U. Kagan Tekin

First evidence of Late Carnian radiolarians from the Izmir-Ankara suture complex, central Sakarya, Turkey: implications for the opening age of the Izmir-Ankara branch of Neo-Tethys

Within the Late Cretaceous melange complex of the Izmir–Ankara suture zone in central Sakarya area, north-western Turkey, a megablock with radiolarian cherts associated with basaltic pillow lavas has been dated by radiolarians. The studied radiolarian assemblage and conodonts yielded an early Late Carnian age. This age is the oldest obtained from the chert blocks all along the suture belt and has important implications for the rifting/opening age of the Izmir–Ankara branch of the Tethys ocean in north-western Turkey. Based on this new data, it is concluded that during the Late Triassic the Izmir–Ankara seaway was connected to the other Tethyan oceanic branches and deep enough to provide chert sedimentation and exchange radiolarians with the main open oceans. It is further suggested that the long-lasting misinterpretation of a Liassic rifting/opening of the Izmir–Ankara ocean should be revised.

Late Middle Jurassic (Late Bathonian-early Callovian) radiolarian cherts from the Neotethyan Bornova flysch zone, Spil Mountains, Western Turkey

Alternating radiolarian cherts and mudstones associated with basaltic lavas occur in a olistolith within the Late Cretaceous Bornova Flysch in W Anatolia. Cherts yielded diverse and moderately preserved, Nassellaria-dominated radiolarian faunas of late Bathonian-early Callovian age. Associated volcanic rocks are geochemically classified as remnants of oceanic seamounts. This is so far the first late Middle Jurassic age from the crust of the Neotethyan Izmir-Ankara Ocean in W Anatolia, and suggests that its spreading started earlier. Similar ages were reported from the Vardar and Meliata-Hallstadt Tethyan oceanic branches in Greece and Serbia, which also opened in Late Triassic but closed earlier.

Middle to Upper Tournasian Radiolaria of the Baltalimani Formation, Istanbul, Turkey

Abstract Radiolarians collected from five localities of the Baltalimani Formation in the Istanbul region are described in detail, and the local stratigraphic ranges and persistence of biostratigraphically important radiolarian species are documented. The spumellarian component is published for the first time, and four new species are described: Albaillella kayai n. sp., Ceratoikiscum jucundum n. sp., Meschedea akcetensis n. sp., and Stigmosphaerostylus istanbulensis n. sp. Two assemblages are recognized: the A. paradoxa and the A. sp. aff. A. undulata-A. deflandrei assemblage. The older A. paradoxa assemblage contains Traenosphaera sicarius, Pararchocyrtium serrensis, Cyrtisphaeractenium mendax, and common to abundant A. paradoxa and Popofskyellium. Albaillella paradoxa is not restricted to the older assemblage but is the only species of Albaillella present. The younger A. sp. aff. A. undulata-A. deflandrei assemblage contains either A. sp. aff. A. undulata or A. deflandrei. Albaillella indensis ambigua, A. kayai n. sp., and Kantollium sp. A occur exclusively in the A. sp. aff. A. undulata-A. deflandrei assemblage, but are rare and patchy in their occurrence. Distinctive taxa common to both assemblages are Archocyrtium lagabriellei, Pylentonema antiqua, C. avimexpectens, C. umbraculatum, C. jucundum n. sp., Trilonche palimbola, M. akcetensis n. sp., S. tortispina, Polyentactinia polygonia, P. aranea, and Cubaxonium? octaedrospongiosum. Many of the taxa present occur in middle and upper Tournasian sections from France, the central Pyrenees, and Germany and provide a solid basis for re-assessing the age of the Baltalimani Formation as middle to late Tournasian (Tn2–Tn3).

