Age Constraints of the Sturtian Glaciation on Western Baltica Based on U-Pb and Ar-Ar Dating of the Lapichi Svita

The sedimentary cover of the western part of the East European Craton contains records of glacial periods. Their age has been constrained untill recently by 1000 Ma detrital zircons and overlying basalts of the Volyn Large Igneous Province, dated at c. 580 Ma. In Belarus, the dolomitic Lapichi Svita is sandwiched locally between the glacial and periglacial sediments. The underlying Orsha Svita contains evidence of a periglacial climate, whereas the overlying Vilchanka Series contains tillites, deposited during a major glacial period. Petrographic observations of the Lapichi dolostones revealed two minerals potentially suitable for stratigraphic dating: penecontemporaneous dolomite and early diagenetic potassium feldspar. In situ U-Pb dating of the dolomite by laser ablation ICP-MS yielded an age of 709.3 +/- 11.8 Ma and 40Ar/39Ar dating of the feldspar revealed a mixture of detrital and authigenic components, with a minimal (authigenic) age of c. 714 Ma. The combined result dates the Lapichi Svita, thus providing a maximum age of c. 710 Ma for the overlying Vilchanka glacial deposits (at least its lower part - the Blon Svita), while the age of the periglacial period at the top of the underlying Orsha Svita must be older than c. 710 Ma. The obtained age provides the first direct dating of the Sturtian glaciation on western Baltica.