Late Cenozoic extensional faulting in Central-Western Peloponnesus, Greece

N Lapithas Kyparissia S Mt Mt 2000 Olympia 2000 Zacharo Neda Kalo Nero - Kyparissia basin 1000 basin basin basin 1000 Sections Legend E. Skourtsos, I. Fountoulis, S. Mavroulis & H. Kranis 0 0

-1000 -1000 [email protected] [email protected] [email protected] [email protected] Post-alpine deposits Erymanthos Mt

A A’ Pindos Unit

W Mainalon Mt E Tripolis Flysch Megalopolis Basin Asea 2000 Lykeo Mt 2000 Neda Basin 1000 1000 Tripolis carbonates 0 0 Department of Dynamic, Tectonic & Applied Geology, Faculty of Geology & Geoenvironment, -1000 -1000 Phyllites-Quartzites Marker National & Kapodestrian University of Athens, Panepistimioupoli Zografou, Athens, 15784, Greece B B’ Ryrgos Basin Fig. 5 Megalopolis Basin Mainalon Mt SW NE Kalo Nero - Kyparissia Filiatra Lykeo Mt Vytina syncline 2000 basin 2000 1000 1000 C’

0 0 V -1000 -1000 A ytina syncline

C C’ Mainalon Mt 1 Introduction and background The NW-SE trending extensional structures form the Lapithas Mt eastern boundary of a series of Neogene-Quaternary Map Legend Alluvial High-angle normal fault Scree Fault probable Aegean Fig. 6 Fig. 3 A complex strain field is established during the Late tectonic depressions located in western Basins deposits Pindos flysch (Paleocene) Peloponnesus Low-angle normal fault Ithaki Pliocene - Quaternary times in Peloponnesus, SW Pleistocene lacustrine deposits Pindos limestones (Upper Creatceous) Thrust Zacharo Basin Fig. 4 Hellenic Peloponnesus, which in turn are separated by E-W Cephalonia Πατραϊκός Crete Cherts and pelites (Upper Jurrasic-Cenomanian Κόλπος GULF OF Pleistocene continental deposits Aegean (Fig. 1). The western part of Peloponnesus, CORINTHOS Arc horsts controlled by high-angle ESE-WNW, ENE- Drymos limestones (Upper Triassic-Middle Jurrasic) Megalopolis Basin 1a Upper Pliocene continental deposits Lykeon Mt B’ closest to the Hellenic trench, is dominated by NE - Upper Pliocene lacustrine and fluvial deposits Tripolis Flysch (Oligocene) Kyparissiakos Gulf Neda Basin Fig. 2 WSW and E-W normal faults. The geometry of the SW compressive stress field and N-S stretching Upper Pliocene-Lower Pleistocene marine deposits Tripolis carbonates (Mesozoic-Eocene) B faults suggests a general N-S stretching direction, Upper Miocene-Lower Pliocene marine deposits Tyros Beds (Upper Permian-Upper Triassic) Zakynthos Saronikos direction while the central and south Peloponnesus is Gulf although this may have been distorted locally by Upper Miocene-Lower Pliocene lacustrine deposits Phyllites-Quartzites Unit (HP/LT) characterized by E-W extension and N-S extension in Gulf of Mainalon Kyparissia diapiric movements of the Triassic evaporites its northern sector. (Hatzfeld et al., 1990). IONIAN SEA (Kamberis et al., 1992). Figure 2. Geological map of the study area showing the extent of the Neogene-Quaternary deposits and the distribution of the Kyparissia Basin This study