Middle-Late Triassic radiolarian cherts from the Arkotdağ mélange in northern Turkey: implications for the life span of the northern Neotethyan branch

Moderately to well-preserved, relatively diverse Middle and Late Triassic radiolarian assemblages have been obtained from the chert slide-blocks within the Late Cretaceous mélange of the IntraPontide Suture Zone at the Pelitören village to the NE of Kastamonu- Araç in northern Central Anatolia. In this locality, chert slide-blocks are tectonically overlain by metamorphic sole of the serpentinized peridotites belonging to the IntraPontide ophiolites. The oldest radiolarian assemblages, with the middle Late Anisian and late Early Ladinian ages, were found in green cherts in a pebbly mudstone. They are underlain by a larger slide-block composed of an alternation of radiolarian cherts and mudstones with late Early and early Late Carnian radiolarians. Another slide-block with cherts and mudstones between the sub-ophiolitic amphibolite and the Carnian cherts includes the late Early to early Middle Norian radiolarian assemblages. These new data reveal that the IntraPontide basin was already open during the Middle to Late Triassic time and deep enough for radiolarian cherts to deposit. Moreover, it suggests that the IntraPontide Ocean is contemporaneous with a number of inferred Paleo- and Neotethyan oceanic basins in SE Europe and NW Anatolia, which were proposed in copious tectonic models.

New age data from the tectonostratigraphic units of the Istranca “Massif” in NW Turkey: a correlation with SE Bulgaria

Abstract The Istranca Crystalline Complex in NW Anatolia and SE Bulgaria includes structural units that differ in lithostratigraphy, metamorphism, age and structural position. They are collectively named as the “Istranca nappes” comprising from bottom to top the Sarpdere, Mahyadağ and Doğanköy Nappes. The Sarpdere Nappe consists of Lower Triassic arkosic metasandstones with slate interlayers, followed by Middle to Upper Triassic carbonates and an alternation of Upper Triassic clastics and carbonates. The Mahyadağ Nappe comprises a low-grade metamorphic Late Paleozoic- Triassic carbonate-siliciclastic sedimentary succession. The Doğanköy Nappe includes Precambrian?-Paleozoic metasediments, intruded by Late Carboniferous-Early Permian calc-alkaline granitoids. Its Triassic cover comprises metaclastics and metacarbonates. The Istranca nappes were juxtaposed at the end of the Triassic and transgressively covered by Lower Jurassic coarse clastics, followed above by Middle to Late Jurassic carbonates, black shales and carbonate-siliciclastic sedimentary succession. The phosphate concretions in black shales yielded radiolarian assemblages indicating Late Bajocian-Early Bathonian, Early Bathonian and Early Kimmeridgian ages. These nappes and their Jurassic cover are unconformably overlain by the Cenomanian-Santonian volcano-sedimentary successions intruded by Santonian-Campanian Dereköy-Demirköy intrusive suite. The preliminary data suggest that the Variscan basements of the Mahyadağ and Sarpdere Nappes were juxtaposed prior to the Triassic and overridden by the Doğanköy Nappe of possible Rhodopean origin from S to N during the Cimmerian compressional events

Middle Carnian Arc-Type Basalts from the Lycian Nappes, Southwestern Anatolia: Early Late Triassic Subduction in the Northern Branch of Neotethys

The Turunç Unit, which represents one of the tectonic slices within the Lycian Nappes in southwestern Anatolia, preserves the remnants derived from the northern branch of Neotethys. The unit includes basalts intercalated with pelagic limestones of middle Carnian age (early Late Triassic) based on the characteristic radiolarian assemblage of the Tetraporobrachia haeckeli Zone. The Turunç lavas reflect trace element signatures resembling those from subduction zones, displaying selective enrichment of Th and light rare earth elements over high-field strength elements and heavy rare earth elements. Considering the overall geochemical characteristics of the Turunç basalts and given that they are found to be associated with no continent-derived detritus, the Turunç lavas appear to represent fragments of a Late Triassic island arc formed on the Neotethyan oceanic lithosphere. This result is of particular importance, since it reflects the oldest subduction age obtained from the entire Neotethyan realm to date. It may further indicate that the Neotethyan oceanic lithosphere had already been formed by the early Late Triassic, thus suggesting a pre–early Late Triassic oceanization of the northern branch of Neotethys. On the basis of this, we also suggest that the initial rifting leading to the opening of the northern branch of Neotethys should have taken place during the Middle Triassic or earlier.

