Titel: | Reconstruction of tectonically induced vertical motions and paleo-ecological evolution of the Island of Rhodes during the Plio-Pleistocene | Sprache: | Englisch | Autor*in: | Eichner, Daniela | Schlagwörter: | Island of Rhodes; orbital driven climate changes; paleo-water depth reconstruction; tectonically induced vertical motions; Eastern Mediterranean Sea; foraminiferal-based transfer function | GND-Schlagwörter: | MikropaläontologieGND ForaminiferenGND NeotektonikGND PaläoklimaGND PleistozänGND |
Erscheinungsdatum: | 2024 | Tag der mündlichen Prüfung: | 2024-09-19 | Zusammenfassung: | The Island of Rhodes, located in the Eastern Mediterranean Sea and at the eastern end of the Hellenic forearc, has been a vulnerable area for tectonic and climatic processes in the past. Due to its position at the subduction zone of the African and Eurasian plate, the island experienced intense tectonic motions, including several cycles of subsidence and uplift. Marine and fossil-rich sediments of Plio- to Pleistocene age, of the so-called Lindos Bay Formation, have been uplifted and are outcropping in graben structures along the eastern coast of the island. Despite some studies on the tectonic evolution of the island, it has not been investigated whether the individual depocenters underwent similar or different vertical motions and the quantification of long- and short-term vertical motions have not yet been studied. Besides the tectonic influence, the Mediterranean Sea is sensitive to climate variability, and the sedimentary archive records orbital-driven climate changes, for example as organic-rich layers, called sapropels. An enhanced rainfall in phase with the African monsoon and Mediterranean sapropel formation has also been reported for the northern borderlands of the Eastern Mediterranean Sea. However, until now evidence for orbital-induced climate changes that affected the Island of Rhodes during the Plio-Pleistocene are missing and information on local and regional responses to global forcing as well as the effects on the near-shore environments are still limited. The doctoral thesis follows the approach to reconstruct the tectonically induced vertical motions on the eastern coast of the Island of Rhodes, to quantify the large- and small-scale cycles of subsidence and uplift and to unravel the hydrological and climatic impact on the benthic foraminiferal assemblage during the Plio-Pleistocene. This was achieved through a detailed study of four sedimentary deposits of the Lindos Bay Formation, distributed from the northern (Cape Vagia), over the middle eastern (Agathi Beach and Lardos), and towards the southern (Plimiri) coast. The investigation of benthic foraminiferal assemblages and the analysis of stable oxygen and carbon isotopes revealed that the individual depocenters reflect orbital-driven climate changes differently. Periodic, precession-driven changes can primarily be seen in the increase of eutrophic indicator species and in the decrease of δ13C values in Agathi Beach and Plimiri. Lardos and Cape Vagia on the other hand revealed long-lasting, most-likely not precession-driven, eutrophication in the Middle and Early Pleistocene, respectively. Especially the Pliocene Plimiri section suggest a strong periodicity in the assemblage composition and diversity, with thick intervals mainly dominated by eutrophic indicator species, which has been attributed to an increased primary production of the near-coastal environments. This is suggested to be triggered by enhanced precipitation and higher river-run off. These phases are interpreted as near-coastal equivalents of deep sea sapropels of the Eastern Mediterranean Sea. The use of a benthic foraminiferal-based transfer function, and its correction for glacio-eustatic seal level and precession-driven changes, proved to be a useful tool to quantify and better understand tectonically induced vertical motions in the Pleistocene on a much smaller scale than previously done. Apart from the long-term trend of subsidence (Agathi Beach and older part of Cape Vagia) and uplift (younger part of Cape Vagia and Lardos), each depocenter also reflects small-scale motions with rates up to 10.4 mm a-1. The integration of the new data sets with previous studies, allowed to reconstruct the full cycle of subsidence (transgression) and uplift (regression) on the Island of Rhodes during the Pleistocene, lasting from 1.97 Ma to 0.47 Ma, with a maximum uplift of about 700 m in the last 1.40 Myrs. Differences in the rates of vertical motions and amplitudes are observed between individual depocenters. When comparing sedimentary sections deposited at the same time, higher rates are observed in the northern part of the island compared to the middle part. The vertical motions and differences between the individual depocenters are explained by a combination of large-scale subsidence and uplift processes and locally induced and site-specific processes on the island and in the graben structures. |
URL: | https://ediss.sub.uni-hamburg.de/handle/ediss/11187 | URN: | urn:nbn:de:gbv:18-ediss-121680 | Dokumenttyp: | Dissertation | Betreuer*in: | Milker, Yvonne Schmiedl, Gerhard |
Enthalten in den Sammlungen: | Elektronische Dissertationen und Habilitationen |
Dateien zu dieser Ressource:
Datei | Beschreibung | Prüfsumme | Größe | Format | |
---|---|---|---|---|---|
Dissertation_Eichner.pdf | Dissertation_Eichner | b48ee5b849044b4e885c9a9e1c20133f | 28.96 MB | Adobe PDF | Öffnen/Anzeigen |
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