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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by National Documentation Centre - EKT journals Bulletin of the Geological Society of Greece Vol. 50, 2016 ON COAST LINE OSCILLATIONS DURING LAST DECADES. BORSHI BEACH CASE, ALBANIAN RIVIERA Marku S. Albanian Geological Survey Doda V. Albanian Geological Survey https://doi.org/10.12681/bgsg.11745 Copyright © 2017 S. Marku, V. Doda To cite this article: Marku, S., & Doda, V. (2016). ON COAST LINE OSCILLATIONS DURING LAST DECADES. BORSHI BEACH CASE, ALBANIAN RIVIERA. Bulletin of the Geological Society of Greece, 50(1), 441-447. doi:https://doi.org/10.12681/bgsg.11745 http://epublishing.ekt.gr | e-Publisher: EKT | Downloaded at 23/03/2020 06:05:56 | Δελτίο της Ελληνικής Γεωλογικής Εταιρίας, τόμος L, σελ. 441-447 Bulletin of the Geological Society of Greece, vol. L, p. 441-447 Πρακτικά 14ου Διεθνούς Συνεδρίου, Θεσσαλονίκη, Μάιος 2016 Proceedings of the 14th International Congress, Thessaloniki, May 2016 ON COAST LINE OSCILLATIONS DURING LAST DECADES. BORSHI BEACH CASE, ALBANIAN RIVIERA Marku S.1 and Doda V.1 Albanian Geological Survey, Rruga e Kavajës Nr. 153, Tiranë, Albania, [email protected] Abstract The oscillations of coast line in Albania, and simultaneously the Quaternary deposits in Albania were little studied until the decade of 90th of 20th century. Up to now, the studies consider those deposits as fluvial sediment; meanwhile, the coast line was categorized as of erosional and accumulative type. In those studies, the role of sea waves and euastatic change of sea level in the process of sediment supply in coastline is neglected. Transgression and regression was interpreted according to Theory of Geosynclinals, as tectonic subsidence or uplift of continental area. From observations in Borshi beach, during August 2013 and September 2015, result that the sediment in this area originate mainly from the erosion of coast line rocks, and less from sediments transported by continental flows. Some traces of marine sediments inside the continental area, in a higher hypsometric quote regarding the actual coastline traces of erosion in some infrastructure works dated of the decade 70’ and 80’ of 20th century, are argument of a temporal rise of sea level during the decade 90’ of past century. Keywords: Sea level rise, gravel, sediments. Περίληψη Οι αλλαγές της παράκτιας γραμμής της Αλβανίας, και μαζί τους και οι αποθηκεύσεις αδρανών υλικών της Τεταρτογενούς περιόδου ήταν ιδιαίτερα ελάχιστες μέχρι της δεκαετία του 90 του 20-ουαιώνα. Οι μέχρι πρότινος μελέτες έχουν χειριστεί τις αποθηκεύσεις στην παράκτια περιοχή ως προερχόμενες από προσχώσεις των ποταμών, ενώ η ίδια η ακτή έχει ταξινομηθεί ως δυο μορφών, διαβρωτική και συσσωρευτική. Στις εν λόγω μελέτες έχει αποφευχθεί ο ρόλος των θαλάσσιων κυμάτων και η αλλαγή της ευστάθειας της θάλασσας κατά τη διάρκεια των προσχώσεων στις ακτές. Η πλημμυρίδα και η άμπωτη έχουν εξεταστεί βάσει της θεωρίας των Γεωσυγκλινουσών ως ανυψώσεις είτε τεκτονικά φαινόμενα των ηπειρωτικών περιοχών. Από τις παρατηρήσεις στην παραλία του Μπόρσι τον Αύγουστο του 2013 και τον Σεπτέμβριο του 2015 προκύπτει ότι οι επιχωματώσεις αυτής της παραλίας θα πρέπει να έχουν την προέλευσή τους κυρίως από τις διαβρώσεις των παράκτιων βράχων εξαιτίας των θαλάσσιων κυμάτων και λιγότερο από υλικά των ρευμάτων των ηπειρωτικών ρυακιών. Μερικά σημάδια των θαλάσσιων επιχωματώσεων στο βάθος της ηπειρωτικής ζώνης σε υψηλότερα σημεία από τη σημερινή ακτή και ορισμένες δομές των υποδομών είτε επιχωματώσεις λειψάνων με ανθρώπινη προέλευση που οριοθετούνται των δεκαετιών 70 και 80 του 20ου αιώνα, μαρτυρούν για προσωρινή ανύψωση της στάθμης της θάλασσας στη δεκαετία του 80 και 90. Λέξεις κλειδιά: Η άνοδος της θάλασσας, χαλίκι, ιζήματα. 441 http://epublishing.ekt.gr | e-Publisher: EKT | Downloaded at 23/03/2020 06:05:56 | 1. Introduction The importance of coast lines cause of high concentration near them of urban areas (Proust et al., 2013), touristic infrastructure and others activities of great economic importance, justify the increasing attention of researches of different scientific fields. Up to the beginning of 21st century, the attention on the Quaternary deposits in Albania was scarce. This was argued by the absence in important mineral resources of those deposits (Marku, 2014). In the traditional geological mapping, the quaternary cover, particularly in the area of the contact between those deposits and the older formation, is not designed. Meanwhile by the geological maps of Albania on scale 1:200,000 (Biçoku et al., 1967; Vranai et al., 1997 and Collective, 2012), as marine sediments are treated only the sandy sediments of coastlines. Albanian geology has suffered by a great discordance with the concepts of European geology, because until the end of 80’ decade of 20th century, it has elaborated thesis according to the Theory of Geosynclinals, and although some updates performed some questions still continue to be discussed on the reminiscences of this theory. The main problem