fig06.htm

Figure 6. Scheme showing the Vendian foreland basin of the Siberian cratonic margin and distribution of glacial deposits within it.
(A) Cis-Sayan foredeep. Post-Vendian deposits: 1 - Lower Jurassic, 2 - Lower Carboniferous, 3 - Middle Devonian, 4 - Lower Ordovician, 5 - Lower Cambrian. Lithostratigraphic units of Vendian deposits: 6 - Ust-Tagul Formation, 7 - Oselkovaya Group (Marnya, Uda, and Aisa Formations). Pre-Vendian deposits: 8 - Karagas Group, Early Neo-Proterozoic, 9 - metamorphic and igneous basement assemblages. Faults: 10 - post-Vendian, 11 - marginal tectonic suture of the Siberian craton.
(B) Marnya segment of the Cis-Sayan foredeep. Pre-Vendian rocks: 1 - metamorphic and igneous basement, 2 - Karagas Group. Lower stratigraphic units of the Vendian (Oselkovaya) molasse: 3 - Marnya Formation and lower portion of the Uda Formation, 4 - upper portion of the Uda Formation. Finds of tillites and traces of nonskeletal faunas: 5 - diamictites (tillites) at the base of the Ulyakh Member, 6 - faceted boulder breccias at the base of the Plitninskaya Member, 7 - traces of vital activity of nonskeletal Metazoa (ichnofossils), 8 - faults, principal and subsidiary.
(C) Assemblage of deposits of the lower portion of the Vendian (Oselkovaya) molasse. 1 - diamictites (tillites), glaciofluvial faceted boulder breccias and eolian sandstones, lacustrine siltstones and bituminous shales. Sandstones of marine environments: 2 - nearshore, 3 - storm-dominated, 4 - hurricane current-dominated. Gravelstones, sandstones, and siltstones of terrestrial and transitional environments: 5 - fluvial (cratonic), 6 - deltaic, 7 - fluvial (orogenic), 8 - fluvial, recording main stages of fluvial plain progradation. Limestones and dolomites of (9) microphytolith bars and stromatolite buildups, (10) distal shelf silt zone, and (11) postglacial (cap) laminated, bioherm, and of sand waves; 12 - units of the Karagas Group and depth of erosion in molasse. Stratigraphic position of (13) tillites and (14) finds of ichnofossils and molds of nonskeletal Metazoa. Three eustatic cycles (arrows) with intervals of deposits of sea-level lowstand, rapid marine transgression, and sea-level highstand.


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