Southern Neotethys Research Articles

Middle triassic magmatism in the Afyon Zone of the Anatolides/Eastern Mediterranean: Implications for the extension of the Northern margin of Gondwana and opening of the Inner-Tauride Ocean

The northward subduction of the Paleo-Tethys beneath the southern margin of Laurasia during the Triassic caused the development of an extensional tectonic regime on the northern Gondwana by pull-forces. The Middle Triassic volcanic activity on the passive continental margin of Gondwana can be attributed to this rifting stage. The Afyon Zone represents the deeply buried northern margin of the Anatolide-Tauride Block (ATB), which was rifted from Gondwana in the Triassic by the opening of the southern Neo-Tethys. It is characterized by the existence of widespread Middle Triassic volcanic activity, which unconformably cover deeply eroded pre-Triassic basement. Early Middle Triassic rhyolites and andesites (245.2 ± 2.0 Ma) represent the first stage of the magmatic activity and exhibit a subduction signature, attributed to the former short-lived southward subduction of the Paleo-Tethys beneath northern Gondwana during the Carboniferous. The second stage of magmatic activity is dominated by trachyandesitic volcanic rocks (243.1 ± 1.9–239.2 ± 1.2 Ma) and rhyolites (243.0 ± 2.9–238.2 ± 1.2 Ma), which were generated in a rift setting. The final stage of magmatic activity at the northern margin of the ATB is characterized by extensional anorogenic alkaline rhyolitic volcanism (237.2 ± 2.3–229.4 ± 2.7 Ma), following the earlier stages described. During Middle to Late Triassic, this rifting on the northern Gondwana led to the synchronous opening of the Inner Tauride Ocean in the north and the southern branch of the Neo-Tethys in the south. The generation of these two oceans and the separation of the ATB and Kırşehir blocks from the northern margin of Gondwana should have resulted in the failure of the northern branch of the Neo-Tethys to open as a new oceanic basin.

Dwarfing of calcareous nannofossils during the Norian warming event in the Palaeo-Tethys

The Late Triassic marks the inception of marine calcareous nannoplankton. However, calcareous nannofossil of this period have been found so far only in successions of the eastern Panthalassa Ocean, and from the western and southern Neo-Tethys Ocean. A new middle to late Norian (Late Triassic) calcareous nannofossil association is presented for the first time from Hongyan section at Baoshan block in the Palaeo-Tethys. Here, the calcareous nannofossils association is composed of Prinsiosphaera triassica, P. sp., and Orthopithonella geometrica and calcispheres. The assemblage is predominantly composed of Prinsiosphaera, accounting for >90% of the relative abundance, with a small amount of calcispheres and Orthopithonella geometrica. Similar to the western Tethys, Prinsiosphaera makes up 0.1–1.1% of the limestone volume in the Baoshan block. The mean diameter of Prinsiosphaera decreases from approximately 8.0 to 6.2 μm in the upper Norian (Sevatian), and average volume reduction of approximately 50%. The change in size is coeval with negative carbon and oxygen isotope excursions of the Norian, suggesting a temporal coincidence between C-cycle perturbations, global warming and a dwarfing of Prinsiosphaera.

Reducing-condition reworked phosphorite sedimentary model: Petrographic and geochemical evidence from the Lower Cretaceous in the Thaniyat area, northern Saudi Arabia

The Thaniyat phosphorite, occurred in northern Saudi Arabia, is a component of a massive phosphorite deposit that was formed in the Late Cretaceous to Paleogene era within the southern Neo-Tethys Ocean. To gain insights into the sedimentary environments and formation processes of these phosphorites, samples were collected from the Thaniyat Phosphorite Member in northern Saudi Arabia and analyzed using petrological and geochemical methods. To ensure a comprehensive understanding, the obtained results were compared with results from nearby sites. The Thaniyat phosphorite is composed of phosphatic grains and quartz grains with distinctive granular textures. The phosphatic grains were derived from pristine phosphorite present along the shelf margin, while the quartz grains were supplied by terrestrial input. The presence of this dual provenance is furtherly supported by the negligible correlation observed between P2O5 content and the content of Al2O3 and TiO2. Trace element proxies provide additional insights into the sedimentary setting of the phosphorite, indicating that it occurred in an upwelling environment, which caused relative enrichment of Cr and a positive correlation between the value of Co × Mn and Al2O3 content of the phosphorite. Proxies related to Fe and Mn were found to be unsuitable for predicting the redox conditions in this area. A combination of V, Mo, and U proxies suggests a prevailing suboxic environment during the deposition of the Thaniyat phosphorite. A comparative analysis with contemporaneous phosphorite samples from Jordan and Iran demonstrated consistent characteristics of the sedimentary environment. Building upon these findings, a sedimentary model was proposed to elucidate the depositional processes of the phosphorite in a suboxic environment, where an upwelling with an extensive oxygen minimum zone dominated the sedimentary environment. The extensive reducing sedimentary environment likely facilitated carbon fixation and subsequently climate change. These findings contributed to a better understanding of the role of phosphorite in the paleoenvironmental context of the southern Neo-Tethys Ocean.

