ALBERT

Description: To quantitatively reconstruct the kinematic evolution of Central and Eastern Anatolia within the framework of Neotethyan subduction accommodating Africa-Eurasia convergence, we paleomagnetically assess timing and amount of vertical axis rotations across the Ulukisla and Sivas regions. We show paleomagnetic results from ~30 localities identifying a coherent rotation of a block - comprising the southern Kirsehir Block, the Ulukisla basin, the Central and Eastern Taurides, and the southern part of the Sivas basin. This block experienced a ~30° counter-clockwise vertical axis rotation since Oligocene time. Sediments in the northern Sivas region show clockwise rotations. We use the rotation patterns together with known fault zones to argue that the counter-clockwise rotating domain of south-central Turkey was bounded by the Savcili Thrust Zone and Deliler-Tecer Fault Zone in the north and by the African-Arabian trench in the south, the western boundary of which is poorly constrained and requires future study. Our new paleomagnetic constraints provide a key ingredient for future kinematic restorations of the Anatolian tectonic collage.

Description: The upper Tortonian Metochia marls on the island of Gavdos provide an ideal geological archive to trace variations in Aegean sediment supply as well as changes in the North African monsoon system. A fuzzy-cluster analysis on the multiproxy geochemical and rock magnetic dataset of the astronomically tuned sedimentary succession shows a dramatic shift in the dominance of 'Aegean tectonic' clusters to 'North African climate' clusters. The tectonic signature, traced by the starvation of the Cretan sediment, now enables to date the late Tortonian basin foundering on Crete, related to the tectonic break-up of the Aegean landmass, at c. 8.2 Ma. The synchronous decrease in the North African climate proxies is interpreted to indicate a change in the depositional conditions of the sink rather than a climatic change in the African source. This illustrates that interpretations of climate proxies require a multiproxy approach which also assesses possible contributions of regional tectonism.

Description: 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 (~92Ma), 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 ~56Ma. 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 northwardadvancingAfrica-AnadolutrenchresultingfromcollisionofcontinentalrocksaccretedtoAnadolu with Eurasia, until the gradual demise of the Anadolu-Eurasia subduction zone.

Description: Published

Description: 2385-2416

Description: 7T. Struttura della Terra e geodinamica

Description: JCR Journal

Description: To quantitatively reconstruct the kinematic evolution of Central and Eastern Anatolia within the framework of Neotethyan subduction accommodating Africa–Eurasia convergence, we paleomagnetically assess the timing and amount of vertical axis rotations across the Ulukıs¸la and Sivasregions.Weshowpaleomagneticresultsfrom ∼30localities identifying a coherent rotation of a SE Anatolian rotating block comprised of the southern Kırs¸ehir Block, the Ulukıs¸la Basin, the Central and Eastern Taurides, and the southern part of the Sivas Basin. Using our new and published results, we compute an apparent polar wander path(APWP)forthisblocksincetheLateCretaceous,showing that it experienced a ∼30–35◦ counterclockwise verticalaxisrotationsincetheOligocenetimerelativetoEurasia. Sediments in the northern Sivas region show clockwise rotations. We use the rotation patterns together with known fault zones to argue that the counterclockwise-rotating domain of south-central Anatolia was bounded by the Savcılı Thrust Zone and Deliler–Tecer Fault Zone in the north and by the African–Arabian trench in the south, the western boundary ofwhichispoorlyconstrainedandrequiresfuturestudy.Our new paleomagnetic constraints provide a key ingredient for future kinematic restorations of the Anatolian tectonic collage.

