Tectonostratigraphic position of the Finnish Caledonides at the Fennoscandian margin of the northern Scandes

The Finnish Caledonides consist of the lower structural units characteristic of much of the northern Scandes, whose foreland is now known to be Archaean throughout its extension in Finland. The autochthonous Dividal sedimentary rocks pass very gradually into the somewhat overthrust Jerta rocks. These are capped by the Nalganas meta-arkosites, which have undergone considerable displacement. The overlying Nabar plate consists of a lower sequence of heterogeneous amphibolite ‒ pegmatitic gneiss and an upper part of very homogeneous acidic gneiss intruded and thrust by ultramafic to mafic ophiolitic material. The origin and tectonostratigraphic correlation of the conventional Nabar Nappe are discussed in more detail, because it has features suggesting it may be part of the overlying Seve Nappe Complex. Direct proof of this is lacking, however, and so only the special characteristics of the units are discussed and comparisons made with the adjacent Norwegian and Swedish terrains. The topmost Kalak unit, the Corrovarre Nappe, also occurs in the Finnish part of the Kalak Nappe Complex

Stratigraphical section through Lower Cambrian at Söderfjärden, Vaasa, western Finland

The Lower Cambrian sedimentary rocks form a doughnut-shaped deposit on the bottom of the Söderfjärden depression. The sedimentary pile was first established and has now been penetrated by drilling. The remaining thickness of sedimentary rocks at the drilling site is 244 m under 74 m of glacial overburden. Sediments in the lower half of the sequence are clayey and continue in the upper half mixed with sandy and silty beds. Thin phosphoritic conglomerates intercalate with any other rocks. Syndepositionary sedimentary structures and penecontemporaneous soft-state deformations are well preserved in these completely unmetamorphosed rocks. Indications of rapid basin filling are met with throughout the sequence. A volcanic origin of Söderfjärden basin, Lower Cambrian in age, is claimed to have implications with coeval alkaline magmatism in the Fennoscandian Shield

Fossiliferous boulders of Lower Cambrian phosphoritic sandstone in southwestern Finland

The paper deals with fossiliferous sandstone boulders from three localities in southwestern Finland. The largest of the boulders was found on the west coast west of Olkiluoto. It is conglomeratic with an abundance of worn remains of lingulid and obolellid brachiopod valves. Its rock type is made up of a relatively coarse, bimodal quartz sandstone containing a few phosphoritic siltstone fragments. The main part is sandy and practically free of glauconite, which is more common in the phosphoritic fragments. A few of the phosphoritic pieces are tubular in form having phosphorite enriched in an outer ring and a one-grain-thick outermost crust of quartz. They may be worn remains of Hyolithellus micans. Some of the brachiopod shells contain small calcitic globules in a carbonaceous phosphorite matrix. Tasmanites sp. is one of the few preserved forms of the Acritarch genera. According to the fossils, the sandstone dates to the upper part of the Lower Cambrian, corresponding to the Lingulid sandstone facies in Västergötland, which in turn corresponds to the Holmia kjerulfi-group Zone in southern Scandinavia. Mineralogically and petrologically, too, the rock could be derived from such lithostratigraphical units. Sandstones of the same age have not been reported previously from Finland. The present boulders would seem to derive from the bottom of the Bothnian Sea. Although smaller and not so conglomeratic the boulders from Säkylä and Uusikaupunki are fossiliferous. The fossil fragments in the boulder from Pyhäjärvi, Säkylä, are probably remains of the brachiopod Mickwitzia, and thus refer to a Lower Cambrian stratum still older than the former. The worn brachiopod fragments in the boulder from North Viisastenkari, Uusikaupunki, did not allow the boulder to be dated more accurately within the Lower Cambrian