Browsing by Author "Gildir, Semih"

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The Geo/Thermochronology of Dismal Island (Marguerite Bay, Antarctic Peninsula)
(Tubitak Scientific & Technological Research Council Turkey, 2023) Karaoglan, Fatih; Karatas, Burcu; Ozdemir, Yavuz; Gulyuz, Erhan; Vassilev, Oleg; Selbesoglu, Mahmut Oguz; Gildir, Semih
Dismal Island is located at the entrance of Marguerite Bay between Adelaide Island to the northeast and Alexander Island to the southwest within the Antarctic Peninsula (AP). Its unique position between Alexander and Adelaide islands provides the opportunity to perform testing and link these regions through Cenozoic magmatism and tectonics due to the subduction of the Pacific plate beneath the AP along the northern margin. Dismal Island was visited in February 2021 within the framework of the sixth Turkish Antarctic Expedition (TAE-VI). Thirteen samples were collected for petrography, geochronology, and low-temperature thermochronology (LTT). Of the samples, 3 were dated using laser ablation-inductively coupled plasma-mass spectrometer zircon U-Pb geochronology, 2 were dated using apatite fission-track (AFT) analysis, and 1 was dated using apatite uranium-thorium-helium (U-Th/He) (AHe) thermochronology. The island comprises massif quartz-diorite, tonalite, mafic, and felsic dikes, indicating a hybrid magma source. The 3 zircon U-Pb ages yielded a crystallization age of 47-48 for the magmatic body. The AFT ages yielded a cooling age of 41 Ma, suggesting either a shallow emplacement at a depth of similar to 4 km or an uplift/exhumation during middle-late Eocene boundary. In contrast, the AHe age of 1 sample was 20.1 +/- 1.1 Ma, together with a fast-cooling profile during the same period, which indicated an early Miocene uplift in the region. Similar early-middle Eocene crystallization ages within similar rock outcrops were determined on Adelaide and Alexander islands, Adelaide Island Intrusive Suite. The AFT ages obtained in this study (similar to 41 Ma), close to formation age, were also found on Adelaide and Alexander islands. The (LTT) literature of the region shows that the LTT ages get younger to the north along the AP, reflecting the northward migration of the ridge-trench collision and opening of the slab window along the western coast of the AP. The AHe age and the fast-cooling profile suggested that the ridge-subduction between the Tula and Adelaide fracture zones to the north of Dismal Island reached the region during Aquitanian-Burdigalian.
Low-Temperature Thermochronology Records the Convergence Between the Anatolide-Tauride Block and the Arabian Platform Along the Southeast Anatolian Orogenic Belt
(Mdpi, 2024) Gildir, Semih; Karaoglan, Fatih; Gulyuz, Erhan
SE Anatolia is witnessing the final stage of the Wilson Cycle, where a continental collision between the Tauride-Anatolide block and Arabian platform occurred, and a 1.5 km Eastern Tauride mountain chain formed. We present new low-temperature thermochronology (LTT) ages, including eight apatite fission track (AFT) and seven apatite and zircon U-Th-Sm/He (AHe, ZHe) ages, for the metamorphic rocks from the Nappe Zone of the Southeast Anatolian Orogenic Belt. The ZHe ages vary from 51.2 +/- 0.7 Ma to 30.4 +/- 0.6 Ma, the AFT ages range from 33.1 +/- 1.6 Ma to 18.1 +/- 0.9 Ma, and the AHe ages range from 23.6 +/- 2.5 Ma to 6 +/- 1.9 Ma. The LTT data show a continuous slow uplift of the region. However, the thermal modeling results suggest an Eocene and middle-late Miocene fast uplift of the region. Similar to our results, the LTT studies along the SAOB show that the vertical movements initiated during the Eocene period have continued in a steady-state regime to recent times. The Eocene epoch is identified by arc-back-arc setting in the region, whereas the Miocene epoch is marked by the continental collision. Within this tectonic framework, vertical movements on the overriding plate are controlled by both extensional and compressional tectonics. The LTT data obtained along the SAOB show fingerprints of thrust propagation from north to south.