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 Tsitre Formation was introduced by Popov and Khazanovich (1985) with the stratotype in the Turjekelder section. Earlier, this part of the succession belonged to the Kallavere Formation (Kaljo et al. 1986, Resheniye… 1986). Currently, the Tsitre Formation (Table 6) includes also the underlying beds containing kerogen-bearing argillaceous interlayers and differing in fossil record from the Ülgase Formation (Mens et al. 1993).

The Tsitre Formation expands as a narrow belt from Tallinn to Kohtla-Järve (Fig. 23). Its thickness in the outcrop sections is a bit more than 3 m. In the drill core sections its thickness is unclear due to the low core yield, but probably it is less than 10 m.

The formation is typically represented by light-grey weakly cemented fine-grained quartzose sandstones, with a few thin interbeds of variegated, dominantly brownish-grey clayey rocks. These interlayers are often accompanied by bedding planes covered with convex-up lingulate shells. This has been considered in drawing the boundary between the Ülgase and Tsitre formations.

The co-occurrence of Trunculumarinum revinium and Dasydiacrodium caudatum in the lower part of the Tsitre Formation suggests that these deposits belong to the upper part of the Parabolina spinulosa Zone (Martin & Dean 1988, Paalits 1992b). The upper part of the Tsitre Formation contains a rather rich fossil record and its relationship with the trilobite zones is shown in Table 6.