Introduction
Sedimentary basins and their filling products give important information for the structural evolution of orogenic belts and have been broadly used as guide indicators for the analysis of tectonic events related to plate movements.
There are numerous different shapes of sedimentary basins. They can be approximately circular or elongate depressions, troughs, or embayments, but often they have irregular boundaries. Most of the recent attempts to classify sedimentary basins were based on the modern concepts of global plate tectonics, as well as regional tectonics. We distinguish basins related to extension, compression and strike-slip movements during plate convergence or divergence. Based on the modern concept of global plate tectonics, the different types of sedimentary basins can be grouped as following (Busby and Ingersoll 1995; Einsele 2000): I. Continental, intracratonic sag basins, II. Continental fracture basins, including the rift basins and supradetachment basins, III. Basins on passive continental margins, IV. Oceanic sag basins, V. Basins related to subduction or active continental margins and island arc systems, including the deep-sea trenches, forearc- and backarc basins, VI. Basins related to continental collision, including the foreland and retroarc basins, usually with substratum of continental origin and VII. Strike-slip and wrench basins, including the transtensional (pull-apart) or transpressional basins.
Crustal subsidence (tectonic, thermal or sediment overload subsidence) is the main motor to initiate the basin formation and the sediment deposition but it is often associated, especially in an extensional tectonic regime, with uplift /exhumation of deep crustal metamorphic rocks, and formation of the metamorphic core complexes (Friedman and Burbank 1995; McGlaughry and Gaylord 2005).Two end-member of extensional basins can be rerecorded during a continuous extensional tectonism: rift basins and supradetachment basins. The differences in magnitude and rate of extension, volcanism, heat flow and structural architecture define the basin style and suggest the geotectonic setting related to the basin evolution (Friedman and Burbank 1995; Einsele 2000; McGlaughry and Gaylord 2005).
The Mesohellenic Trough (MHT) in NW Greece (Brunn, 1956; Doutsos et al. 1994; Zelilidis et al. 2002; Ferrière et al. 2004, 2011, 2013; Vamvaka et al. 2006, 2010) and the Thrace Basin (THB) in NE Greece (Christodoulou, 1958; Lescuyer et al. 2003; Kilias et al. 2006, 2012; Maravelis et al. 2007; Mainhold and BonDagher-Fadel 2010), including its possible continuation into the Axios Basin (AXB; Dumurtzanov et al. 2005), constitute two large late to synorogenic Tertiary molassic-type basins in the Hellenides (Figure 1).
Figure 1. The MHT and THB including the Axios Basin (AXB)
The paleogeographic extension of the MHT and THB including the Axios Basin (AXB)in Greece and surrounding countries is shown (dark gray, the outcrops of the molassic strata in Northern Greece and the study areas in the box; light gray, the possible continuation of the basins in Northern Greece and the neighbouring countries). A-A’ cross section of Figure 16. Insert: The Major tectonic units of the Hellenides and their continuation to the surrounding orogenic belts. The position of the Mesohellenic Trough (MHT) and the Greek Thrace basin (THB) with yellow color, as well as the SSW-ward migration of the Cenozoic magmatic activity are shown.
Younger, Neogene-Quaternary, unconformably overlying clastic sediments are not considered. Although these basins dominate with their size in the Hellenic orogen and the surrounding region (Figure 1; Albania, Bulgaria, Turkey; References herein-see above), and while a lot of works with different approaches were published for each one basin, there still doesn’t exist any comparison between the two basins until today, concerning their structural and stratigraphic evolution during the Alpine orogeny in the Hellenides, as well as their geodynamic setting. Besides, the knowledge of the structural evolution of both basins, as well as their geotectonic setting and structural relationships are of great importance to the better understanding of the tectonic evolutionary history of the Hellenides. Furthermore, it is known the great industrial potential of both basins due to gold-mineralizations and their possible hydrocarbon supplies (Kontopoulos et al. 1999; Zelilides et al. 2002; Lescuyer et al. 2003).
This work is the first attempt to compare the evolutionary history of the two basins, as well as their paleogeographic and geotectonic setting in the Hellenic orogen, at least during their molassic-type sedimentation period, taking into account our previous studies on both basins and any different published work referred to each basin’s development. Furthermore, paleostress analysis based on fault-slip data, used in order to calculate the paleostress tensor, for each tectonic event affected the molassic strata of both basins. The direct stress inversion method of Angelier (1979, 1990) was used.Although, both basins have a similar lithostratigraphic age, evolved mainly during the Tertiary, they differ in their structural evolution and geotectonic position in the frame of the Hellenic orogen and its evolutionary stages.