Implications of U–Pb and Lu–Hf isotopic analysis of detrital zircons for the depositional age, provenance and tectonic setting of the Permian–Triassic Palaeotethyan Karakaya Complex, NW Turkey

New zircon U-Pb age data, combined with Lu-Hf isotopic data, are presented here for sandstones of mainly arkosic composition from the Permian-Triassic Karakaya Complex. Predominantly, Carboniferous, Triassic and Devonian zircon age groups are recognised, most of which have a Late Triassic (Carnian-Norian) maximum depositional age. Carboniferous- and Devonian-aged zircon populations exhibit intermediate epsilon (Hf(t)) values (-11 to +2), consistent with formation in a continental margin arc setting where juvenile mantle-derived magma mixed with (recycled) old crust of Palaeoproterozoic Hf model age. In contrast, the Triassic-aged zircon population exhibits higher epsilon (Hf(t)) values (-5 to +4), consistent with mixing of juvenile mantle-derived melts with (recycled) old crust of Neoproterozoic Hf model age. Potential igneous source rocks for the sandstones of the Karakaya Complex exist in the Devonian and Carboniferous granitic rocks of the Sakarya continental basement to the north. Their epsilon (Hf(t)) and corresponding model ages are nearly identical to the age-equivalent zircon populations within the Karakaya Complex sandstones. However, the Triassic granitic rocks of the Sakarya continental crust differ significantly in epsilon (Hf(t)) and corresponding model age from the sandstones of the Karakaya Complex. Late Triassic sandstones from the Tauride continental unit to the south lack the dominant Late Palaeozoic and Triassic zircon populations of the Karakaya Complex sandstones. Triassic granitic bodies and intermediate-composition extrusive rocks in the Tauride continental unit also differ in epsilon (Hf(t)) and corresponding Hf model ages from the Karakaya Complex sandstones. In addition, Late Triassic sandstones of the Kocaeli Triassic unit (A degrees stanbul Terrane) in the north differ strongly from the Karakaya Complex sandstones in zircon population ages and epsilon (Hf(t)). In the regional context, the new zircon age and lutetium-hafnium isotopic data are consistent with derivation of the Late Triassic Karakaya Complex sandstones from a Late Palaeozoic-Triassic continental margin arc located somewhere along the southern margin of Eurasia, although its exact position cannot be pinpointed at present owing to lack of suitable outcrop and comparable isotopic data

New Geosite Candidates at the Western Termination of the Büyük Menderes Graben and their Importance on Science Education

The Buyuk Menderes Graben (BMG) is one of the best-known and the largest geological structure of the West Anatolian Extensional Province. It includes two nature conservation parks and twelve cultural heritage sites within and in its vicinity. Four geologically distinct features/locations within and in the vicinity of the BMG have been previously enlisted as geosite candidates in the provisional Geological Heritage Inventory of Turkey compiled in 2002 by the Turkish Association for the Conservation of the Geological Heritage (JEMRKO): (1) the horst-graben structure of the Buyuk Menderes region itself, (2) the tafoni from the augen-gneiss from the east of Bafa Lake, (3) the zultanite crystals from the northeast of lbir Mountain, and (4) the tourmaline (dravite) crystals from the Camzal, Cine. In the current study, we are introducing additional three new geosite candidates at the western termination of the BMG with three different main geological subjects. The first one is the Yavansu Fault. Located 2 km south of the Kuadas village, it has a clearly exposed unique fault surface which is one of the best examples of structural indicators for the WAEP with respect to the normal faulting events. The second one is located in the Hisartepe Volcanics exposed between Kuadas and Soke, and consists of basaltic lava flows with remarkable prismatic cooling joints and a gorgeous feeder dome reaching up to 150 m height. Final suggestion is the Karina marine fan-delta complex located at the south-eastern border of the Dilek Peninsula National Park. This fan-delta complex is the largest one in the Western Anatolian scale and has remarkable paragon outcrops up to 20 m high between Doanbey and Karina Lagoon

Detrital zircon geochronology of the Cretaceous succession from the Iberian Atlantic Margin: palaeogeographic implications

Detrital zircon U–Pb data performed on eight Cretaceous sandstone samples (819 age isotopic results) from the Lusitanian basin (west Portugal) constrain the history of uplift and palaeodrainage of western Iberia following break-up of Pangaea and opening of the North Atlantic Ocean. We examined the links between shifts in provenance and known basinwide unconformities dated to the late Berriasian, Barremian, late Aptian and Cenomanian–Turonian. The detrital zircon record of sedimentary rocks with wider supplying areas is relatively homogenous, being characterized by a clear predominance of late Palaeozoic ages (c. 375–275 Ma) together with variable proportions of ages in the range c. 800–460 Ma. These two groups of ages are diagnostic of sources within the Variscan Iberian Massif. A few samples also reveal significant amounts of middle Palaeozoic (c. 420–385 Ma) and late Mesoproterozoic to early Neoproterozoic (c. 1.2–0.9 Ga) zircon, which are almost absent in the basement to the east of the Lusitanian basin, but are common in terranes with a Laurussia affinity found in NW Iberia and the conjugate margin (Newfoundland). The Barremian unconformity marks a sudden rise in the proportion of c. 375–275 Ma zircon ages accompanied by a decrease in the abundance of the c. 420–385 Ma and c. 1.2–0.9 Ga ages. This shift in the zircon signature, which is contemporaneous with the separation of the Galicia Bank from Flemish Cap, reflects increased denudation of Variscan crystalline rocks and a reduction in source material from NW Iberia and adjoining areas. The late Aptian unconformity, which represents the largest hiatus in the sedimentary record, is reflected by a shift in late Palaeozoic peak ages from c. 330–310 Ma (widespread in Iberia) to c. 310–290 Ma (more frequent in N Iberia). It is considered that this shift in the age spectra resulted from a westward migration of catchment areas following major uplift in northern Iberia and some transport southward from the Bay of Biscay under the influence of a well-established Atlantic circulation