Litofácies, ambientes deposicionais e ciclicidade do Grupo Paranoá: exemplo da regi?o da Serra de S?o Domingos, Minas Gerais

摘要

In Serra de S?o Domingos (SSD), a succession of Mesoproterozoic rocks of the Paranoá Group comprises dominantly siliciclastic?rocks along more than 1,000 m thick. Two stratigraphic sections were measured and described in scale of 1:300 and subdivided?in eleven lithofacies: De (stromatolites dolomite), Dl (laminated dolomite), AFl (laminated fine grained sandstone), AFm (fine?grained sandstone with wave and current ripple), AFh (fine grained sandstone with hummocky cross-stratification), AMc 1 (medium?grained sandstone with unidirectional cross-stratification), AMc 2 (medium grained sandstone with bidirectional or multidirectional?cross-stratification), AMe (stratified medium grained sandstone), AMs (medium grained sandstone with sigmoidal?geometry), Pl (laminate pelite) and PAht (pelite and sandstone with heterolithic laminations). Five facies associations were identified:?FA-I is characterized by lithofacies AFm and PAht, in an intertidal subsystem; FA-II is characterized by AMc 1 , AMc 2 , AMs,?AMe in a subtidal subsystem; FA-III is characterized by lithofacies AFm, AFl, AFh and Pl in a proximal shelf with a tidal, wave?and storms influence; FA-IV is characterized by lithofacies AFl, Pl, AFh, De and Dl, in an intermediate-distal shelf subsystem;?and FA-V is characterized by lithofacies Dl and De in a shallow shelf subsystem. FA-III, FA-IV and FA-V facies’ associations?were deposited in a mixed carbonate-siliciclastic depositional shelf system, while FA-I and FA-II were deposited in tidal flat.?The depositional systems along the SSD range from deposits of the proximal offshore at their lower intervals, passing upwards to?an inner platform with tidal influence (subtidal-intertidal), evidencing a shallow upward succession.?