Quaternary paleogeographic & sea-level change reconstructions in the Eastern Mediterranean

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Γεωργίου, Νίκος
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Coastal areas provide multiple support for life on earth and are expected to play a major role in society’s development in the near future. The rising human activities and resources exploitation have increased pressure in the coastal zone and the marine environment, causing marine pollution, climatic crisis, and nature-cultural heritage loss. This has forced the governments to enact Marine Spatial and Integrated Coastal Zone Management plans. However, before establishing these plans, stakeholders and decision-makers should be aware of the resources' spatial extent in order to plan a sustainable future that will allow the balanced management of sea resources’ exploitation and nature-cultural heritage preservation. The main pillar for achieving this purpose in the marine environment is the establishment of multileveled and multi-thematic geodatabases that will allow users to correlate, join and combine datasets of different spatial analyses and information. This thesis is separated into six chapters: ▪ The 1st chapter is the introduction of the thesis and is dedicated to the description of the main processes that affect the sea level through the geological time. These are separated in the eustatic and the relative sea-level change processes that affect the sea level in a global and regional/local scale respectively. Scientists use the geological and archaeological remains, for the reconstruction of the past sea-level, which are called “Relative sea-level indicators” (RSLi). These RSLi consist of geological formations such as marine terraces, notches, coral reefs etc. and archaeological indicators such as harbor facilities, fish tanks etc, while each one allows specific precision in the sealevel change reconstruction. The analysis of these indicators are playing a major role in the climate reconstruction, especially during Interglacial periods, during the Last Interglacial periods (Georgiou et al. 2019), when the climatic conditions were similar to the present. In this way, we will be able to evaluate the modern accelerating rates and estimate/model the future ones. Such an example is presented in an article related to sealevel reconstruction through a tidal notch shape analysis which was published during the Ph.D. period and is included in the dissertation’s broader scientific field: Georgiou N., Stocchi P., Rovere A., Elisa Casella E. (2020) IMEKO TC-19 International Workshop on Metrology for the Sea Naples, Italy, October 5-7, 2020 Reconstructing past sea level through notches: Orosei Gulf (Indexed in Scopus) The Eastern Mediterranean is one of the most complete and diverse databases of global sea-level and human history. The Underwater Cultural Heritage (UCH) in the Eastern Mediterranean and the testimonies that are laying on the seafloor constitute part of our history which should be mapped, protected and preserved for the future generations. Marine geophysics are the main tool to map and delimit the submerged archaeological remains and consists the pillar to the creation of extended databases of different spatial resolution and information regarding the seafloor. Extensive work has been performed in the marine environment raising the awareness in the Greek UCH, in the context of the dissertation’s broader scientific field: Papatheodorou G., Geraga M., Christodoulou D., Fakiris E., Iatrou M., Georgiou N., Dimas X., Ferentinos G. (2021). The Battle of Lepanto search and survey mission (1971-72) by Throckmorton, Edgerton and Yalouris: Following their traces a half century later using marine geophysics. Remote Sensing.; (Q1) (ISSN 2072-4292) https://doi.org/10.3390/rs13163292 Geraga M, Christodoulou D, Eleftherakis D, Papatheodorou G, Fakiris E, Dimas X, Georgiou N., Kordella S, Prevenios M, Iatrou M, Zoura D, Kekebanou S, Sotiropoulos M, Ferentinos G. (2020). Atlas of Shipwrecks in Inner Ionian Sea (Greece): A Remote Sensing Approach. Heritage.; 3(4):1210-1236. https://doi.org/10.3390/heritage3040067 Ferentinos G., Fakiris E., Christodoulou D., Geraga M., Dimas X., Georgiou N., Kordella S., Papatheodorou G., Prevenios M., Sotiropoulos M. (2020). Optimal sidescan sonar and sub-bottom profiler surveying of ancient wrecks: The ‘Fiskardo’ wreck, Kefallinia Island, Ionian Sea, Journal of Archaeological Science, Volume 113, 105032, ISSN 0305-4403, (Q1) https://doi.org/10.1016/j.jas.2019.105032. Geraga M., Papatheodorou G., Ferentinos G., Fakiris E., Christodoulou D., Georgiou N., Dimas X., Iatrou M., Kordella S., Sotiropoulos G., Mentogiannis V., Delaporta K. The study of an ancient shipwreck using marine remote sensing techniques, in Kefalonia Island (Ionian Sea), Greece, Archaeologia Μaritima Μediterranea - International Journal on Underwater Archaeology, v. 12, pp. 183-200. (Q4) The two areas presented in the current thesis are situated in the Eastern Mediterranean