Juha Köykkä - Oulu

Res Terrae, Ser. A 32, J. Köykkä, Sedimentology of the Mesoproterozoic Telemark basin-fills, South Norway: implications for
sedimentation processes, depositional environments and tectonic evolution
3.3.2 Early Sveconorwegian units
The sedimentation of the early Sveconorwegian units is bracketed between ca. 1170
and 1019 Ma (Lamminen et al., 2009b and Fig. 4). These units are more complex due
to deformation and faulting, and the lithostratigraphical correlation of different units is
problematic. The early Sveconorwegian units comprise the Oftefjell, Høydalsmo, Lifjell,
and Heddals Groups; the Brunkeberg and Eidsborg formations; the Transtaulhøgdi supra-
crustals, which are separated by the sub-Lifjell, sub-Røynstaul, and sub-Heddal unconfor-
mities; and a possible sub-Eidsborg unconformity (Figs. 3, 4). The whole succession con-
sists mainly of coarse-grained sedimentary rocks interbedded with bimodal magmatic
rocks. On a regional scale, the formations are laterally restricted and lithologically varia-
ble, and their true thickness is unknown. Although the sedimentary features, depositional
environments, and lateral correlations of the different units are not well known, some of
the general lithostratigraphical features are summarized here.
The sub-Svinsaga angular unconformity is overlain by the ca. 1-km-thick Oftefjell
Group. The Oftefjell Group starts with the ca. 250-m-thick Svinsaga Formation, which
consists of basal sedimentary breccias, conglomerates, sandstones and mudstones de-
posited in the fluvial-lacustrine environment. The sedimentation patterns and paleohy-
drology of the Svinsaga Formation are treated in Paper VI. The Svinsga Formation is
overlain by the felsic porphyres, minor volcanic conglomerates and sandstones inter-
beds of the Robekk and Ljosdalsvatnet Formations. The age determinations from the
Ljodalsvatnet felsic porphyre (ca. 1155 ± 3 Ma) indicate that it can probably be corre-
lated with the Brunkeberg Formation (ca. 1155 ± 2 Ma) in the east (see Laajoki et al.,
2002).
The Oftefjell Group is overlain by the ca. 1-1.5-km thick Høydalsmo Group, sepa-
rated by the sub-Røynstaul unconformity (Fig. 4). The volcanic-sedimentary Høydalsmo
Group starts with the conglomerate-dominated Røynstaul Formation followed by the mafic
lava-dominated Morgedal Formation. The Morgedal Formation is overlain by the porphyre
of the Dalaå Formation (ca. 1150 ± 4 Ma, Laajoki et al., 2002) and, again, the mafic lavas
of the Gjuve Formation with minor sedimentary interbeds (Fig. 4). In the west, the Brun-
keberg Formation is overlain by the Transtaulhøgdi supracrustals and the Lifjell Group,
and the two are separated by the sub-Lifjell unconformity (Fig. 4). The Lifjell Group com-
prises the Heksfjellet conglomerates followed by the sedimentary-dominated Vallar Bru
34