Tecctonostratigraphy of the Argolis Peninsula (Peloponnesus, Greece) – A multiphase telescoped transect of Pelagonia, Maliac and Vardar oceanic realms

The outcrops of the Argolis Peninsula reveal a multiphase orogen consisting of Upper Jurassic Pelagonian and Upper Cretaceous Sava type, W-Vardar, nappe stacks included in Paleogene composite nappes.

During the early Middle Triassic, the Pelagonian realm became a microcontinent between the opening branches of Neotethys, the Pindos (SW) and the Maliac (NE) ocean basins. Carbonate Platforms encroached on Middle Triassic Pietra Verde and persisted, up to the Early Jurassic. During the Middle Jurassic the Pelagonian/Maliac margin and adjacent parts of the Maliac ocean became the lower plate of the intraoceanic subduction that in turn reached the Pelagonian. The Pelagonian carbonate platforms drowned and during the late Middle Jurassic the first ophiolitic detritus derived from the approaching accretionary prism and the associated island arc reached the site of radiolarite deposition on the Maliac margin. During the Late Jurassic the emplacement of large-scale thrust nappes affected the entire Pelagonian.

1-2. The Jurassic nappe stack includes from W to E:  1a. Externally, the Marathia and Vivari Units contain Upper Jurassic pelagites and deep-water syn-orogenic breccias without ophiolitic detritus, probably formed along the slope towards the Pindos basin. 1b. The Adhami Basal Series, thrust over 1a., contain eastward increasing ophiolite detritus. 1c. The Didhimi-Trapezona Basal Series, thrust over 1b. (Vourlias), contain much coarser Upper Jurassic ophiolite detritus culminating in megabreccias. 1d. The Asklipion Nappe represents the Pelagonian-Maliac margin. It includes Middle Triassic to Upper Jurassic deep-water sediments. 1d. is overthrust by 2. the Migdhalitsa Unit, interpreted as the Middle Jurassic accretionary prism containing Middle-Late Triassic basalt and radiolarite, covered by Middle Jurassic radiolarites.

3. Meso-autochthonous Series unconformably overlie the Jurassic nappe edifice: Albian–Cenomanian deep-water calciturbidites (Ermioni) and Turonian to lower Paleocene pelagites, overlain by flysch.

4. The Akros Nappe, internalmost Pelagonian, contains latest Jurassic to Cenomanian continental/paralic conglomerates and shallow-water carbonates encroaching on ophiolites, overlain by pelagites. Flysch sedimentation started in early Paleocene or Campanian–Maastrichtian in the internalmost series (Dokos).

5-6. The Upper Cretaceous nappe stack records the closure of the Vardar remnant ocean in the Sava, W-Vardar-type units. 5. The Poros Units represent a stack of imbricates with basal serpentinite overlain by Upper Cretaceous proximal to distal deep-water terigenous and carbonate resdiments. The imbricates formed during the Campanian–Maastrichtian but were emplaced on 4. during the Paleogene. 6. The Adheres Unit represents an accretionary prism containing exclusively Upper Cretaceous pelagic and redeposited shallow- carbonates in a flysch matrix. It rests on the Upper Cretaceous arc remnant (Cambrorosso) and associated pelagic limestones that grade upsection into the Adheres flysch.

The Paleogene nappe stack incudes the Adhami and Didhimi-Trapezeona Composite Units (1.–3.), the Akros Nappe (4.), and the Poros-Adheres nappe stack (5.–6.).

Two Cenozoic tectonic phases assembled the Jurassic and Cretaceous nappe stacks into composite Units. A first, SW-vergent phase emplaced the Akros Unit (4.) and the Poros-Adheres stack (5-6.) on the Pelagonian Meso-autochthonous (3.). A second, S-vergent phase of thrusting affected the Palaeogene nappe edifice, producing km-scale recumbent folds. Finally, Aegean extensional faults dissected the Alpine nappe edifice.