Date

2022-08-22

Author

Yılmaz, İsmail Ömer
Özer, Sacit
Mülayim, Oğuz
Tasli, Kemal
Sari, Bilal
Hoşgör, Izzet

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Measured stratigraphical sections (İnişdere-Adıyaman, Türkoğlu-Kahramanmaraş and Sabunsuyu-Kilis) have enabled us to determine carbonate platform evolution during the Aptian–Campanian interval in south-east Turkey. It starts with thin clastics and an overlying alternation of carbonates and clastics (3–50 m thick Areban Formation; Barremian–Albian) overlying basement rocks unconformably (Mülayim et al, 2019). A thicker carbonate sequence follows; the 40–410 m thick Sabunsuyu Formation (Albian–Cenomanian), characterised by shallow subtidal carbonate facies and thicker dolostones. The Derdere Formation (Cenomanian) with an average thickness of 50-250 m overlies conformably the Sabunsuyu Formation and is characterised by cyclic shallow-water facies, while the platform evolved as a ramp type (Simmons et al, 2020). The 10–180-m-thick Karababa Formation (Turonian–Santonian) is represented by organic-rich, hemi-pelagic to pelagic facies below becoming shallower upwards (bioclastic facies). Hardgrounds at the top of Derdere Formation were recognised by the presence of glauconite and phosphate at the base of the Karababa Formation. The latter is among the main source rocks in the region and is overlain by the 10–60-m-thick Karaboğaz Formation, the a second main source rock in the region (Santonian–Campanian) with a “drowning” unconformity (Mülayim et al, 2019). The latter comprises organic-rich clayey limestones with chert nodules, being conformably overlain by shallow-water platform carbonates with udists, calcareous algae, Actaeonella, sponges and bryozoans in the south or its pelagic equivalents (Saytepe Member, Campanian) in the north and by an alternation of pelagic limestone, marl, black shale, clayey limestone and cherty limestone facies (Sayındere Formation, Campanian–Maastrichtian, around 30–250 m thick). Abundant macrofossil occurrences in Saytepe and lateral equivalents and the Sayındere Formation can also be considered as bioevents related to changes in sea level/depth/nutrients in carbonate platform evolution. The contact between the Saytepe Member and Sayındere Formation is a drowning unconformity. A hardground surface is reflected by iron and manganese oxide crusts and a thin layer of sandy carbonate with abundant glauconite. Aptian–Campanian successions are characterised by rudists, actaeonellids, benthic and planktic foraminifera and calcareous algae of biostratigraphical importance (Mülayim et al, 2019). In the intervals studied, multiple hardgrounds were seen at three levels (Cenomanian, Turonian/Coniacian–Santonian and Campanian). The sudden changes triggered halts in platform development, accompanied by regeneration after sudden deepening. Thus, the platform could not regenerate or partially developed as a small platform on tectonically elevated areas. However, earlier carbonate generations are well developed and can be correlated over long distances. Therefore it can concluded that Cenomanian, Turonian/Coniacian–Santonian and Campanian platform regenerations can also be associated with collaboration of sea level, palaeoceanographical changes and tectonics (Yılmaz et al, 2018). Settlement of phosphate and the main source rocks directly above the hardgrouds can be associated with global oceanographical events and sea level changes during these time intervals. However, the last drowning event might have been mostly controlled by tectonics. This study was financially supported by TÜBİTAK Project no 118Y425.

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https://www.cretaceous2022.com/
https://hdl.handle.net/11511/100952

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Department of Geological Engineering, Conference / Seminar