and more specifically in the countries of Lebanon and Greece. Byblos (Lebanon) and Aegina (Greece) are two of the most continuously inhabited ancient cities which are both globally known as two of the greatest maritime centers during the Bronze age, renowned primarily as chief harbours either for trading or naval purposes. As expected, for the cities to serve this purpose, important harbour facilities must have been built to support their status. ▪ The 2nd chapter describes the chronicles of the field trips and the equipment used in each survey. More specifically, the offshore surveys in Byblos were completed in three different phases (2014, 2016, 2017). During the first survey in 2014 a first approach was made in the offshore coastal zone using the available marine geophysical equipment: i)Side-scan sonar, ii) sub-bottom profiler (3.5kHz) and iii) a single beam echosounder. In 2016 the survey was divided in an offshore marine geophysical survey (using sub-bottom profiler-“Chirp”, ADCP, single-beam echosounder) and a sampling survey along the coastal zone of Byblos. The last survey in Byblos, was operated during 2017 and was focused on a focused detailed geomorphological mapping of the geological sea-level indicators detected during the previous surveys using a multibeam echosounder and on an underwater diving survey that aimed in the acquisition of underwater images of these findings. The second survey area, Aegina-Greece, was mapped during 2018. A research vessel was equipped with a side-scan sonar, a sub-bottom profiler and a multibeam echosounder, in order to map in detail, the geomorphology of the area and the extent of the submerged archaeological remains. An ROV was also used to ground-truth the findings of the survey and perform photogrammetry on one of the archaeological findings. The methodology that was used for the data acquisition is described below. ▪ The 3rd one (Chapter 3) is based on the article: “Integrated Methodological Approach for the Detection and Mapping of Marine Priority Habitat Types and Submerged Antiquities: examples implemented in the Saronic Gulf, Greece” Georgiou N., Dimas X., Papatheodorou G. which was published in Sustainability-MDPI (I.F. 3.25) Q1. & The book chapter: The palaeogeography of the strait of Salamis: Marine geoarchaeological survey in the strait of Salamis and the Ampelakia Bay. In Salamis 480 B.C; Papatheodorou, G.; Geraga, M.; Georgiou, N.; Christodoulou, D.; Dimas, X.; Fakiris, E.; Ferentinos, G. Hellenic Maritime Museum, 2020, 2020; pp. 392–411 ISBN 13 9786188218178. This article proposes an integrated downscale methodological approach that summarizes the existing and developing methodologies for mapping the seafloor/substrate in offshore coastal environments and detecting archaeologicalgeomorphological features and marine priority habitats. The methodology proposed is based on three main methodological axes of increasing spatial resolution: i) desk-based research, ii) marine geophysics/ seafloor classification, and iii) in-depth visual inspection /3D mapping. In this way, it is possible to produce datasets of different spatial analyses (meter to millimeter scale). The results of this methodology were integrated into a Marine Spatial Planning map regarding the area of the Saronic Gulf in Greece. Regarding the main parts of the thesis the 4th (Chapter 4) and 5th (Chapter 5) parts, they are dedicated to the implementation of the previously proposed methodology especially for the detection of underwater cultural heritage and geomorphological-geological features which were finally interpreted as relative sea-level indicators. Sea level rise drove to the submersion of coastal archaeological remains, disappearing their traces and risking their very existence while submerging important evidence related to sea-level fluctuation, human evolution, and dispersal. In addition, sea-level change research through geological/geomorphological indicators is of crucial importance against climatic change. At present, it is important to know the extent of natural phenomena based on natural variability and be able to quantify the influence of humans on them. To do so, it is essential to reconstruct past sea-level using the RSLi and establish the sea level rise rate during the late Holocene but also during the Last Interglacial periods, when climatic conditions were similar to the present. In this way, we will be able to evaluate the modern accelerating rates and model the future ones. The two survey areas that combine both those archaeological and geomorphological criteria are Byblos in Lebanon (Chapter 4) and Aegina in Greece (Chapter 5). ▪ Regarding the 4th part of the thesis (Chapter 4): Chapter 4.1, 4.2 & 4.4 is based on the final report to the DGA (Directorate General of Antiquities) titled “Offshore Geo-archaeological Research in Byblos, Lebanon”. Chapter 4.1 is based on the article: “Marine geophysical survey offshore Byblos: preliminary results” Papatheodorou G., Geraga, M., Georgiou N., Christodoulou D. published in BAAL: bulletin