The Jurassic–Early Cretaceous basalt–chert association in the ophiolites of the Ankara Mélange, east of Ankara, Turkey: age and geochemistry

This study is focused on slide blocks including oceanic lavas associated with pelagic sediments within the eastern part of the Ankara Melange. A detailed petrological characterization of the volcanic rocks and a detailed biochronological investigation of the associated radiolarian cherts in eight sections (east of Ankara) was carried out. The volcanic rocks are largely represented by basalts and minor ferrobasalts and trachytes. They show different geochemical affinities and overlapping ages including: (a) Late Jurassic – Early Cretaceous garnet-influenced MORB (middle late Oxfordian to late Kimmeridgian–early Tithonian and early–early late Tithonian; late Valanginian–early Barremian); (b) Early Cretaceous enriched-MORB (middle late Barremian–early early Aptian; Valanginian to middle Aptian–early Albian); (c) Middle Jurassic plume-type MORB (early–middle Bajocian to late Bathonian–early Callovian); (d) Late Jurassic – Early Cretaceous alkaline basalts (middle–late Oxfordian to late Kimmeridgian–early Tithonian; late Valanginian to late Hauterivian). All rock types show a clear garnet signature, as testified to by their high MREE/HREE (middle rare earth element/heavy rare earth element) ratios. The coexistence of chemically different rock types from Middle Jurassic to Early Cretaceous times suggests that they were formed in a mid-ocean ridge setting from partial melting of a highly heterogeneous mantle characterized by the extensive occurrence of OIB-metasomatized portions, which were likely inherited from Triassic mantle plume activity associated with the continental rift and opening of the Neotethys branch.

Discovery of a long-term refuge for ostracods (Crustacea) after the end-Permian extinction: a unique Carnian (Late Triassic) fauna from the Mersin Mélange, southern Turkey

The Mersin Mélange, located in southern Turkey north-west of the city of Mersin, includes blocks and tectonic slices of different origins. The Kilek section in the Mersin Mélange was sampled for a thorough examination of its lithology, biostratigraphy and fossil content. Two samples from the cherty limestone layers within the Huglu Tuffites at the top of the section yielded a rich silicified ostracod fauna of late Early Carnian (based on a two-fold Carnian subdivision) or middle Middle Carnian age (based on a three-fold Carnian subdivision), deposited in an open marine environment, in the outer platform-upper slope zone. We report 121 ostracod species belonging to 53 genera. Two new genera are described: Edithobairdia Forel gen. nov. and Gencella Forel gen. nov., as well as 16 new species: Acanthoscapha mersinella Forel sp. nov., Bairdia hugluensis Forel sp. nov., Acratia kollmanni Forel sp. nov., Citrella? carniana Forel sp. nov., Cytheropteron? schornikovi Forel sp. nov., Eucytherura lacerata Forel sp. nov., Gencella taurensis Forel sp. nov., Kerocythere dorsidenticulata Forel sp. nov., Kerocythere tricostata Forel sp. nov., Monoceratina praevulsaformis Forel sp. nov., Patellacythere tourkosella Forel sp. nov., Polycope kilekensis Forel sp. nov., Ptychobairdia praekristanae Forel sp. nov., Simeonella daginikella Forel sp. nov., Spinomicrocheilinella reliquiaella Forel sp. nov. and Triassocythere tavuscayiriensis Forel sp. nov. The diagnosis of Acratia goemoeryi Kozur is emended. The Kilek fauna retains primitive characteristics illustrated by the first known occurrence of Palaeocopida and Rectonariidae (typical Palaeozoic forms) in the Late Triassic, associated with typical Triassic–modern elements such as thick-shelled and ornamented Bairdiidae and diverse Cytheroidea known from the Middle and Late Triassic worldwide. The unique composition of Palaeozoic and Mesozoic taxa from the Kilek section illustrates unexpected long-term survival in a deep-sea refuge zone following the end-Permian extinction, and the diachronous character of the ostracod recovery in different environments. http://zoobank.org/urn:lsid:zoobank.org.pub:662C3D5C–2B86–4D7B–BDB5–8F8B6A1AD1E7