Some Problems of Biostratigraphy and Palynological Correlation of Upper Formation (Tg. 4) from Tulghes Group, East Carpathians (Romania)

For the biostratigraphical characterization of the metamorphic formations, beside the structure and tectonic particularities, the only biostratigraphical guide – marks are represented by the acritarchs and chitinozoans assemblages. For Upper Formation (Tg. 4) of Tulghes Group from Eastern Carpathians is an example difficult to study and biostratigraphical correlation due to its boundary position between Upper Cambrian and Lower Ordovician. Previous studies on chitinozoan and acritarch assemblages allowed some interesting palynological and biostratigraphical conclusions. The position of our country's territory in Perigondwanaland, at the intersection of warm and cold microfloristic element, from Upper Cambrian and Lower Ordovician, as well as the total lack of trilobite and graptolite fossil rests, for zonation and analogy, tectonization and the powerful metamorphism of the analyzed samples induced great difficulties in the biostratigraphical characterization of these formations. We consider that any biostratigraphical boundary between different geological formations represents a palaeobiological transitory zone, with an exchange and a gradual replacement of faunistic and floristic elements, with the turning up of palaeobiological assemblages with biostratigraphical provincialism characters. For a correct positioning we have considered that Tremadocian represent Arenigian or Early Ordovician stage, considering the interlaying of Tremadocian acritarch assemblage with Arenigian chitinozoan ones, both identified on the same analyzed samples from the Upper Formation (Tg. 4) of Tulghes Group.