A lower Cambrian eodiscoid trilobite fauna and an associated holmiid trilobite, Holmia sp., are described from a bioclastic limestone at the top of the Tornetrask Formation in the Luobakti section, south of Lake Tornetrask, northern Sweden. Other associated polymerid trilobites include Orodes? lapponica and Strenuaeva inflata. The precise age of the trilobite fauna cannot be determined, but its generic composition and stratigraphical position at the top of the lower Cambrian suggest that it was recovered from the Ornamentaspis? linnarssoni Assemblage Zone. Two species of eodiscoids are present: Neocobboldia aff. dentata and Chelediscus acifer. The latter species is known previously from England and southeastern Newfoundland, and provides a novel link between upper lower Cambrian successions in Baltica and Avalonia.

Trepostome bryozoan Dianulites borealis Astrova, 1965, the earliest known member of this genus, has been identified from the Early Ordovician of Severnaya Zemlya, Arctic Russia. This species developed hemispherical colonies which indicate that it lived on a relatively soft substrate with moderately low rates of sedimentation and erosion. The new record from Severnaya Zemlya expands the palaeogeographical distribution of Dianulites, known before from the Early Ordovician of Novaya Zemlya, Arctic Russia.

The Caledonian Hecla Hoek succession in Ny Friesland, eastern Svalbard has been interpreted, for many decades, to be a continuous stratigraphic sequence. Early Palaeozoic and Neoproterozoic strata in its upper parts pass more or less conformably down into amphibolite facies rocks (Stubendorffbreen Supergroup) at depth. Recent isotopic age-determination and structural studies have indicated that the Stubendorffbreen succession is tectonostratigraphic and made up of at least three major thrust sheets. This paper provides new data from two meta-igneous units within the succession, the Bangenhuk and Instrumentberget gneisses. Both are granitoid sheets, consisting mainly of red, strongly lineated gneisses of monzogranitic composition; the Bangenhuk unit also contains some lenses of little deformed granitoids, as well as cross-cutting aplite dykes, amphibolitized dolerites and subordinate metasedimentary rocks. The latter are locally cut by granitoids. U-Pb zircon dating of six samples of variably deformed Bangenhuk granitoids, including one cross-cutting aplitic dyke, has yielded ages between 1720 and 1770 Ma, the higher values generally from the less deformed samples. The Instrumentberget gneissic granite yielded an age of 1737(-41)(+46) Ma. These ages are interpreted to date the time of intrusion of the granitoids at around 1750 Ma; the younger ages may have been slightly lowered by Caledonian deformation, particularly those from specimens located close to a major fracture (the Billefjorden Fault Zone) in Wijdefjorden-Austfjorden. U-Pb dating of titanite from the least deformed granitoid also yields comparable Palaeoproterozoic ages; in the more deformed rocks, however, titanites give evidence of Caledonian ductile deformation at c. 410 Ma. The Rb-Sr system of the corresponding whole rock samples has been disturbed and yields an errorchron age of about 1650 Ma and, for some samples, an impossibly low initial Sr ratio. The Sm-Nd system may be more intact and yields initial a,, values of -2 to -3, suggesting some contribution from older crustal material to the granitoid magmas. The results indicate the presence of extensive units of Palaeoproterozoic granitic basement within the Lower Hecla Hoek succession of Ny Friesland, supporting the hypothesis that the latter is composed of tectonically intercalated basement and cover units.

Throughout the high Arctic, from northern Canada (Pearya) to eastern Greenland, Svalbard, Franz Josef Land, Novaya Zemlya, Taimyr and Severnaya Zemlya and, at lower Arctic latitudes, in the Urals and the Scandinavian Caledonides, there is evidence of the Grenville-Sveconorwegian Orogen. The latest orogenic phase (c. 950 Ma) is well exposed in the Arctic, but only minor Mesoproterozoic fragments of this orogen occur on land. However, detrital zircons in Neoproterozoic and Palaeozoic successions provide unambiguous Mesoproterozoic to earliest Neoproterozoic (c. 950 Ma) signatures. This evidence strongly suggests that the Grenville-Sveconorwegian Orogen continues northwards from type areas in southeastern Canada and southwestern Scandinavia, via the North Atlantic margins to the high Arctic continental shelves. The widespread distribution of late Mesoproterozoic detrital zircons far to the north of the Grenville-Sveconorwegian type areas is usually explained in terms of long-distance transport (thousands of kilometres) of either sediments by river systems from source to sink, or of slices of lithosphere (terranes) moved on major transcurrent faults. Both of these interpretations involve much greater complexity than the hypothesis favoured here, the former involving recycling of the zircons from the strata of initial deposition into those of their final residence and the latter requiring a diversity of microcontinents. Neither explains either the fragmentary evidence for the presence of Grenville-Sveconorwegian terranes in the high Arctic, or the composition of the basement of the continental shelves. The presence of the Grenville-Sveconorwegian Orogen in the Arctic, mainly within the hinterland and margins of the Caledonides and Timanides, has profound implications not only for the reconstructions of the Rodinia supercontinent in early Neoproterozoic time, but also the origin of these Neoproterozoic and Palaeozoic mountain belts.