Application of the parasequence concept to the Paleoproterozoic record of the northern Fennoscandian Shield

Paleoproterozoic (ca 2450 to 2000 Ma) sedimentary sequences covering Archea n blocks of the Fennoscandian Shield outcrop as discontinuous belts in nort hwest Russia, eastern and northern Finland, northern Sweden and northern No rway. This fragmentary distribution hampers conventional correlations. More robust inter-basin correlations can be established by applying principles of sequence stratigraphy to particularly well-preserved sections such as th e Kovasinvaara Formation (Kainuu belt) and the Rukatunturi Quartzite Format ion (Kuusamo belt) exposed in northern Finland. In the East Puolanka Group (Kainuu Belt) depositional systems (fluvial, hig h wave-energy shoreline, tidally influenced shoreline, inner shelf) define four transgressive systems tracts followed by highstand periods. Rocks in t he Kuusamo Belt, ca 130 km to the north, display a similar stratigraphic ev olution. Extensive tidal deposits in these areas record periods of high sea level. The sets of identified parasequences in both areas are retrogradati onal and indicates migration of shoreline landwards enable the deeper water tidal channel-fill deposits to occur at the top of an overall transgressiv e system tracts. Parasequences identified in this study are related to high -frequency cycles of relative sea-level change. Major sequences reflect low er order fluctuations related to heterogeneous lithospheric subsidence. As the eustatic origins for individual boundaries become more firmly establish ed, it may be possible to proceed to more detailed correlations between coe val sequences deposited on other early Precambrian cratons. (C) 1999 Elsevi er Science B.V. All rights reserved.