Lithostratigraphic subdivision of the phosphate-bearing (C3 - O1kl) strata in the Rakvere area of northern Estonia

The Rakvere Phosphorite Area (RP A) holds the central position in northern Estonia not only geographically, but also from the aspect of the lithologic structure of the phosphate-bearing Kallavere Formation. In the course of years it has been investigated by numerous scientists. Until quite recently there existed different views about the subdivision of the phosphate-bearing strata of the RP A into members. The authors of this article have tried to find solution to these problems by the revision and detailed analysis of vast amounts of material. On the whole, in the RP A about 2000 boreholes have been drilled, but the present account is mainly based on data from 500 drill cores investigated in detail. The article presents geological and lithological characterization of all lithostratigraphic units of the abovementioned strata: Tsitre and Kallavere formations; Maardu, Suurjoe, Rannu, Katela and Orasojamembers. In the distribution of the sediments included into the described lithostratigraphic units some detrite patterns have been established.