Bora Rojay

Neotectonic and volcanic characteristics of the Karasu fault zone (Anatolia, Turkey): The transition zone between the Dead Sea transform and the East Anatolian fault zone

AbstractThe Karasu Rift (Antakya province, SE Turkey) has developed between east-dipping, NNE-striking faults of the Karasu fault zone, which define the western margin of the rift and westdipping, N-S to N20°-30°E-striking faults of Dead Sea Transform fault zone (DST) in the central part and eastern margin of the rift. The strand of the Karasu fault zone that bounds the basin from west forms a linkage zone between the DST and the East Anatolian fault zone (EAFZ). The greater vertical offset on the western margin faults relative to the eastern ones indicates asymmetrical evolution of the rift as implied by the higher escarpments and accumulation of extensive, thick alluvial fans on the western margins of the rift. The thickness of the Quaternary sedimentary fill is more than 465 m, with clastic sediments intercalated with basaltic lavas. The Quaternary alkali basaltic volcanism accompanied fluvial to lacustrine sedimentation between 1.57 ± 0.08 and 0.05 ± 0.03 Ma. The faults are left-lateral oblique-slip f...

Episodic, two-stage Neogene extension and short-term intervening compression in Western Turkey: field evidence from the Kiraz Basin and Bozdağ Horst

Western Anatolia (Turkey) is a region of widespread active N-S continental extension that forms the eastern part of the Aegean extensional province. The extension in the region is expressed by two distinct/different structural styles, separated by a short-term gap: (1) rapid exhumation of metamorphic core complexes along presently low-angle ductile-brittle normal faults commenced by the latest Oligocene-Early Miocene period, and; (2) late stretching of crust and, consequent graben evolution along Plio-Quaternary high-angle normal faults, cross-cutting the pre-existing low-angle normal faults. However, current understanding of the processes (tectonic quiescence vs N-S continental compression) operating during the short-time interval is incomplete. This paper therefore reports the results of recent field mapping and structural analysis from the NE of Küçük Menderes Graben—Kiraz Basin—that shed lights on the processes operating during this short-time interval. The data includes the thrusting of metamorphic rocks of the Menderes Massif over the Mio-Pliocene sediments along WNW-ESE-trending high-angle reverse fault and the development of compressional fabrics in the metamorphic rocks of the Menderes Massif. There, the metamorphic rocks display evidence for four distinct phases of deformation: (1) southfacing top-N ductile fabrics developed at relatively high-grade metamorphic conditions, possibly during the Eocene main Menderes metamorphism (amphibolite facies) associated with top-N thrust tectonics (D1); (2) top-S and top-N ductile gentle-moderatley south-dipping extensional fabrics formed at relatively lower-grade metamorphic (possibly greenschist facies) conditions associated with the exhumation of Menderes Massif along presently low-angle normal fault plane that accompanied the first phase of extension (D2); (3) moderately north-dipping top-S ductile-brittle fabrics, present configuration of which suggest a thrust-related compression (D3); and (4) south-facing approximately E-W-trending brittle high-angle normal faults (D4) that form the youngest structures in the region. It is interpreted that D4 faults are time equivalent of graben-bounding major high-angle normal faults and they correspond to the second phase of extension in western Anatolia. The presence of thrust-related D3 compressional fabrics suggests N-S compression during the time interval between the two phases of extension (D2 and D4). The results of the present study therefore support the episodic, two-stage extension model in western Anatolia and confirm that a short-time, intervening N-S compression separated the two distinct phases.

Plio-Quaternary evolution of the Küçük Menderes Graben Southwestern Anatolia, Turkey

The Küçük Menderes Graben (KMG) is part of the horst-graben system of southwestern Anatolia (Turkey), bounded by the Bozdağ horst in the north and the Aydın horst in the south. The Plio-Quaternary evolution of the KMG has been evaluated using the nature of the Miocene-Quaternary fill sediments and palaeostress analysis of slip data measured in different parts of the graben. The graben is composed of five subbasins—the Kiraz, Ödemiş, Bayındır, Dağkızılca-Torbalı and Selçuk—that are connected to each other through narrow Quaternary troughs. The Dağkızılca, Kiraz and Selçuk basins bear Miocene and younger sequences whereas the other subbasins are largely filled by Quaternary sediments. The maximum thickness of the Quaternary fill reaches about 270 m in the Ödemiş and Bayındır subbasins. The calculated slip results indicate multidirectional extension, three successive deformational periods, and possible counterclockwise rotation in the KMG during the post-Miocene period. The first phase was a strike-slip regime under N-S compression, followed by a second phase of deformation which resulted in ENE-WSW extension with strike-slip components. The final phase of deformation was NE-SW extension which constituted the final evolution of the KMG. The graben gained its present morphological configuration via the onset of E-W-trending, high-angle normal faulting imposed on the regionwide synformal structure during the Plio-Quaternary. The KMG evolved as a result of rifting during the Plio-Quaternary which followed Late Miocene unroofing of the Menderes Massif and the evolution of the Büyük Menderes and Gediz grabens.

