Demircan H.,Mineral Research and Exploration MTA |
Uchman A.,Jagiellonian University
Acta Geologica Polonica | Year: 2012
The pascichnial trace fossil Bichordites kuzunensis isp. nov. occurs as an epichnial complex structure in early Oligocene prodelta sediments of the Thrace Basin in Gökçeada Island, northwest Turkey. It displays characteristics of irregular echinoid burrows such as overall shape and a double meniscate filling with a chevron dorsal suture, in addition to the feature typical of the so far monospecific Bichordites Plaziat and Mahmoudi, 1988, that is a single central core around a single drainage tube. Its miniature size can be related to the small size of the tracemaker (ontogenic feature) or to its dwarfism in a stressed deltaic environment (palaeoecological feature). Its occurrence indicates a period of fully marine conditions during accumulation of the deltaic sediments of the Mezardere Formation.
Kadir S.,Eskiehir Osmangazi University |
Eren M.,Mersin University |
Atabey E.,Mineral Research and Exploration MTA
Clays and Clay Minerals | Year: 2010
The origins of dolocrete and associated palygorskite in the Çanakkale region of Turkey have been little studied, but are of fundamental importance for a more complete understanding of the mineralogy of this region. The present study was undertaken in order to narrow this gap. Siliciclastic red mudstones within alluvial-fan deposits of the Middle Miocene Sariyer Formation locally contain dolocretes in various forms (powdery, nodular, and fracture-filling) and scarce matte-brown, authigenic clay lenses. The mineralogical characteristics of dolocrete and authigenic clay lenses were examined using polarized-light microscopy, X-ray diffraction, differential thermal analysis and thermal gravimetry, scanning-electron microscopy, and infrared spectroscopy, as well as by chemical and isotopic methods. These analyses indicate that the dolocretes are indeed predominantly dolomite, coexisting with variable amounts of palygorskite. The authigenic clay lenses are composed mainly of palygorskite. Dolomite appears as euhedral crystals, whereas palygorskite developed authigenically as interwoven fibers on and between resorbed dolomite crystals, rimming euhedral crystals, and as fiber bundles (where dolomite ± magnesite is absent). The stable-isotope values and some petrographic features, such as alveolar texture and dolomite needles, support a pedogenic origin for the dolocretes. In the initial stage, dolomite formed by replacement of siliciclastic red mudstones and/or by precipitation from percolating soil-derived water in a near-surface setting. Subsequently, palygorskite either precipitated on the dolomite crystals from relatively more evaporative water, replaced the host-rock mudstone in the presence of Al + Fe, or formed directly from solution where the Ca/Mg ratio decreased and the Al + Fe increased. In view of the large Cr and Ni contents of the bulk-rock samples, the elements required for the crystallization of dolomite and palygorskite (namely Mg, Ca, Si, Al, and Fe) may have been supplied by weathering of ophiolitic rocks that crop out in the area.
Kadir S.,Eskiehir Osmangazi University |
Akbulut A.,Mineral Research and Exploration MTA
Neues Jahrbuch fur Mineralogie, Abhandlungen | Year: 2011
The Upper Miocene - Lower Pliocene clayey sedimentary units of the çameli formation in the Sapaca area (DenizliProvince, Turkey) were deposited in an areally limited, shallow-lacustrine environment and consist of mainly grey-green clays withintercalations of scarce detrital material, clayey dolomite and dolomite. The clayey units are dominated by palygorskite, associatedmainly with smectite and abundant dolomite, with accessory chlorite, illite, quartz, amphibole, feldspar and amorphous material.The distribution of palygorskite and smectite varies with lithological changes. Smectite- and chlorite-bearing intervals werelargely due to partial increase in detrital-sediment input throughout the sequence especially in the lower and upper levels, whereaspalygorskite predominates in the middle level of the sequence throughout the basin in association with scarce dolomitic material.Development of sedimentary structures, such as dessication cracks, root imprints, and sinusoidal ripple marks, was widespread inthe Sapaca lake particularly during some late carbonate precipitation and periods of emergence. Observations via scanning andtransmission electron microscopy indicate that short palygorskite fibres and fan-shaped fibre bundles grew from partiallly erodedsmectite and on dolomite grains. Based on field evidence and mineralogical determinations, the palygorskite is presumed to haveformed authigenically either by conversion from detrital smectite or by direct precipitation in a dolomite-mixing environment. TheSi, Mg, Al + Fe and Ca required for palygorskite formation and dolomitization were supplied in solution(s) from the basement units,namely, ultrabasic rocks, ophiolitic m61ange and ophiolite gravel-bearing conglomerate, smectitic clays and dolomitic carbonates. © 2011 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany.
Middle-late Asselian (Early Permian) fusulinid fauna from the post-Variscan cover in NW Anatolia (Turkey): Biostratigraphy and geological implications [Faunes de fusulines de l'Assélien moyen-supérieur (Permien inférieur) de la couverture postvarisque du Nord-Ouest de l'Anatolie (Turquie): implications biostratigraphiques et géologiques]
Okuyucu C.,Mineral Research and Exploration MTA |
Cemal Goncuoglu M.,Middle East Technical University
Geobios | Year: 2010
The earliest autochthonous cover of the Variscan basement of the Sakarya Composite Terrane (SCT) in NW Anatolia is represented by basal conglomerates and limestones. The microfacies types of the limestones in ascending order are: (1) bioclastic grainstone/packstone, (2) fusulinid grainstone/packstone, (3) smaller foraminiferal grainstone/packstone, (4) Anthracoporella (dasycladale) grainstone/packstone, and (5) wackestones. Twenty-three species assignable to 15 genera of fusulinids were recovered from the studied materials of the Kadirler section; Quasifusulina guvenci nov. sp. and Pseudoschwagerina beedei magna nov. subsp. are created. Rugosofusulinids, sphaeroschwagerinids, pseudoschwagerinids, occidentoschwagerinids, pseudochusenellids, quasifusulinids, rugosochusenellids and paraschwagerinids are the main faunal elements of the succession, which shows two distinct faunal intervals. Eoschubertella, Schubertella, Biwaella?, Rugosofusulina stabilis group, and Pseudochusenella correspond to the first interval at the base; the second interval is characterized by the species of Sphaeroschwagerina, Pseudoschwagerina, Occidentoschwagerina, the Rugosofusulina latispiralis group, and diverse quasifusulinids. A biostratigraphic correlation shows that the Kadirler section in the SCT in NW Anatolia shares many common species with Central Asia in the East but especially with the Carnic Alps and Karavanke Mountains in the West. The new data suggest that the close faunal relationship in the Late Carboniferous between eastern Alps, Ural Mountains, NW Turkey and Central Asia also continued during the Asselian. © 2009 Elsevier Masson SAS.