On the age and stratigraphic position of the Niskavaara Formation, Posio, North Finland

Räsänen & Vaasjoki (2001) stated, that the age of a felsic volcanic rock at Niskavaara located in southwestern tip of the Palaeoproterozoic Kuusamo belt, North Finland, is 2800 ± 8 Ma and consequently, the Niskavaara Formation should be considered as an individual stratigraphic unit belonging to the late Archaean belt extending from Sodankylä via Kuusamo to Puolanka. We restudied and sampled the Niskavaara area. The hill of Niskavaara itself is poorly exposed and only a few, small outcrops occur at the lakeside north of it (Fig. 1). At Niskavaara, the rocks dip moderately and face to the southeast. They are subdivided into a schist-dominated lower part and overlying arkosite unit. The lowermost unit of the western part consists of greenish, massive-looking, but thinly laminated, chloritic sericite schists. These are overlain by laminated – thinly bedded and graded bedded heteroliths (Fig. 2). Up-section, structurally similar sericite schists overlie the latter. The dated sample A906 (op. cit.) has been collect-