Keryneia Terrane

The Keryneia Range is the northernmost geomorphological feature of Cyprus, comprised of a series of narrow, steep-sided mountains stretching from Kormakitis in the west to Apostolos Andreas in the east. The altitude of the range varies from 700 to 1024 m and the highest peak is Kyparissovounos. To the north, this rugged range is separated from the sea by a 5-kilometer narrow terraced coastal plain, while to the south it is flanked by the broad lowland of the Mesaoria plain.

The three main geological formations of the Keryneia Range, aged between 250 to 135 million years, are the Dhikomo, Sykhari, and Agios Hilarion Formations, which form the main carbonate masses of this Range (also known as the Pentadaktylos Range). These carbonate masses formed in a shallow marine environment on the slopes of a continent, which existed south of the current location of Cyprus. During the Triassic (220 million years ago) the northern slopes of this continent, were fragmented into blocks of hundreds of kilometers in size. These continental fragments were separated by the newly formed Neotethyan Ocean, most of which were destroyed between 90-10 million years ago. The remaining continental fragments were attached to younger sediments, creating a geological mosaic that characterizes the geology of Greece and Turkey. Cyprus is the southernmost part of this mosaic, where limestone fragments of the Dhikomo, Sykhari and Agios Hilarion Formations were thrust southward towards their present position, over the younger autochthonous marine sediments, which are known as the Lapithos, Kalogrea-Ardana and Kythrea Formations, approximately 10 million years ago. These limestone fragments are described as allochthonous rocks, a term used to describe rocks that were transported from their place of origin due to tectonic activity. Impressive and continuous outcrops of limestones occur in the central part of the Range, whereas in the eastern part they occur in the form of olistholiths of the Kantara Formation over younger sediments.The Kantara Formation consists of brown to yellow-brown, massive, hard fine-grained limestones, which are exposed at the easternmost part of the Pentadaktylos Range between the villages of Lefkoniko and Eptakomi. The largest olistholiths have a width and thickness in the order of 200 meters and a length of about 1.5 kilometers. Based on microfossils, some limestone olistholiths are of Permian age (280-230 million years ago) and constitute the oldest rocks on Cyprus.

The Dhikomo Formation consists of deformed thin to thick-bedded limestones (marbles), which in places are micaceous, with intercalations of grey to green phyllites. The mean bed-thickness, ranges from a few millimeters up to 3 meters, while their color is usually black with calcite veins, however white and yellow beds are also reported. The rocks of this formation are considered to be the base of the Mesozoic limestone series. Their contact with the overlying Sykhari Formation rocks is tectonic, making their stratigraphic correlation unclear. The thickness of the formation varies from 20 to 100 meters.

The Sykhari Formation consists of massive to thick-bedded dolomitic limestones of light to dark grey color. The rock texture varies from fine to coarse-grained crystals, depending on the degree of the tectonic deformation. Along faults and thrust zones, the rocks are highly fragmented and difficult to distinguish. At highly brecciated zones, the rocks appear like coarse-grained sandstones with a low degree of cementation. The undisturbed rocks exhibit a fine-grained porcelaneous texture, resembling that of the lithographic limestone. From the study of thin sections from the basal fine-grained dolomitic limestones, small, thin-shelled ostracoda of Mesozoic age were identified, indicating a shallow brackish marine depositional environment. The Sykhari Formation is exposed on the southern flank of the central part of the Pentadaktylos Range. Based on the fossils record, its stratigraphic position and the presence of similar rock formations in neighboring countries, the age of the Sykhari Formation is considered as Jurassic (200-140 million years).

The Agios Hilarion Formation consists of greyish-blue to white medium-bedded to massive limestones, which were subjected to a very low degree of metamorphism. The white limestones, are observed at the highest stratigraphic horizons of this formation and are usually laminated. In comparison, the lower stratigraphic horizons are comprised of greyish-blue medium-bedded limestones, with small elongated and tubular occurrences of the algae species Cladocoropsis, which indicate a Jurassic age (200-140 million years ago). These are the only fossils that were identified, while other tubular forms probably represent non-distinctive coral remains. Locally, limestones are brecciated but less tectonized than those of the Sykhari Formation. The thickness of the Agios Hilarion Formation is estimated between 100 to 200 meters. The age of the formation based on the presence of the fossil Cladocoropsis, its stratigraphic position and the comparison of its rocks with similar formations in neighboring countries, is considered between Jurassic to Early Cretaceous (200-130 million years ago).

