Department of Geology and Geoenviromment
Library of the School of Science

2020-07-06

2020

Tzortzaki Efsevia

Καθηγητής Βασίλειος Καρακίτσιος (Επιβλέπων), Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ
Καθηγητής Γεώργιος Αναστασάκης, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ
Καθηγήτρια Μαρία Τριανταφύλλου, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ
Καθηγήτρια Χαρίκλεια Ντρίνια, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ
Καθηγήτρια Ασηµίνα Αντωναράκου, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ
Καθηγητής Αβραάµ Ζεληλίδης, Τμήμα Γεωλογίας, Πανεπιστήµιο Πατρών
Καθηγητής Νικόλαος Πασαδάκης, Τμήμα Μηχανικών Ορυκτών Πόρων, Πολυτεχνείο Κρήτης

Στρωµατογραφία και ανάλυση του οργανικού υλικού των ανοξικών οριζόντων του Κρητιδικού της ∆υτικής Ελλάδας

English
Greek

Stratigraphy and organic matter analysis of the Cretaceous anoxic horizons from Western Greece

In the first part of this thesis, new biomarker evidence is presented that constrains the conditions of deposition and preservation of sediments rich in extractable organic matter from the Aptian–Albian sedimentary record of the Ionian Zone in NW Greece. Analyses were specifically carried out on total lipid extracts from 12 organic rich samples from the Vigla Shale Member, two of which represent the regional record for the early Albian Paquier Event of OAE1b. In the aliphatic fractions, compound groups such as n-alkanes, isoprenoid alkanes, steroids, hopanoids and terpenoids were recognized, pointing to a mixed origin from algae and prokaryotes with an additional measurable contribution from terrigenous plant matter. These compounds suggest deposition of the primary organic sediments under conditions of decreased bottom water oxygen concentrations. Mass spectral evidence from the aromatic fractions of most samples reveal the variable presence of diagenetic and catagenetic derivatives of carotenoid pigments (including some with bound sulfur) that are characteristic of photoautotrophic sulfur bacteria. The presence of specific biomarkers originating from photosynthetic anaerobic microorganisms, similar to those in ancient and contemporary euxinic basins such as the Black Sea, suggest that photic zone euxinic conditions were intermittently operative in the Aptian–Albian stages of the Ionian Basin, but were not exclusively characteristic of the black shale representing the Paquier Event itself.
In the second part of the thesis new biostratigraphic, stable isotope (C,O) and organic geochemical data are presented for the Pindos Zone in NW Greece (SE Epirus region) in order to investigate whether the organic carbon rich strata of the Kalarrytes sections A and B correspond to a local expression of the early Aptian Oceanic Anoxic Event (OAE1a or Selli Event) or not. The Pindos Zone Mesozoic to Tertiary sedimentary sequence constitutes the deep-sea sedimentary cover of the Pindos Ocean, which was separated from its oceanic basement as an accretionary prism during the complete closure of this ocean, and was emplaced westwards onto the adjacent Gavrovo-Tripolis carbonate platform. Stable carbon and oxygen isotope data from the Kalarrytes sections reveal an isotopic composition compatible with the characteristic features of the OAE1a. Calcareous nannofossil and radiolarian biostratigraphy indicates an early Aptian age for both sequences. Biomarker analysis on the organic-rich intervals reveals the primary marine origin of the organic matter, with substantial contribution from bacteria, cyanobacteria and dinoflagellates, as well as a significant terrigenous input. Findings of authigenic framboidal pyrite provide evidence for the prevalence of sulphidic conditions during deposition. Furthermore, similarities between the biomarker signatures of the Pindos organic-rich strata and coeval strata of early Aptian age where the impact of OAE 1a has previously been recorded, are identified. The presented data show that the organic-rich intervals of both Kalarrytes sections constitute the first records of the OAE1a in oceanic deposits of Greece.

Science

Stratigraphy, organic matter analysis, anoxic sediments, Cretaceous

Yes

5

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https://pergamos.lib.uoa.gr/uoa/dl/object/2918106