ИСТИНА

The paleobotanical material from two localities and two boreholes, collected on the north of the Arkhangelsk Region (East Coast of the White Sea), has been studied (Alekseev et al., 2005). The collection basically consists of imprints and casts of arthrophytes, lycopsids, and seed ferns and, more rarely, their petrifactions. The richest locality (the Verkhny Gruby Brook) contains about 200 specimens of fossil plant remains, which come from cherry ferruginous sandstones. Arthrophytes dominated among other fossil plant groups, constituting 65% of the assemblage. They are represented by impressions and casts of stems and leaf imprints of an only species - Archaeocalamites radiatus (Br.) Stur. Besides arthrophytes, there are some pteridosperms in the collection. Sterile leaf structures are represented by the fragments of fronds of Adiantites antiquus (Ett.) Stur, A. machanekii Stur, A. sp. 1 and A. sp. 2. There is also a small pinnule imprint of Cardiopteridium. Among fertile structures it should be noted that the seed cast of Boroviczia sp. 1 and the imprints of isolated synangia and sporangia of Telangiopsis were found. As for lycopsids, there were determined Lepidodendron sp. 1, L. veltheimii Sternb., L. cf. kidstonii Nath., Lepidofloyos laricinum Sternb., ?Lepidostrobus sp., Knorria acicularis Goepp., and Stigmaria sp. In the other locality (the Tovskoe Lake), which is situated in 8 km on the north-west from the first one, more than 100 specimens of fossil plants from brown ferruginous sandstones were collected. Arthrophytes (Archaeocalamites radiatus) are abundant (over 80% of the total of the assemblage). Besides their casts and stem imprints, there are also the remains of permineralised stems. A few imprints of pteridosperm pinnae (15%) were found, belonging to the following taxa: Adiantites, Sphenopteridium, and Lyginorachis. Only four lycopsid imprints were identified (Lepidodendron, Lepidostrobus, and Stigmaria). Apart from the above-mentioned localities, some pteridosperm imprints (Adiantites sp., A. antiquus) were discovered from the borehole EM-6. The other borehole (155-5) contains a lot of arthrophyte stem casts and wood remains, which are now under study with a SEM. Notably, the majority of the taxa were recognized in this region for the first time. No other fossil remains (invertebrates, spores) were found in the localities and bores. Based on the composition of the plant assemblages, the beds which include these plant remains are related to the Lower Carboniferous (most likely the Upper Visean). It is necessary to note that the composition of this flora is similar to that of the late Visean flora of the Moscow Sineclise, in particular, its northwestern part. However, some characteristic taxa (for example, Stigmaria) are found in the Arkhangelsk region extremely rarely. Nevertheless, it is clear that the areas of both the Arkhangelsk region and Moscow Sineclise belonged to the Euramerian paleophytogeographical realm in the Early Carboniferous.