Impact of maturity on producible shale oil volumes in the Silurian (Llandovery) hot shales of the northern Arabian plate, southeastern Turkey

The Silurian (Llandovery) hot shales in southeastern Turkey have excellent source rock potential, with an average total organic carbon (TOC) of 5.9 wt. % and generation potential values of 14.9 mg HC/g TOC. The hot shales contain type II organic matter and demonstrate oil and secondary gas generation potential. Hydrogen indices range from 36 to 510 mg HC/g TOC, depending on maturity. The hot shales in the Gulf Kevan 1 and Turkish Petroleum (TP) Dogan 1 wells are immature-early mature with a vitrinite reflectance equivalent (R-equ) of 0.58%-0.76%. The hot shales in the TP Soguktepe 1 and TP K. Migo 2 wells are mature and in the oil window at 0.78%-0.92% R-equ. The hot shales are interpreted to be in the wet gas-condensate maturity window with 1.08%-1.30% R-equ in the TP G. Hazro 2 and TP-Arco Abdulaziz 1 wells. Corrected (evaporation loss restored using oil API gravity values) oil saturation index values (OSIc) within the Gulf Kevan 1, TP Dogan 1, and TP-Arco Abdulaziz 1 wells are less than 100 mg HC/g TOC, which indicates that unconventional commercial oil production is not probable. The OSIc values of the mature hot shales at the TP Soguktepe 1, TP K. Migo 2, and TP G. Hazro 2 wells all exceed 100 mg HC/g TOC, indicating potentially producible oil and wet gas condensate. Thus, producible oil and wet gas condensate in the hot shale play appear present in areas that have been assessed as having between 0.8% and 1.1% R-equ

Thuringian affinity of the Silurian-Lower Devonian succession from the Eastern Taurus, Turkey

The Silurian-Lower Devonian succession in the Degirmentas-Halevikdere section (E Taurides) shows considerable lithostratigraphic similarities to the three-partite subdivision, initially documented in the same stratigraphic interval in Saxo-Thuringia and later in other peri-Gondwanan terrains. The Llandovery-Wenlockian part of the studied section (ca. 40 m) is characterized by black graptolitic shales. The Llandoverian part is dominated by radiolarian ribbon cherts (ca. 20 m). The Rhuddanian Akidograptus ascensus, Parakidograptus acuminatus, and Cystograptus vesiculosus biozones have been recognized in its lower part, while in the upper part of the succession, the lowermost Telychian Rastrites linnaei Biozone has been documented. The Telychian Spirograptus turriculatus and Streptograptus crispus biozones, as well as the Sheinwoodian Cyrtograptus rigidus/Monograptus belophorus Biozone, have been identified within this succession. Graptolites of the Homerian (Colonograptus deubeli + Col. praedeubeli and Col. ludensis biozones) are only found in the Pekmezkoy and Gurlesen areas, in the black shales, immediately before the first ocher-colored limestone, which is characteristic for the Ockerkalk Formation in the Thuringian facies. The dominantly ocher-colored shale-limestone alternation in the Degirmentas-Halevikdere section is ca. 50 m in thickness. The lower Ludlowian part is enriched by nautiloids, while in the Pridolian part crinoids are abundant. It is covered by 60-m-thick black shales and siltstones, corresponding to the Upper Graptolite Shale Formation in the Thuringian. The Silurian-Devonian boundary is located in the lower part of this unit on the basis of lobolith findings. The depositional model proposed here accounts for the migration of the considered peri-Gondwana terrains from high to low paleogeographic latitudes that has triggered changes not only in the ocean water thermohaline circulation but also in the wind-driven downwelling or upwelling systems. These changes are responsible for the progressive transition from an oxic regime to an anoxic one in the deep oceanic depositional environments (outer continental shelf, slope, and ocean basin settings) and the deposition of light and dark sediments there

Neoproterozoic continental arc volcanism at the northern edge of the Arabian Plate, SE Turkey

New geochemical, Sr/Nd isotope and zircon U-Pb LA-ICP-MS data from the Derik Volcanics in the Southeast Anatolian Autochthone Belt of Turkey are consistent with an Andean-type Cadomian arc that developed along the northern edge of the Arabian Plate during the Late Neoproterozoic. The Derik Volcanics represent a volcanic complex including andesites, rhyolites and basalts, with volcanoclastic and fluvial sediments. They are unconformably overlain by playa sediments with Early Cambrian ichno-fossils, followed by Middle Cambrian-Silurian shallow marine deposits