The impact of topography on isotopes in precipitation across the Central Anatolian Plateau (Turkey)

Paleoelevation reconstructions of mountain belts and orogenic plateaus based on stable isotope climate and precipitation records benefit greatly from present-day calibrations that relate the fractionation of hydrogen (δD) and oxygen (δ18O) isotopes in precipitation to orographic rainfall. Here, we establish a first-order template of δD and δ18O of modern meteoric waters across the Central Anatolian Plateau (CAP) and its bordering Pontic and Taurus Mountains. We identify key regions in the plateau interior and along the plateau margins that have the potential to reliably record topography-related paleotemperature and paleoprecipitation changes as recovered from stable isotope paleosol, fossil teeth or lipid proxy data. Based on δD and δ18O data of more than 480 surface water samples from small catchments and springs, we characterize moisture sources affecting the net isotopic budget of precipitation over the CAP and analyze how orographic rainout and plateau aridity shape modern patterns of δD and δ18O in precipitation. The Taurus Mountains bordering the CAP to the south act as a major orographic barrier for transport of predominantly winter moisture and exhibit isotopic lapse rates of approximately −20‰/km for δD and −2.9‰/km for δ18O across an elevation range of nearly 3000 m. The Pontic Mountains at the northern margin of the CAP force perennial moisture to ascend and condensate revealing lapse rates of −19‰/km for δD and −2.6‰/km for δ18O. The difference in the predominant moisture source for the southern and northern margins of the CAP (North African versus Atlantic air masses) is manifested in systematic north-south differences in near-sea level meteoric water compositions of Δ(δDN-S) ∼20 permil and Δ(δ18ON-S) ∼3 permil in a swath across the central part of the plateau. Stable isotope data from the semi-arid plateau interior with rainfall as low as 300 to 500 mm/yr and mean summer temperatures attaining 23 °C, provide clear evidence for an evaporative regime that drastically affects surface water and runoff compositions and results in a local meteoric water line for the plateau interior that follows δD = 4.0 · δ18O − 29.3. Strongly evaporitic conditions contrast rainfall patterns along the plateau margins including their immediate leeward flanks where δD- and δ18O-elevation relationships are reliable predictors of modern topography.

MIDDLE JURASSIC-LOWER CRETACEOUS BIOSTRATIGRAPHY IN THE CENTRAL PONTIDES (TURKEY): REMARKS ON PALEOGEOGRAPHY AND TECTONIC EVOLUTION

The deposition of Jurassic-Lower Cretaceous carbonates in the Pontides was controlled mainly by the evolution of an Atlantic-type continental margin in the Tethys. The study of several stratigraphic sections from allochthonous slices and blocks of the North Anatolian Ophiolitic Melange provided insight into the Middle Jurassic-Early Cretaceous paleogeographic evolution of the Central Pontide Belt. The Callovian-Aptian successions span the Globuligerina gr. oxfordiana, Clypeina jurassica (equivalent of the Tubiphytes morronensis zone), Protopeneroplis ultragranulata (with the Haplophragmoides joukowskyi subzone), Montsalevia salevensis , Hedbergella delrioensis - Hedbergella planispira - Leupoldina - Globigerinelloides and Globigerinelloides algerianus biozones. Two major stratigraphic gaps corresponding to the pre-Callovian and Hauterivian-Early Aptian ages are recognised within the successions. Lithostratigraphic and biostratigraphic studies indicate strong similarities in the evolution of the successions in the Amasya region (Central Pontides) and Biga-Bursa-Bilecik (BBB ) Platform (North-western Anatolia).

