Unit:
Department of Geology and GeoenvirommentLibrary of the School of Science
Dissertation committee:
Νίκη Ευελπίδου, Αναπληρώτρια Καθηγήτρια, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Μιχαήλ Σταματάκης, Καθηγητής, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Χαμπίκ Μαρουκιάν, Ομότιμος Καθηγητής, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Christophe Morhange, Professor, Aix-Marseille University, CEREGE
Θεόδωρος Γκουρνέλος, Καθηγητής, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Σεραφείμ Πούλος, Καθηγητής, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Ευθύμιος Καρύμπαλης, Αναπληρωτής Καθηγητής, Τμήμα Γεωγραφίας, Χαροκόπιο Πανεπιστήμιο
Original Title:
Study of the geomorphological and environmental evolution of the coastal zone of Central Cyclades
Translated title:
Study of the geomorphological and environmental evolution of the coastal zone of Central Cyclades
Summary:
The purpose of this thesis was to collect and study geomorphological, sedimentological and archaeological data in order to evaluate the evolution of sea level in Central Cyclades during the Late Holocene and assess the contribution of local tectonics. The ultimate goal was to trace the palaeoshorelines in central Cyclades, the effects of sea level changes in palaeoenvironmental evolution and to propose a reliable palaeogeographical reconstruction during the Late Holocene.
A multiproxy analysis took place through the study of submerged beachrocks, sediment corings in coastal lagoons and archaeological remains in order to accomplish the aforementioned goals. Detailed underwater surveys of Paros and Naxos beachrocks, found down to about -6 m depth, took place along with luminescence dating. The selected beachrock samples were dated by using both OSL dating of quartz and infrared stimulated luminescence (IRSL) of feldspars. Petrographic and microstratigraphic analysis of beachrock cements was accomplished in order to identify the type of cement and determine the spatial relationship between the past shoreline and beachrock formation zone. Each beachrock dated sample, showing clear intertidal formation was transformed to a relative sea level (RSL) index point. Sedimentological and paleontological data of Late Holocene coastal deposits derived from lagoonal environments of Paros Island were studied along with radiocarbon dating. Archaeological remains were revisited and evaluated in order to understand their significance in the evolution of the coastal zone of both Islands.
The west sandy beaches of Naxos are dominated by the presence of multiple submerged beachrock slabs, while for Paros only two sites were identified. Ιn both Islands they reach a maximum depth of -6.3 m. The beachrocks in Naxos are markedly more extensive in relation to the beachrocks of Paros. Notably, in both islands the beachrock thickness ranges between 0.25-1 m. Cement examination of the dated samples has shown that bounding material between grains was mostly early intertidal cement. Shallower beachrock samples (<2 m) suggested a RSL rise of ~2 m for the last 2.0 ka. However, in the case of deeper samples (between -4 and -5.7 m), some inconsistencies were noted with expected ages and with the tectonic regime of the study area. Overall, some major palaeogeographical changes were spatially and chronologically constrained for a number of coastal sectors of the two islands, based on the morphology of submerged beachrock slabs and luminescence dating.
The multiproxy analysis of coastal cores from Paros Island allowed to reconstruct the coastal landscape evolution of selected sites and further provided a significant collection of data for the reconstruction of relative sea-level fluctuations in Paros. New data derived from two coastal drillings in the western part of Paros allowed reconstructing the palaeogeographic evolution of Livadia for the last ~4500-4864 cal BP and of Pounta for the last ~721-986 cal BP. Sedimentological and paleontological observations have shown that a semi-enclosed lagoon existed until at least ~780-436 BC (2385-2729 cal BP) in Livadia bay that was later slowly infilled probably due to human activities. Conversely, Pounta has been primarily influenced by coastal-marine processes and the evolution of the coastal landscape is more recent.
All the data produced in this work were compiled in order to produce RSL index points and reconstruct the relative sea level changes in the study area. The resultant RSL index points were compared with RSL reconstructions from previously available data in central Cyclades. Data suggest a RSL that rose by ~2 m in the last 2000 years at an average rate of ~1.2 mm/yr. Furthermore, the new index points indicate that RSL rose at least by ~3.9 m in the last ~4500 years. A relative sea level curve has been suggested based on the compilation of data. Overall, the data indicated a slight underestimation of the RSL position in Paros and Naxos, which may reflect higher subsidence rates for the Late Holocene. This observed subsidence may be the combinatory result of eustatic sea level rise along with land subsidence. Reported submerged tidal notches suggest that subsidence is at least partly owed to coseismic events that have taken place during the last ~2800 years.
Overall, this work has contributed to the better understanding of the RSL changes in Paros and Naxos Islands and improved the chronological framework for the Late Holocene and has further shown the significance of using multiproxy investigations to better assess sea-level evolution. This study has further shown the great potential of beachrocks as a tool to track major changes in shoreline positions and to precisely assess the palaeogeographical evolution of the coastal zone, especially in the eastern Mediterranean.
Main subject category:
Geomorphology
Other subject categories:
Geology
Keywords:
sea level changes, beachrocks, paleogeography, coastal geomorphology, geoarchaeology, Central Cyclades, luminescence dating, Holocene
Number of references:
309