Calcium isotopes reveal shelf acidification on southern Neotethyan margin during the Smithian-Spathian boundary cooling event

The Smithian-Spathian transition of the late Early Triassic was a critical period of environmental and biological upheavals, following the end-Permian mass extinction. Changes in carbonate deposition during this period have been attributed to intensified upwelling along shelf margins, but relevant studies are scarce. Here, we present calcium isotopes of bulk marine carbonate (δ44/40Cacarb) from a Smithian–Spathian boundary (SSB) succession (Guryul Ravine section, Kashmir) on the southern margin of the Neo-Tethys. Our smoothed δ44/40Cacarb curve reveals a ∼ 0.2‰ negative shift (from ∼ − 1.1‰ to ∼ − 1.3‰) across the SSB, concurrent with a ∼ +10‰ shift in δ13Ccarb. While increased Ca isotopic fractionation could play a role, we specifically examine potential impacts due to changes in marine Ca fluxes. Using a Ca-cycle mass balance model, we explore scenarios of decreased carbonate burial flux (Fcarb), decreased riverine flux (Friv), and a combination of these processes. The modeling suggest that a pulse decrease in Fcarb by 40% over ∼0.06 Myr match the negative shift in δ44/40Cacarb at Guryul Ravine. We infer that this decrease was likely related to intensified upwelling of acidic deep seawater due to invigorated global-oceanic circulation during the SSB cooling event. We suggest that the regionally diverse excursions in δ44/40Cacarb in the Tethyan region could be attributed to spatially varied upwellings in the shelf margin. The upwelling of acidic and anoxic deep seawater may have driven the second-order extinction of ammonoids and conodonts at the beginning of the SSB cooling event.

New planktonic foraminiferal record across the Aptian–Albian transition in Interior Fars, Zagros Basin, SW Iran: Implication for latest Aptian paleogeography along the southern shallower Neo-Tethys

The Aptian–Albian (A–A) transition encompassed a critical timing in the evolution of Fars Platform (Zagros Basin, SW Iran), such that a number of previous studies on its proximal part (called “Coastal Fars”) illustrated platform recovery after sustained demise due to latest Aptian maximum sea-level lowstand. So far, much less attention has been given to the distal part of the platform – “Interior Fars” – where the lack of proper geological age interpretations, in particular, has been limiting a full paleoenvironmental reconstruction of the southern shallower Neo-Tethys. In order to establish the chronostratigraphic framework of Interior Fars, this study presents a novel set of planktonic foraminiferal record for the A–A Kazhdumi Formation at the Saroie section. The identified fauna comprises nine species from four genera, all of which are reported for the first time from Fars Platform. The observed new bioevents are generally consistent with those of the proposed reference section at a deeper intrashelf setting (Tang-e-Maghar, Dezful Embayment), allowing for the establishment of a local upper Aptian–Lower Albian zonation and leading to adequate constraints on the local Aptian/Albian boundary and the timing of prominent black shale deposition (possible “Jacob” equivalent). Based on this new Saroie chronostratigraphic scheme, it is evident that sedimentation across the A–A transition was maintained fully marine at the Saroie section, Interior Fars. This finding does not support the previous inference of extensive subaerial exposure of the entire Fars Platform at that time, thereby calling for a major revision of the published prevailing model for latest Aptian paleogeography of this region. These new insights will facilitate better understanding of the Fars Platform evolution in the Zagros Basin as well as paleoenvironmental reconstructions along the southern Neo-Tethys.

