Early Ordovician shelly phosphorites of the Baltic Phosphate Basin

The Baltic Phosphate Basin contains a condensed sequence of late Upper Cambrian-early Ordovician sediments. These consist mainly of mature quartz sandstones with debris of phosphatic shells of inarticulate brachiopods, notably Schmidtites and Ungula. The sequence also contains Dictyonema shales and glauconitic sandstones. A large-scale exploration project completed recently has delineated several new promising areas, including the Rakvere deposit in northeastern Estonia where resources amount to as much as 700 Mt of P2O5 contained in easily beneficiated ores grading 10% P2O5. Palaeogeographically, the Baltic phosphate basin opened westwards into a large euxinic basin that occupied Sweden, southern and central Norway, and Denmark. Alum shales accumulated in the latter basin from early Middle Cambrian times. Further west, the basin joined the Iapetus Ocean.