Aalenian-Early Bathonian (Middle Jurassic) radiolarian assemblages in the Tavas nappe within Lycian nappes in the western Taurides (SW Turkey): The first dating of carbonate platform drowning

摘要

Stratigraphic sections (Kizilca and Kizilca North) in the Tavas nappe, western Taurides, Turkey records the event of carbonate platform drowning in the western Tethyan realm. Our detailed biostratigraphic study of radiolarians and other microfossils places the important temporal constraints on this event and indicates that drowning occured in the geochronological interval from Early Jurassic (Hettangian-Sinemurian) through to Middle Jurassic (early Bathonian). The basal part of the Kizilca section is represented by platform carbonates with abundant benthic foraminifera and algae of Hettangian-Sinemurian to Pliensbachian age. Toward the upper part of the section, the occurrence of brecciated limestones with some ammonites and belemnites reveals that the drowning event began in the Pliensbachian. The first radiolarian assemblages of early-middle to late Aalenian age were obtained from the overlying units characterized by pelagic limestones and chert alternation. Just after the subsidence of the platform, ribbon chert sedimentation began in the late Aalenian, as indicated by the radiolarians. Successively, early-late Bajocian and latest Bajocian-early Bathonian radiolarian assemblages were obtained from overlying chert with mudstone-silicified mudstones. Similar to that observed in the Kizilca section, the Kizilca North section include successively pelagic limestones, pelagic limestone-chert alternation and chert-mudstone alternation of late Aalenian to early-middle Bajocian age according to radiolarian biostratigraphy. All of these observations indicate that a continuous stratigraphy recorded the drowning event without a large gap from Hettangian-Sinemurian to early Bathonian in the Tavas nappe. This drowning event has close similarities with coeval events in other Tethyan realms in terms of mechanism, facies characteristics and fossil assemblages. Therefore, this study can aid correlation studies of the Tavas nappe with the Jurassic paleogeography worldwide. (C) 2014 Elsevier Ltd. All rights reserved.