A Miocene Palaeovalley Network in the Western Taurus (Turkey)
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Turkish Journal of Earth Sciences (Turkish J. Earth Sci.), Vol. 15, 2006, pp. 1-23. Copyright ©TÜB‹TAK A Miocene Palaeovalley Network in the Western Taurus (Turkey) OLIVIER MONOD1, CATHERINE KUZUCUO⁄LU2 & ARAL ‹. OKAY3 1 ISTO, UMR 6113, Université d’Orléans, 45067–Orléans, France (E-mail: [email protected]) 2 Laboratoire de Géographie Physique, UMR 8591, 1 pl A. Briand, 92195–Meudon, France 3 ‹stanbul Technical University, Eurasian Institute of Earth Sciences, Ayaza¤a, TR–80626 ‹stanbul, Turkey Abstract: Lower Miocene conglomerates in the Köprü and Manavgat basins contain pebbles that can be confidently traced back to their source areas, owing to their distinctive lithologies. Among others, are the green Hu¤lu volcanics (Late Trias), known only in allochthonous units from the Beyflehir region, or the Alanya blueschists, restricted to the Sugözü unit in the Alanya Massif. The problem is to find out how this detrital material could have travelled about eighty kilometres through the Taurus calcareous units during the Miocene. Fortunately, the present drainage system is not yet fully reorganised in the Taurus, and large areas of the chain still retain fossil morphologies. These may be seen in the upper karstic areas of the chain, where a large part of a high surface (1500–2200 m) is preserved. On this surface several dry valleys, some of them 400 m deep, with meanders and tributaries, have been recognised. They are disconnected from the present drainage, and represent fragments of a former network directed NE–SW, at right angles to the structures of the Taurus chain. The age of this network may be attributed indirectly to the Early Miocene. On the other hand, the presence of blueschist fragments in conglomerates of the Aksu Basin cannot be explained through a NE–SW-directed drainage system, and implies instead that the Alanya Massif extends to the west below the Miocene cover of the Antalya Gulf. Later, Late Miocene faulting fragmented the high surface and disrupted the drainage system. Uplift of the Taurus chain followed in the Pliocene and Quaternary, and is responsible for the extensive karstic circulation seen today, which left aside remnants of the ancient morphology of the chain. Key Words: fluviatile network, tracer pebbles, Miocene morphology, karst, Taurus, Turkey Bat› Toroslar'da Miosen Yaflta Bir Akaçlama Sistemi Özet: Köprü ve Manavgat havzalar›nda bulunan Alt Miyosen konglomeralar›n›n kaynak alan›n›n saptanmas›, çak›llar›n karakteristik litolojik özellikleri nedeni ile kolayd›r. Örne¤in, baz› çak›llar sadece Beyflehir bölgesindeki allokton birimlerden bilinen, Erken Triyas yaflta yeflil Hu¤lu volkanitlerinden, veya Alanya Masifi'nin Sugözü Nap›'nda tan›mlanan maviflistlerden oluflmufltur. Bu klastik malzemenin Miyosen'de Toroslar›n karbonat birimleri üzerinden akarsular ile nas›l 80 km tafl›nd›¤› önemli bir sorundur. Bu konuya ›fl›k tutabilecek bir gözlem, Toroslarda günümüz akaçlama sisteminin tam geliflmedi¤i ve genifl alanlarda akaçlaman›n fosil özellikler tafl›d›¤›d›r. Fosil akaçlama bilhassa Toroslar›n yüksek k›s›mlar›nda (1500–2200 m) korunmufltur. Bu yüzeylerde, yer yer derinlikleri 400 metreye ulaflan, yan kollar› bulunan menderesli kuru vadiler yer al›r. Bu eski vadiler modern akaçlama sisteminden izole olmufl, Toros da¤ silsilesi yönüne dik, KD–GB gidiflli eski bir akaçlama sisteminin art›klar›n› oluflturur. Dolayl› veriler eski akaçlama sisteminin yafl›n›n Erken Miyosen oldu¤unu gösterir. Köprü ve Manavgat havzalar›ndan farkl› olarak Aksu Havzas› konglomeralar›ndaki maviflist çak›llar›n› KD–GB gidiflli bir akaçlama sistemi ile aç›klamak mümkün de¤ildir. Aksu Havzas›ndaki maviflist çak›llar›n›n varl›¤›, Alanya Masifi'nin Antalya Körfezi Miyosen örtüsünün alt›ndan bat›ya do¤ru uzand›¤›na iflaret eder. Geç Miyosen'deki faylanma ile yüksek düzlükler parçalanm›fl, ve KD–GB gidiflli akaçlama sistemi bozulmufltur. Toros da¤ silsilesinin Pliyosen ve Kuvaterner'de tekrar yükselmesi sonucunda bugünkü kapsaml› karstik akaçlanma geliflmeye bafllam›fl, ve eski akaçlama sistemi ancak izole olarak baz› yüksek bölgelerde korunmufltur. Anahtar Sözcükler: akaçlama sistemi, k›lavuz çak›llar, Miyosen morfolojisi, karst, Toroslar, Türkiye 1 MIOCENE PALAEOVALLEY NETWORK, WESTERN TAURUS Introduction from three major fluviatile basins (Köprüçay River, In southern Turkey, Miocene deposits generally Manavgat River and Alaraçay River), whereas to the unconformably overlie pre-existing structures of Late north – the other base level – at about 1000 m altitude, Cretaceous to Late Eocene age (Blumenthal 1951; Gutnic corresponds to an endoreic depression in central Anatolia, et al. 1979; Koçyi¤it et al. 2000; fienel 2002). Within the where the Beyflehir and Su¤la lakes are situated. In