deals with the western and central GULF extensional fault in the western Peloponnesus. The alpine Compressional field OF In the Pyrgos Basin Late Cenozoic sedimentation N sectors of the Peloponnesus focusing on the ARGOLIS structure is also visible. Geological cross sections of the study Extensional field started in the Upper Miocene – Lower Pliocene with the Messinian Gulf area. Notice that the Megalopolis Basin has been formed on the following aspects: 1) how the extensional structures Post-alpine sediments Lakonian Taygetos mt Gulf deposition of lacustrine successions (Hageman 1977, hanging wall of a detachment fault (cross sections B-B’ and C-C’). Kyparissia Mt were superimposed on pre-Neogene compressional Volcano A’ CRETAN Kamberis et al.,1992) and it was restricted to outcrops Compression ones, 2) the timing of the Late Cenozoic extension Kythira Extension SEA along the southern and northern margins of the C and 3) the geometry and kinematics of the extension Compression - extension boundary Front of Ionian thrust Lapithas Mountains which evidently was part of this systems in order to understand how the transition in Thrust faults Antikythira subsided area. In the Kyparissia Basin the older different stretching regimes is expressed and how Front of Gavrovo-Tripolitza thrust Front of Pindos thrust successions are Upper Miocene-Lower Pliocene 3. Synthesis and Geodynamic Implications - Conclusion these different regimes interact. Main normal faults Anticline structure Modified from Hatzfeld et al. (1990) sediments of marine origin. Figure 4. Touthoa Fault strikes NE-SW and juxtaposes either Two nearly orthogonal and synchronous extensional The Upper Cenozoic successions of the western the Tripolis limestones against its flysch or the Pindos Unit or systems affect different parts of the study area: a Peloponnesus show an extremely complex the Pindos limestones against the Pleistocene continental deposits of the Pyrgos basin. It has a considerable fault system with NNW-SSE trends causing sedimentary pattern revealing the influence of 2 Late Cenozoic extensional faulting and basin configuration displacement, ca. 700 m. The fault data set gives nearly a extension perpendicular to the belt axis and an E- tectonic movements in their development in space Bedding horizontal T-axis oriented NNW-SSE, while the mean slip vector W trending fault system causing orogen-parallel and time. A series of forearc-dipping, orogen-parallel faults (Fig. 5). Sedimentation started with lacustrine is 315/61, on a mean NE-SW, NW-dipping fault, that is an almost pure dip-slip structure. stretching. extensional faults are found in the central-western and fluvial deposits occurring at the eastern margins The NW-NE trending extensional fault architecture has 20° E 21° E 21° E 22° E 22° E I resulted (i) in the Pindos thrust stepping down from Peloponnesus, which control the western margin of of the basin (Vinken 1965). In Pleistocene time (after G 38° N

