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ABSTRACT

The Famennian-Tournaisian conglomerates and sandstones of the Ksiaz Formation are interpreted as marine resedimented deposits. Matrix- and clast-supported conglomerate beds are equally common, and two textural sequences (motifs) have been recognized: (I) matrix-rich conglomerate [RIGHTWARDS ARROW] pebbly sandstone [RIGHTWARDS ARROW] sandstone, and (II) clast-supported conglomerate [RIGHTWARDS ARROW] sandstone. Variation in clast type partly controls motif type, and therefore, to some extent, matrix percentage in the conglomerates generally. Grading is extremely common in both clast- and matrix-supported conglomerates: inverse (19%), inverse-to-normal (14%) and normal (26%). The studied succession, itself part of a 4 km thick, fan delta, basin-fill sequence, is organized into large (110–150 m) and small-scale (5–30 m) sequences, both of which show (1) upward coarsening and thickening, (2) upward trend of sandstones and pebbly sandstone [RIGHTWARDS ARROW] matrix-rich conglomerates [RIGHTWARDS ARROW] clast-supported conglomerates and (3) a less clear upward tendency of massive and normally graded beds [RIGHTWARDS ARROW] inversely graded beds. Variation in matrix percentage in beds is therefore also partly controlled by fan processes, during the progradation of fan bodies and lobes. It is predicted that individual resedimented conglomerate beds or motifs show general downfan trends in thickness, texture and structure opposite to those evident in the vertical sequences.