Application of the parasequence concept to the Paleoproterozoic record of the northern Fennoscandian Shield
1999; Elsevier BV; Volume: 97; Issue: 3-4 Linguagem: Inglês
10.1016/s0301-9268(99)00034-0
ISSN1872-7433
Autores Tópico(s)Geology and Paleoclimatology Research
ResumoPaleoproterozoic (ca 2450 to 2000 Ma) sedimentary sequences covering Archean blocks of the Fennoscandian Shield outcrop as discontinuous belts in northwest Russia, eastern and northern Finland, northern Sweden and northern Norway. 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 the Kovasinvaara Formation (Kainuu belt) and the Rukatunturi Quartzite Formation (Kuusamo belt) exposed in northern Finland. In the East Puolanka Group (Kainuu Belt) depositional systems (fluvial, high wave-energy shoreline, tidally influenced shoreline, inner shelf) define four transgressive systems tracts followed by highstand periods. Rocks in the Kuusamo Belt, ca 130 km to the north, display a similar stratigraphic evolution. Extensive tidal deposits in these areas record periods of high sea level. The sets of identified parasequences in both areas are retrogradational and indicates migration of shoreline landwards enable the deeper water tidal channel-fill deposits to occur at the top of an overall transgressive system tracts. Parasequences identified in this study are related to high-frequency cycles of relative sea-level change. Major sequences reflect lower order fluctuations related to heterogeneous lithospheric subsidence. As the eustatic origins for individual boundaries become more firmly established, it may be possible to proceed to more detailed correlations between coeval sequences deposited on other early Precambrian cratons.
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