Antalya Nappes Research Articles

Origin and Evolution of Turkish blocks during the Late Triassic from magnetostratigraphic data

A palaeomagnetic and magnetostratigraphic study has been carried out on lower Carnian and Norian rocks (Late Triassic) from four different sections of two different units of the Upper Antalya Nappes in the Taurus region of southwestern Turkey, the Bakirli Dag unit and the Kaymaz Dag unit. The origin of these nappes is uncertain and under debate. This study provides well defined directions of probable primary origin and good magnetostratigraphic correlations between the different sections, which allows us to propose a palaeogeographic interpretation. The Bakirli Dag unit of the Upper Antalya Nappes were located at a palaeolatitude of 6.9°N ± 1.5° during the early Carnian and at 10.2°N ± 1.0° during the latest Carnian-middle Norian. This slight northward movement is accompanied by a large clockwise rotation (29.5° ± 6.7°) which may correspond to an important breakup-phase of the north African margin during middle-late Carnian time. The palaeo­magnetic results from the Kavur Tepe section of the Kaymaz Dag unit, previously considered to belong also to the Upper Antalya Nappes, show a palaeolatitude of 17.4°S ± 1.1° during Norian time. This result surprisingly indicates that this unit was located in the vicinity of the northern Indian margin during the Late Triassic.

Obduction-related ophiolitic polymict breccias covering the ophiolites of Antalya (southwestern Turkey)

The ophiolites of the Antalya nappes, cropping out in the area of Kemer (southwestern Turkey), are capped by a spectacular detrital sequence composed of various ophiolitic breccias whose total thickness reaches 1000 m. Four main formations have been distinguished within the breccias. The basal formations are in depositional contact over the previously tectonized and eroded deepest part of the ophiolites. The upper breccias are dated as middle Maastrichtian, which is the age of the deposition of synchronous serpentinitic olistostromes onto the continental margin. These data suggest that the breccias formed as debris slides from bathymetric highs on the ocean crust as a result of renewed tectonic activity accompanying ob-duction onto the continental margin.

Hydrothermal alteration of submarine basalts : from zeolitic to spilitic facies in the upper Triassic pillow-lavas of Antalya, Turkey

The upper Triassic alkalic basalts of the Alakir Çay valley (Antalya nappes, Turkey) have been hydrothermally metamorphosed under the zeolite facies conditions. Two of these submarine volcanic massifs, mainly made of pillow-lavas flows, offer good field sections over more than 650 m thick. In the Çalbali Dag massif, the zeolite and associated minerals have been analyzed inside and outside the pillow-lavas (inter-pillow matrix), from bottom to top of the volcanic pile. Natrolite, gonnardite, thomsonite, analcite, gmelinite, stilbite, heulandite and laumontite have been determined, associated with calcite, K-feldspar, celadonite, smectites and chlorite. No evolution of the zeolite assemblages with depth has been detected : this fact implies a rather smooth thermal gradient in the volcanic pile during the hydrothermal circulation. In the Sayrun massif , the same widespread development of zeolites, calcite and smectite is observed, with the addition of true albite-chlorite spilitic paragenesis, well developed in some areas. The reality of a progressive transition from zeolitic assemblages to spilitic ones is an important conclusion of this study.

Le volcanisme alcalin du sud-ouest de chypre et le probleme de l'ouverture des regions tethysiennes au trias

An important volcanism of Late Triassic age is known from SW Cyprus. It occurs in the Mamonia nappe system emplaced during the Late Maastrichtian. Three main volcanic episodes interbedded with detrital and pelagic sediments can be seen from the base to the top: 1. (1) pyroclastic rocks (breccias, tuffs) associated with coarse-grained sandstone, suggesting explosive eruptions in grabens 2. (2) basaltic or andesitic pillowed flows, interbedded first with fine-grained sandstone and small Halobia limestone strata, then with pelagic limestones and radiolarian red cherts 3. (3) columnar trachyte flows. The whole volcanic series belongs to a very differenciated sodic suite with high titanium contents. The Mamonia lavas are very similar to the Afar volcanics and can be considered as belonging to an interplate volcanism in a rift system. This alkaline basaltic suite is found in many places of the East Mediterranean Alpine orogenic domain, especially in the Antalya nappes (South Turkey) and in the Baer-Bassit (Syria). In Greece, a similar volcanism has been noticed (Othrys—Pindos). In Italy there exists a Middle or Late Triassic volcanism with alkaline affinities. Therefore, this Late Triassic magmatism, which is widespread in the whole Mediterranean Alpine region and always in tectonic association with ophiolites, has a very great paleogeographic significance. We thus propose the existence of a rift system associated with an alkaline basaltic suite along the northern edge of the African plate during Norian—Carnian times. Afterwards a mid-oceanic ridge would have been formed during the Jurassic and Cretaceous. To explain this evolution two hypotheses can be proposed: 1. (1) A single mid-Tethysian ridge existed and all the ophiolites (Greece, Turkey, Cyprus, the ‘croissant ophiolitique peri-arabe’) have been thrust from the same area. 2. (2) A marginal sea existed along the mid-Tethysian ridge north of the African plate but separated from the Tethys by a carbonate shelf, where, after the Triassic events, oceanization began with slightly different ophiolites (a large sheeted complex, low-K tholeiites with some calc-alkaline affinities). Therefore, Troodos, Hatay, Zagros and Oman would not have come from the main ophiolite zone present further north, but from a marginal ocean, now obducted on the African plate. We think that the second hypothesis is more reasonable because the Upper Cretaceous sedimentary cover (Kannaviou Formation) of the Troodos is very similar to the detritic formation present in South Turkey (Kastel Formation) which is known to grade to shelf carbonates belonging to the Arabian plate towards the south.