In English. Summaries in Estonian and Russian

Proceedings of the Estonian Academy of Sciences


Volume 49 No. 1 March 2000

The Billingen and Volkhov stages in the northern East Baltic: detailed stratigraphy and lithofacies zonation; 3–16
Andrei DRONOV, Tõnu MEIDLA, Leho AINSAAR, and Oive TINN
Abstract. The formal stratigraphical subdivision of the Billingen–Volkhov interval is combined with informal detailed subdivision of the Volkhov sequence in the eastern part of the Baltic–Ladoga Klint area. A detailed correlation of the successions east and west of the Narva River is provided, using for the near-klint belt in North Estonia the bed nomenclature employed by Russian quarrymen, and the principal trends of the lithofacies changes in the study area are documented. The affinity of sections in northwestern Russia and Central Estonia is demonstrated and two lithofacies zones within the North Estonian Confacies Belt are distinguished.
Key words: Ordovician, Billingen Stage, Volkhov Stage, lithofacies zones, lithostratigraphy, ostracodes, Estonia, northwestern Russia.

Grain micromorphology in the Rannamõisa section, Lower Cambrian, Estonia; 17–27
Tiia KURVITS, William C. MAHANEY, and Volli KALM
Abstract. Sand and silt grains of Lower Cambrian siliciclastic rocks in Estonia were studied by the scanning electron microscope and energy dispersive spectrometer to find out if grain micromorphology might prove useful in determining clast sedimentologic and diagenetic history. The majority of grains studied fall in the range of 40–70 mm diameter, have angular shapes, and show considerable dissolution. The predominant minerals, quartz with minor amounts of K-feldspar are cemented by silica. Quite possibly these aggregates are the result of fluctuating water tables in weathering conditions over a long period of time. Prevalent etching on most grain surfaces obscures microfeatures that might reveal exact transport histories.
Grain shape, size, and sorting, also sedimentary structures suggest the material of sandstones at Rannamõisa was transported into the sedimentary basin mainly in suspension, aeolian and/or fluvial, which permitted no rounding of grains.
Key words: grain micromorphology, sandstones, silica, weathering, sedimentology, Lower Cambrian, Estonia.

The new trilobite genus Valdariops from the Harju Series (Upper Ordovician) of Estonia; 28–43
Abstract. The species Phacops (Chasmops) eichwaldi Schmidt, 1881 from the previous Lyckholm Stage, corresponding to the Nabala, Vormsi, and Pirgu stages, has been defined by Schmidt (1881, Mém. Acad. Imp. Sci. St.-Petersb., Sér. 7, 30, 1) in a very wide sense and is virtually a composite species. This species-group is here assigned to a new genus Valdariops, with the species Veichwaldi (emended), Valiquantulus sp. nov., Vangustus sp. nov., and Vkernuensis sp. nov. Two additional forms are figured as Valdariops sp. nov. A and Valdariops sp. nov. B. All these species have a stratigraphically limited range as guide fossils for different parts of the sequence of the Harju Series in the North Estonian Confacies Belt.
Key words: trilobites, Valdariops gen. nov., Ordovician, Estonia.

Latest Silurian (Ohesaare Stage) conodonts and the detorta Zone in the northern East Baltic; 44–62
Abstract. The latest Silurian conodonts from the Sõrve Peninsula of Saaremaa Island, Ruhnu Island, and western Latvia include Ozarkodina remscheidensis remscheidensis, Oz. confluens, Oz. nasuta, and Oulodus elegans. They represent the local nearshore remscheidensis remscheidensis Subzone of the remscheidensis Zone. The Oulodus elegans detorta Zone occurs as a short interval in the upper part of the Ohesaare Stage. Three new species are described: Amydrotaxis? praecox, Oz. denticulata, and Oz. inordinata. Ozarkodina nasuta (Viira, 1983) was originally described as the subspecies of Oz. confluens.
Key words: conodonts, taxonomy, biostratigraphy, Upper Silurian, East Baltic.

Instructions to authors; 63