Middle Eocene (Lutetian-Bartonian) larger benthic foraminifera assemblages from Batman and Siirt (Southern Neotethys, SE Turkey): a new assessment

The benthic foraminifera assemblage has been described in the limestones outcropped in Kurtalan and Eruh district of Hoya formation which is one of autochthonous units of Arabian Platform (SE Turkey). From the two measured sections, one of them has rare fossil content due to dolomitization (DH-Dodan section),while the other is fairly remarkable in terms of fossil content (EH-Eruh section). The foraminiferal assemblages are represented by Asterigerina rotula (Kaufmann), Operculina ex. gr. gomezi Colom and Bauza, Victoriella conoidea Rutten, Amphistegina sp., Elphidium sp., Peneroplis sp., Carpenteria sp., Stomatorbina sp., miliolid and rotaliid forms and echinoderms, coral fragments in the Dodan section. The foraminiferal assemblages are represented by Nummulites biedai Schaub, Nummulites maximus d’Archiac, Nummulites perforatus de Montfort, Nummulites postfossulatus Sirel and Deveciler, Nummulites praeaturicus Schaub, Assilina exponens (Sowerby), Sphaerogypsina globulus (Reuss), Asterigerina rotula (Kaufmann), Lockhartia cf. hunti Ovey, Neoratlia sp., Operculina sp., Discocyclina sp., Asterocyclina sp., Lockhartia sp., Lenticulina sp., miliolid-rotaliid forms and echinoderms in the Eruh section. The fossil assemblage described shows that the limestones are of Lutetian-Bartonian and this assemblage indicates a very shallow marine deposition environment. This study provides biostratigraphic and stratigraphic data that help to reassess the Eocene geological evolution of the region. Paleobiogeographically, larger benthic foraminiferal assemblages recorded on carbonate platforms in southeastern Turkey show an affinity to Arabian and Middle Eastern platforms.

Austral and Subtropical Gyre Radiolaria – latest Jurassic to Early Cretaceous Leg 123, Site 765, Argo Abyssal Plain revisited: Southern Hemisphere paleobiogeography and global climate change

The aim of this report is to 1) to formally describe Austral and Subtropical Gyre Radiolaria recovered from ODP Hole 123-765C), 2) to compare them with published records of Southern Hemisphere “non-Tethyan” assemblages and 3) to discuss radiolarian paleobiogeography of the Southern Hemisphere and its implications for global climate change during the Jurassic–Cretaceous transition. The Tithonian to Aptian/early Albian radiolarian record recovered from Hole 765C, Cores -62R to -36R in the Argo Abyssal Plain (AAP) is unique in its density of well-preserved samples and in its faunal contents. Radiolaria recovered from claystones yielded the low diversity, ecologically tolerant “Crypto-Archaeo” Assemblage, (chiefly cryptocephalic and cryptothoracic nassellarians and Archeodictyomitra spp.) interpreted herein as originated in the Subtropical Gyre (STG). In contrast, assemblages extracted from radiolarite layers, interpreted as pelagic turbidites derived from the deeper Australian margin, are dominated by Austral taxa. Neotethyan taxa are very rare to absent before the late Hauterivian/Barremian, when they gradually gain in diversity and abundance. Described Austral and STG taxa include 10 families, of which Fusitanellidae n. fam. and Windaliinae n. subfam. are new. Of 18 genera 7 are new (Nodosphaera, Praewindalia, Pachycingula, Archaeotanella, Morchella, Fusitanella, Argofusus) and of 55 species 30 new ones are formally described and 14 new ones are left in open nomenclature. The southern hemisphere Late Jurassic to Early Cretaceous radiolarian biogeography is defined from low- to high latitude: 1. the Neotethyan (NT) and 2. the Central Panthalassan (CP) realms, 3. Eastern Boundary Current (EBC) realm, 4. the Subtropical Gyre (STG) and the Austral (A) circum south-polar realm. Radiolarian biogeography and plate tectonic models support a scenario of palaeoceanographic and global climatic change during the Jurassic–Cretaceous transition related to progressive Pangea break-up with the following consequences: 1. an increased heat transfer to the Southern hemisphere which caused cooling of Neotethyan regions during the Late Tithonian dry event. 2. A northward shift of the southern summer Intertropical Conve nience Zone reduced the Neotethyan monsoon area and allowed the establishment of a southern Neotethyan subtropical gyre documented by the “Crypo-Archaeo” Assemblage. 3. The south-polar West Wind Drift may have forced a circum Antarctic-Australian cold current through the epicontinental rift between India and Antarctica-Australia since the Berriasian (140 my), transporting Austral Radiolaria into the AAP where they accumulated in radiolarite layers.

