Palaeoenvironmental and sedimentological formation conditions of North-Aegean beachrocks

Παλαιοπεριβαλλοντικές και ιζηματολογικές συνθήκες σχηματισμού των ακτόλιθων (ψηφιδοπαγών αιγιαλών) του Βόρειου-Αιγαιακού χώρου

Palaeoenvironmental and sedimentological formation conditions of North-Aegean beachrocks

Psomiadis, David

Ψωμιάδης, Δαυίδ

PhD Thesis

2011

This dissertation incorporates the study of the palaeoenvironmental and sedimentological conditions that prevailed in Northern Aegean area, using multi-methodological approach on multiple sedimentary proxies (beachrocks, speleothem, clastic deposits. The reconstruction of the conditions under which the beachrocks of North-Aegean region were formed took place by the application of advanced methods on the carbonate cement, by analysis and comparison of modern unconsolidated beach deposits and the clastic fraction of the respective beachrocks and finally by the high-resolution analysis of MAR_L stalagmite from Thassos island. In this study, 20 beachrock formations from 11 different sites of North Aegean Sea were used. The analysis results of the carbonate precipitates which cemented the coastal sediments and formed the beachrocks indicated three main mechanisms that acted in the coastal micro-environment. The two first are quite similar in that they took place in marine water, either with evaporation and carbonate precipitaion, or with intense evaporation and CO2 degassing. Different precipitation conditions were found in specific sites, where lithification took place due to mixing of marine and meteoric water. Clastic sedimentology offered important information relatively to the depositional processes that prevailed in the coastal zone in comparison to the modern environment. The results indicate two differentiating factors; a) an early immature sedimentological stage of the beaches during the formation of beachrocks in comparison with modern regime and b) impact of the beachrock outcrops in the modern coastal energy regime, which prevents the processing and reworking of the beach deposits from waves. The high-resolution dating of MAR_L stalagmite from Skala Marion cave (Thassos) in combination with the multi-methodological analysis of its carbonate layers led to a detailed reconstruction of the palaeoenvironment in North-Aegean region from 4900 to 1400 yr BP. The combination of all data-proxies made possible to determine a distinct period in Late Holocene (2950-1950 yr BP), which was characterized by prolonged arid conditions in the coastal areas. This phase differed from all other phases in that all parameters analyzed were affected immensely. The combination of all data of this dissertation concluded in the time window that the majority of beachrocks were formed in North Aegean Sea. That was the dry phase of Holocene that was spotted in MAR_L. During this period, the arid environmental conditions favored the evaporation of sea water in coastal sediments and the stabilization of sea level allowed the lithification of the deposits of the immature coasts of North Aegean. The posterior wet period (Roman Warm Period, 1950-1500yr BP in the study area) favored the influx of meteoric waters in the coastal aquifer, resulting in the precipitation of carbonate sediments from the mixing of meteoric and marine waters in the upper level of the beach and the formation of beachrocks.

Άλλες Φυσικές Επιστήμες

Φυσικές Επιστήμες

Γεωεπιστήμες και Επιστήμες Περιβάλλοντος

Σπηλαιόθεμα

Άλλες Φυσικές Επιστήμες

Ακτόλιθοι

Κλαστικά ιζήματα

Speleothem

Palaeoenvironment

Φυσικές Επιστήμες

Other Natural Sciences

Clastic sediments

Γεωεπιστήμες και Επιστήμες Περιβάλλοντος

Παλαιοπεριβάλλον

Beachrocks

Natural Sciences

Earth and Related Environmental Sciences

Greek

Αριστοτέλειο Πανεπιστήμιο Θεσσαλονίκης (ΑΠΘ)

Aristotle University Of Thessaloniki (AUTH)

Αριστοτέλειο Πανεπιστήμιο Θεσσαλονίκης (ΑΠΘ). Σχολή Θετικών Επιστημών. Τμήμα Γεωλογίας. Τομέας Φυσικής και Περιβαλλοντικής Γεωγραφίας

National Documentation Centre (EKT)

National Archive of PhD Theses

Συλλογή ΕΑΔΔ