Geodynamic significance of the Cretaceous pillow basalts from North Anatolian Ophiolitic Mélange Belt (Central Anatolia, Turkey): geochemical and paleontological constraints

The most widespread blocks within the Cretaceous ophiolitic mélange (North Anatolian ophiolitic mélange) in Central Anatolia (Turkey) are pillow basalts, radiolarites, other ophiolitic fragments and Jurassic-Cretaceous carbonate blocks. The pillow basalts crop out as discrete blocks in close relation to radiolarites and ophiolitic units in Cretaceous ophiolitic mélange. The geochemical results suggest that analyzed pillow basalts are within-plate ocean island alkali basalts. The enrichment of incompatible elements (Nb, Ta, Light REE, Th, U, Cs, Rb, Ba, K) demonstrates the ocean island environment (both tholeiites and alkali basalts) and enriched MORB. Dated calcareous intrafills and biodetrital carbonates reveal an age span of Callovian—Early Aptian. The thin-shelled protoglobigerinids, belonging to the genus Globuligerina, in the calcareous intrafills between pillow basalt lobes indicates a Callovian—Barremian age interval, most probably, Valanginian to Late Barremian. The volcanic and radiolarite detritus-bearing orbitolinid—Baccinella biodetrital carbonates dated as Late Barremian-Early Aptian in age, were probably deposited around atolls and have a close relationship with the ocean island pillow basalts. The results collectively support the presence of a seamount on the Neo-Tethyan oceanic crust during the Valanginian—Late Barremian and atolls during the Late Barremian-Early Aptian interval. The presence of an oceanic crust older than that seamount along the Northern Branch of Neo-Tethys is conformable with the geodynamic evolution of the Tethys.

Age and Chemistry of Miocene Volcanic. Rocks from the Kiraz Basin of the Küçük Menderes Graben: Its Significance for the Extensional Tectonics of Southwestern Anatolia, Turkey'

Neogene volcanic rocks and granitoid plutons are among the most important geological components of western Turkey. Although they are voluminous north of the Gediz Graben, they are very scarce to the south, where volcanic rocks occur as isolated small exposures in a small number of localities. The Kiraz Basin of the Küçük Menderes Graben is a key locality, in which Tertiary volcanic rocks crop out at three locations. These rocks have been chemically analysed and dated (39Ar-40Ar whole rock and biotite analyses) in order to understand their tectonic setting of emplacement and its relation to the wider structure of western Anatolia. Whole rock and biotite 39Ar-40Ar ages vary between 13.9 ± 0.2 Ma and 14.6 ± 0.2 Ma. The Kiraz volcanic rocks are calc-alkaline, with a compositional range from basaltic andesite to dacite. They are strongly enriched in the light ion lithophile elements (LILE) and have chemistries typical of lavas erupted in subduction-related settings. Their close association with rift-bounding faults suggests eruptions via conduits flanking grabens in an extensional environment. The difference in chemical composition and age between the Kiraz volcanic rocks and the slightly older calc-alkaline volcanic rocks north of the Gediz Graben is attributed to their relatively younger ages and greater proximity to the Aegean Arc. Their calc-alkaline chemistry reflects magma generation influenced by the slab descending beneath this arc and eruption/emplacement in an extensional setting.

Early Miocene rodents of Gökler (Kazan Basin, Central Anatolia, Turkey)

Abstract The rich and relatively diverse fossil mammalian assemblage from Gökler is of special importance for understanding of faunal evolution in Central Anatolia. Large mammals were not recovered, but insectivores and rodents are abundant. The assemblage of rodents is studied in detail and comprises mainly diversified cricetids. Dormice are abundant, but are represented by only one species. Squirrels are represented only by few specimens and also beaver remains were identified. Spanocricetodon sinuosus is referred to a new genus Latocricetodon nov. gen that is tentatively assigned to the Pseudocricetodontinae. Newly named species are Cricetodon goklerensis sp. nov., Democricetodon haltmari sp. nov., Eumyarion lukasi sp. nov. and Glirudinus matusi sp. nov. The rodent assemblage is assigned to local zone C which is correlated to the European biounit MN2 (early Miocene). Our biochronological assessment is supported by radiometric dating from two volcanic ash layers. Latocricetodon LSID http://zoobank.org/urn:lsid:zoobank.org:act:3414DB1E-0C5E-4154-BE5E-02A9ED183B1A Cricetodon goklerensis LSID http://zoobank.org/urn:lsid:zoobank.org:act:1B658872-6C10-4355-B87C-3E6277AF4EDA Democricetodon haltmari LSID http://zoobank.org/urn:lsid:zoobank.org:act:9B13F956-7F8C-406A-9970-1F5E999E54C6 Eumyarion lukasi LSID http://zoobank.org/urn:lsid:zoobank.org:act:34DED87E-855F-4969-AB84-10BED5C572BF Glirudinus matusi LSID http://zoobank.org/urn:lsid:zoobank.org:act:798ECB9A-E3B5-4C38-B5B3-FEB17AF734FE