The Amanos–Elazığ–Van Suture Belt (Göncüoğlu, 2010 and Göncüoğlu et al., 1997) in SE Turkey is represented by an almost 700 km long and 70 km wide zone (Fig. 1 and Fig. 2). The oceanic assemblages of the suture belt are accreted between the continental crust units and/or their metamorphic equivalents. The northerly-located piece of continental crust represents the metamorphosed S margin sediments (the Malatya–Keban Metamorphics) of the Tauride–Anatolide Platform. The southerly located one, known as the Bitlis–Pütürge Metamorphics, on the other hand, stands for the northern margin of the Arabian Platform in the south (Göncüoğlu and Turhan, 1984). These continental crusts are believed to be separated from each other by the opening of the southern Branch of Neotethys during the Upper Permian–Lower Triassic period. By this, the pre-rifting successions of both units are very similar and the differences in stratigraphy concern their Mesozoic cover.

The remnants of the Southern Neotethys Ocean is found today as nappes and slide blocks of oceanic lithosphere origin together with rocks derived from oceanic islands, and island arcs forming a huge mélange complex. The accretion of the oceanic units was mainly realized at the end of Cretaceous. However, ongoing convergence along the suture belt at the end of Miocene resulted in an imbricated structure, where rock packages of syn -to post-accretional basins were also incorporated into the suture complex.

In the area between Malatya and Elazığ (Fig. 2), the mantle rocks of the oceanic lithosphere are best represented by the Guleman Ophiolite and its equivalents that occur as ultramafic bodies of variable sizes within the mélange complexes. The Guleman Ophiolite comprises its lower part abundant peridotites against lherzolites with podiform chromites and plagiogranites. Another body in Kömürhan consists of a very thick sequence (> 1 km) of ultramafic cumulates followed by massive and cumulate gabbros (Robertson, 2002). Geochemically, the Guleman Ophiolite is characterized by depleted mantle composition and its REE-patterns indicate to supra-subduction setting (Bağcı et al., 2005, Beyarslan and Bingöl, 2000, Parlak et al., 2004, Robertson, 2002 and Robertson et al., 2007).

The crustal rocks of the Southern Neotethys are named as the Yüksekova Complex (Perinçek, 1979) and attributed (e.g., Yazgan, 1984 and Yazgan et al., 1983) to the remains of an “ensimatic arc”. The intra-oceanic arc or supra-subduction character of the Yüksekova volcanic rocks have been confirmed by several recent geochemical studies (e.g., Parlak et al., 2009, Rızaoğlu et al., 2009 and Robertson et al., 2007). The name “Elazığ Magmatics” has been used in the last years (e.g., Beyarslan, 2005, Beyarslan and Bingöl, 2000, Bingöl and Beyarslan, 1996 and Turan and Bingöl, 1991) for the same oceanic assemblage to include also plutonic and volcanic rocks of granodioritic-tonalitic-dacitic composition intruding them.

The Yüksekova Complex is made of massive/pillowed lavas and dykes associated with volcano-clastics, green and red mudstones and radiolarian cherts (Fig. 3). It locally shows several hundred meters thick, continuous and undisturbed successions. More commonly, however, the volcanic and sedimentary lithologies are blocks, embedded in a chaotic mélange, displaying both tectonic (Fig. 3a) and depositionary (Fig. 3c–g) contacts. Individual chert and/or micritic limestone sequences within the volcanic-volcanoclastic units are up to 3 m thick, brick red–violet in color and may comprise decimeter-thick radiolarian cherts alternating with micritic limestones and green–red mudstones.

The most common block types are the pillow lavas (Figs. 3b–e, g) with intra-pillow radiolarian cherts and mudstones, which were sampled to study their geochemical characteristics. The pillow lavas are variably altered and cut by diabase dykes. They include calcite- and zeolite-filled vesicles at the rim of the pillows. Petrographically, they are mainly basaltic in composition, and show tholeiitic to tholeiitic calc-alkaline transitional character (Ural, 2012 and Ural et al., 2013). The petrological evaluation of about seventy samples of the Yüksekova volcanic rocks reveal two different compositional groups (Fig. 4) with characteristic features of supra-subduction setting. The detailed evaluation of these compositional groups by trace and rare earth elements (REE) is published in another study (Ural et al., 2014). The evaluation suggests that the first compositional group (Group I) should be considered as product of a back-arc system and the second one (Group II) as representative of the arc-intra arc volcanism. Obviously, both types were developed above an intra-oceanic subduction within a convergent setting. From a large number of radiolarian cherts and mudstones collected from the Group I volcanic rocks of the Yüksekova Complex, only two samples (for sample locations see Fig. 2) yielded radiolarians with an age range of upper Cenomanian to Lower Turonian. The age of the radiolarians obtained from seven chert samples associated with pillow lavas of Group II, on the other hand, range between Lower Coniacian to Lower Maastrichtian.

