Alternative models for the late Cenozoic tectonostratigraphic evolution of Cyprus: New evidence from southern Cyprus.
Inaugural International Meeting of IGCP 518: Fluvial sequences as evidence for landscape and climatic evolution in the Late Cenozoic., (2005)Аннотация
The neotectonic setting of Cyprus is controversial and several models exist including, (i) subduction/incipient collision, (ii) advanced collision and (iii) transpression. In the first model, a subduction zone, commonly referred to as the Cyprus Arc, is believed to exist between the Eratosthenes Seamount and the south coast of Cyprus. Subduction in its present setting was initiated in the Mid-Miocene (c. 15Ma). Extension in the overlying plate, forming the Polis and Mesaoria Basins, was caused by retreat of this trench. The Eratosthenes seamount is believed to have collided with the arc in the Pliocene (c. 3Ma); this obstructed subduction and initiated rapid uplift of the island.
In a second interpretation, a series of south-verging, thick-skinned linked imbricate thrusts are believed to occur at depth in the forearc region of the Cyprus arc, between the Kyrenia Range in the north (i.e. the Kyrenia fold/thrust belt) and the Eratosthenes Seamount in the south (i.e. the ‘Paphos Thrust’). It is argued that the present thrust geometry was initiated in the Eocene (c.45 Ma); when imbricate thrusting developed in the forearc region, forming the ‘Troodos-Larnaka culmination’. In this model, the Mesaoria Basin evolved in the Miocene to Pliocene as a piggy-back basin.
In a third hypothesis, a system of left-lateral faults are inferred between two restraining blocks; the Kyrenia Range in the north and the Eratosthenes Seamount in the south. In this model late Miocene tectonism was dominated by transpression. Cyprus is envisaged as being extruded westwards, similar to (and related to) the escape tectonics, resulting in the Anatolian Plate motion.
To test these tectonic models we are currently investigating the structural and sedimentological evolution of southern Cyprus, during the Neogene-Recent. We have found that sedimentation since Late Miocene time was in structurally controlled depressions/basins, elongated NNW-SSE; consistent with a localised WSW-ENE extensional tectonic regime. Geophysical evidence (focal earthquake mechanisms, seismic tomography) suggests that collision is nowadays occurring at depth beneath Cyprus. However, at a higher structural level our data are consistent with gravity spreading outwards from the developing collision/’subduction’ zone. The argument that southern Cyprus, specifically, has been in a syn-collisional setting since the Mid-Miocene is not been supported by our studies. Evidence for this model apparently came from the appearance of Troodos ophiolite-derived conglomerates within latest Miocene non-marine facies (Lago Mare facies) in SW Cyprus. However, detailed sedimentary logging, facies analysis and geomorphological studies indicate that these conglomerates are instead terrace deposits of Early-Mid Pleistocene age (when by general agreement collision-related uplift was taking place). Other reported evidence for the ‘collisional’ models is inferred compression-related thrusting in SW Cyprus (i.e. “Paphos thrust’). However, this deformation could also relate to high-level extensional gravity tectonics. Our present view is that southern Cyprus continues to undergo WNW-ENE extension related to the southwest-ward retreat of the Cyprus active margin in a regional setting of incipient continental collision.