isotopes and hydrochemistry of pore-water and ice. Modern field observations of water quality and basin morphometrics complete the environmental investigations. The investigated sediment cores reveal permafrost degradation and thermokarst dynamics on different time scales. The analysis of a sediment core from GG basin on the northern Seward Peninsula (Alaska) shows prevalent terrestrial accumulation of yedoma throughout the Early to Mid Wisconsin with intermediate wet conditions at around 44.5 to 41.5 ka BP. This first wetland development was terminated by the accumulation of a 1-meter-thick airfall tephra most likely originating from the South Killeak Maar eruption at 42 ka BP. A depositional hiatus between 22.5 and 0.23 ka BP may indicate thermokarst lake formation in the surrounding of the site which forms a yedoma upland till today. The thermokarst lake forming GG basin initiated 230 ± 30 cal a BP and drained in Spring 2005 AD. Four years after drainage the lake talik was still unfrozen below 268 cm depth. A permafrost core from Mama Rhonda basin on the northern Seward Peninsula preserved a full lacustrine record including several lake phases. The first lake generation developed at 11.8 cal ka BP during the Lateglacial-Early Holocene transition; its old basin (Grandma Rhonda) is still partially preserved at the southern margin of the study basin. Around 9.0 cal ka BP a shallow and more dynamic thermokarst lake developed with actively eroding shorelines and potentially intermediate shallow water or wetland phases (Mama Rhonda). Mama Rhonda lake drainage at 1.1 cal ka BP was followed by gradual accumulation of terrestrial peat and top-down refreezing of the lake talik. A significant lower organic carbon content was measured in Grandma Rhonda deposits (mean TOC of 2.5 wt\%) than in Mama Rhonda deposits (mean TOC of 7.9 wt\%) highlighting the impact of thermokarst dynamics on biogeochemical cycling in different lake generations by thawing and mobilization of organic carbon into the lake system. Proximal and distal sediment cores from Peatball Lake on the Arctic Coastal Plain of Alaska revealed young thermokarst dynamics since about 1,400 years along a depositional gradient based on reconstructions from shoreline expansion rates and absolute dating results. After its initiation as a remnant pond of a previous drained lake basin, a rapidly deepening lake with increasing oxygenation of the water column is evident from laminated sediments, and higher Fe/Ti and Fe/S ratios in the sediment. The sediment record archived characterizing shifts in depositional regimes and sediment sources from upland deposits and re-deposited sediments from drained thaw lake basins depending on the gradually changing shoreline configuration. These changes are evident from alternating organic inputs into the lake system which highlights the potential for thermokarst lakes to recycle old carbon from degrading permafrost deposits of its catchment. The lake sediment record from Herschel Island in the Yukon (Canada) covers the full Holocene period. After its initiation as a thermokarst lake at 11.7 cal ka BP and intense thermokarst activity until 10.0 cal ka BP, the steady sedimentation was interrupted by a depositional hiatus at 1.6 cal ka BP which likely resulted from lake drainage or allochthonous slumping due to collapsing shore lines. The specific setting of the lake on a push moraine composed of marine deposits is reflected in the sedimentary record. Freshening of the maturing lake is indicated by decreasing electrical conductivity in pore-water. Alternation of marine to freshwater ostracods and foraminifera confirms decreasing salinity as well but also reflects episodical re-deposition of allochthonous marine sediments. Based on permafrost and lacustrine sediment records, this thesis shows examples of the Late Quaternary evolution of typical Arctic permafrost landscapes in central-eastern Beringia and the complex interaction of local disturbance processes, regional environmental dynamics and global climate patterns. This study confirms that thermokarst lakes are important agents of organic matter recycling in complex and continuously changing landscapes.},
  language  = {en}
}
@phdthesis{Radeff2014,
  author    = {Radeff, Giuditta},
  title     = {Geohistory of the Central Anatolian Plateau southern margin (southern Turkey)},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-71865},
  school      = {Universit{\"a}t Potsdam},
  year      = {2014},
