Browsing by Author "Sayit, Kaan"

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Citation - WoS: 6
Citation - Scopus: 7
Biostratigraphy of Lower Permian Foraminiferal Assemblages From Platform-Slope Carbonate Blocks Within the Mersin Melange, Southern Turkey: Paleogeographical Implications
(ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER, 2020) Okuyucu, Cengiz; Tekin, U. Kağan; Bedi, Yavuz; Sayit, Kaan
The Mersin Melange (MM) as a part of the Mersin Ophiolitic Complex in southern Turkey is a sedimentary complex including blocks and tectonic slices within a Late Cretaceous matrix. Two blocks (Keven and Cingeypinari) within the MM originated from the northern branch of Neotethys (Izmir-Ankara-Erzincan Ocean) and have been studied in detail using foraminiferal assemblages to correlate them with coeval successions in the Taurides and to approach the Early Permian evolution of the northern branch of the Neotethys. The Keven block includes mainly slope deposits (poorly-sorted carbonate breccia and fossiliferous calcarenite) and dated as late Asselian-Sakmarian, whereas the Cingeypinari block consists of platform deposits (fossiliferous platform carbonate and quartz sandstone alternation) assigned to the Sakmarian-early Artinskian. These Early Permian Cingeypinari and Keven blocks from the Beysehir-Hoyran Nappes are biostratigraphically well correlated to the northerly originated Hadim nappe and its equivalents in the Tauride Belt. Considering recent studies on the Mersin Melange, a possible mantle plume existed during the Late Carboniferous-Early Permian time interval along the northern Gondwanan margin. This event led to the opening of the northern Neotethys and deposition of the pelagic Karincali sequence with volcanic material in the basinal conditions. The data presented suggest that the Keven block relates to the slope and the Cingeypinari block to platform conditions deposited as a lateral equivalent of the Karincali sequences during the Early Permian. (C) 2020 Elsevier Masson SAS. All rights reserved.
Citation - WoS: 12
Citation - Scopus: 11
Carnian (upper Triassic) Lavas and Tuffites From the Mersin Melange: Evidence for Intraoceanic Arc Rifting in the Northern Neotethys
(UNIV CHICAGO PRESS, 2020) Sayit, Kaan; Bedi, Yavuz; Tekin, U. Kağan; Okuyucu, Cengiz
In Anatolia, the northern branch of Neotethys is represented by Izmir-Ankara-Erzincan (IAE) Ocean, whose fragments and associated continental entities are preserved in the IAE Suture. However, the traces of this northerly located ocean are not solely bound to the IAE Suture, but can also be found further to the south. The Mersin Melange, situated in southern Turkey, is such a place that preserves the southerly transported remnants of the northern Neotethys. The Mersin Melange essentially displays block-in-matrix features, with blocks/slices of different age and lithological characteristics embedded in a clastic matrix. Within the melange, the Degirmenocagi region consists of a volcano-sedimentary sequence of middle Carnian age, which is characterized by lavas and tuffites interbedded with pelagic sedimentary lithologies. The lavas are chemically of basaltic/basaltic-andesitic composition, whereas the tuffites are of rhyolitic composition. Both lavas and tuffites display negative Nb anomalies, suggesting the involvement of subduction-related components. The high Zr/Nb and low Nb/Yb ratios (compared with normal mid-ocean ridge basalt [N-MORB]) imply a variably depleted mantle source, which has experienced previous melt extraction. The ratio-based melting systematics reflects melt generation largely dominated by spinel-facies melts. The overall geological and geochemical characteristics of the Degirmenocagi sequence suggest an oceanic backarc setting during the Carnian, which may have developed by the rifting of the Sorgun Arc. Although this new finding shows that the Triassic intraoceanic subduction is not uncommon in the Neotethys, it also strengthens a pre-Liassic opening of the northern domain (i.e., the IAE Ocean) and may further explain the longevity of the Middle-Late Triassic intraoceanic subduction in the northern Neotethys.