Description: Published

Description: 295-322

Description: 1T. Struttura della Terra

Description: JCR Journal

Description: The Oligocene-Miocene was a time characterized by major climate changes as well as changing plate configurations. The Middle Miocene Climate Transition (17 to 11 Ma) may even have been triggered by a plate tectonic event: the closure of the eastern Tethys gateway, the marine connection between the Mediterranean and Indian Ocean. To address this idea, we focus on the evolution of Oligocene and Miocene foreland basins in the southernmost part of Turkey, the most likely candidates to have formed this gateway. In addition, we take the geodynamic evolution of the Arabian-Eurasian collision into account. The Mu[s] and Elaz[i][g] basins, located to the north of the Bitlis-Zagros suture zone, were most likely connected during the Oligocene. The deepening of both basins is biostratigraphically dated by us to occur during the Rupelian (Early Oligocene). Deep marine conditions (between 350 and 750 m) prevailed until the Chattian (Late Oligocene), when the basins shoaled rapidly to subtidal/intertidal environment in tropical to subtropical conditions, as indicated by the macrofossil assemblages. We conclude that the emergence of this basin during the Chattian severely restricted the marine connection between an eastern (Indian Ocean) and western (Mediterranean) marine domain. If a connection persisted it was likely located south of the Bitlis-Zagros suture zone. The Kahramanmara[s] basin, located on the northern Arabian promontory south of the Bitlis-Zagros suture zone, was a foreland basin during the Middle and Late Miocene, possibly linked to the Hatay basin to the west and the Lice basin to the east. Our data indicates that this foreland basin experienced shallow marine conditions during the Langhian, followed by a rapid deepening during Langhian/Serravallian and prevailing deep marine conditions (between 350 and 750 m) until the early Tortonian. We have dated the youngest sediments underneath a subduction-related thrust at c. 11 Ma and suggest that this corresponds to the end of underthrusting in the Kahramanmara[s] region, i.e. the end of subduction of Arabia. This age coincides in time with the onset of eastern Anatolian volcanism, uplift of the East Anatolian Accretionary Complex, and the onset of the North and East Anatolian Fault Zones accommodating westward escape tectonics of Anatolia. After c. 11 Ma, the foreland basin south of the Bitlis formed not (or no longer) a deep marine connection along the northern margin of Arabia between the Mediterranean Sea and the Indian Ocean. We finally conclude that a causal link between gateway closure and global climate change to a cooler mode, recorded in the Mi3b event ({delta}18O increase) dated at 13.82 Ma, cannot be supported.

Description: Shortly after the recognition of plate-tectonics, Wilson (1966) proposed his now famous cycle describing the creation and demise of ocean basins. His original four stages still form the basis for plate-tectonic discussions today: (1) rifting of a continent; (2) continental drift, sea-floor spreading and formation of ocean basins; (3) subduction initiation and progressive closure of ocean basins by subduction of oceanic lithosphere; and (4) continent–continent collision and final closure of an ocean basin. The Mediterranean basin constitutes the westernmost extremity of the Tethyan domain (e.g. Stampfli & Borel 2002). Here, the last remains of this former oceanic basin have nearly disappeared, thus representing stage (4). This final closure phase is associated with rifting and drifting in the Western Mediterranean (Dercourt et al. 1986), and with initiation of the Tyrrhenian–Calabrian and Alboran subduction zones, i.e. all of Wilson's phases are occurring concurrently. Imprints of previous Wilson stages are preserved in the geological record. Detailed geochemical and metamorphic-petrological study of ophiolites – on-land relics of oceanic crust in mountain belts – (Spadea & D'Antonio 2006; Barth et al. 2008), paleogeographic reconstructions (Hall & Spakman 2003), as well as numerical and analogue modeling experiments (Chemenda et al. 2001; Toth & Gurnis 1998) have revealed that initiation of oceanic subduction, as the first part of Wilson's phase 3, may start in various ways, e.g. by inversion of a mid-oceanic ridge or fracture zone, or subduction polarity reversal. The subsequent oceanic subduction stage closes...

Description: The southern limit of the Menderes metamorphic core complex has recently been proposed to be formed by an Oligocene-early Miocene top-to-the-north breakaway detachment fault, the Datca-Kahle fault running across the Lycian nappes in southwestern Turkey. Proving a breakaway detachment fault as opposed to a simple' local high-angle normal fault is generally hampered by absence of a metamorphic contrast between hanging wall and footwall. The island of Kos lies close to the inferred southern breakaway fault. It exposes Permo- Carboniferous anchimetamorphic rocks, intruded and contact-metamorphosed at upper crustal levels by a 12 Ma old monzonite during or close to peak-burial conditions. Here, we show that exhumation of these rocks occurred along a top-to-the-north brittle extensional detachment fault underneath upper Mesozoic and Palaeogene non-metamorphic carbonates after 12 Ma, and that any (undocumented) earlier extension did not lead to significant exhumation of the Permo-Carboniferous rocks. Kos should thus be placed within the Cyclades-Menderes extensional province since 12 Ma. The age of exhumation is younger than the proposed activity of the breakaway fault, the existence of which we cannot corroborate. We conclude that the brittle detachment of Kos cannot be straightforwardly correlated to any ductile-to-brittle detachments of the Menderes or eastern Cycladic metamorphic core complexes further to the north and may represent a relatively isolated structure.