Ion-probe (SIMS) U-Pb geochronology and geochemistry of the Upper Cretaceous Kızıldağ (Hatay) ophiolite: Implications for supra-subduction zone spreading in the Southern Neotethys

The Kızıldağ (Hatay) ophiolite in southern Turkey represents a complete, although fault-dissected, remnant of oceanic lithosphere that formed within the South Tethyan ocean during the late Cretaceous. The Kızıldağ forms part of the Upper Cretaceous belt which includes the Troodos (Cyprus), Baer-Bassit (Syria), Amanos (S Tukey), S Iran and Semail (Oman) ophiolites. Ion-probe (SIMS) dating of seven samples of crustal rocks (cumulate gabbro, isotropic gabbro and isolated dykes in mantle tectonite), and a plagiogranite intrusion provides important clues concerning the temporal development of the emplaced oceanic crust. Single grain 206Pb/238U dates that overlap within analytical uncertainty for four samples, including the plagiogranite (93.83 ± 0.46 Ma), the isotropic gabbro (92.9 ± 0.52 Ma) and the isolated dykes (92.54 ± 0.44 Ma to 93.6 ± 0.75 Ma), are interpreted as magmatic crystallisation ages, and suggest that the Kızıldağ ophiolite formed within 1-2 Ma. Three other samples with single grain 206Pb/238U dates that are outside the range of analytical uncertainty yielded nearly identical lower intercept ages of 94.2 ± 2.5 Ma to 94.4 ± 0.97 Ma for two cumulate gabbros and 90.0 ± 6.4 Ma for an isotropic gabbro. Comparison of the new and published radiometric ages of the Kızıldağ suggest that this ophiolite is ∼1.5 Ma older than previously believed, and is similar to the crystallisation ages of plagiogranites from the Troodos (Cyprus) and the Semail (Oman) ophiolites. The new age data emphasise the value of dating a range of ophiolitic rocks. Geochemically, the crustal rocks of the Kızıldağ ophiolite formed from boninitic magmas (cumulate gabbros and isolated dykes) and from island arc tholeiitic magmas (isotropic gabbro). The new whole-rock chemical data support a subduction-initiation (fore-arc) setting for the Kızıldağ ophiolite, in common with the Troodos, Semail, Baër-Bassit and other Upper Cretaceous ophiolites of the South-Tethyan region.

Facies analysis and depositional model for the Oxfordian Hanifa Formation, Central Saudi Arabia

The Jurassic was a time for major global changes in climate, tectonics, and oceanography, reflected in the southern Neo-Tethys Ocean by a distinct transition from carbonate-poor to carbonate-dominated sedimentation. To better constrain the effect of this turning point in the Late Jurassic, key outcrops of Oxfordian deposits of the Arabian Plate were investigated through detailed sedimentologic analysis. High-resolution (centimeter-scale) description and analysis of eight outcropping sections with a cumulative thickness of 461 m through the Oxfordian Hanifa Formation along a N–S 535 km-long transect in central Saudi Arabia are used to develop a comprehensive conceptual depositional evolution through time. Nine sedimentary lithofacies are interpreted and grouped into four facies associations. These associations include: I) outer-ramp association (FA1), II) mid-ramp association (FA2), III) inner-ramp grainy-facies association (FA3), and VI) inner-ramp reefal association (FA4). The lithofacies succession distinguishes two depositional phases, a middle Oxfordian homoclinal ramp (Phase 1) that corresponds to the Hawtah Member, and a late Oxfordian reef-bearing carbonate ramp (Phase 2) that corresponds to the Ulayyah Member. After being restricted to the high latitudes in the northern Neo-Tethys during early and middle Oxfordian ages, the carbonate ramp evolution within the Hanifa Formation reflects the expansion of scleractinian coral reefs over the southern Neo-Tethys passive margin in the late Oxfordian. However, the distribution of the corals in the Arabian Plate is mainly controlled by water salinity and siliciclastic input; they are absent northward due to hypersalinity and southward due to siliciclastic input. Furthermore, the differential subsidence and the resulting uneven topography, in addition to the eustatic sea level variation during the Oxfordian age, controls the distribution of different depositional styles over the Arabian Plate (homoclinal ramp, distally-steepened ramp, rimed shelf, and intrashelf basin).

Geochemical and geochronological constraints on origin of the Sawlava ophiolite (NW Iran): Evidence for oceanic mantle evolution beneath Iran-Iraq border