In the Early Pleistocene, rapid subsidence of the Zakynthos ( altitudes higher than 1000 m in Mainalon Mt in the

( Mt Mainalon (Fig. 2). The latter comprises HP/LT 0.78 Ma (Okuda et al., 2002)) tectonic movements ( Pi rocks of the Phyllites-Quartzites Unit (PQ), overlain by resulted in the subsidence and submergence of the Tripolis northern part of the Pyrgos Basin resulted in east, to negative heights in North Messinia and the carbonates and flysch of the Tripolis Unit while larger part of the basin, while the areas with greatest flysch Ng another transgression and the accumulation of at I Southern Ilia in the west; and (ii) the gradual least one thousand meters of lagoonal, lacustrine and P T disappearance of the metamorphics towards the west. the uppermost nappe is the Pindos Unit, a Mesozoic subsidence had clearly shifted westwards. 38° N Mainalon Mt pelagic sequence, topped by a Paleocene flysch. Most fluviatile deposits. It is likely that the southern part of Pi 38° N The combination of these extensional faults (which may the basin was subjected to uplift and erosion because Kyparissiakos of the extensional structures were previously thought N Gulf reach down to the Ionian décollement) with the low- of as the original thrust between the Pindos and of the overall tilting to the north or northwest. angle floor thrusts of the Pindos, Tripolis and Ionian Pi Tripolis Units. However, the cross-cutting T Units leads to additional ENE-WSW shortening, FiliatraG N relationships among these structures indicate that 37° N I T normal to the Hellenic Arc, west of the Peloponnesus aygetos Mt P 37° N these are forearc (SW-dipping) extensional faults, Figure 5. The northeastern margin of the Megalopolis basin is a Pt o Messiniakos References downthrowing the Pindos thrust by a few tens or σ1 normal fault dipping 30-40 NW. The Upper Pliocene fluvial o Gulf σ2 Papoulia & Makris (2010) Hageman, J., (1977). Stratigraphy and sedimentary history of the upper Cenozoic of the Pyrgos area (W. σ3 deposits have been backtilted 35-40 . View to the SE. hundreds of meters each, rooting onto different levels Peloponnesus, Greece). Ann. Geol. Pays Hell., 28. 299-333. of the nappe pile (Fig. 3). In SW Mainalon the Hatzfeld, D., et al. (1990). The strain pattern in the western Hellenic arc deduced from a microearthquake survey. 0½ 40 80 37° N Geophys. J. Int., 101, 181-202. lowermost of the extensional faults is a low-angle kilometers 37° N Kamberis, E., et al.., 1992. Geodynamic and palaeogeographic evolution of western Peloponnesus (Greece) normal fault dipping SW juxtaposing the In Late Pliocene time tectonic movements resulted 20° E 21° E 21° E 22° E 22° E 23° E during the Neogene. Paleontologia i Evolucio, 24-25, 363-376. in the subsidence and submergence of the larger Figure 7. Section C-C’ fits nicely with the offshore ENE-WSW Okuda, M., et al. (2002). Palynological evidence for the astronomical origin of lignite-detritus sequence in the metamorphic rocks of the PQ Unit against the non- Middle Pleistocene Marathousa Member, Megalopolis, SW Greece. Earth and Planetary Science Letters, 201: part of current eastern, southern and central part of crustal section (Papoulia and Makris 2010). It remains open 143-157. metamorphic sequence of the Tripolis Unit. High- whether the NW-SE faults root in the mechanically weak layer Papoulia, J. and Makris, J., (2010). Tectonic processes and crustal evolution on/offshore Western Peloponnese angle normal faults, found further to the west, sole the basin, while Lapithas Mountains begun to rise. between the two carbonates, or it goes deeper, to root in the derived from active and passive seismic. Bull. Geol. Soc. Greece, 43/1, 357-367. Later, the continued subsidence was accompanied by Vinken, R., (1965). Stratigraphie und Tektonik des Beckens von Megalopolis (Peloponnes, Griechenland). Geol. onto or even have truncated the low-angle ones and basal thrust of the sedimentary cover of the subducting Jarb., 83, 97-148. control the eastern margin of the Megalopolis basin. a simultaneous rise of the hinterland, which soon lithosphere. caused the supply of large amounts of clastic SW NE Mainalon Mt In the NW, these faults are truncated by NE to NNE- material. H e l l e n i c t r e n c h Filiatra Figure 3. The Western Mainalon Fault is a 18-20 km long 2 Pindos Unit 2 striking, NW-dipping faults, which relay the whole complex structure on the western flanks of Mainalon Mt. It 0 0 upper limestone Tripolis Unit fault activity to the eastern margin of the Pyrgos sedimentary layer comprises anastomozing faults of varying dip values. Slip sense In the south, southeast and east, a sudden increase Figure 6. South Lapithas Fault is the boundary fault of the Ionian Unit ? lower limestone -10 graben (Figs 2, 4). on the constituent faults is quite variable, ranging from pure in the amount of the clastic supply reflects a strong Zacharo Basin to the south which has been filled by Upper -10 oceanic crust upper crust ? normal to strike-slip faulting. Despite the variety of kinematics increase in relief by a intense uplift along the basin Pliocene - Lower Pleistocene marine sediments that exhibit high- Megalopolis Basin is a continental basin and its on the individual fault, the whole data set is fairly lower crust Underplating margin of the alpine rocks bordering the eastern and angle southerly dips, from the Tripolis limestones of the -20 -20 formation took place during the Upper Pliocene as a homogeneous and can be attributed to NE-SW extension. elongated Lapithas Mt to the north. It has a fresh fault mantle southeastern basin margins and a rise of the escarpment with distinct striae that show significant right- result of NE-SW stretching caused by NW-SE normal -30 -30 southern part of the area. lateral sense of movement. Based on Papoulia & Makris (2010) Based on section C-C’