Oligo–Miyosen Sedimanlarının Palinomorf, Foraminifer ve Nannoplankton Biyostratigrafisi, Muş Havzası, Doğu Anadolu, Türkiye

Autor: SANCAY, Recep Hayrettin, BATI, Zühtü, IŞIK, Uğraş, KIRICI, Sabri, AKÇA, Nihal
Jazyk: angličtina
Rok vydání: 2014
Předmět:
Zdroj: Volume: 15, Issue: 3 259-319
Turkish Journal of Earth Sciences
ISSN: 1300-0985
1303-619X
Popis: Oligo-Miocene sediments have not been adequately studied biostratigraphically, and a detailed bio-chronostratigraphic framework has not yet been established in Eastern Anatolian basins. Palynomorphs have therefore been correlated with the biozonations of marine dinoflagellates, planktonic foraminifera and calcareous nannoplankton of similar latitudes in combined samples from the Ebulbahar and Kelereşdere measured stratigraphic sections, which are located in the northeastern part of Muş. Palynological (dinoflagellate), foraminiferal micropalaentological, and nannopalaeontological events, correlatable with worldwide defined biozonations, have been documented from uppermost Rupelian to Upper Miocene-Pliocene sediments. First occurrences (FOs) and and last occurrences (LOs) of selected dinoflagellates are important in establishing the biostratigraphic framework. The LO of Wetzeliella gochtii in the latest Rupelian, the LO of Deflandrea phosphoritica in the latest Chattian, peak occurrences of Chiropteridium spp. in the early and late Aquitanian, the FO of Hystrichosphaeropsis obscura, followed by the FO of Membranilarnacea? picena in the late Aquitanian are of particular significance for regional correlations. Based on established marine zonations and the presence of characteristic Oligocene taxa such as Slowakipollenites hipophäeoides and Mediocolpopollis compactus, stratigraphic ranges of relatively less known pollen taxa in the region, especially those of Compositae (tubuliflorae-type), Umbelliferae, Gramineae, considered to have their first occurrences at the beginning of Neogene in earlier studies, have been calibrated. In the light of this study, the Late Oligocene-Early Miocene zonation of some palynomorphs should be emended and the stratigraphic ranges of the Compositae (tubuliflorae-type), Umbelliferae, Gramineae pollen should be extended into the Chattian and even the Rupelian in this region. As far as depositional conditions are concerned, palynomorph and organic facies properties indicate deposition under brackish water, shallow (restricted) and relatively deeper marine conditions related to fluctuating sea level during the Oligocene and Early Miocene. Shallowing-upwards deposition during the Late Oligocene was followed by restricted marine and brackish conditions at the Oligocene-Miocene boundary and in the early Aquitanian. Relatively deeper conditions in the late Aquitanian continued as extensive reef accumulations due to shallowing in the early Burdigalian. Finally, after the last deepening event at the end of Burdigalian and ?early Langian, completely terrestrial (lacustrine and fluvial) deposition predominated in the Muş Basin due to withdrawal of the sea. Terrestrial palynomorphs reflect temperate to subtropical climates in which mean annual temperatures vary between 15.6 and 21.3 °C, and mean temperatures of the coldest month (CMT) were between 5.0 and 13.3 °C.
Do¤u Anadolu Bölgesi sedimanter havzalar› biyostratigrafik aç›dan yeterince çal›fl›lmad›¤› için, sedimanter istifin biyo-kronostratigrafik özellikleri tam olarak bilinmemektedir. Bu çal›flmada, söz konusu belirsizliklere çözüm sa¤lamak amac›yla, Ebulbahar ve Kelerefldere (KD Mufl) ölçülmüfl stratigrafi kesitlerinden derlenen örneklerde, en üst Rupeliyen–Üst Miyosen/Pliyosen sedimanlar›nda dinoflagellat biyozonlar› tan›mlanm›fl ve bu biyozonlar benzer paleoco¤rafik kuflaklarda yer alan istiflerde tan›mlanan dinoflagellat, foraminifer ve nannoplankton biyozonlar› ile denefltirilmifltir. Baz› indeks dinoflagellat taksonlar›n›n ilk ortaya ç›k›fl› (FO) ve son görünüfllerine (LO) dayanarak tan›mlanan bu dinoflagellat zonlar› aras›nda, Wetzeliella gochtii’nin LOsunun en üst Rupeliyen; Deflandrea phosphoritica’n›n LOsunun en üst fiattiyen, Chiropteridium spp.’nin bolluk zonunun alt ve üst Akitaniyen, Membranilarnacea? picena’n›n FOsu taraf›ndan izlenen Hystrichosphaeropsis obscura’n›n FOsunun üst Akitaniyen’in bölgesel denefltirilmesi için önemli palinolojik de¤iflimler oldu¤u ortaya konmufltur. Söz konusu denizel dinoflagellat zonlar› ile baz› indeks pollenlere dayanarak (Slowakipollenites hipophäeoides ve Mediocolpopollis compactus), Do¤u Anadolu Tersiyer çökelleri içindeki startigrafik da¤›l›mlar› çok iyi bilinmeyen Compositae (tubuliflorae-tip), Umbelliferae ve Gramineae familyalar›na ait taksonlar›n stratigrafik da¤›l›mlar› da kalibre edilmifl, bölgede ilk ortaya ç›k›fllar›n›n bilinenin aksine fiattiyen, hatta Rupeliyen’e kadar uzand›¤› ortaya konmufltur. Biyostratigrafik veriler ile organik fasiyes özellikleri birlikte de¤erlendirildi¤inde, Oligosen–Erken Miyosen döneminde çal›fl›lan bölgede deniz seviyesindeki de¤iflimlere ba¤l› olarak ac› sulu gölsel ortamlardan, s›¤-derin denizel ortamlar›n etkili oldu¤u söylenebilir. Geç Oligosen boyunca giderek s›¤laflan bir ortamda süren çökelim, Oligosen–Miyosen s›n›r›nda ve erken Akitaniyen’de s›n›rl› denizel ve ac› sulu gölsel ortamlarda devam etmektedir. Geç Akitaniyen’deki nispeten derin koflullar erken Burdigaliyen’de meydana gelen s›¤laflma nedeni ile genifl yay›l›ml› resif oluflumlar› taraf›ndan izlenmifltir. Geç Burdigaliyen–?erken Langiyen’deki son derinleflme faz›ndan sonra ise Mufl Havzas›’ndan denizin çekilmesi nedeni ile tamamen karasal (gölsel ve flüviyal) çökelim koflullar› hakim olmaya bafllam›flt›r. Çal›fl›lan karasal palinomorf taksonlar› ile yap›lan paleoiklimsel de¤erlendirmeler y›ll›k ortalama s›cakl›klar›n (MAT) 15,6–21,3 °C, en so¤uk ay s›cakl›k ortalamas›n›n (CMT) 5,0–13,3 °C oldu¤u ›l›man-yar›tropik iklim koflullar›na iflaret etmektedir.
Databáze: OpenAIRE
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