Sedimentary response to the tectonic uplift of the Kyrenia Range, northern Cyprus, in its Eastern Mediterranean tectonic setting
Palamakumbura, Romesh Niranjan
The Kyrenia Range forms part of an approximately east-west lineament extending from northern Cyprus to southern Turkey. During Plio-Pleistocene the northern Cyprus segment of the lineament uplifted to ca. 1000 m above modern sea level. Plio- Pleistocene sediments document the uplift of the Kyrenia Range. A combination of sedimentology and a range of dating techniques including uranium series, optical stimulated luminescence (OSL), strontium isotopes and magnetostratigraphy are used to help understand the geological processes controlling uplift. Shallowing from a deepmarine basin to a shallow-marine, cool-water carbonate ramp represents the earliest uplift of the Kyrenia Range. The base of the carbonate ramp is made up of thick-bedded, benthic foraminiferal-rich grainstones, which are discontinuously overlain by calcareous red algal-rich rudstones. Erosively overlying this sequence is a coral- and molluscrich conglomerate, representing a short-lived relative sea-level fall. The upper part of the carbonate ramp sequence is composed of cross-bedded grainstone representing a shoreface environment. Interbedded with the upper grainstone facies are occasional fluvial conglomerates. The shallowing-upward marine environment represents the earliest emergence of the Kyrenia Range. After a major break in deposition, six marine and non-marine terraces (K0 to K5) reflect the sedimentary response to the main phase of tectonic uplift of the Kyrenia Range. The K0 terrace, the oldest and highest terrace, is composed of megabreccia and is interpreted as representing a major phase of rapid tectonic uplift. The K2-K5 terraces form a series marine to non-marine terraces on the northern flank of the range and also non-marine terraces on the southern flank of the range. The terraces on the northern flank each begin with a major marine transgression followed by a regressive sedimentary sequence. Marine environments range from nearshore open-marine below the storm-wave base, to shoreface, foreshore (beachrock), and backshore lagoonal environments. The non-marine environments range from aeolian dune to fluvial drainage systems. The fluvial systems are characterised by channelised debris-flow deposits interbedded with mudstones and palaeosols. The non-marine deposits on the southern flank of the range comprise a series of fluvial drainage systems. The fluvial systems on the southern flank of the range comprise a mixture of planar-bedded and channelised conglomerates, mudstones and aeolianites. Portable luminescence data are used to correlate quantitatively the K4 and K5 terraces on both the northern and southern flanks of the range. Each of the K4 and K5 terraces produce a unique luminescence signal, which is used as the basis for correlating the lower terraces. The unique luminescence signals of the K4 and K5 terraces are likely to be caused by varying sedimentary histories of the quartz and feldspar grains within the two terraces. The shallow-marine environments surrounding the Kyrenia Range prior to major uplift were dated using strontium isotopes and palaeomagnetism. The results of this dating suggest that marine environments persisted throughout the Early Pleistocene. U-series and OSL dating were used to date the K4 and K5 terraces on the northern flank of the range. The U-series results indicate that the marine deposits of the K4 terrace formed during several Middle Pleistocene interglacial stages. The OSL dating shows that the aeolian dunes of the K5 terrace formed during a Late Pleistocene glacial stage. The formation of the K2-K5 terraces was controlled by the interaction between tectonic uplift, climatic change and global eustatic sea-level change. The basal marine deposit of each terrace formed during an interglacial stage. Major fluvial deposition also occurs during the interglacial period as a result of a wetter climate. The inter-glacialglacial transition resulted in major fluvial erosion as a result of falling global sea-level. Aeolian carbonate deposition was dominant during the glacial stage, which represent arid climatic conditions. The only exception to this is the K4 terrace, which represents three glacial stages. The K1-K3 terraces can be correlated with the global sea-level curve suggesting approximate ages for each terrace, and ca. 600 ka for the entire K1- K5 terrace sequence. The Kyrenia Range underwent rapid uplift during the late Early Pleistocene at >1.2 mm/yr, followed by continuous but slower uplift during the Middle to Late Pleistocene. These results indicate that the uplift occurred in tandem with the Troodos Massif in southern Cyprus. The driving mechanism of the uplift of the Kyrenia Range is likely to be related to the collision of the Eratosthenes Seamount with the Cyprus trench to the south of the island. The seamount-trench collision resulted in compressional tectonics around Cyprus within the large-scale tectonic setting resulting from the early stages of convergence of the African and Eurasian plates.