The Sawlava ophiolite is situated on the Iran–Iraq border within the Walash-Kermanshah ophiolitic belt and represents remnants of the Cenozoic southern Neo-Tethys Ocean, which was located between the Arabian plate and the Sanandaj–Sirjan zone. It contains a complete ophiolitic sequence started from harzburgites with foliated/discordant dunites, gabbroic bodies, a dyke complex, and pillow as well as massive basaltic lavas. The whole-rock and mineral chemistry of the Sawlava peridotites suggest that they are a mantle residuum after ca. 20–30% partial melting and melt extraction in the suprasubduction zone (SSZ) setting. The volcanic rocks generally range from island arc tholeiite to calc-alkaline affinities. Whole-rock chemistry indicates that volcanic units have compositions akin to depleted- and enriched-types mid-ocean ridge basalts (E-MORB). Layered- and isotropic gabbros show geochemical affinity similar to the normal mid-ocean ridge basalt (N-MORB) and E-MORB compositions, respectively. Their llight rare earth elements (LREE) observed in both N-MORB-like and E-MORB-like rocks, define two main basic geochemical types (LREE-enriched and LREE-depleted), suggesting several magmatic pulses from different mantle compositions that reveal mantle evolution and heterogeneity across the study area. Basaltic lavas weakly depleted in LREE show relatively flat REE patterns and (La/Yb)N values of 0.77 to 1.24, whereas LREE-enriched rocks have a (La/Yb)N mean values of 1.7, and lack an Eu anomaly. These subgroups of basaltic rocks show different extrusion ages – Paleocene–Eocene (59–50 Ma) and Oligocene (29 Ma), respectively. Petrogenetic modeling shows that mafic N- and E-MORB type rocks of Sawlava, which have (La/Yb)N = 0.97 and 1.7 and (Dy/Yb)N = 1.13 and 1.1, respectively, formed due to partial melting of a mantle source less enriched in LREE than an garnet lherzolite ((La/Yb)N = 0.88 and (Dy/Yb)N = 0.94) source or, alternatively, from very low degree (<2%) partial melting of a spinel-bearing DMM. The La/Yb–Dy/Yb systematics of these rocks are interpreted to be compatible with ~2 to 10% and ~ 20% of partial melting of a garnet bearing spinel lherzolite source for the N- and E-MORB type rocks, respectively. The geochemical data and results reveal that magmatic-originated rocks from both Paleocene-Eocene and Oligocene lavas seem to be less heterogeneous compared with the mantle sources of the Walash-Kermanshah ophiolites, likely due to different slab-fluid components and variations of partial melting degrees. The studied volcanic rocks therefore possibly record chemical heterogeneity due to magmatic activity at an oceanic spreading center alongside slab rollback and back-arc extension at the Eurasian continental margin.

What's in a name? Revision of Peneroplis turonicus Said and Kenawy, 1957 (benthic foraminifera), an inappropriately-named taxon from the Cenomanian of the southern Neotethys margin

Peneroplis turonicus Said and Kenawy is a poorly known benthic foraminifer that was originally described based on isolated specimens from the Upper Cretaceous of Egypt. Specimens from the Cenomanian Sarvak Formation of Iran indicate the presence of a finely agglutinated test wall displaying a pseudo-keriothecal texture, therefore, excluding this taxon from the porcelaneous Miliolida, namely family Peneroplidae. Based on the test morphology, wall structure and foraminal features, the species is herein tentatively assigned to Neodubrovnikella Schlagintweit and Rashidi (order Loftusiida), with the new combination Neodubrovnikella turonica (Said and Kenawy). A critical literature review leads to the conclusion that N. turonica represents a southern Neotethys Cenomanian marker taxon reported so far from Italy, Slovenia, Croatia, Kosovo, Greece, Lebanon, Syria, Morocco, Egypt, Turkey, Iraq, and Iran. Therefore, Neodubrovnikella does not represent a Maastrichtian genus as previously assumed but is as old as Cenomanian, disappeared from the fossil record in the proximity of the Cenomanian-Turonian boundary and reappeared after a considerable gap and ghost range.

3-D numerical constraints for the Triassic mafic igneous system of Antalya (SW Turkey): Magma generation associated with southern Neotethyan slow seafloor spreading

A ~ 400 m thick Middle-Late Triassic volcano-sedimentary succession crops out in a relatively narrow corridor ~75 km long and ~ 25 km wide close to Antalya Gulf, SW Turkey. The volcanic and subvolcanic rocks represent the majority of the succession and are associated with epiclastic breccia, turbiditic sediments as well as chert and limestone layers. The igneous rocks are alkali basalts, with incompatible element content matching the classical HiMU-OIB types. These are considered as the precursors of a rift system that would have later evolved into a mature Neotethyan oceanic system, with emplacement of massive tholeiitic basalt sequences, not recorded in the investigated area.Clinopyroxene-melt thermobarometric constraints indicate the presence of two main magma chambers, one equilibrated at ~7–10 km depth and ~ 1070 °C and the other at ~15–21 km depth and ~ 1300 °C. Based on these estimates, a 3-D finite element modelling has been applied, simulating the presence of ellipsoidal magma chambers at different depths and with variable sizes, applying different boundary loading conditions. The scenario that best fits the distribution of the volcanic rocks assumes the contemporaneous presence of two magma reservoirs. One is shallow, with a size of ~17 × 1.5 × 1.5 km, and the second is deeper, with a size of ~37 × 3 × 3 km. Numerical simulations show maximum 6 m opening and dilation through horizontal plane at the surface during the Permian/Triassic intracontinental rift phases. Morphological constraints of this rift zone, with the presence of massive lava eruptions also as pillow facies, have been simulated with the existence of a slowly opening rift system. In order to produce the voluminous magma batches in the Antalya region, pure extensional tectonic regimes seem insufficient, and the presence of a transtensional regime must have accompanied the tectonic forces during the Triassic intracontinental rifting stage.

