Sedimentary Architecture Characteristics of Tidal Bars and Dunes:An example from Roda Sandstone in Pyrenean Foreland Basin, NE Spain
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摘要: 以位于西班牙东北部的比利牛斯前陆盆地(Pyrenean Foreland Basin)南部的Roda砂岩组三段为对象，研究潮流沙脊、沙波的内部结构特征。主要的沉积结构为大型楔状、板状交错层理，局部发育大型槽状交错层理，平行层理和小型波纹层理等。垂向上，板状交错层理呈向上变粗变厚的趋势。潮汐束厚度周期性变化，复活面众多，双泥层不发育，局部可见鱼骨状交错层理。交错层理底部生物扰动强，内部较弱，贝壳碎屑常见，泥粒在交错层理底部普遍，古水流方向多变但主要以向西方向为主，主流方向与三角洲的前积方向呈锐角至平行关系，指示潮流沙脊和沙波共存。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 crossstrata as well as planeparallel 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 crossstrata can be. Bioturbation can be intense in the bottomsets of the crossbedding. 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.
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Key words:
- Roda sandstone
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