Ordovician-Silurian palynostratigraphy (Chitinozoa and acritarchs) of the G14-1/86 borehole, southern Baltic Sea

Borehole G 14-1/86, located in the Baltic Sea between the Tornquist Zone an d the Caledonian Deformation Front/Thor Suture, penetrates a Lower Palaeozo ic sedimentary succession deposited on the south-western margin of the East European Platform. Detailed palynological analysis of the Ordovician and S ilurian successions enables precise dating and facilitates provenance inter pretation of the sedimentary sequence. The following chitinozoan biozones a re identified: Cyatho-chitina primitiva Biozone (early - early late Arenig) ; Laufeldochitina striata Biozone (late Abereiddian - late Llandeilan) and Ancyrochitina merga Biozone (Cautleyan - Rawtheyan, middle Ashgill). A furt her chitinozoan assemblage is possible to be correlated with the global Spi nachitina maennili Biozone (uppermost Rhuddanian - lower Telychian). A rela tively diversified acritarch assemblage of Ashgill age (independently dated by Chitinozoa) also occurs. This assemblage contains numerous reworked for ms of Llanvirn, Tremadoc and late Cambrian ages. The reworked Llanvirn acri tarchs are typical of the high-latitude Perigondwanan micro-phytoplankton p alaeobioprovince and testify to detrital input of Gondwanan-related source during the Ashgill, suggesting that by this time the Tornquist Ocean was cl osed.