A condensed Cretaceous succession from the Beyaz Aladağ Unit (Aladağlar, Eastern Taurides, South Türkiye): calpionellids and planktonic foraminiferal biozones

Abstract

The Aladağlar region is located at the west end of the Eastern Taurides and is characterized by napped structures/thrust sheets. The thrust sheets named “Beyaz Aladağ” form the most prominent mountainous part of the Aladağlar to the east of the Ecemiş strike-slipe fault. A previously unidentified condensed pelagic succession was discovered in small outcrops which are difficult to access. This study describes the Cretaceous condensed pelagic succession and produces a biostratigraphic framework based on the present calpionellids and planktonic foraminiferal assemblages studied in thin sections. A complete Cretaceous succession was identified by combining different outcrops affected by regional tectonic and erosional processes. We define the Cretaceous succession as “a chaotic succession” that includes gravity slide limestone blocks and debris flow intercalations which constitute approximately half of the 50 m thick succession. In different localities, different stratigraphic intervals (Berriasian-Valanginian, Albian, and Turonian) of the Cretaceous succession unconformably overlie the Triassic-Lower Jurassic shallow marine platform carbonates. The succession is composed of pinkish and light beige colored, thin-bedded cherty pelagic limestones together with carbonate breccias and boulders mainly derived from Lower Jurassic shallow marine limestones. The Berriasian-Valanginian interval is characterized by the occurrence of abundant calpionellids, sparse radiolarians, and calcispheres. This interval is constrained by the presence of Calpionella gr. alpina/elliptica, Remaniella sp., and Crassicollaria sp. It is conformably overlain by an unfossiliferous interval which is considered Hauterivian-early Albian(?) in age since sedimentation seems to be continuous. The upper Albian-Coniacian interval is characterized by the presence of abundant and well-preserved planktonic foraminifera. The upper Albian Pseudothalmanninella ticinensis and Thalmanninella appenninica Zones and the upper Cenomanian Rotalipora cushmani Zone are distinguished. The Turonian-Coniacian interval is the most complex part of the succession because it also contains gravity-slide blocks of Albian and Cenomanian pelagic limestones as well as carbonate breccias. The Helvetoglobotruncana helvetica (lower-middle Turonian), Marginotruncana schneegansi (upper Turonian), and Dicarinella concavata Zones (upper Turonian-Coniacian) are identified in the Turonian-Coniacian interval. The condensed Cretaceous succession can be correlated in terms of tectonostratigraphic position, stratigraphy, and paleoenvironmental setting with the Boyalı Tepe unit in the Beyşehir-Hoyran nappes of the Central Taurides, with the Domuzdağ unit in the Lycian nappes and with the Urbut succession in the Bornova Flysch Zone of the Western Taurides. These successions have been interpreted as platform margin deposits (Tauride Carbonate Platform) or as off-margin drowned carbonate platforms removed from a continental source. The absence of platform margin bioclasts confirms the latter interpretation.