Cambrian-Ordovician boundary beds in the Pakri Cape section, NW Estonia

For obtaining new information on the biostratigraphy and mineralogy of the Pakerort Stage in its type area, the Cambrian-Ordovician sequence in the Pakri Cape section (previously known as Pakerort) located 1 km southeast of the promontory of the Pakri Peninsula, NW Estonia, is described. The varigrained quartzose sandstones of the Kallavere Formation, representing a disputable part of the Cambrian-Ordovician boundary interval in Estonia, lie discontinuously on the sand- and siltstones of the Lower Cambrian Tiskre Formation. Lithological subdivisions of the Kallavere Formation, the Maardu and Suurjõgi members, differ in the structure and grain size, but show close mineral composition. The biostratigraphical age can be established only for the lower part of the Maardu Member which belongs to the Cordylodus proavus conodont Zone; the C. andresi Zone is apparently missing. Younger conodont zones cannot be established with confidence owing to scarcity and poor preservation of conodont elements. The overlying Türisalu Formation yields Rhabdinopora flabelliformis and R. cf. desmograptoides.