Silurian dolostones of eastern Lithuania

Silurian dolostones representing the Jaani (Verknė and Jočionys formations (Fms)) and Minija (Pabradė Formation (Fm.)) regional stages were studied in the Jočionys 299 borehole located in eastern Lithuania. In addition to petrological studies, dolostones were subjected to XRD, XRF and ICP-MS analyses. X-ray diffraction analysis revealed that dolomite crystals in dolostones were very close to stoichiometric and well ordered and could be interpreted as early diagenetic. Strontium in dolostone of the Pabradė Fm. is comparable to that of other ancient dolomites, and is much lower than Sr concentrations in typical modern marine dolomites. Slight enrichment in Sr and S in the Verknė and Jočionys Fms is due to the presence of celestine (SrSO4) and gypsum. Evaporative (sabkha), seepage-reflux, mixing-zone, burial and seawater dolomitization models of modern and ancient examples from literature were considered. For the Jočionys Fm. we suggest seepage-reflux and burial(?) models. Evaporative (sabkha) and mixing-zone dolomitization models may be applied to the Verknė Fm. and the Pabradė Fm., respectively.