Citation - WoS: 4
Citation - Scopus: 4
First Recovery of Late Early Triassic (spathian) Pelagic Assemblages (radiolarians and Conodonts) From Block in the Upper Karakaya Complex Near Ankara City, Central Turkey: Biostratigraphical Remarks and Correlation
(PERGAMON-ELSEVIER SCIENCE LTD, 2021) Tekin, U. Kağan; Kamata, Yoshihito; Krystyn, Leopold; Okuyucu, Cengiz; Sayit, Kaan; Nalbantlı, Mustafa
The Upper Karakaya Complex, belonging to the Karakaya Complex, includes different blocks and tectonic slices within a Triassic sheared matrix. This wide-spread unit mainly exposed in northern Turkey also crops out to the southern part of Ankara city near Gokcehuyuk village. Instead of a continuous sequence of Carboniferous to Permian age described in a previous study, five different blocks of various origins and ages are identified in this study. One of the pelagic blocks composing of cherty limestone includes radiolarian and conodont assemblages typical of Spathian age, representing the Triassospathodus homeri Conodont Zone. It corresponds also to the Hozmadia ozawai Radiolarian Zone although the zonal guide could not be obtained from the radiolarian assemblage. This is so far the first recovery of pelagic assemblages (radiolarians and conodonts) from the Karakaya Complex. This result clearly indicates that pelagic sedimentation took place in the Karakaya Complex during late Early Triassic time. Compared to previous studies, it can be stated that radiolarian cherts have been deposited in the Karakaya Complex in two different time span from Middle to Late Devonian and Late Permian (Changhsingian) to early Late Triassic (Carnian) time, respectively.
Citation - WoS: 12
Citation - Scopus: 13
Late Triassic To Early Jurassic Radiolarian, Conodont and Ammonite Assemblages From the Tavuscayiri Block, Mersin Melange, Southern Turkey: Time Constraints for the T/J Boundary and Sedimentary Evolution of the Southern Margin of the Northern Neotethys
(MUSEUM NATL HISTOIRE NATURELLE, 2020) Tekin, U. Kağan; Krystyn, Leopold; Okuyucu, Cengiz; Bedi, Yavuz; Sayit, Kaan
The Mersin Melange (northwest of Mersin city) includes a variety of large sedimentary blocks/tectonic slices of Palaeozoic and Mesozoic origins. Of these, the latter represents facial and tectonostratigraphic counterparts of the Beysehir-Hoyran Nappes (remnants of the northern Neotethys). The Tavuscayiri Block, located at the center of the melange and dose to the Orbuklukeli hill, is one of such Mesozoic occurrences, with a continuous pelagic sequence from the Upper Triassic to Lower Jurassic. At the Orbuklukeli hill, a succession of middle Norian to Toarcian age has been precisely dated, which starts with conodont assemblages for the Norian and Rhaetian and includes radiolarians for the upper Rhaetian. An acidic tuff layer corresponds to the T-J boundary, which passes above to an increasingly dominating chert-bearing limestone series, marking a gradually deepening-upward of the sequence. The early Hettangian radiolarians are poorly represented, but diverse and well-preserved radiolarians have been retrieved from the middle Hettangian to the Pliensbachian. A total of eighty-five taxa, including fourteen new species, have been determined. In addition to these, one new genus (Praeudalia Tekin, n. gen.) has been described from the Rhaetian part of the section. The top of the section is represented by nodular limestones in Ammonitico rosso facies, including a diverse Toarcian ammonite fauna. All lithologies of the Orbuklukeli section along the Tavuscayiri Block can be correlated with the previously described lithologies of the Kayabasi Group/Formation in the Bozkir Unit, and Gulbahar/Gumuslu units in the Lycian Nappes.
Citation - WoS: 4
Citation - Scopus: 3
Latest Carboniferous-Early Permian Rifting of the Northern Gondwanan Margin and the Opening of the Northern Neotethys: New Evidence From the Carboniferous and Permian Foraminiferal Assemblages From the Beysehir-Hoyran Nappes, Central Taurides (southern Turkey)
(China Univ Geosciences, Wuhan, 2024) Okuyucu, Cengiz; Tekin, U. Kağan; Güzgün, Çağrı; Sayit, Kaan
