. Bulletin of the British Museum (Natural History), Geology. 88 KALJO, NESTOR & POLMA Ordovician is represented by marls and argillaceous limestones with the Dalmanitina Fauna (Kuldiga Formation). Above this occur biosparitic, oolitic and arenaceous limestones of the Saldus Formation. The Silurian begins with marls and argillaceous limestones of the Ohne Formation with the Clorinda community (Rubel 1970). Type IV—sections in southeast Estonia, considerable part of Latvia, west Lithuania and the Kaliningrad Region. The studied stratigraphical interval begins and ends with dark graptolitic m
. Bulletin of the British Museum (Natural History), Geology. 88 KALJO, NESTOR & POLMA Ordovician is represented by marls and argillaceous limestones with the Dalmanitina Fauna (Kuldiga Formation). Above this occur biosparitic, oolitic and arenaceous limestones of the Saldus Formation. The Silurian begins with marls and argillaceous limestones of the Ohne Formation with the Clorinda community (Rubel 1970). Type IV—sections in southeast Estonia, considerable part of Latvia, west Lithuania and the Kaliningrad Region. The studied stratigraphical interval begins and ends with dark graptolitic mudstones with the assemblage of the Pleurograptus linearis Zone in the Ordovician part (Fjacka Formation) and of the Coronograptus cyphus-Monograptus sedgwickii Zones in the Silurian (Dobele Formation). Between these key beds there occur red and grey calcareous mudstones, marls and aphanitic limestones. The uppermost Ordovician is analogous to the sections of Type III. The Silurian begins with marls and aphanitic limestones of the Staciunai Formation which have yielded few fossils good for correlation. Type V—sections in east Lithuania and southeast Latvia with an extensive hiatus at the boundary interval. More or less continuous Upper Ordovician deposits are represented by marls and various limestones which end at the top of the Pirgu Regional Stage with the aphanitic limestones of the Taucionys Formation which yield a Holorhynchus fauna. There is a hiatus at the level of the Porkuni, Juuru and Raikkiila Regional Stages, or in places there occur thin residual tongues and lenses of the Kuldiga, Saldus and Apascia Formations, which are transgressively overlain by mudstones and marls of the late Llandovery Adavere Regional Stage. In the westernmost part of Lithuania and in the Kaliningrad District the rocks of the Ordovician-Silurian boundary interval become still more argillaceous and graptolites occur throughout the whole section, with the exception of the uppermost Ordovic
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