Correlation between the structural pattern and the development of the hydrographic network in a portion of the western thessaly basin (Greece)

In the context of the present study the structural pattern in the Western Thessaly Basin (Greece) has been examined, based on structural data collected from the entire study area that were further correlated to the hydrographic network. The structural pattern of the area was revealed from tectonic analysis. Additionally, the topography, stratigraphy and sedimentology of the study area were taken into account. GIS techniques were used to map the spatial distribution of the geological and tectonic features on the topographic relief of the area. The oldest structures are contractional in nature, deformed by normal faulting related to the extensional episodes initiated in Serravallian times. It is inferred that the orientation of the stress field in the area has changed several times: the N-S stress field which was dominant during Late Serravallian times changed to NW-SE (Messinian- Zanclian) up to E-W in Zanclian and subsequently to roughly NNW-SSE (in late Piacencian). The NE-SW stress that was dominant in Pleistocene became N-S in later times. In addition, some changes in orientation are also indicated for the transitional periods of the pre-mentioned extensional episodes, possibly related to local events, or as a block-related deformation. The development of the 7th order streams is probably related to the N-S extensional faulting initiated in Pliocene times, while the dominant direction of the 6th, 5th and 4th order streams is possibly connected with the presence of the NNE-SSW and NW-SE extensional faults. Finally, the lower order streams are probably related to the most recent E-W striking normal faults. © Versita sp. z o.o

Thrust sequences in the central part of the External Hellenides

The model of a foreland propagating sequence already presented for the External Hellenides is significantly modified in this paper. New data are used, including structural maps, cross-sections, stratigraphic determinations and seismic profiles. In general, thrusts formed a foreland propagating sequence but they acted simultaneously for a long period of time. Thus, during the Middle Eocene the Pindos thrust resulted in the formation of the Ionian-Gavrovo foreland and acted in tandem with the newly formed Gavrovo thrust within the basin until the Late Oligocene. The Gavrovo thrust consists of segments, showing that out-of-sequence thrusting was important. Thrust nucleation and propagation history is strongly influenced by normal faults formed in the forebulge region of the Ionian-Gavrovo foreland basin. Shortening rates within the Gavrovo-lonian foreland are low, about 1 mm/year. Although thrust load played an important role in the formation of this basin, the additional load of 3500 m thick clastics in the basin enhanced subsidence and underthrusting

Paleogene terrigenous (flysch) sequences in Etoloakarnania region (W. Greece). Plankton stratigraphy and paleoenvironmental implications

Based on calcareous nannofossils and planktonic foraminifera1 biostratigraphic data from flysch sequences, we give evidence for the paleoenvironmental evolution of Gavrovo and Ionian foreland basins (External Hellenides, Etoloakarnania region). Our data suggest that the onset of clastic sedimentation in both foreland basins in the study area is chronostratigraphically placed at Late Eocene (from 36.2-34.4 Ma; nannofossil biozones NP19-20, planktonic foraminifera biozones P16-17). During the earliest Oligocene (NP21-22 nannofossil biozones/34.4-32.45 Ma), both basins represent restricted accumulation of sediments, mainly composed of clays and silts. The presence of thick flysch deposits, accumulated during Early Oligocene (33.4-30 Ma, nannofossil zone NP23), indicates an increasing rate of sediment supply. The flysch sequences in the Ionian basin are associated with a distal depositional environment, while in the same time the sedimentation in the external part of Gavrovo basin is related to a more proximal environment that is gradually deepening. On the contrary, the internal part of Gavrovo basin is characterised by deep-water facies, deposited in the Early Oligocene. At the end of Early Oligocene and the onset of Late Oligocene (nannofossil zone NP24/30-27.2 Ma, planktonic foraminifera zone P21), the deposition of coarse grained sediments in both basins indicates a shift to shallower depositional environment. The accumulation of fine-grained sediments during Late Oligocene (27.2-23.2 Ma, NP25 nannofossil biozone) in the Ionian basin marks the youngest flysch sediments in the Etoloakarnania region and specifies the time of the Gavrovo nappe emplacement on the Ionian zone. Moreover the emplacement of Pindos nappe on the Gavrovo zone is estimated between 30-27.2 Ma (NP24 biozone) as supported by the nannofossil analysis of samples in front of Pindos thrust. © 2008 Elsevier Masson SAS. All rights reserved

Late Cenozoic deformation of the Gavrovo and Ionian zones in NW Peloponnesos (Western Greece)

The structural deformation of Mesozoic-Tertiary sediments of the Ionian and Gavrovo zones in NW Peloponnesos is related to the propagation of a fold-thrust system during the Cenozoic. The sediments of the Gavrovo zone have been deformed by high angle reverse faulting generating an imbricate fan. Skolis mountain represents the Gavrovo thrust front. The detachment occurred in the underlying flysch of the Ionian zone. The Ionian zone has also been affected by shortening above a detachment horizon situated in the lower horizons of Triassic evaporites. The main compressional structure of the Ionian zone is a broad anticline revealed by a seismic survey west of Skolis mountain. The Gavrovo-sheet emplacement caused the downthrow and bending of the eastern part of the Ionian zone followed by halokinesis of Triassic evaporites to the west. Post-compressional normal faulting has predominated since the Pliocene, resulting in the formation of the Kato Achaia and Simopoulo basins in the peripheral area of Skolis mountain. Diapirs of Triassic evaporites occur in the mentioned basins that complicate the tectonic pattern in front of the Skolis thrust

Late Cenozoic deformation of the Gavrovo and Ionian zones in NW Peloponnesos (Western Greece)

The structural deformation of Mesozoic-Tertiary sediments of the Ionian and Gavrovo zones in NW Peloponnesos is related to the propagation of a fold-thrust system during the Cenozoic. The sediments of the Gavrovo zone have been deformed by high angle reverse faulting generating an imbricate fan. Skolis mountain represents the Gavrovo thrust front. The detachment occurred in the underlying flysch of the Ionian zone. The Ionian zone has also been affected by shortening above a detachment horizon situated in the lower horizons of Triassic evaporites. The main compressional structure of the Ionian zone is a broad anticline revealed by a seismic survey west of Skolis mountain. The Gavrovo-sheet emplacement caused the downthrow and bending of the eastern part of the Ionian zone followed by halokinesis of Triassic evaporites to the west. Post-compressional normal faulting has predominated since the Pliocene, resulting in the formation of the Kato Achaia and Simopoulo basins in the peripheral area of Skolis mountain. Diapirs of Triassic evaporites occur in the mentioned basins that complicate the tectonic pattern in front of the Skolis thrust