Mens, K. & Pirrus, E. (1997). Cambrian. In: Raukas, A., Teedumäe, A. (eds). Geology and Mineral Resources of Estonia. Estonian Academy Publishers, Tallinn. 436 pp. ISBN 9985-50-185-3. 

The Vaki Formation occurs in central and eastern Estonia (Table 6), being probably a shallow‑water equivalent of the Soela and Irben formations. It is known only from core sections (Fig. 21). The formation rests with a stratigraphic unconformity on rocks of the Dominopol’ or the Lontova Stage. In the latter case, or if the Tiskre Formation is absent, the topmost layers of the underlying units are weathered (Mens et al. 1984).

The Vaki‑67 (Fig. 21 - 148) drill core in the interval of 284.4 to 322.0 m has been selected as a type section for the formation (Resheniya… 1978). The maximum thickness of the formation (more than 35 m) has been registered in its type area (Fig. 20).

The Vaki Formation consists of weakly cemented glauconite‑bearing light-coloured fine‑grained or very fine‑grained sandstones, or of both, with thin interlayers of greenish‑grey and bleached‑purplish argillaceous rocks. On some levels the latter are highly micaceous and often contain ichnofossils of Skolithos affinites filled with fine sandy material. Besides ichnites, the formation contains scarce fragments of inarticulate brachiopods and in the Oostriku‑700 (Fig. 20-155) drill core at the depth of 256.2 m also a pauperized acritarch assemblage (further above‑ the Vērgale Stage).