The Tylawa Limestones – a regional marker horizon in the Lower Oligocene of the Paratethys : diagnostic characteristics from the type area

Three units of laminated coccolith limestone are used as regional chronohorizons in the Oligocene of the Outer Carpathians. Two of them – the Tylawa Limestones and the Jasło Limestone display a similar type of lamination and their discrimination is in some cases problematic. We provide a detailed mesoscopic and microscopic lithological description of the Tylawa Limestones from the type locality at Tylawa and from Rudawka Rymanowska – the best exposure in the Polish Carpathians. The finely laminated limestone layers are up to 5.5 cm thick and are dispersed through a section more than 100 m thick. They are grouped in clusters. They differ from the younger Jasło Limestone in: (1) an absence of foraminifers, (2) a mass occurrence of Reticulofenestra ornata Müller, (3) the presence of voids after pennate diatoms, (4) dark laminae which are more pronounced than in the Jasło Limestone.