western Taurus range, this disposition implies that a addition to these catchment areas, the drainage of a large period of exhumation and erosion occurred before the surface of the Taurus chain (HS in Figure 2) is not yet Miocene marine transgression, as shown by polymict connected to any organised surficial system. Due to this conglomerates which are usually present at the base of disposition, this high, isolated area is itself subdivided into the Miocene basins (Blumenthal 1951; Monod 1977, a number of closed depressions, and includes the two 1979). These conglomerates are irregularly distributed largest poljes (Kembos Ova and Eynif Ova, cf. Louis from Adana to Antalya and reflect a rugged topography 1956) of the chain. The high surface is almost entirely (Akay et al. 1985; Flecker et al. 1995; Ocako¤lu 2002). comprised of Mesozoic carbonates (Jurassic–Cretaceous) Clast composition suggests that the pebbles were and exhibits an intense karstic morphology. Surprisingly, generally derived from the surrounding mountains, although no organised drainage exists in this part of the typically made up of Mesozoic carbonates, or from Taurus, many large, dry valleys are present on the high overlying nappes, which often include ophiolitic rocks. In surface (Figure 3). As shown below, we suggest that most cases, however, the exact origin of the Miocene these fossil valleys are remnants of a former fluviatile pebbles cannot be assigned more precisely, owing to the network situated upon a Miocene erosion surface. ubiquity of neritic carbonates and the widespread distribution of ophiolitic units in the Taurus range. Only a The High Palaeosurface few particular lithologies can be recognised unambiguously among the pebbles, and these crop out in The general topography of the high surface (HS) of the such restricted areas of the western Taurus that it is Taurus, at present between 1500 m and 2000 m altitude, is rather smooth, albeit intensively karstic (cf. possible to identify their origin with a good precision. Nazik 1992; Ekmekçi 2003), but is not a structural Among them, the Precambrian diabases of Bozburun surface, as shown by the various underlying carbonate Da¤, red Carboniferous sandstones of Dipoyraz Da¤, formations ranging in age from Late Trias to Late metamorphic limestones and blueschists of the Alanya Cretaceous. Limiting the high surface, very steep slopes Massif and the green Hu¤lu volcanics (Trias) are excellent generally result from regressive and differential erosion source indicators (Figure 1). The problem is to find out or younger faulting (Figure 3). To the south, the Karpuz how these materials travelled across the Taurus chain River, the Alara River and the Manavgat River have early in the Miocene. The aim of this paper is to point out carved extremely steep gorges (over 1000 m deep) ancient morphological features still preserved in the through Mesozoic carbonates, demonstrating the young western Taurus and, with the help of these markers, to uplift of the Taurus chain. The Manavgat River, in reconstruct and date the river network which brought particular, flows down through three deep gorges, and detrital material from the Miocene catchment areas down near Üzümdere village a sharp bend at a right angle to the to the Antalya Basin. NW probably reflects a former capture (Figure 2). To the northeast, the high karstic surface is limited by high Evidence for Fossil Morphological Features calcareous cliffs above Seydiflehir (Figure 3), which Preserved in the High Western Taurus probably reflect an important fault line, as suggested by Birot & Dresch (1956). Last but not least, Miocene to The Present Drainage System Recent normal faulting has uplifted or lowered parts of Superficial drainage in the western Taurus exhibits many the Taurus chain and has thus fragmented this surface, irregularities, showing that its evolution is far from which rises to 2250 m in Burmahan Da¤, but disappears complete. A simplified topographical sketch (Figure 2) at 1100 m under Pliocene sediments along Beyflehir Lake. shows five major drainage basins, with two different base Thus, owing to the importance of Pliocene–Quaternary levels: to the south, the Mediterranean receives water erosion and tectonics (cf. Koçyigit & Özacar 2003) only 2 O. MONOD ET AL. 31° 00' 30° 30' 31° 30' Ýstanbul Anamas Dað TurkeAnkaray Beyþehir ISPARTA Lake BD Western v v Taurus Beyþehir Lycian Eastern v Taurus Taurus Central AN Taurus LN Dipoyraz AN Dað 0 km 200 BHN AA Bozburun T. v BD AKSU THRUST a Kasýmlar AKSU BASIN 37° 30' HUÐLU 37° 30' UNIT Seydiþehir Sarýalan o v Suðla Lake KÖPRÜÇ KÖPRÜÇ KÖPRÜÇ AN AA BD AN AY AY AY BAS AY AY BAS AY BHN Section + (Figure 13) + BASIN BHN IN IN Ýbradi Yarpuz * KIRKKAVAK FAULT HUÐLU ? Eynifova PEBBLES P PATHWAYS 37° 00' P Akseki 37° 00' ? AA * Sevinç Serik AN MANAVGAT BASIN ANTALYA Kepez t AN