Abstract This paper summarizes recent knowledge on the palaeontology, biostratigraphy, correlation, sea-level and climate history and isotopic geochemistry of the Ordovician rocks in the western and central parts of the East European Craton, in the area extending from the southern margin of the Fennoscandian Shield to the western margin of the Ukrainian Shield. The regional chronostratigraphic standard is briefly summarized and its correlation to the global standard of the Ordovician is addressed. A two-part correlation chart of 10 areas with unique local Ordovician successions is aligned with the most recent international correlation standard of the Ordovician System and presented against the regular timescale. An updated summary of the evolution of the marine assemblages is provided, the principal gaps in the existing extremely rich palaeontological database are identified and the main bioevents are discussed.

Abstract Lithuania is a comparatively small country (65 000 km 2 ) with prevailing flat, glacial and post glacial relief composed of soft sediments without any rocky formations visible on the surface. There are no underground mines, but rather only pits for sand and gravel and few quarries of dolomite and limestone. Oil is produced from 15 oil fields in the west of the country. All potable water is taken from aquifers, with negligible if any concern. Most people, therefore, know very little about the geology of Lithuania and hardly realize what the Geological Survey is doing. Only in rare cases of hazardous events, like the Kaliningrad earthquake in 2004, or landslides devastating Gediminas Hill in 2016–17, or the largest karst sinkholes, is the name of the Geological Survey visible in the mass media. Nevertheless, the Geological Survey operates with several duties, private sector geological companies are generating business, and geosciences are on the agenda of scientific institutions. The aim of this study is to take a deeper look into the current factors that are determining the role of the Geological Survey of Lithuania at present, and to outline circumstances which could influence the role of the Survey in the future.

An accurate chronology for the exchange of aquatic species between water basins is important for paleoenvironmental reconstruction on both regional and continental scales. During the early Holocene, the range of zebra mussels, Dreissena polymorpha , was limited to the Black, Azov, Caspian, and Aral Seas, as well as the estuaries and lower and middle reaches of the Pontic-Caspian rivers. We present new findings that challenge the currently held view that this species migrated into the Baltic Sea watershed during the early 1800s through the canals joining the tributaries of rivers that drain into the Black and Baltic Sea basins. Geological investigations along the southeast Baltic Sea coast (Curonian and Vistula spits and lagoons) have uncovered shells of D. polymorpha that yielded radiocarbon ages older than 1000 radiocarbon yr B.P. We propose two scenarios to explain the new radiocarbon dates for D. polymorpha . The first scenario involves an anomalously large reservoir effect—as large as 600–800 yr—however, several lines of evidence cast doubt upon the validity of such a large reservoir correction. The second scenario that might explain the old zebra mussel ages is the earlier arrival of Dreissena polymorpha into the Baltic region. Natural exchange may have been facilitated by the proximity of the tributaries draining the Pontic and Baltic watersheds. Human-mediated transport is also considered in association with Viking voyages from the Baltic to the Black and Caspian Seas between A.D. 800 and 1000, and the riverine trade exchange during the Lithuanian expansion into the Pontic steppe in subsequent centuries. It is likely that both scenarios played a role, with implications for late Holocene biogeography and paleoecology of the Pontic-Caspian and Baltic basins.