HR: 0830h
AN: T31D-0871    [PDF]
TI: Late Neoproterozoic Paleogeography of the Western Part of Baltica- Constraints From Paleomagnetic and Tectonic Analysis.
AU: * Nawrocki, J
EM: jnaw@pgi.waw.pl
AF: Polish Geological Institute, Rakowiecka 4, Warsaw, 00-975 Poland
AU: Poprawa, P
EM: ppop@pgi.waw.pl
AF: Polish Geological Institute, Rakowiecka 4, Warsaw, 00-975 Poland
AU: Boguckyj, A
EM: lanczont@biotop.umcs.lublin.pl
AF: Lviv University, Dorosenka 41, Lviv, 290 000 Ukraine
AB: Neoproterozoic break-up of supercontinent Rodinia resulted with development of several individual lithospheric plates, including Baltica. Global configuration of continents after break-up, in particular paleogeographic position of Baltica and its relation to Godwana, are the matter of recent disputes. According to Scandinavian paleomagnetic poles (c.f. Torsvik and Rehnstr”m, 2001) in the late Neoproterozoic and Cambrian time the Baltic plate occupied moderate paleolatitudes of southern hemisphere. Vendian paleomagnetic pole from the White Sea region (Popov et al., 2002) is, however, completely different. It implies moderate northern paleolatitudes of Baltica in the Vendian time and probably equatorial position of this plate in the Early Cambrian (c.f. Nawrocki, 2003). In the present contribution we discuss impact of recent paleomagnetic and tectonic analysis conducted for the western part of Baltica on the above mentioned issue. As a consequence of the break-up process the western and central part of Baltica became a site of intensive basic volcanism (Orsha-Volhyn Zone) and development of sedimentary basins related to rifting. Geochronology of volcanic processes at the western slope of Baltica is poorly controlled, except of its expiring, dated by U/Pb method as 551 Ma (Compston et al., 1995). However its geotectonic setting is geochemically documented as rift-related (Bialowolska et al., 2002). Subsequently during the late-most Neoproterozoic-Middle Ordovician a system of sedimentary basins developed, controlled by post-rift thermal sag mechanism. Regional pattern of their subsidence allows to reconstruct passive continental margin along western margin of Baltica (Peri-Tornquist Zone, corresponding to later Trans-European Suture Zone) (Poprawa et al., 1999). Preliminary paleomagnetic analysis of the Vendian basalts and underlying basaltic tuffs from the Volhynia (NW Ukraine) revealed paleomagnetic directions concordant with the data from the White Sea region (Popov et al., 2002) . Paleomagnetic pole from tuffs (pole long. 145oE, pole lat. 37oS) is close to the late Vendian pole of Popov et al. (op. cit). Paleomagnetic data from basalts indicate subsequent drift of Volhynian part of Baltica from moderate paleolatitudes (c.a. 40o) to its equatorial position in the latest Vendian - early Cambrian. References: Bialowolska A., Bakun-Czubarow N., Fedoryshyn Y., 2002. Neoproterozoic flood basalts of the upper beds of the Volhynian Series (East European Craton). Geol. Quart., 46 (1): 37-53. Compston W., Sambridge M.S., Reinfrank R.F., Moczydlowska M., Vidal G. \& Claesson S., 1995. Numerical ages of volcanic rocks and the earliest faunal zone within the Late Precambrian of the east Poland. Journ. Geol. Soc. London, 152: 599-611 Nawrocki J., 2003. Where was the Baltic plate in the Early Cambrian ? Prz. Geol., 51(9): 750-753 Popov., Iosifidi A., Khramov A., Tait J., Bachtadse V., 2002. Paleomagnetism of Upper Vendian sediments from the Winter Coast, White Sea region, Russia: Implications for the paleogeography of Baltica during Neoproterozoic times. Journal of Geophysical Research, 107: B11, EPM 10, 1-8. Poprawa P., Sliaupa S., Stephenson R.A. \& Lazauskiene J., 1999. Late Wendian-Early Palaeozoic tectonic evolution of the Baltic basin and its regional implications. Tectonophysics, 314: 219-239 Torsvik T.H., Rehnstr”m E.F. 2001. Cambrian palaeomagnetic data from Baltica: implications for true polar wander and Cambrian palaeogeography. Journal of the Geological Society, London, 158: 321-329.
DE: 8105 Continental margins and sedimentary basins
DE: 8157 Plate motions--past (3040)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting