The Nurmekund Formation is subdivided into more heterogeneous, cyclostratigraphical units--the Jarva-Jaani, Vandra, Jogeva, Imavere, and Mohkula beds, whereas the Saarde Formation consists of more homogeneous, lithostratigraphical units--the Heinaste (new unit), Slitere, Kolka, Ikla, Lemme, and Staicele members.
The Mohkula Beds in the Poltsamaa and Heimtali cores are practically barren of chitinozoans, whereas in the Staicele Member in Ikla the abundance and diversity of chitinozoans decreases considerably.
Nestor (1994), corresponds to the Staicele Member in the Ikla core (322.3-361.0 m) and contains a poor assemblage of chitinozoans including rare representatives of the transitional species Conochitina malleus, C.
In southern Estonia, the Saarde Formation and Raikkula Stage end with the Staicele Member.
The Llandovery sequence reaches 231 m thick in the Ikla drill core (Estonia) and 222 m in the Staicele drill core (Latvia) (Fig.
Only scanty published data are available on the upper part of the Ikla and Staicele cores which contain argillaceous rocks of the upper Llandovery (Velise Formation) and the lower-middle Wenlock (Jaani and Jaagarahu regional stages).
The present paper is based on the macrolithological investigation and sampling of the Staicele core at the Katlakalns depository of the Latvian Geological Survey near Riga and the Ikla core at the Keila depository of the Estonian Geological Survey near Tallinn.
The Adavere Stage is represented in the Staicele and Ikla cores by the Rumba (below) and Velise (above) formations (Figs.