From the Yüksekova Complex several rock samples obtained from different locations (see Fig. 2 and Table 1 for coordinates) are productive for radiolarians. Oldest radiolarian assemblage [Patellula verteroensis (Pessagno)] (Fig. 5.1), Dactyliosphaera sp. (Fig. 5.2), Pseudodictyomitra pseudomacrocephala (Squinabol) (Fig. 5.3), Pseudodictyomitra tiara (Holmes) (Fig. 5.4), Thanarla veneta (Squinabol) (Fig. 5.5) and Dictyomitra formosa Squinabol (Fig. 5.6) have been determined from 09-SIV-5. Although many taxa have long ranges, the age of the sample is assigned as Upper Cenomanian (Fig. 6) based on the FAD of Patellula verteroensis at the base of Upper Cenomanian and LAD of Thanarla veneta at the top of Upper Cenomanian (Bragina, 2004, O’Dogherty, 1994, Pessagno, 1963 and Pessagno, 1977).

Radiolarian assemblage of sample 09-SC-3 is very similar to those of obtained from sample 09-SIV-5 and characterized by Alievium sp. (Fig. 5.7), Pseudoaulophacus aff. putahensis Pessagno (Fig. 5.8), Patellula verteroensis (Pessagno) (Fig. 5.9), Crolanium sp. (Fig. 5.10), Pseudodictyomitra pseudomacrocephala (Squinabol) (Fig. 5.11), Ps. tiara (Holmes) (Fig. 5.12). Based on the studies of Pessagno (1977), O’Dogherty (1994) and Bragina (2004), Patellula verteroensis appears for the first time at the base of Upper Cenomanian and Pseudodictyomitra pseudomacrocephala last appears at the top of Lower Turonian. Presence of these two taxa clearly reveals the Upper Cenomanian to Lower Turonian age for the sample 09-SC-3 (Fig. 6). These two samples (09-SIV-5 and 09-SC-3) are in primary relation with lavas that were geochemically incorporated into Group I (Fig. 4).

Sample 09-KV-4 includes three important and characteristic radiolarian taxa [Alievium gallowayi (White)] (Fig. 5.13), Patellula verteroensis (Pessagno) (Fig. 5.14) and Dictyomitra koslovae Foreman (Fig. 5.15). According to Pessagno, 1972 and Pessagno, 1976, Foreman (1975), Taketani (1982), Sanfilippo and Riedel (1985) and Bandini et al. (2008), Alievium gallowayi first appears at the base of Coniacian and disappears at the end of Maastrichtian. Similar to this taxon, a range of the Dictyomitra koslovae has been reported as Lower Coniacian to Upper Maastrichtian by Foreman, 1971 and Foreman, 1975, Nakaseko and Nishimura (1981), Sanfilippo and Riedel (1985) and Khokhlova et al. (1994). While considering ranges of these taxa and LAD of Patelulla verteroensis (Bandini et al., 2008, Ordoñez Alban, 2007, Pessagno, 1972 and Pessagno, 1976), the age of the sample 09-KV-4 is Lower Coniacian to Lower Maastrichtian (Fig. 6).

Radiolarian assemblages are similar and not diverse in samples 09-MDN-1 (Dictyomitra formosa Squinabol (Fig. 5.16), D. koslovae Foreman (Fig. 5.17), Stichomitra sp. (Fig. 5.18)), 09-MDN-3 (Pseudoaulophacus sp. (Fig. 7.9), Dictyomitra formosa Squinabol (Fig. 7.10) and Dictyomitra koslovae Foreman (Fig. 7.11)) and 09-US-8 (Patellula verteroensis (Pessagno), Fig. 7.19), Dictyomitra koslovae Foreman (Fig. 7.20). Dictyomitra formosa is worldwide well-known taxa and has a range from Middle Cenomanian to Lower Maastrichtian (Bandini et al., 2008, O’Dogherty, 1994, Ordoñez Alban, 2007 and Pessagno, 1976). While considering co-occurrence of this taxon together with Dictyomitra koslovae, Lower Coniacian to Lower Maastrichtian age could be assigned to sample 09-MDN-1 and 09-MDN-3 (Fig. 6). Furthermore, a same age could be also assigned to sample 09-US-8 based on the co-occurrence of Patellula verteroensis and Dictyomitra koslovae (Fig. 6).