P-T-t evolution of eclogite/blueschist facies metamorphism in Alanya Massif: time and space relations with HP event in Bitlis Massif, Turkey

The Alanya Massif, which is located to the south of central Taurides in Turkey, presents a typical nappe pile consisting of thrust sheets with contrasting metamorphic histories. In two thrust sheets, Sugozu and GundogmuAY nappes, HP metamorphism under eclogite (550-567 A degrees C/14-18 kbar) and blueschist facies (435-480 A degrees C/11-13 kbar) conditions have been recognized, respectively. Whereas the rest of the Massif underwent MP metamorphism under greenschist to amphibolite facies (525-555 A degrees C/6.5-7.5 kbar) conditions. Eclogite facies metamorphism in Sugozu nappe, which consists of homogeneous garnet-glaucophane-phengite schists with eclogite lenses is dated at 84.8 +/- A 0.8, 84.7 +/- A 1.5 and 82 +/- A 3 Ma (Santonian-Campanian) by Ar-40/Ar-39 phengite, U/Pb zircon and rutile dating methods, respectively. Similarly, phengites in GundogmuAY nappe representing an accretionary complex yield 82-80 Ma (Campanian) ages for blueschist facies metamorphism. During the exhumation, the retrograde overprint of the HP units under greenschist-amphibolite facies conditions and tectonic juxtaposition with the Barrovian units occurred during Campanian (75-78 Ma). Petrological and geochronological data clearly indicate a similar Late Cretaceous tectonometamorphic evolution for both Alanya (84-75 Ma) and Bitlis (84-72 Ma) Massifs. They form part of a single continental sliver (Alanya-Bitlis microcontinent), which was rifted from the southern part of the Anatolide-Tauride platform. The P-T-t coherence between two Massifs suggests that both Massifs have been derived from the closure of the same ocean (Alanya-Bitlis Ocean) located to the south of the Anatolide-Tauride block by a northward subduction. The boundary separating the autochthonous Tauride platform to the north from both the Alanya and Bitlis Massifs to the south represents a suture zone, the Pamphylian-Alanya-Bitlis suture

Ordovician chitinozoans and acritarchs from southern and southeastern Turkey

International audienceRevision of the lithostratigraphy of Ordovician deposits in southern and southeastern Turkey led to a re-evaluation of the age assignments of formations identified in the subsurface and at outcrop. Previous datings were based on macrofauna (mainly trilobites and graptolites). The present paper focuses exclusively on organic-walled microfossils (chitinozoans and acritarchs), which provide numerous chronostratigraphical improvements, especially in successions barren or poor in macrofossils. Close to 200 samples were collected in the Taurus chain (i.e. from Kemer, Seydisehir, Ovacik, Kozan, to Sariz regions in southern Turkey) and in the Border Folds (Mardin and Hakkari regions), usually regarded as part of the Arabian Plate in palaeogeographical reconstructions. Many samples are productive and yield chitinozoans and/or acritarchs of extremely variable preservation, depending on their geographical and geological location. In the Taurus chain, the material is “coalified” and frequently fragmented whereas, in the Border Folds, maturation of the organic matter is much lower and preservation of the microfossils is good to excellent. Several Ordovician chitinozoan biozones (northern Gondwana zonation) as well as diagnostic acritarch assemblages are identified in southern and southeastern Turkey. These Ordovician formations are assigned here to the new global stages of the Ordovician chronostratigraphical scale. The Seydisehir (upper part), Sobova, and Kilgen Lake (lower part) formations are referred to the Darriwilian. The Kilgen Lake (upper part), Sort Tepe, and Bedinan formations are attributed to the Sandbian and to the Katian, and the Halevikdere Formation (glacio-marine part) is assigned to the Hirnantian. Reworking of Early Ordovician acritarchs is documented in pre-glacial and in glacial Late Ordovician deposits. They indicate that active erosive processes occurred during the Middle and Late Ordovician sedimentation. The organic-walled microfossils recorded in the Ordovician of south and southeastern Turkey belong to the northern Gondwana realm. Interestingly however, some Baltoscandian influences are noted in the Border Folds during Early Late Ordovician