  abstract  = {The Adana Basin of southern Turkey, situated at the SE margin of the Central Anatolian Plateau is ideally located to record Neogene topographic and tectonic changes in the easternmost Mediterranean realm. Using industry seismic reflection data we correlate 34 seismic profiles with corresponding exposed units in the Adana Basin. The time-depth conversion of the interpreted seismic profiles allows us to reconstruct the subsidence curve of the Adana Basin and to outline the occurrence of a major increase in both subsidence and sedimentation rates at 5.45 - 5.33 Ma, leading to the deposition of almost 1500 km3 of conglomerates and marls. Our provenance analysis of the conglomerates reveals that most of the sediment is derived from and north of the SE margin of the Central Anatolian Plateau. A comparison of these results with the composition of recent conglomerates and the present drainage basins indicates major changes between late Messinian and present-day source areas. We suggest that these changes in source areas result of uplift and ensuing erosion of the SE margin of the plateau. This hypothesis is supported by the comparison of the Adana Basin subsidence curve with the subsidence curve of the Mut Basin, a mainly Neogene basin located on top of the Central Anatolian Plateau southern margin, showing that the Adana Basin subsidence event is coeval with an uplift episode of the plateau southern margin. The collection of several fault measurements in the Adana region show different deformation styles for the NW and SE margins of the Adana Basin. The weakly seismic NW portion of the basin is characterized by extensional and transtensional structures cutting Neogene deposits, likely accomodating the differential uplift occurring between the basin and the SE margin of the plateau. We interpret the tectonic evolution of the southern flank of the Central Anatolian Plateau and the coeval subsidence and sedimentation in the Adana Basin to be related to deep lithospheric processes, particularly lithospheric delamination and slab break-off.},
  language  = {en}
}
@phdthesis{Swierczynski2012,
  author    = {Swierczynski, Tina},
  title     = {A 7000 yr runoff chronology from varved sediments of Lake Mondsee (Upper Austria)},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-66702},
  school      = {Universit{\"a}t Potsdam},
  year      = {2012},
  abstract  = {The potential increase in frequency and magnitude of extreme floods is currently discussed in terms of global warming and the intensification of the hydrological cycle. The profound knowledge of past natural variability of floods is of utmost importance in order to assess flood risk for the future. Since instrumental flood series cover only the last ~150 years, other approaches to reconstruct historical and pre-historical flood events are needed. Annually laminated (varved) lake sediments are meaningful natural geoarchives because they provide continuous records of environmental changes > 10000 years down to a seasonal resolution. Since lake basins additionally act as natural sediment traps, the riverine sediment supply, which is preserved as detrital event layers in the lake sediments, can be used as a proxy for extreme discharge events. Within my thesis I examined a ~ 8.50 m long sedimentary record from the pre-Alpine Lake Mondsee (Northeast European Alps), which covered the last 7000 years. This sediment record consists of calcite varves and intercalated detrital layers, which range in thickness from 0.05 to 32 mm. Detrital layer deposition was analysed by a combined method of microfacies analysis via thin sections, Scanning Electron Microscopy (SEM), μX-ray fluorescence (μXRF) scanning and magnetic susceptibility. This approach allows characterizing individual detrital event layers and assigning a corresponding input mechanism and catchment. Based on varve counting and controlled by 14C age dates, the main goals of this thesis are (i) to identify seasonal runoff processes, which lead to significant sediment supply from the catchment into the lake basin and (ii) to investigate flood frequency under changing climate boundary conditions. This thesis follows a line of different time slices, presenting an integrative approach linking instrumental and historical flood data from Lake Mondsee in order to evaluate the flood record inferred from Lake Mondsee sediments. The investigation of eleven short cores covering the last 100 years reveals the abundance of 12 detrital layers. Therein, two types of detrital layers are distinguished by grain size, geochemical composition and distribution pattern within the lake basin. Detrital layers, which are enriched in siliciclastic and dolomitic material, reveal sediment supply from the Flysch sediments and Northern Calcareous Alps into the lake basin. These layers are thicker in the northern lake basin (0.1-3.9 mm) and thinner in the southern lake basin (0.05-1.6 mm). Detrital layers, which are enriched in dolomitic components forming graded detrital layers (turbidites), indicate the provenance from the Northern Calcareous Alps. These layers are generally thicker (0.65-32 mm) and are solely recorded within the southern lake basin. In comparison with instrumental data, thicker graded layers result from local debris flow events in summer, whereas thin layers are deposited during regional flood events in spring/summer. Extreme summer floods as reported from flood layer deposition are principally caused by cyclonic activity from the Mediterranean Sea, e.g. July 1954, July 1997 and August 2002. During the last two millennia, Lake Mondsee sediments reveal two significant flood intervals with decadal-scale flood episodes, during the Dark Ages Cold Period (DACP) and the transition from the Medieval Climate Anomaly (MCA) into the Little Ice Age (LIA) suggesting a linkage of transition to climate cooling and summer flood recurrences in the Northeastern Alps. In contrast, intermediate or decreased flood episodes appeared during the MWP and the LIA. This indicates