Several sedimentary structures serve as reliable 'way-up' (stratigraphic top) indicators, revealing the original depositional top of a bed even if the sequence has been tectonically overturned: asymmetric current ripples and their cross-lamination, wave (symmetric) ripples, and normal graded bedding (fining upward) all directly indicate the top of the bed in which they occur, whereas sole marks (flute casts, tool marks, load casts) are impressions formed on the base (sole) of an overlying bed and are conventionally used to identify the base of a bed, not its top.
Current ripples produce asymmetric cross-lamination with a characteristic geometry (steeper lee-side foresets truncated by the overlying bed) that directly indicates the younging direction, i.e., the...
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