d'archéologie et d'architecture libanaises (BAAL is the annual journal issued by the Directorate General of Antiquities in cooperation with the Lebanese Ministry of Culture since 1996) & Chapter 4.3 is based on the article: “Late Pleistocene submarine terraces in the Eastern Mediterranean, central Lebanon, Byblos: Revealing their formation time frame through modeling” Georgiou N., Papatheodorou G., Francis-Allouche M., Geraga M., Christodoulou D., Stocchi P., Fakiris E., Dimas X., Zoura D., Iatrou M. submitted in Quaternary International-Elsevier (I.F. 2.13) Q1 This chapter describes the implementation of the proposed methodology (Chapter 3) in the area of Byblos, Lebanon, primarily contributing to detecting the location of the renowned Phoenician harbor. To add to that, two different sequences of submarine terraces (nearshore, distant sequences) were mapped in detail, at the offshore coastal area of Byblos and interpreted as relative sea-level indicators. A semi-automatic technique for the analysis of the acoustic data was used to detect the submarine terraces and acquire their morphometry. Then, this was combined with a model that uses their morphometry as input, and which is set to test it towards existing sea-level curves, uplift rates, and cliff retreat rates in order to find the most possible time frame of the submarine terraces’ formation. In this way, it was revealed that the distant sequence was possibly formed during the MIS3 interglacial period, ranking them among the unique MIS3 submarine terraces found in the Eastern Mediterranean. Finally, this contributed to the paleogeographic reconstruction of the area. The 5th part of the thesis (Chapter 5) is based on the article: “A multidisciplinary approach for the detection, mapping and morphometric analysis of ancient coastal installations: The case study of the ancient Aegina harbour complex” Georgiou N., Dimas X., Fakiris E., Christodoulou D., Geraga M., Koutsoumpa D., Baika K., Kalamara P., Papatheodorou G., Ferentinos G. published in Remote Sensing-MDPI (I.F. 4.84) Q1. This chapter uses the proposed methodology (Chapter 3) in the coastal area of Aegina island in Greece, where a one-of-a-kind submerged harbour complex is apparent. This approach succeeded in obtaining information that serves both geomorphological and archaeological purposes in a time- and cost-effective way, while obtaining information of centimeters to millimeters scale. The geomorphology of the area was mapped in detail through marine geophysical means while ancient submerged conical rubble structures and breakwaters were delimited using automatic seafloor segmentation techniques, revealing previously unknown sites of archaeological interest. Part of the seafloor classification techniques were developed and used in the articles below, which were also included in the dissertation’s broader scientific field: Fakiris E., Blondel P., Papatheodorou G., Christodoulou D., Dimas X., Georgiou N., Kordella S., Dimitriadis C., Rzhanov Y., Geraga M., Ferentinos G. (2019). Multi-Frequency, Multi-Sonar Mapping of Shallow Habitats—Efficacy and Management Implications in the National Marine Park of Zakynthos, Greece. Remote Sensing; 11(4):461. (Q1) https://doi.org/10.3390/rs11040461 Fakiris E., Zoura D., Ramfos A., Spinos E., Georgiou N., Ferentinos G., Papatheodorou G., (2018). Objectbased classification of sub-bottom profiling data for benthic habitat mapping. Comparison with sidescan and RoxAnn in a Greek shallow-water habitat, Estuarine, Coastal and Shelf Science, Volume 208, p. 219-234, ISSN 0272-7714, (Q1) https://doi.org/10.1016/j.ecss.2018.04.028. The structures’ parameters were extracted from the acoustic data to analyze their morphometry, while photogrammetry was realized using a Remotely Operated Vessel to expose their microstructure. The spatial distribution of the structures revealed the construction of a well-planned harbour complex with multiple entrances, while based on different sea-level scenarios in the Holocene, different possible functionalities were assumed (shielding-sheltering). Finally, through the structures’ morphometric analysis (geometry and terrain statistical parameters) their preservation status was revealed, uncovering the anthropogenic impact on the submerged antiquities due to the modern harbor activity. ▪ The 6th and last chapter of the thesis (Chapter 6) is the synthesis of this thesis where a summary of the surveys’ results is presented and questions of broader scientific context but also of site-specific scientific interest are answered. Finally, the limitations of the implemented methodological approach are referred, and the future/missing directions are proposed.
Marine geophysics, Sea level change, Long-term cliff retreat rate, Long-term uplift rate, MIS5, MIS3, Side-scan sonar, Sub-bottom profiler, Ancient coastlines, Multibeam echosounder, Maritime and harbour archaeology, Morphometry, Photogrammetry, ROV, Marine spatial planning, Downscaling, Posidonia oceanica, 3D seismic profiles, Seafloor classification, Aegina