Sedimentary Architecture Characteristics of Tidal Bars and Dunes:An example from Roda Sandstone in Pyrenean Foreland Basin, NE Spain

Key words: 
• Roda sandstone

Abstract: The outcrops of Roda SandstoneⅢ are located in the southern Pyrenean Foreland Basin, in the northeast of Spain. The key sedimentary structures of the tidal ridges or waves are stacked sets of large scale wedge and tabular crossstrata as well as planeparallel lamination, ripple lamination. In vertical section, the tidal ridges or waves show a trend of thickening and coarsening upwards. The thickness of tidal bunches vary periodically and the reactivation surfaces are common; double mud drapes are rare, but herringbone crossstrata can be. Bioturbation can be intense in the bottomsets of the crossbedding. Shell fragments and mud clasts are common. The directions of paleocurrent were polydirectional, but most concentrated on westward direction, which is parallel to acute angle with the orientation of the progradation of delta front. The result suggests the tidal ridges and waves coexisted.