a non-straightforward relationship between temperature and flood recurrence, suggesting higher cyclonic activity during climate transition in the Northeast Alps. The 7000-year flood chronology reveals 47 debris flows and 269 floods, with increased flood activity shifting around 3500 and 1500 varve yr BP (varve yr BP = varve years before present, before present = AD 1950). This significant increase in flood activity shows a coincidence with millennial-scale climate cooling that is reported from main Alpine glacier advances and lower tree lines in the European Alps since about 3300 cal. yr BP (calibrated years before present). Despite relatively low flood occurrence prior to 1500 varve yr BP, floods at Lake Mondsee could have also influenced human life in early Neolithic lake dwellings (5750-4750 cal. yr BP). While the first lake dwellings were constructed on wetlands, the later lake dwellings were built on piles in the water suggesting an early flood risk adaptation of humans and/or a general change of the Late Neolithic Culture of lake-dwellers because of socio-economic reasons. However, a direct relationship between the final abandonment of the lake dwellings and higher flood frequencies is not evidenced.},
  language  = {en}
}
@misc{Gassner2012,
  type      = {Master Thesis},
  author    = {Gassner, Alexandra Carina},
  title     = {The character of the core-mantle boundary : a systematic study using PcP},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-63590},
  school      = {Universit{\"a}t Potsdam},
  year      = {2012},
  abstract  = {Assuming that liquid iron alloy from the outer core interacts with the solid silicate-rich lower mantle the influence on the core-mantle reflected phase PcP is studied. If the core-mantle boundary is not a sharp discontinuity, this becomes apparent in the waveform and amplitude of PcP. Iron-silicate mixing would lead to regions of partial melting with higher density which in turn reduces the velocity of seismic waves. On the basis of the calculation and interpretation of short-period synthetic seismograms, using the reflectivity and Gauss Beam method, a model space is evaluated for these ultra-low velocity zones (ULVZs). The aim of this thesis is to analyse the behaviour of PcP between 10° and 40° source distance for such models using different velocity and density configurations. Furthermore, the resolution limits of seismic data are discussed. The influence of the assumed layer thickness, dominant source frequency and ULVZ topography are analysed. The Gr{\"a}fenberg and NORSAR arrays are then used to investigate PcP from deep earthquakes and nuclear explosions. The seismic resolution of an ULVZ is limited both for velocity and density contrasts and layer thicknesses. Even a very thin global core-mantle transition zone (CMTZ), rather than a discrete boundary and also with strong impedance contrasts, seems possible: If no precursor is observable but the PcP_model /PcP_smooth amplitude reduction amounts to more than 10\%, a very thin ULVZ of 5 km with a first-order discontinuity may exist. Otherwise, if amplitude reductions of less than 10\% are obtained, this could indicate either a moderate, thin ULVZ or a gradient mantle-side CMTZ. Synthetic computations reveal notable amplitude variations as function of the distance and the impedance contrasts. Thereby a primary density effect in the very steep-angle range and a pronounced velocity dependency in the wide-angle region can be predicted. In view of the modelled findings, there is evidence for a 10 to 13.5 km thick ULVZ 600 km south-eastern of Moscow with a NW-SE extension of about 450 km. Here a single specific assumption about the velocity and density anomaly is not possible. This is in agreement with the synthetic results in which several models create similar amplitude-waveform characteristics. For example, a ULVZ model with contrasts of -5\% VP , -15\% VS and +5\% density explain the measured PcP amplitudes. Moreover, below SW Finland and NNW of the Caspian Sea a CMB topography can be assumed. The amplitude measurements indicate a wavelength of 200 km and a height of 1 km topography, previously also shown in the study by Kampfmann and M{\"u}ller (1989). Better constraints might be provided by a joined analysis of seismological data, mineralogical experiments and geodynamic modelling.},
  language  = {en}
}
@article{KabothBahrBahrStepaneketal.2021,
  author    = {Kaboth-Bahr, Stefanie and Bahr, Andr{\´e} and Stepanek, Christian and Catunda, Maria Carolina Amorim and Karas, Cyrus and Ziegler, Martin and Garc{\´i}a-Gallardo, {\´A}ngela and Grunert, Patrick},
  title     = {Mediterranean heat injection to the North Atlantic delayed the intensification of Northern Hemisphere glaciations},
  series = {Communications Earth \& Environment},
  journal   = {Communications Earth \& Environment},
  publisher = {Springer Nature},
  address   = {London},
  issn      = {2662-4435},
  doi       = {10.1038/s43247-021-00232-5},
  pages     = {1 -- 9},
  year      = {2021},