The Bey & scedil;ehir-Hoyran Nappes, one of the tectonostratigraphic units of the Taurides, are thought to be originated from the Izmir-Ankara Ocean (northern branch of Neotethys). In this study, Late Paleozoic rock units from the blocks of Bey & scedil;ehir-Hoyran Nappes were studied in detail using foraminiferal assemblages in two different locations from the southwest of Karaman City (southern Turkey). In both places, blocks/slices and pebbles of various origins are embedded within a highly sheared matrix of Late Cretaceous Age, and the whole unit can be regarded as a sedimentary m & eacute;lange. The ages of the blocks from the southwest of Karaman City range from the Late Serpukhovian (Late Mississippian) to Late Capitanian (Middle Permian) with some depositional breaks (e.g., Bashkirian, Kasimovian). Combined with the previous data from the Mersin M & eacute;lange, which also include the remnants of the Bey & scedil;ehir-Hoyran Nappes, our new findings suggest that a shallowing-upward sequence, characterized by a shallow water environment with foraminifera-bearing limestones, was deposited over the Tournaisian pelagic sequence in the Bey & scedil;ehir-Hoyran Nappes till the Early Moscovian (Early Middle Pennsylvanian). This shallowing-upward sequence in the Bey & scedil;ehir-Hoyran Nappes could be related to the Late Paleozoic Glaciation on the Gondwana supercontinent (Glacial II), which resulted in a sea-level drop and deposition of platform carbonates during the Vis & eacute;an-Early Moscovian (Middle Mississippian to Early Middle Pennsylvanian) time interval. The absence of the main part of the Middle-Upper Pennsylvanian deposits (continental phase during the Middle Moscovian-Middle Gzhelian) in the Bey & scedil;ehir-Hoyran Nappes can be mainly attributed to the occurrence of a mantle plume and partially to the effect of Late Paleozoic Gondwanan Glaciation (Glacial III). Progressive uplifting by the buoyant mantle plume material has resulted in rifting at the center of the basin where the Bey & scedil;ehir-Hoyran Nappes have deposited. The rifting process led to tectonic destabilization of the platform in the basin, causing accumulation of the Upper Gzhelian (uppermost Pennsylvanian) detrital limestone with broken and abraded foraminiferal shells. Following this, deep basinal conditions prevailed during the Late Asselian-Kungurian (Early Permian), as revealed in the Mersin M & eacute;lange, where radiolarian cherts are associated with continental within-plate lavas of extreme incompatible trace element enrichment. Similar processes were responsible for the continual deposition of detrital limestones in the same basin until the end of Late Capitanian (Middle Permian). Based on all these, the uplifting process followed by rift-related volcanic rocks and detrital limestones can be interpreted as the opening of the Izmir-Ankara Ocean (northern Neotethys).
Citation - WoS: 1
Citation - Scopus: 1
Radiolarian and Planktonic Foraminiferal Biochronology of the Soğukçam Limestone Group, Elmadağ Olistostrome, and Unaz Formation (ankara Region, Central Türkiye): Insights Into the Cretaceous Evolution of the Sakarya Continent and Overlying Units
(Carnets Geologie, 2024) Tekin, U. Kagan; Sari, Bilal; Tuncer, Alaettin; Sayit, Kaan; Okuyucu, Cengiz; Guzgun, Cagri
The Ankara region (central T & uuml;rkiye) comprises a part of the Sakarya Terrane and the accretionary remnants inherited from the Izmir-Ankara-Erzincan (IAE) branch of the Northern Neotethys. The Sakarya Terrane is characterized by a pre-Jurassic basement overlain by Jurassic-Cretaceous sedimentary assemblages, collectively known as the Sakarya Continent Cover. In this study, we aim to elucidate the Jurassic-Cretaceous evolution of the Sakarya Terrane through detailed geological mapping in the regions of Haymana, Yakac & imath;k, north of Alag & ouml;z and west of Memlik, located to the west and southwest of Ankara city, central T & uuml;rkiye. By analyzing radiolarian and planktonic foraminiferal assemblages, we provide precise dating for three key lithological units: the So & gbreve;uk & ccedil;am Limestone Group (part of the Sakarya Continent Cover), the Elmada & gbreve; Olistostrome, and the Unaz Formation (from the overlying units). The oldest rock unit exposed in the Haymana region, south of Ankara city, is the Bilecik Limestone Group, consisting of Tithonian to lower Berriasian platform carbonates. A drowning unconformity separates the Bilecik Limestone Group from the overlying middle Berriasian-uppermost Albian So & gbreve;uk & ccedil;am Limestone Group, which has been elevated to "group" status in this study. The So & gbreve;uk & ccedil;am Limestone Group is subdivided into two formations-the Seyran Formation and the Akkaya Formation- separated by a disconformity surface. The Seyran Formation, at the base, consists of middle Berriasian limestone breccia in a micritic pelagic matrix, and upper Berriasian-lower Aptian micritic clayey, cherty pelagic limestones with abundant and diverse radiolarians in its upper part. The disconformity between the Seyran and Akkaya formations represents a small depositional gap corresponding to the middle to late Aptian. The lower part of the Akkaya Formation contains lower to middle Albian debris flow deposits while the upper part is composed of clayey pelagic limestones rich in glauconite and planktonic foraminifers, dating to the latest Albian. Overall, the Akkaya Formation is roughly assigned to the Albian stage.