Although slightly diverse radiolarian assemblage [Alievium superbum (Squinabol)] (Fig. 7.1), Pseudoaulophacus floresensis Pessagno (Fig. 7.2), P. lenticulatus (White) (Fig. 7.3), P. pargueraensis Pessagno (Fig. 7.4), Spongodiscus aff. multus Kozlova (Fig. 7.5), Archaeospongoprunum cf. bipartitum Pessagno (Fig. 7.6), Dictyomitra koslovae Foreman (Fig. 7.7) and Spongocapsula aff. coronata (Squinabol) (Fig. 7.8) have been obtained from sample 09-MDN-2, many of taxa (e.g., Alievium superbum, Pseudoaulophacus floresensis and P. lenticulatus) have longer ranges from Lower Turonian to Lower and Upper Maastrichtian (Bandini et al., 2008, Bragina, 2004, Koslova and Gorbovets, 1966, O’Dogherty, 1994, Pessagno, 1972, Pessagno, 1976 and Sanfilippo and Riedel, 1985). On the other hand, Pseudoaulophacus pargueraensis is well-known taxon with range from Upper Cenomanian to Lower Maastrichtian (Bandini et al., 2008, Bragina, 2004, Foreman, 1975, Ordoñez Alban, 2007, Pessagno, 1963, Pessagno, 1972, Riedel and Sanfilippo, 1974 and Sanfilippo and Riedel, 1985). Co-occurrence of Pseudoaulophacus pargueraensis and Dictyomitra koslovae clearly reveals the Lower Coniacian to Lower Maastrichtian age for the sample 09-MDN-2 (Fig. 6).

Diverse radiolarians [Alievium gallowayi (White)] (Fig. 7.12–13), Pseudoaulophacus lenticulatus (White) (Fig. 7.14), Patellula verteroensis (Pessagno) (Fig. 7.15), Dictyomitra formosa Squinabol (Fig. 7.16) and Dictyomitra koslovae Foreman (Fig. 7.17–18) have been encountered from sample 09-SIV-9. As FAD of Dictyomitra koslovae is at the base of Coniacian and LAD of the Pseudoaulophacus lenticulatus , Patellula verteroensis and Dictyomitra formosa are at the top of Lower Maastrichtian (Bandini et al., 2008, Bragina, 2004 and Foreman, 1975; O’Dhogerty, 1994; Ordoñez Alban, 2007, Pessagno, 1963, Pessagno, 1972, Pessagno, 1976 and Sanfilippo and Riedel, 1985), Lower Coniacian to Lower Maastrichtian age is assigned for the sample 09-SIV-9 (Fig. 6). All these fossiliferous samples (09-KV-4, 09-MDN-1, 09-MDN-2, 09-MDN-3, 09-SIV-9 and 09-US-8) are found in primary depositional contact with volcanic rocks geochemically assigned to Group II (Fig. 4).

The available data on the age of the opening as well as closure ages of the southern Branch of Neotethys to the North of the Bitlis–Pütürge Massifs are only limited to a few findings. The first set of indirect data comes from radiometric ages from mantle rocks, represented by the Kömürhan and Ispendere ophiolites. Together with a group of other mantle rocks towards the east (e.g., Çolakoğlu et al., 2013), the radiometric ages indicate formation of a supra-subduction-type oceanic lithosphere during the Upper Cretaceous (85 to 105 Ma).

The second set of age data is derived from the crustal rocks of the Southern Neotethys. In this group, blocks of oceanic sediments within the mélanges were sampled and their pelagic foraminifers were dated (e.g., Hempton, 1985, Perinçek, 1979 and Perinçek, 1980). This conventional approach of dating mélange blocks has provided some valuable information on the maximum and minimum ages of the oceanic basin evolution, but has not helped to decipher the details of the oceanic crust formation. To overcome this shortage the authors tried to combine geochemical methods to interpret the tectonomagmatic settings of the volcanic rocks in mélange complexes and radiolarian biostratigraphy to date the associated sediments in different areas (e.g., Bortolotti et al., 2013, Bragin and Tekin, 1996, Göncüoğlu et al., 2010, Göncüoğlu et al., 2006 and Tekin and Göncüoğlu, 2009;Tekin et al., 2002 and Tekin et al., 2012a in Izmir-Ankara Suture zone of Northern Neotethys; Göncüoğlu et al., 2008, Göncüoğlu et al., 2012 and Göncüoğlu et al., 2014, Tekin et al., 2012b in Intra-Pontide Suture Belt; Uzunçimen et al., 2011 and Varol et al., 2011 in the volcano-sedimentary rocks belonging to the Koçali Complex to the South of Bitlis–Pütürge massifs).

