Mixed‐diurnal tidal record from a Palaeoproterozoic embayment in the Par Formation, Gwalior Group, Central India

Abstract

Group, central India contains a mixed, predominantly diurnal, tidal record in an embayment-like estuarine setting where flood energy exceeded the ebb energy. From two order differences in set thickness between flood-and ebb-generated bedforms an asymmetry in peak tidal current velocity of flood and ebb is inferred with domination of flood current. From the presence of crossover in successive neap records and 27.75 neap-spring cycles per year, an unambiguous clue for tidal forcing by lunar declination rather than lunar phase is inferred. Harmonic analysis of foreset-lamina thickness from tidal sand waves suggests that a tropical month of minimum 26 lunar days was in effect at the Gwalior Sea during the late Palaeoproterozoic (2,000-1,791 Ma).