ANALYSIS OF THE TAXONOMIC COMPOSI TION OF THE LLANDOVERIAN AND WENLOCKIAN FOSSILS OF MOLDAVIAN PRIDNESTROVYE ENTERED IN THE ELECTRONIC DATABASE “THE PALAEONTOLOGY OF PRIDNESTROVYE”
Authors: Anastas A. V. 
Published: September 2021

Problem statement and purpose. In geological surveys of the territory of the Moldavian SSR from the 1960th to the 1990th, deep horizons of Palaeozoic sedimentary rocks were discovered, the leading place among which belongs to the Silurian deposits. At that time, several dozen species and genera of fossils were identified in the Silurian of Moldavian Pridnestrovye. In 2020, as part of the work financed from the state budget on the theme of the creation of GIS “The Geology of Pridnestrovye”, the laboratory “The Geological Resources” developed an electronic database called “The Palaeontology of Pridnestrovye”. The fauna included in the database of palaeontology was divided into groups corresponding to their palaeontological classes and stratigraphic horizons: “Ordovician brachiopods”, “Silurian tabulates”, “Palaeogene foraminifers”, “Neogene bivalves”, etc. Species and genera of the fauna were linked to specific formations and locations, which provides good opportunity for palaeontological analysis of individual formations, horizons, cores of drilling and outcrops. The purpose of this article is to compile lists of fauna from the Llandoverian and Wenlockian formations of Moldavian Pridnestrovye and to compare their chronology with fossil fauna data on the sameage rocks of Podillia, Estonia and Lithuania.
Material and methods. Four survey reports deal that on sheets L‑35-V and L‑35-XII were used as the material. The goal was concerning the sedimentary rocks of Llandovery and Wenlock Series. In the local scheme it corresponds to the Marasesti, Step-Soci, Cioc-Maidan (all in Llandovery), Balti formations and Lower Puhoi subformation (Wenlock). The intervals of the formations in boreholes are composed of organogenic limestones, silty, argillaceous stones, argillites and dolomites. The species and genera of the fauna from these intervals are compared with the biostratigraphic data from Podillia, Estonia and Lithuania.
Results. In the stratigraphic sequences of Llandovery and Wenlock of the Moldavian Pridnestrovye, (in most cases) species and genera unique to those divisions of brachiopods, tabulates, stromatoporoids, ostracods, rugosans, and trilobites were identified by specialists; a smaller part of the taxa pass between the lowest formations of the Silurian and the overlying Balti formation. Most taxa have correspondences in the Podillian and Baltic basins; however, in these regions, the species and genera identified in Llandovery or Wenlock of Moldavian Pridnestrovye are mostly transitive between Silurian divisions, up to the Ludlow and Pridoli Series. There is practically no identified fauna in the Lower Puhoi sub-formation of Moldavian Pridnestrovye because of its facial specifics. The species Acidolites lateseptatus (Lindstroem), Altha modesta Neckaja, Longiscula caudalis (Jones) in Llandovery and Pentamerus oblongus Sowerby, Halysites catenularius Linnaeus = Halysites priscus Klaamann in Llandovery and Wenlock Series were the only guideing fauna for the first two Silurian series of Moldavian Pridnestrovye. Due to the attribution of the Muksha sub-formation of Podillia to Ludlow Series, no guiding species of the Wenlock stage was identified in the Balti formation of Moldavian Pridnestrovye.