Supervisors info:
Ιωάννης Παπανικολάου, Επίκουρος Καθηγητής, Τμήμα Αξιοποίησης Φυσικών Πόρων και Γεωργικής Μηχανικής, Γεωπονικό Πανεπιστήμιο Αθηνών
Μαρία Τριανταφύλλου, Καθηγήτρια, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Ευθύμιος Λέκκας, Καθηγητής, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Summary:
The area North of Lake Trichonis in Aetolo–Akarnania is characterized by a massive exposure of flysch formations. No distinction between the Ionian and the Gavrovo flysch sequences has been established in this area or a thrust separating the two has been identified. Insufficient biostratigraphic data open questions regarding the age of the flysch.
An area of 173km2 was studied in E-W and SW-NE trending sections involving mapping and microscopic analysis. Bedding, fold axes plunge and fold limp dipping, as well as fault strike and slip readings were gathered, and these data were inserted on three tectonic maps.
A total of 31 smear slides were prepared from material collected in the study area, and then examined with the use of an optical polarizing lighting microscope, regarding their content in nannofossils. Biozones NP23, NP24 and NP25 according to Martini (1971) and biozones CNO4 and CNO5 according to Agnini et al. (2014) were established, dating Ionian Flysch at Late Oligocene (27,14 – 24,13Myrs) and the Gavrovo Flysch strata at Early - Late Oligocene (30,0 – 26,03Myrs). These data were then added to the tectonic maps.
Near Pyrgi village, biozones NP25 by Martini (1971) and CNO5 by Agnini (2014) were established, stipulating that the material was collected from beds comprising Ionian Unit flysch, of Late Oligocene age.
Close to the Skoutesiada village, the presence of biozone NP23 on top of biozone NP24, with the latter on lower altitude, along with a significant disturbance in bedding dip and lithology, with blocks of conglomerates and sandstone fragments within mudstone, strongly support the suggestion of the Gavrovo Thrust existing in this area. A possible locality for the Gavrovo Thrust is proposed, in an abrupt conglomerate surface, dipping towards the East. An abrupt change in the lithology of the study area, with fine-grained formations restricted west of Skoutesiada village and coarse-grained formations east of Skoutesiada village, strongly supports this suggestion.
Field mapping allowed the comparison of the deformation extent of the two flysch sequences. The Ionian Flysch comprises formations with constant dip towards the NE, which appear deformed in the area between Pyrgi and Skoutesiada villages, where a location for the Gavrovo Thrust is suggested. The Gavrovo flysch beds are strongly deformed by folds, faults and thrusts, throughout the area between Gavrovo and Pindos Thrusts.
Biostratigraphy allowed the estimation of the minimum thickness of the flysch sequences, along the three cross-sections that were constructed. In the Pyrgi – Skoutesiada section, a minimum thickness of 1520±100m was calculated for Ionian flysch. In the middle section (Elliniko – Agia Paraskevi), a minimum thickness of 1260±100m for Gavrovo flysch was established close to the village of Agia Paraskevi. In the southern section (Kakavas – Agia Varvara), a minimum thickness of 1330±100m was estimated for Gavrovo flysch, close to Kakavas village.
Keywords:
Flysch, Ionian Unit, Gavrovo Unit, Biostratigraphy, Biozones, Gavrovo Thrust
