Tectonic and sedimentary response to oblique and incipient continental - continental collision the easternmost Mediterranean (Cyprus)
Kinnaird, Timothy C.
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The main objective of this work was to understand fundamental processes related to incipient continental collision through studying the tectonostratigraphic evolution of Cyprus, in its Easternmost Mediterranean context. This was achieved by compiling structural, sedimentological and stratigraphic evidence from Late Cenozoic to Recent sequences, and by applying palaeomagnetic and luminescence methods of dating. In particular, the basin-fill of the Neogene basins provides a temporal and palaeogeographic control to interpret syn-depositional and post-depositional structural assemblages. Four neotectonic deformation phases are recognised. The Polis and Pissouri Basins originated as Tortonian depocentres in response to syn-depositional W-E/WSW-ENE D1 extension. The Maroni Basin originated as a Tortonian depocentre in response to syn-depositional NW-SE D1 extension. The difference in extension direction between west and south-central Cyprus is attributed to the curvature of the Cyprus Arc. The Middle - Late Pliocene D2 extensional/transtensional phase re-orientated the Neogene basins and resulted in syn-depositional NW-SE extension. A kinematic change occurred at ~3 Ma, attributed to the collision of the Eratosthenes Seamount with an active trench, the ‘Cyprus Arc’. Early Pleistocene to Recent D3a transpression generated strike-slip faulting along E-W trends, conjugate left-lateral NNE-SSW-trending and right-lateral NNW-SSE-trending strike-slip faults and reactivated Tortonian D1 NW-SE and NE-SW structures. Middle Pleistocene to Recent D3b compression produced intense NE-SW contractional deformation orientated along NW-SE trends. Optically stimulated luminescence (OSL) dating was used as a tool to constrain the D3a/D3b events, by generating a chronology for their associated sediments. D3 transtensional lineaments originated in the early Pleistocene (174.1 ± 20.9 ka < D3a < 76.6 ± 16.43 ka), and are still active today (Cape Kiti: 38.1 ± 13.2 ka < D3a < 12.1 ± 0.1 ka). D3 compressional lineaments originated in the middle Pleistocene, and were still actively growing at 76.8 ± 31.6 ka. To constrain the timing of regional uplift in south and central Cyprus, a magnetostratigraphy was generated for the Plio-Pleistocene units of the Pissouri and Mesaoria Basins. The results indicate that rapid uplift began in the latest Pliocene (c. 2.14 – 1.95 Ma), coincident with the large-scale progradation of Gilbert-type fan deltas into the Pissouri Basin, and the incursion of large fluvial networks into the Mesaoria Basin. In light of the new evidence, three alternative models for the Early Cenozoic to Recent tectonostratigraphic evolution of Cyprus are considered: model 1, subduction/incipient collision; model 2, advanced collision; and model 3, transpression. Some difficulties exist in detail, with all three models. However, at present the working hypothesis is as follows: areas to the east of Cyprus (Syria, S Turkey) were in a collisional setting from Mid-Miocene time onwards. Cyprus remained in an oceanic embayment (Levant Sea) further west and subduction continued during Miocene time. Compressional processes may have been active at depth during this time. Southward extension (trench roll-back) was taking place at a high structural level in S Cyprus, as with many other convergent margin settings (e.g. SW Peloponnese; Aleutians; Sunda arc). Subsequently, the collision of the Eratosthenes Seamount with the Cyprus Arc obstructed subduction and initiated rapid uplift of the Troodos Massif. The initial manifestation of this kinematic change was the generation of E-W-trending strike-slip faults and the development of conjugate left-lateral NNE-SSW-trending and right-lateral NNW-SSE-trending strike-slip faults. Transpression resulted in the reactivation of D1/D2 E-W, NE-SW and NW-SE structures. Subsequent deformation is documented in a compressional lineament in SW Cyprus. In addition, the over-riding plate in southwest Cyprus still appears to be undergoing gravity spreading outwards from the developing collision zone.