IV. REGIONAL TECTONIC SETTING
Understanding the nature and origin of the sedimentary rocks exposed on Mt. Lykaion requires examining the Triassic through Eocene regional tectonic history of this part of the Aegean region (Robertson and Dixon, 1984; Golonka, 2004). Prior to approximately middle Triassic (~210 Ma), the regions we now refer to as northern Africa, southwestern Europe, and northeastern North America were close neighbors within the Pangaea super continent. The rifting apart of Pangaea then took place, and the North Atlantic began to open (Degnan and Robertson, 1998). Major faults associated with the rifting broke eastward to the Neotethyan Ocean. Within a part of the Neotethyan Ocean, a very deep, narrow (~160 km wide) oceanic basin opened up, known as the Pindos basin (Pe-Piper and Piper, 1984; Degnan and Robertson, 1998; Piper, 2006). In it was deposited a sequence of sedimentary rocks of Late Triassic (~200 Ma) through late Oligocene (~25 Ma) age. These now comprise the “Pindos Group” stratigraphy of mainland Greece and the western Peloponessos (Degnan and Robertson, 1998; Skourlis and Doutsos, 2003). Not all of the stratigraphy of the Pindos Group is represented at Mt. Lykaion, but the sequence is reasonably complete, with units as old as mid-Jurassic (~180 Ma) and as young as late Eocene (~34 Ma).
Two different tectonic conditions are revealed in the Pindos Group stratigraphy of the Peloponessos (Degnan and Robertson, 1998). Rocks in the lower part of the Pindos Group, which range in age from latest Triassic (~210 Ma) to latest Cretaceous (~65 Ma), are preorogenic and reveal a period during which the Pindos Basin was deep, far from shore, sediment starved, and slowly accumulating the tests of pelagic organisms that accumulated in silica- and carbonate-rich mud and ooze (Bosellin and Winterer, 1975; Baltuck, 1982). From time to time this basin received influxes of carbonate-rich debris flows propelled from the basin margin(s) down the continental slope to the abyssal depths via turbidity currents (Richter and Mueller, 1993; Walgreich and others, 1996; Avramidis and Zelididis, 2001; Degnan and Robertson, 1994, 2006).
Rocks in the upper part of the Pindos Group, which range in age from early Paleocene (~64 Ma) to latest Oligocene (~25 Ma), are synorogenic, and reveal a period in which the Pindos basin was being closed and tectonically inverted into a mountain through faulting and folding (van Hinsbergen and others, 2006, see Figure 14, p. 483). Turbidity currents moved sediments from the basin margin(s) to the ocean floor, this time in the form of sand, silt, and mud derived from erosion of uplifts created by faulting and folding (van Hinsbergen and others, 2005). Thus Pindos Group limestones in the upper part of the stratigraphic column become dominated by large influxes of sandstones derived from the tectonically uplifted parts of the closing basin. The thickness of the pre-orogenic sedimentary section throughout most of the Pindos Group is ~1000 m; the thickness of the syn-orogenic sedimentary section in the Peloponessos is ~300m, though becoming much thicker to the north of the Gulf of Corinth (Skourlis and Doutsos, 2003).