THE NEOPROTEROZOIC OF BALTICA - STRATIGRAPHY, PALEOBIOLOGY AND GENERAL GEOLOGICAL EVOLUTION

Western Baltica contains numerous Neoproterozoic rock successions recording deposition in a variety of settings, including basinal, deep and shallow-shelf passive margin and intracratonic continental, fluvial and shallow-marine environments. Neoproterozoic pre-Varangerian episodic emplacement of dolerite swarms (1020-870 Ma; 720 +/- 260-665 +/- 10 Ma) and post-Varangerian (late Vendian or Ediacaran similar to 551 +/- 4.0 Ma) basaltic volcanism in western Baltica are related to episodes of rifting and paroxysmal stages of faulting that were followed by erosion and basin infilling. Tentative biostratigraphic correlation of successions in the western Baltoscandian basins and in the Volhyn Aulacogen in the East European Platform (EEP) suggests that initial rifting, formation of embryonic fault basins in western Baltica and infilling of rift basins within the core of Baltica might be largely contemporaneous events restricted to the late Riphean and bracketed in time to around 800-750 Ma. The biostratigraphic correlation and radiometric age control of pre-Varangerian rift deposition in the Lake Vattern Graben in South Sweden with allochthonous rock succession in the Hedmark Basin in southern Norway (Vidal and Nystuen, 1990a) provide additional evidence to confirm the time frame of basin formation as a response to crustal fracturing of western Baltoscandia similar to 800-700 Ma ago. Sedimentation following late Riphean and Vendian rifting in Baltica was dominated by quartz arenites of considerable thickness on stable shallow shelves, thus indicating stabilization at the onset of the Early Cambrian transgressions. The earliest Cambrian successions on the western border of Baltica witness of moderate basin subsidence and crustal instability extending well into early Holmia times.