Ripple-drift cross-lamination is the name given to a series of ripples which "climb upon the backs" of each other as a result of the addition of sediment from suspension during ripple migration. The type found in turbidites is characterized by continuity of lamination across the ripple system, changing composition of laminae from lee side (mud) to stoss side (silt and sand), and gradual upward decrease of ripple amplitude.

Geometric analysis has shown that the angle at which the ripples climb is a function of lamina thicknesses on the lee and stoss sides, the angle of the lee and stoss slopes, and the symmetry of the ripples. Computation of many angles of climb and different ripple geometries has shown that all three factors (thickness, angle, and symmetry) are equally important in determining the angle of climb. Field measurements of ripple-drift morphology in Ordovician turbidites of the Gaspe Peninsula, Quebec, indicate angles of climb from about 3 to 40°, with cosets of ripple-drift cross-lamination ranging in thickness from 4 to 37 cm. There is a direct correlation between coset thickness and angle of climb, and lee-side lamina thicknesses tend to be two to four times greater than stoss-side t icknesses. The factor controlling the angle of climb is the ratio of volume of sediment deposited from suspension to the volume of sediment moved on or very close to the bed and deposited on the lee sides. The velocity at which the ripples move downstream is also a function of the same ratio, plus a function of the hydraulic parameters controlling the formation of the ripples. Because of the complex interactions of these variables, it is not yet possible to estimate accurately the time taken for formation of the ripple-drift cosets. Crude estimates suggest a period of less than 1 or 2 hours for a coset 40 cm thick.

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