The origin of manganese formations at Çağalali Hill and Kevri̇kevr Hill related to the late Triassic rifting of the South Neotethys, SE Turkey: The geological, mineralogical and geochemical components

The Koçali Complex includes continental rifting and subduction-related units that make up the southern Neotethys. This complex is a folded, tectonic-segmented succession with lavas, volcaniclastic sediments, pelagic carbonates, radiolarites and manganese deposits (the Tarasa and Konak formations) and ophiolitic units (the Kale formation). Manganese mineralizations in the host formation are found in banded, lenticular and massive forms within red to brown radiolarian cherts. Pyrolusite and polianite are the main manganese minerals, while psilomelane, manganite and minor hausmannite are other manganese minerals. Gangue minerals include quartz and carbonate, with minor barite being observed. The geochemical proofs (MnO: 8.98–73.64%, SiO2: 3.26–86%) originating from the main oxides indicates a hydrothermal rooted source for the manganese mineralization. This is confirmed by anomalies and trace element patterns including very low Fe/Mn (<0.1), low Co/Zn ratios (mean 0.86), very low ∑REE contents (mean 34.67), slightly negative Eu* value (mean 0.74) and low Ce* value (mean −0.23). Manganese-oxide mineralizations observed in the volcanic sedimentary succession of the Koçali Complex have been interpreted as hydrothermal deposits associated with volcanism during the post-rifting seafloor extension of the southern Neotethys during the Late Triassic period.

The Kyrenia Terrane (Northern Cyprus): Detrital Zircon Evidence for Exotic Elements in the Southern Neotethys

AbstractThe Kyrenia terrane of northern Cyprus comprises a tectonic stack of Triassic to Eocene rock units interleaved with basic and acid volcanics and minor metamorphic inliers, alongside an Oligocene‐Miocene flysch. Our U‐Pb‐Hf detrital zircon investigation in the Kyrenia Triassic to Eocene section reveals Precambrian, Silurian (∼430 Ma), Carboniferous (∼300 Ma), Triassic (∼240 Ma), and Upper Cretaceous (∼85 Ma) zircons. The presence of 300 Ma zircons, as early as in Triassic sediments, is enigmatic because Carboniferous magmatism is confined to the Paleotethyan realm which is traced north of the Taurides. Deposition of the Kyrenia sequence closer to a Northern Tethyan province would better fit its detrital zircon signal. The detrital signal of the Kyrenia, indicative for derivation from areas north of the Mediterranean, also differs significantly from that of the Mamonia Complex (SW Cyprus) in which only Afro‐Arabian sources are distinguished. Thus, in view of its unusual detrital zircon content, the Kyrenia sequence stands out in the Eastern Mediterranean as an exotic rock pile that cannot be straightforwardly correlated with its neighboring geologic environment. We defined the metamorphic inliers of Kyrenia as an ophiolitic mélange and recognized blueschist‐greenschist facies metamorphism to which we infer an Upper Cretaceous age. A U‐Pb zircon age of 555 ± 9 Ma (Cadomian) was obtained for the crystallization of a metabasic rock in the mélange. These findings support the geodynamic linkage of the Kyrenia with the Alanya and Bitlis massifs that were also affected by Upper Cretaceous HP‐LT metamorphism and accreted to the southern Tauride.

New biostratigraphic observations of planktonic foraminifera and ammonites on the Aptian–Albian intrashelf succession, Zagros Basin, SW Iran

A detailed planktonic foraminiferal biostratigraphic framework, associated with supporting ammonite data, is presented for Aptian–Albian intrashelf sedimentary succession (Kazhdumi Formation) at the Tang-e-Maghar section, Zagros Basin, SW Iran. Most of the identified planktonic foraminiferal species are reported for the first time from this region, and the fauna permits five biozones to be newly proposed from the upper Aptian Globigerinelloides aptiensis Zone to the middle Albian Ticinella primula Zone. Notably, we recognize a narrow interval of faunal turnover in the Microhedbergella miniglobularis Zone, the base of which is delimited by the highest occurrences of Aptian-representing taxa and the top by the lowest occurrence of the Albian Microhedbergella praeplanispira. The proposed Aptian/Albian boundary should lie within this interval accordingly. In addition, we report on 12 ammonite levels that can be used to constrain the Aptian–Albian Substages. The proposed planktonic foraminiferal biozonation of the studied section will be an important step toward better understanding of the nature of the biotic and global changes across the Aptian/Albian boundary on the Arabian Plate in the paleotropical southern Neo-Tethys.

