Us, Muhammed Sami; Tekin, Erdoğan; Akgün, Funda; Kayseri-Özer, Mine Sezgül; Varol, Baki Erdoğan

This study presents an integrated sedimentological, microfacies, and palynological analyses of the Late Eocene–?Early Oligocene (Priabonian–?Rupelian) Akçapınar Formation, exposed along the Soğanlı Stream in the Intra-Pontide Belt of the Western Black Sea region, Turkey. The formation, which overlies the evaporitic Pürçükören Formation and locally the Soğanlı Formation, records deposition in restricted shallow-marine to a lagoonal setting during a phase of significant tectonic and climatic reorganization. Detailed field mapping and measured stratigraphic sections, supported by petrographic, XRD, and SEM analyses, reveal mud-supported textures, limited faunal diversity, and thin-shelled gastropods, consistent with low-energy, brackish conditions. Palynological assemblages, identified here for the first time, refine the age constraints and document freshwater influence, whereas mineralogical data indicate alternating arid (smectite-rich) and humid (chlorite–illite-rich) intervals. Microfacies patterns (Mf1–Mf4) and lithofacies associations (Lf1–Lf8) were synthesized into three-dimensional depositional models, illustrating progressive basin restriction, episodic subaerial exposure, and evaporite precipitation. The multi-proxy approach, integrating sedimentology, microfacies, palynology, and mineralogy, refined the depositional model of the Akçapınar Formation, revealing facies heterogeneity driven by the interplay of tectonically induced basin isolation, relative sea-level fluctuations, and paleoclimatic oscillations during the Eocene–Oligocene transition, and providing new insights into the paleogeographic evolution of the northern Neo-Tethys during the final stages of its closure.

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Görmüş, Muhittin; Kadioğlu, Yusuf Kağan; Varol, Baki Erdoğan; Us, Muhammed Sami

Seed like fossils recognized by their distinctive orbicular in shape are seen in the early Miocene of the Nallıhan area (NW Türkiye). We examined more than one hundred specimens and facies associations for interpreting of fossil morphology and its paleoenvironment. The fossils as dark crystallized dots on the bedding surface of clayey limestones are characterized by a thick edged lenticular shape with a smooth one side and concave another side with circular nucleus. Their internal structures have circular a few whorlings, too often radial calcitic lamellae on the upper side and a few circular coiling at the bottom side. SEM, EPMA and RAMAN data of soft nucleus, hard part, filling materials and surrounding sediments support its plant origin. The Paleogene aged Kızılbayır formation and early Miocene aged Karadoruk and Akpınar formations include the following facieses: non-channelized red sandstone and mudstone (F1), channelized “confined” reddish-beige pebbly sandstone and conglomerate (F2), medium to coarse siliciclastics (F3), mudstones interbedded with sandstones (F4), thin bedded clayey limestone bearing plant fossils (F5) medium to thick bedded limestone (F6) and rhythmic siliciclastics - clayey limestone including coal occurrences (F7). Abundant plant fossils indicate a planted shallow lake margin with low topography during the early Miocene.

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