  abstract  = {The intensification of Northern Hemisphere glaciations at the end of the Pliocene epoch marks one of the most substantial climatic shifts of the Cenozoic. Despite global cooling, sea surface temperatures in the high latitude North Atlantic Ocean rose between 2.9-2.7 million years ago. Here we present sedimentary geochemical proxy data from the Gulf of Cadiz to reconstruct the variability of Mediterranean Outflow Water, an important heat source to the North Atlantic. We find evidence for enhanced production of Mediterranean Outflow from the mid-Pliocene to the late Pliocene which we infer could have driven a sub-surface heat channel into the high-latitude North Atlantic. We then use Earth System Models to constrain the impact of enhanced Mediterranean Outflow production on the northward heat transport in the North Atlantic. In accord with the proxy data, the numerical model results support the formation of a sub-surface channel that pumped heat from the subtropics into the high latitude North Atlantic. We further suggest that this mechanism could have delayed ice sheet growth at the end of the Pliocene.},
  language  = {en}
}
@phdthesis{Ruch2010,
  author    = {Ruch, Jo{\"e}l},
  title     = {Volcano deformation analysis in the Lazufre area (central Andes) using geodetic and geological observations},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-47361},
  school      = {Universit{\"a}t Potsdam},
  year      = {2010},
  abstract  = {Large-scale volcanic deformation recently detected by radar interferometry (InSAR) provides new information and thus new scientific challenges for understanding volcano-tectonic activity and magmatic systems. The destabilization of such a system at depth noticeably affects the surrounding environment through magma injection, ground displacement and volcanic eruptions. To determine the spatiotemporal evolution of the Lazufre volcanic area located in the central Andes, we combined short-term ground displacement acquired by InSAR with long-term geological observations. Ground displacement was first detected using InSAR in 1997. By 2008, this displacement affected 1800 km2 of the surface, an area comparable in size to the deformation observed at caldera systems. The original displacement was followed in 2000 by a second, small-scale, neighbouring deformation located on the Lastarria volcano. We performed a detailed analysis of the volcanic structures at Lazufre and found relationships with the volcano deformations observed with InSAR. We infer that these observations are both likely to be the surface expression of a long-lived magmatic system evolving at depth. It is not yet clear whether Lazufre may trigger larger unrest or volcanic eruptions; however, the second deformation detected at Lastarria and the clear increase of the large-scale deformation rate make this an area of particular interest for closer continuous monitoring.},
  language  = {en}
}
@article{BrendelMatznerMenzel2021,
  author    = {Brendel, Nina and Matzner, Nils and Menzel, Max-Peter},
  title     = {Geographisches Gezwitscher - Analyse von Twitter-Daten als Methode im GW-Unterricht},
  series = {GW-Unterricht},
  journal   = {GW-Unterricht},
  publisher = {Verlag der {\"O}sterreichischen Akademie der Wissenschaften},
  address   = {Wien},
  issn      = {2414-4169},
  doi       = {10.1553/gw-unterricht164s72},
  pages     = {72 -- 85},
  year      = {2021},
  abstract  = {Soziale Medien sind ein wesentlicher Bestandteil des Alltags von Sch{\"u}ler*innen und gleichzeitig zunehmend wichtig in Wirtschaft, Politik und Wissenschaft. Am Beispiel von Twitter zeigt dieser Beitrag, dass soziale Medien im Unterricht auch f{\"u}r die Beantwortung geographischer Fragestellungen verwendet werden k{\"o}nnen. Hierf{\"u}r eignen sich Twitter-Daten aufgrund ihrer Georeferenzierung und weiterer interessanter Inhalte besonders. Der Beitrag gibt einen {\"U}berblick {\"u}ber die Verwendung von Twitter f{\"u}r sozialwissenschaftliche und humangeographische Fragestellungen und reflektiert die Nutzung von Twitter im Unterricht. F{\"u}r die Unterrichtspraxis werden Beispiele zu den Themen Braunkohle, Flutereignisse und Raumwahrnehmungen sowie Anleitungen zur Auswertung, Anwendung und Reflexion von Twitter-Analysen vorgestellt.},
  language  = {de}
}
@phdthesis{Jentsch2021,
  author    = {Jentsch, Anna},
  title     = {Soil gas analytics in geothermal exploration and monitoring},
  doi       = {10.25932/publishup-54403},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-544039},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xxxi, 162},
  year      = {2021},
  abstract  = {Major challenges during geothermal exploration and exploitation include the structural-geological characterization of the geothermal system and the application of sustainable monitoring concepts to explain changes in a geothermal reservoir during production and/or reinjection of fluids. In the absence of sufficiently permeable reservoir rocks, faults and fracture networks are preferred drilling targets because they can facilitate the migration of hot and/or cold fluids. In volcanic-geothermal systems considerable amounts of gas emissions can be released at the earth surface, often related to these fluid-releasing structures. In this thesis, I developed and evaluated different methodological approaches and measurement concepts to determine the spatial and temporal variation of several soil gas parameters to understand the structural control on fluid