The timing of rifting events in the easternmost Mediterranean: U-Pb dating of zircons from volcanic rocks in the Levant margin

ABSTRACT The Levant basin, at the easternmost Mediterranean, formed during the opening of the Neo-Tethys at Permian to Jurassic times, as recorded by subsidence and magmatism along its SE passive margin. While the subsurface extensional structure was reconstructed in detail, the spatial and temporal distribution of igneous activity is not well known. Here we present new SIMS U-Pb dating of zircons from rifting related volcanic sequences recovered from four deep boreholes in the Levant margin of coastal Israel. The Asher volcanics, a deeply buried 2.5 km thick basaltic sequence, which accumulated within fault-bounded basin, was previously dated by K-Ar and Ar-Ar to early Jurassic times. Zircons (n=46) separated from the bottom and top of the volcanic sequence yielded 206±2 Ma and 205 to 202 Ma, respectively, indicating that Asher volcanics are of Late Triassic (Rhaetian) age. Zircon xenocrysts indicate Permian (289±2 Ma) felsic magmatism. Rifting activity in the Levant margin included several Permian-Triassic pulses of faulting and subsidence, with a prolonged magmatism-bearing rifting event at Late Carnian to Rhaetian times (~230-201 Ma). Pulsed rifting is also indicated in the conjugate, northern, margin of the southern Neo-Tethys, and the timing of subsidence and magmatic pulses well correlate to the Levant margin.

Geochemistry and Zircon U‐Pb Dates of Felsic‐Intermediate Members of the Late Cretaceous Yüksekova Arc Basin: Constraints on the Evolution of the Bitlis–Zagros Branch of Neotethys (Elazığ, E Turkey)

AbstractDuring the Late Cretaceous in the Eastern Mediterranean, the northern branch of the southern Neotethys was closed by multiple northward subductions. Of these, the most northerly located subduction created the Baskil continental arc at around 82–84 Ma. The more southerly and intra‐oceanic subduction, on the other hand, produced an arc‐basin system, the Yüksekova Complex, as early as the late Cenomanian–early Turonian. The abundant and relatively well‐studied basaltic rocks of this complex were intruded by dykes, sills and small stocks of felsic–intermediate rocks, not previously studied in detail. The intrusives collected from five different localities in the Elazığ region of eastern Turkey are all subalkaline, with low Nb/Y values. Most of them have been chemically classified as rhyodacites/dacites, whereas a small number appear to be andesites. In normal mid‐ocean‐ridge basalt (N‐MORB)‐normalised plots, the intrusives are characterised by relative enrichments in Th and La over Nb, Zr, Hf, Ti and high field strength elements (HREEs), indicating their derivation from a subduction‐modified source. While their relatively high, positive &amp;#x03B5;Nd(i) values (+6.4 and +7.2) might suggest a depleted mantle source for their ultimate origin, somewhat radiogenic Pb values indicate a sedimentary contribution to the source of the rocks. The overall geochemical characteristics indicate their generation in an oceanic arc setting. The zircon U‐Pb Laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) data obtained from five felsic‐intermediate rock samples yielded intrusion dates of 80–88 Ma. This suggests that the Elazığ oceanic arc‐related intrusives are slightly younger than those of the Yüksekova arc‐basin system, but coeval with the Baskil continental arc. However, the felsic–intermediate intrusives show different geochemical characteristics (oceanic arc‐type, with a lack of crustal contamination) to those of the Baskil continental arc. This indicates that these two igneous systems are unrelated and likely developed in different tectonic settings. This, in turn, supports a geodynamic model in which the northern strand of the southern Neotethys was consumed by multiple northward subductions.