First of all, the new age data obtained from the radiolarian proved that a considerable part of pelagic rocks in association with basalts in the tectonic slices in Elazığ-Maden area (Fig. 2), previously included into the Eocene Maden Group (e.g., Herece et al., 1992), are actually Upper Cretaceous in age and should be considered as members of the Yüksekova Complex. This finding is important for recognizing the thin-skinned imbrication of Upper Cretaceous mélanges and their post-accretionary Eocene cover that include similar lithologies.

Secondly, it was already reported from different parts of the Southern Neotethyan suture that the oceanic crust generation within this oceanic strand had continued into lower Upper Cretaceous. The geochemical character of the Upper Cretaceous basalts from a number of localities from Cyprus to Oman suggested a supra-subduction setting (e.g., Blome and Irwin, 1985, Çolakoğlu et al., 2012, Pearce, 1980 and Robertson, 2002), generated by the northward subduction of the southern Neotethyan oceanic lithosphere (e.g., Göncüoğlu and Turhan, 1984). Our new data confirms the presence of an “ensimatic arc” (e.g., Yazgan et al., 1983) and hence, the intra-oceanic subduction within the southern Branch of Neotethys. Moreover, the new data provides a more comprehensible picture on the subduction related events during this process. Based upon the Upper Cenomanian–Lower Turonian radiolarian ages obtained from arc related volcanic rocks it is obvious that the generation of an island arc was realized during this time interval. Yet, this is the only reliable finding where paleontological age data is combined with petrogenetic evaluation and contrasts with suggestions (e.g., Perinçek and Özkaya, 1981) that the chert deposition in association with basaltic volcanism commenced not earlier than the Upper Turonian. It is important to note that no evidence for older or younger cherts in association with basalts was encountered during our sampling campaign.

Likewise, the finding of Lower Coniacian–Lower Maastrichian radiolarian cherts within the back-arc type basalts has important constraints on the closing history of the Southern Neotethys. In previous studies, either no distinction was made for different volcanisms of the supra-subduction setting (e.g., Beyarslan and Bingöl, 2000), or an approximate Campanian to Maastrichtian time interval was suggested for back-arc spreading (e.g., Robertson et al., 2007). For a part of the back-arc basalts in Zagros belt in Iran (e.g., Moghadam et al., 2009), a similar age range is suggested. Our new ages, however, suggest that the back-arc spreading has commenced earlier then in Iran, i.e. during Early Coniacian to Early Maastrichtian as proven by the radiolarian assemblages in association with back-arc-type basalt blocks in the Yüksekova Complex. Taking into account the recent finding of pelagic limestones within Back-arc basalts (Çolakoğlu et al., 2013), the spreading in this basin continued during the Upper Maastrichtian. Simultaneously, huge accretionary complexes were formed all along the closing southern Neotethys from Cyprus to Oman (e.g., Robertson et al., 2012). The basaltic blocks, including the studied arc and back-arc rocks that were generated in different tectonomagmatic settings were incorporated during this time interval into the Yüksekova-type mélange complexes.

The most clear-cut tectonic scenario that may comply with these findings is as following: •

the northward intra-oceanic subduction of the Southern Neotethyan oceanic lithosphere generated at least during the Upper Cenomanian to Lower Turonian an island arc;

This scenario is in accordance with the tectonic models proposed by several authors (for a review see Robertson et al., 2007) for the closing Neotethys between the Tauride–Anatolide and the Arabian platforms. Its importance, however, is that it provides the first reliable age constraints of the arc and back-arc systems by dating the radiolarian bearing sediments.

The systematic sampling of radiolarian cherts of the oceanic sediments in association with basalt blocks within the Yüksekova Complex in SE Turkey and the geochemical fingerprinting of the these pillow basalts has resulted in identification of an arc–back-arc pair.

The studied arc basalts were very probably formed during the Upper Cenomanian to Lower Turonian interval by northward intra-oceanic subduction of Southern Neotethys. The arc generation was then followed without a considerable break by the back-arc spreading above the subducting slab during the Lower Coniacian to Lower Maastrichtian period. Regional data suggests that the ongoing compression between the Tauride–Anatolide and the Arabian plates gave way to the formation of the Yüksekova-type subduction–accretion complexes, where all kinds of oceanic lithologies were accommodated to form mélanges along the Amanos–Elazığ-Van Suture Belt in southern Turkey.