Mesozoic/Cenozoic sedimentation and tectonics of the southern Greek Neotethys (Argolis peninsula)

• Main Author: Clift, Peter Dominic
• Published: University of Edinburgh 1990
• Subjects: 551.7
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.643268

The Argolis Peninsula of SE Greece lies within the Alpine orogenic belt, which formed as a result of continental collision, following the closure of a Mesozoic-Tertiary Neotethys oceanic basin. The area is located at the southern end of the Pelagonian Zone, a microcontinental block, which rifted from the northern margin of Gondwana in Middle Triassic times. Anisian-Ladinian rifting was marked in the Argolis Peninsula by the formation of deep-water basins floored by volcanics within a carbonate platform. These basins took the form of two, large, asymmetric half-grabens of opposing polarity. Late Triassic-Early Jurassic times were characterised by gentle subsidence of the platform, unbroken sedimentation and the partial transgression of the deep-water basins by neritic caronates along their unfaulted margins. The nature of sedimentation changed abruptly in Toarcian (Early Jurassic) times, with a switch to nodular, hemipelagic, Ammonitico Rosso limestone, interpreted to be a regional collapse of the platform. Continued subsidence depressed the platform below the carbonate compensation depth (CCD), resulting in the accumulation of radiolarian cherts in Middle-Upper Jurassic (Bathonian-Kimmeridgian) times. A hiatus in sedimentation after obduction was succeeded by a diachronous transgression, which began in the Upper Jurassic (Tithonian) and continued into the Upper Cretaceous. No active subsidence of the platform is recorded until Upper Cretaceous (Turonian) times when rapid deepening of the carbonate facies and intra-platform faulting occurred. Pink pelagic limestones deposited during this episode pass up rapidly into terrigenous flysch of Palaeocene-Eocene age. Early Tertiary thrusting towards the northwest in W Argolis and towards the north in E Argolis, with localised backthrusting towards the south is interpreted to be the result of collision of the Pelagonian, Apulian and Serbo-Macedonian microcontinents. Evidence for a S. Greek Neotethys as late as Upper Cretaceous time is provided by the presence of oceanic basalts and pelagic limestone cover, imbricated within a subduction/accretion complex (Ermioni Complex). In addition, the lowermost thrust sheets within the complex preserve a complete continental margin sequence to the Pelargonian continent during the Cretaceous. These rocks record the collapse of the continental margin during the southeast to northwest emplacement of the Ermioni Complex. By the Quaternary, the area has been affected by a phase of north-south extensional faulting and associated volcanism at Methana, related to post-Miocene subduction around the Aegean arc. This has produced a major east-west trending graben in central Argolis which is linked to a larger graben system in the Saronic Gulf to the north. The area is now tectonically inactive due to a shallowing of the Aegean Benioff Zone and a corresponding northerly migration of the volcanic arc, triggered by the arrival at the trench of thinned African continental crust.