brought by this in the study of quaternary deposits which belong to coastal area, was the neglecting of the eustatic change of the sea level, caused as consequence of global sea level rise or fall, result of climatic changes collected with the combination of glacial-interglacial periods. Consequently was not considered the impact of the sea transgression and regression processes in the forming of quaternary deposits. This because according to the theory of geosynclinals, the transgression happens only in case of downward movement of geosynclinals; meantime the regression happens where geosynclinals is uplifted. In both cases the global sea level remains constant. From this point of view, the Albanian lowland, situated adjacent the Adriatic Sea is considered as an alluvial field constructed by river’s supply of sediments, which rivers in fact are the second supplier of Adriatic basin with sweet waters after Po River. The deposition of alluvial sediments is considered to be performed in a shallow environment, in continue subsidence, and in contrast with surrounding environment which represents this part of geosynclinals in continue uplift. As deposits of marine origin are considered only the sands of beach, the lying of which under newer sediments continent ward was considered as trace of sea regression during a time period, where the rivers was in their youthful age characterized by a higher sediment supply. Meantime the erosion phenomena observed in the end of 80’ decade, are considered as consequence of sediment supply reduction mainly cause by river ageing (Konomi, 2015). All the sediment in Ionian coast line, are designated on maps as alluvions. This brings to conclusion that the absence of large lowlands, as in adjacent area of Adriatic coast line, is dedicated to the absence of important rivers in front of Ionian Sea. So those concepts diminish the role of sea and exaggerate the role of rivers during the process of quaternary deposits forming. In fact worldwide the history of geological science has abandoned geosynclinals concepts more than half century ago, even is concluded that every challenge to update its concept with those of Global Tectonic Theory, as in Albania happen, constitute a useless scientific mistake (Kearey et al., 2009). Following in this conceptual mistake, caused that in studies of coastal area, or of the lowland adjacent to not be taken into consideration the concepts of transgressive or regressive coasts, or the study of system tracks traces and the role of sea waves. The coast was categorized into two types according to its relief (high or low coast) combined with the erosive and accumulative coastline. So isn’t made a categorization of beach based on coast processes. Also neither of studies declares a mean sea level or any base sea level. Every study till now doesn’t mention the term “sea level” referring the sea level in the moment of observation. 442 http://epublishing.ekt.gr | e-Publisher: EKT | Downloaded at 23/03/2020 06:05:56 | Although the tides in Albanian coast line don’t exceed the range of 0.5 meters which classify then in the first group of tidal range according to Davies (1964) those show a visible difference in the sea level change as result of Sun influence, which can have impact in coast processes. This change of level, with falling tendency, particularly from June to September (between summer and autumnal equinoxes) remarked in different coastlines (Shëngjin, Durrës, Borsh) during calm state of sea level observations, isn’t mentioned in precedent studies. 2. Geographic position and geological setting of the Borshi Beach 2.1. Geographic and historical data Borshi Beach is situated in proximity of Ionian coast and is part of this geographical area began to call “Albanian Riviera” after 60th decade of 20th century. Although natural beauty of this beach and others beach of “Riviera” which lay from Llogara Pass, including some villages and the town of Himara, all positioned adjacent of sea and cultural and historical monuments (castles, old churches), until begin of 21st century the touristic potential was unused. Those areas until the end of 80th decade of 20th century were used only for agricultural and military purposes. The area of hilly relief was covered by artificial terraces to plant trees of lemons and oranges. This activity was abandoned after the year 1991, where the collapse of communist state, the only owner of the land, deepened the economic crisis began from the second half of 70’ decade. The crisis was followed by a mass migration of population of this area, mainly toward Greece. The terraced hill degraded, and as consequence the level of erosion began from the first deforestation of hills by natural vegetation four decades ago. Military installations, besides others, consist in some lines of bunkers, very characteristic for the communist Albania, with the purpose to be a defended position for the infantry and artillery corps. The concreting lines were situated parallel to coastline, beginning from its proximity.