flow. In order to validate their potential as innovative geothermal exploration and monitoring tools, these methodological approaches were applied to three different volcanic-geothermal systems. At each site an individual survey design was developed regarding the site-specific questions. The first study presents results of the combined measurement of CO2 flux, ground temperatures, and the analysis of isotope ratios (δ13CCO2, 3He/4He) across the main production area of the Los Humeros geothermal field, to identify locations with a connection to its supercritical (T > 374◦C and P > 221 bar) geothermal reservoir. The results of the systematic and large-scale (25 x 200 m) CO2 flux scouting survey proved to be a fast and flexible way to identify areas of anomalous degassing. Subsequent sampling with high resolution surveys revealed the actual extent and heterogenous pattern of anomalous degassing areas. They have been related to the internal fault hydraulic architecture and allowed to assess favourable structural settings for fluid flow such as fault intersections. Finally, areas of unknown structurally controlled permeability with a connection to the superhot geothermal reservoir have been determined, which represent promising targets for future geothermal exploration and development. In the second study, I introduce a novel monitoring approach by examining the variation of CO2 flux to monitor changes in the reservoir induced by fluid reinjection. For that reason, an automated, multi-chamber CO2 flux system was deployed across the damage zone of a major normal fault crossing the Los Humeros geothermal field. Based on the results of the CO2 flux scouting survey, a suitable site was selected that had a connection to the geothermal reservoir, as identified by hydrothermal CO2 degassing and hot ground temperatures (> 50 °C). The results revealed a response of gas emissions to changes in reinjection rates within 24 h, proving an active hydraulic communication between the geothermal reservoir and the earth surface. This is a promising monitoring strategy that provides nearly real-time and in-situ data about changes in the reservoir and allows to timely react to unwanted changes (e.g., pressure decline, seismicity). The third study presents results from the Aluto geothermal field in Ethiopia where an area-wide and multi-parameter analysis, consisting of measurements of CO2 flux, 222Rn, and 220Rn activity concentrations and ground temperatures was conducted to detect hidden permeable structures. 222Rn and 220Rn activity concentrations are evaluated as a complementary soil gas parameter to CO2 flux, to investigate their potential to understand tectono-volcanic degassing. The combined measurement of all parameters enabled to develop soil gas fingerprints, a novel visualization approach. Depending on the magnitude of gas emissions and their migration velocities the study area was divided in volcanic (heat), tectonic (structures), and volcano-tectonic dominated areas. Based on these concepts, volcano-tectonic dominated areas, where hot hydrothermal fluids migrate along permeable faults, present the most promising targets for future geothermal exploration and development in this geothermal field. Two of these areas have been identified in the south and south-east which have not yet been targeted for geothermal exploitation. Furthermore, two unknown areas of structural related permeability could be identified by 222Rn and 220Rn activity concentrations. Eventually, the fourth study presents a novel measurement approach to detect structural controlled CO2 degassing, in Ngapouri geothermal area, New Zealand. For the first time, the tunable diode laser (TDL) method was applied in a low-degassing geothermal area, to evaluate its potential as a geothermal exploration method. Although the sampling approach is based on profile measurements, which leads to low spatial resolution, the results showed a link between known/inferred faults and increased CO2 concentrations. Thus, the TDL method proved to be a successful in the determination of structural related permeability, also in areas where no obvious geothermal activity is present. Once an area of anomalous CO2 concentrations has been identified, it can be easily complemented by CO2 flux grid measurements to determine the extent and orientation of the degassing segment. With the results of this work, I was able to demonstrate the applicability of systematic and area-wide soil gas measurements for geothermal exploration and monitoring purposes. In particular, the combination of different soil gases using different measurement networks enables the identification and characterization of fluid-bearing structures and has not yet been used and/or tested as standard practice. The different studies present efficient and cost-effective workflows and demonstrate a hands-on approach to a successful and sustainable exploration and monitoring of geothermal resources. This minimizes the resource risk during geothermal project development. Finally, to advance the understanding of the complex structure and dynamics of geothermal systems, a combination of comprehensive and cutting-edge geological, geochemical, and geophysical exploration methods is essential.},
  language  = {en}
}