The Lapithos Formation consists of light-yellow crystallized chalks and breccia, red to pinkish shales as well as chalk with cherts. Intervening pillow lava flows are also observed but not to a big extent. Breccia deposits are locally observed with a thickness of up to 200 meters. From Late Cretaceous (67 million years ago) up to Eocene (38 million years ago), the sediments of the Lapithos Formation in the Pentadaktylos Range were intensively deformed, before the deposition of the clastic sediments of the Kalogrea-Ardana Formation, which are partially chronologically correlated with the sediments of the Lefkara Formation.

The Kalogrea-Ardana Formation is mainly exposed around the area of the homonymous villages and extents from the village of Bellapais up to the Aigialousa village. This formation unconformably overlies the highly deformed sediments of the Lapithos Formation or other formations of the geotectonic zone of Keryneia. The base of the Kalogrea-Ardana Formation consists of a thick recrystallized breccia, made up of mainly angular fragments of older limestones, chalks and lavas within a calcareous matrix. Among other rocks, the breccia may contain fragments of amphibolite, mica schist and schist with talc. The breccia passes upwards to carbonate sedimentary facies, while the uppermost horizon is flysch consisting of sandy facies. The carbonate facies consist of sandy marls, marly chalks and chalks, alternating with breccia from limestone fragments within marls. The sandy facies are flysch deposits, consisting of intercalated layers of coarse sands, sandstones and marls with common interlayers of white limestone breccia. Another characteristic feature of the Kalogrea-Ardana Formation is the presence of a large number of limestone olistoliths of the Kantara Formation. The Kalogrea-Ardana Formation has an estimated maximum thickness of about 670 meters and its age is considered as Late Eocene (40 million years ago).

During the Late Eocene epoch, an elongated east-west trending trench developed on the northern flanks of the Troodos geotectonic zone. Along the southern limits of this trench, carbonate sediments were deposited. At its northern boundaries, which were unstable and continuously changing, periodical displacements of material induced by gravity, resulted in the creation of olistoliths and the deposition of clastic sediments. Simultaneously, turbidite flows (gravity flows) transported material from the eastern and western flanks of the trench, forming the flysch. It is considered that a number of small islands had emerged within the trench that existed north of the present location of the Pentadaktylos Range, in which more than 2.000-meter-thick sandy sediments (flysch deposits) were accumulated. Along both slopes of the Pentadaktylos Range, folded sandstones, siltstones and marls of substantial thickness are exposed. The thickness of these sediments is estimated to be 2.5 kilometers in the area of the Lefkoniko village. The sediments of the Kythrea Formation, also known as Kythrea flysch, were deposited during the Middle Miocene in the elongated trench that existed north of Troodos. At the southern boundary of this trench, the Kythrea flysch is intertwined with the sediments of the Pakhna Formation. Even if Oligocene to Early Miocene sediments are not found on the Keryneia Range, it is possible that the Kalogrea-Ardana Formation covers this period as well. The northern boundary of this trench is currently situated under the sea of Keryneia.

The Kythrea flysch is conformably overlain by 120-meter-thick deposits of chalks and marls with gypsum layers on top. In the Pentadaktylos Range, the Lapatza Formation and especially its upper stratigraphic horizons can be chronologically correlated with the Kalavasos Formation. The Upper Miocene is not only considered as the period of the evaporites deposition, but it is also the geological period when the Pentadaktylos Mountain Range was thrust to its present position. This thrusting and related folding of the Miocene rocks of the Pentadaktylos Mountain Range (Kythrea and Lapatza Formations) continued up to the Pliocene.

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