The distribution of the genus Estlandia is confined to the Middle and Upper Ordovician of the North Estonian Confacies Belt and the northwestern part of the Moscow Basin
(Rubel 1963; Alikhova 1969).
The largest regional falls in output were recorded in the Moscow basin
(Tula region), down 17.7%, and in the Russian part (the rest being in Ukraine) of the Donets basin, down 15.8%.
The Moscow Basin
forms a crescent shape starting to the north of the capital city and running around the west to taper out south of the city.
In the late 1980s in Russia, Kuznetsk was producing around 150 Mt/y, Kansk-Achinsk some 50 Mt/y, with Pechora, the Moscow basin
and the Urals region producing some 30 Mt/y each and South Yakutia about 15 Mt/y.
The connection between the Baltoscandian and Moscow basins
obviously broke off in the early Katian corresponding to the Nabala Stage, because the lithology of the sediments overlying the widespread cryptocrystalline limestones of the Rakvere Stage differs from that in the neighbouring Russian areas.