Tectonic-sedimentary evolution of the Girne (Kyrenia) Range and the Mesarya (Mesaoria) Basin, North Cyprus
McCay, Gillian Anna
The Eastern Mediterranean marks the site of the Southern Neotethys Ocean that was created, then largely destroyed near the northern margin of Gondwana. Sedimentary and structural evidence is well preserved in the Girne (Kyrenia) Range, a several hundred kilometrelong, narrow, E – W-trending, broadly arcuate lineament that encompasses northern Cyprus and a submarine ridge that links southeastern Turkey (Misis–Andırın Complex). This study focuses on the Oligocene-Miocene sequence exposed on both flanks of the Girne (Kyrenia) Range, based on sedimentology, microfacies, Sr-isotope dating and structural analysis. Two related sedimentary basins are today separated by an E – W-trending high-angle, fault zone, the Değirmenlik (Kythrea) Fault. The northern basin encompasses the Range, whereas the southern basin is located between the Değirmenlik (Kythrea) Fault and an E – W trending fault lineament (Dar dere (Ovgos) Fault Zone), to the south of which is the Troodos Ophiolitic Massif. The Değirmenlik (Kythrea) Fault is interpreted as a convergence-related thrust fault that was active during the Mid-Late Miocene creating an E – W submarine ridge that separated subbasins to the north and south. The sedimentary sequence in the northern basin unconformably overlies Mesozoic platform carbonates and latest Cretaceous-Palaeogene pelagic carbonates with interbedded volcanics. Above basal conglomerates (probably derived from underlying Eocene debris flows based on chemical evidence), there is a fining-upward siliciclastic turbidite sequence (Late Oligocene), then biogenic calciturbidites and marls (Aquitanian-Langhian). The northerly basin is characterised by thin-, to medium-bedded, pale hemipelagic calciturbidites and marls (Serravallian; ~400 m thick), overlain by thick-bedded, medium- to coarse-grained lithic sandstones with carbonate concretions (Tortonian; ~250 m thick). The succession in the southern basin, which is more deformed by thrusting, begins with poorly dated pelagic marls (Early Miocene?), followed by regularly bedded siliciclastic turbidites (~1000 m thick), with abundant sole structures (Serravallian-Tortonian). Palaeocurrent evidence shows mainly E to W flow for the southern basin, and locally a generally E to W flow for the northerly basin, at least for the Late Miocene. Gypsum accumulated in local depocentres during the Messinian salinity crisis and was locally deformed by contemporaneous southward thrusting. Petrographic studies of the Serravallian – Tortonian sandstones indicate that the northern basin is richer in recrystallised limestone grains compared to the southern basin, which contains more abundant siliciclastic and ophiolite-derived material; this trend is also present in results from XRD analysis of clays. The likely source area was the Eurasian-African suture zone in the Tauride Mountains to the northeast. The greater detrital limestone abundance in the south may record relatively deep-level erosion of the source area, through ophiolites to an underlying Mesozoic carbonate platform. Two phases of clastic input are recognised from SE Turkey, the first related to Early Miocene continental collision, and the second reflecting Late Miocene suture tightening, both to the east of Cyprus within the Tauride Suture Zone. Based on the measurement and kinematic analysis of a large number (>1290) of faults, combined with a knowledge of the tectono-stratigraphy, the timing and nature of faulting is inferred. The majority of the faults are south-verging, high-angle reverse faults, while sinistral strike-slip faults dominate several areas of the Girne (Kyrenia) Range and the Dar dere (Ovgos) Fault Zone of the south. Most of the faults in the Girne (Kyrenia) Range are attributed to Mid – Late Eocene and Late Miocene – Early Pliocene phase of thrusting, followed by relative quiescence until Pleistocene uplift of the Girne (Kyrenia) Range. The Dar dere (Ovgos) Fault Zone is interpreted as a long-lived terrane boundary that accommodated sinistral movement during Late Miocene to Recent. In summary, the Girne (Kyrenia) Range reflects the diachronous closure of the Mesozoic Southern Neotethys Ocean, culminating in westward tectonic escape from continent-continent collision zone to the east, coupled with thick-skinned uplift that was triggered by collision with a crustal block to the south, the Eratosthenes Seamount.