Kinematics of a former oceanic plate of the Neotethys revealed by deformation in the Ulukışla basin (Turkey)

Abstract

Kinematic reconstruction of modern ocean basins shows that since Pangea breakup a vast area in the Neotethyan realm was lost to subduction. Here we develop a first‐order methodology to reconstruct the kinematic history of the lost plates of the Neotethys, using records of subducted plates accreted to (former) overriding plates, combined with the kinematic analysis of overriding plate extension and shortening. In Cretaceous‐Paleogene times, most of Anatolia formed a separate tectonic plate—here termed “Anadolu Plate”—that floored part of the Neotethyan oceanic realm, separated from Eurasia and Africa by subduction zones. We study the sedimentary and structural history of the Ulukışla basin (Turkey); overlying relics of this plate to reconstruct the tectonic history of the oceanic plate and its surrounding trenches, relative to Africa and Eurasia. Our results show that Upper Cretaceous‐Oligocene sediments were deposited on the newly dated suprasubduction zone ophiolites (~92 Ma), which are underlain by mélanges, metamorphosed and nonmetamorphosed oceanic and continental rocks derived from the African Plate. The Ulukışla basin underwent latest Cretaceous‐Paleocene N‐S and E‐W extension until ~56 Ma. Following a short period of tectonic quiescence, Eo‐Oligocene N‐S contraction formed the folded structure of the Bolkar Mountains, as well as subordinate contractional structures within the basin. We conceptually explain the transition from extension, to quiescence, to shortening as slowdown of the Anadolu Plate relative to the northward advancing Africa‐Anadolu trench resulting from collision of continental rocks accreted to Anadolu with Eurasia, until the gradual demise of the Anadolu‐Eurasia subduction zone.

Paleomagnetic constraints on the timing and distribution of Cenozoic rotations in Central and Eastern Anatolia

“…Broad similarities in their stratigraphy suggest that the Upper CretaceousPaleogene stratigraphic record of the Ulukışla and Sivas basins once formed a contiguous basin. Both overlie the Cretaceous ophiolites and contain stratigraphies that overlap in time with thrusting, metamorphism, exhumation, and accretion of the underlying Tauride units (Akyuz et al, 2013;Robertson, 2002, 2005;Gürer et al, 2016;Poisson et al, 1996). The Ulukışla and Sivas basins became separated due to displacement along the Ecemiş Fault Zone in the late Eocene-Oligocene (Figs.…”

“…Age constraints for the sampled units come from geological maps and accompanying explanatory notes (MTA, 2002). Ages were complemented where available by published biostratigraphic literature (Blumenthal, 1956;Oktay, 1973Oktay, , 1982Demirtasli et al, 1984;Atabey et al, 1990;Clark and Robertson, 2005;Gürer et al, 2016). In a few cases, we obtained new nannofossil biostratigraphy (details supplied in the Supplement).…”

“…The Upper Cretaceous and Paleocene sediments of the Alihoca locality in the southeast of the basin overlying ophiolite yielded a very large counterclockwise rotation of ∼ 90 • . Gürer et al (2016) showed that the southern sediments of the basin revealed phases of rapid uplift and subsequent subsidence in the Late Cretaceous. The uplift-subsidence-uplift-subsidence cycle was interpreted as the response to the underthrusting of the continental Kırşehir Block causing forearc uplift, then the potentially oceanic intra-Tauride basin causing forearc subsidence, and finally the Afyon Zone margin of the Taurides causing renewed uplift .…”

“…One of the most striking features in Anatolian geology are two major strike-slip faults, along which Anatolia is moving westwards relative to Eurasia, associated with major seismicity. This complex orogen with its major seismic hazards has been extensively studied to develop dynamic concepts to explain late Neogene escape tectonics (e.g., Gürsoy et al, 2011), plateau rise, and in deeper geological times, subduction initiation and evolution (e.g., Gürer et al, 2016). …”

“…1;Barrier and Vrielynck, 2008;Boztug et al, 2009;Menant et al, 2016;Moix et al, 2008;Parlak et al, 2012;Robertson, 2002;Robertson et al, 2009;. Ages of accretion, metamorphism, and exhumation are younging from north to south and range from Late Cretaceous to Eocene (Göncüoglu, 1997;Gürer et al, 2016;Okay and Tüysüz, 1999;. The Pontide and Anatolide-Tauride belts are separated by the Izmir-Ankara-Erzincan suture zone (IAESZ) that demarcates the former location of the now subducted Neotethys Ocean and that is thought to result from the latest Cretaceous to Paleogene collision of the Anatolide-Tauride and Pontide belts (Fig.…”