Geology of the Sanctuary of Zeus, Mount Lykaion, Southern Peloponessos, Greece, and Field Guide

George H. Davis

Detailed structural geological mapping of bedrock and structures within the Sanctuary of Zeus on Mt. Lykaion in the Peloponessos (Greece) reveals intimate ties between the archaeological and geological elements at the site. The physiographic setting of this Pan Hellenic mountaintop sanctuary is dramatic visually. The upper part of the sanctuary is situated on top of a high dome-like summit (~1400 m) known as Agios Elias (St. Elijah). Archaeological elements comprising the lower part of the sanctuary are distributed on a broad rolling surface at the base of Agios Elias on its north and west. The east margin of the upper sanctuary is a precipitous landslide-strewn escarpment actively being shaped by normal faulting related to regional extension. Active normal faults criss-cross the very summit of the sanctuary. The abrupt change in geomorphology from the lower to upper sanctuary areas coincides with the trace of a 10°-easterly dipping thrust fault (the Lykaion thrust fault), which was active in the early Tertiary and accommodated kilometers of east-to-west tectonic transport. The bedrock of Mt. Lykaion comprises five rock formations of the Pindos Group, and each has a very distinctive stratigraphic and landscape signature. The oldest sediments of the Pindos Group were deposited in a deep narrow part of the Neotethyan ocean. Pindos Group deposition began in the Jurassic with a restricted-basin phase in which the Pindos basin was deep, far from shore, and sediment starved. The pre-orogenic history continued through late Cretaceous time, producing overall a sedimentary section ~1000m thick. The preorogenic history ended in latest Cretaceous when the Pindos basin began to be inverted and closed through formation of thrust faults and associated macro-folds. Uplifted blocks shed clastic sediments of latest Cretaceous through Oligocene age. Regionally the synorogenic sequence is ~300m thick and represented primarily by Flysch Transition Beds, which in the Mt. Lykaion area is ~100m in thickness.

The Lykaion thrust fault separates two thrust sheets each composed of internally folded and/or sheared Pindos-Group strata. Major flexural-slip fold structures crop out boldly along the eastern margin of the map area, and they tend to be chevron, with tight angular geometries. The folds are overturned and/or asymmetrical westward, consistent with the east-to-west tectonic transport direction defined for the Pindos fold-and-thrust belt as a whole. Superimposed on the fold-and-thrust structures is the ongoing active normal faulting. Traces of the active faults are commonly in the form of scree bands demarcating locations of scarp collapse.

The archaeological elements in the lower sanctuary area reside on bedrock in the lower thrust sheet and include a hippodrome and stadium, bath complex, stoa, seating area, and xenon. These built structures are composed of stylolitic limestone mainly derived from just one of the five stratigraphic formations in the area. The Lykaion thrust location plays an important role in locations of springs and built structures. The archaeological elements in the upper part of the sanctuary reside in the upper thrust sheet (Lykaion klippe) and include temenos (sacred precinct), early stadium (?), and ash altar. These reside within a complex of active normal faulting. The geological relationships illuminate site selection and utilization related to activities and built structures in ancient times.