Mantle melting models of the Kızıldağ ophiolite in SE Turkey: Two types of partial melting processes in the oceanic upper mantle of southern Neo-Tethys

Many ophiolites in southern Neo-Tethys contain complete lithologic sequences, with the dikes and lavas commonly having highly variable geochemical compositions. In this study, we examine the sheeted dikes and layered and isotropic gabbros of the Kızıldağ ophiolite (southern Turkey) and suggest that the compositional variations of the rocks are likely related to melting models of the mantle. The sheeted dikes and gabbros of the ophiolite have 206Pb/204Pb(90 Ma) of 17.765–19.361, 207Pb/204Pb(90 Ma) of 15.570–15.665 and 208Pb/204Pb(90 Ma) of 37.812–39.269, straddling the fields of Indian Ocean MORB and modern marine sediments. The sheeted dikes have low rare earth element (REE) concentrations and LaN/YbN ratios (e.g., Yb < 2.5 ppm and LaN/YbN of 0.33 to 0.62 on average), comparable with those of forearc basalt (FAB), except for a few samples whose trace element concentrations and patterns are similar to those of boninite. All the studied samples have positive anomalies of large ion lithophile elements (LILE) (e.g., Rb, Ba, Th, U and Sr) on a N-MORB-normalized trace element diagram and show considerable scatter on the plot of Th/Yb vs. Nb/Yb, which is attributed to involvement of slab-derived melts/fluids in a protoarc-forearc setting. Thermodynamic modelling results suggest that the parental magmas of the sheeted dikes were combined melts derived by both polybaric continuous melting (<10%) and flux-melting (<25%) of the mantle wedge during subduction initiation. In contrast, clinopyroxene and plagioclase in the layered and isotropic gabbros have compositions similar to those of boninite. The gabbro compositions can be simulated by batch crystallization of the boninitic melts, and the relatively high trace element concentrations of some isotropic gabbros likely reflect a high fraction of interstitial liquid in the crystal mush. Thus, we propose that the compositional variations of the sheeted dikes reflect two types of mantle melting, and that the gabbros were produced by subsequent crystallization within a crystal mush having variable fractions of interstitial liquid. Not only can such complex magmatic processes explain the observed compositional variations of dikes and lavas of the Kızıldağ ophiolite, but may be appliable to other ophiolites in southern Neo-Tethys, such as the Lycian, Pozantı-Karsantı and Troodos massifs.

Petrological and geochemical characteristics of the diabase and metasomatised dikes from the Tekirova ophiolite (SW Anatolia, Turkey): Tectonomagmatic evolution of the southern Neotethys

Ophiolites are widespread across the Anatolian plate and formed during the termination of different branches of the Neotethys ocean. The Tekirova ophiolite, situated in the Antalya ophiolite nappes in Southwest Anatolia, originated in the southern branch of the Neotethys. The former ophiolite consists of mantle and crustal sequences, in which, it is predominantly crosscut by the isolated diabasic dikes. Here, we have distinguished two dike types on the basis of their petrographic features and also degree of alteration. The relatively fresh types are generally named as diabase dikes. While the altered types are called as metasomatised dikes, and these dikes display ophitic to subophitic textures. The diabase and metasomatised dikes show enrichment in LILEs and depletion in HFSEs, indicating characteristics of suprasubduction zone ophiolites. This depletion of mobile elements may have been caused by metasomatism. The HFSEs versus HREEs diagrams show that the dikes were formed from 10 to 30% melting of extracted melts from previous mantle melting in which modified by subduction-derived fluids.

Cenomanian “orbitoliniform” foraminifera—State of the art and description of Ebrahimiella dercourti (Decrouez and Moullade, 1974) gen. et comb. nov. (family Coskinolinidae) from the Sarvak Formation (SW Iran, Zagros Zone)

From surface and subsurface sections of the middle Cenomanian Sarvak Formation of SW Iran (Zagros Zone), specimens of “Valdanchella” dercourti Decrouez and Moullade were recovered. With the occurrence of a pseudo-keriothecal wall structure, a large subapical embryo and the lack of horizontal partitions, this taxon can be assigned neither to the late Berriasian–Valanginian Valdanchella Canerot and Moullade nor to any other known genus. Therefore, the genus Ebrahimiella is established with the new combination E. dercourti (Decrouez and Moullade) and assigned to the family Coskinolinidae. Orbitoliniform larger benthic foraminifera evidenced a distinct radiation, in Cenomanian shallow-water carbonates of the former southern Neotethyan margin, especially the Arabian Plate, including also endemic forms. Whereas the lower (p.p. middle?) Cenomanian exhibits the dominance of Orbitolininae (genera Orbitolina, Mesorbitolina, Conicorbitolina), the middle Cenomanian documents the appearance of new taxa of the Dictyoconinae (e.g. Persiconus sarvaki Yazdi-Moghadam and Schlagintweit). An updated inventory of Cenomanian orbitoliniform taxa with stratigraphic ranges is provided.