Thin units of cross-laminated sandy and silty sediments are common in graded bed sequences and have been commonly interpreted as turbidity-current deposits. Pliocene deep-sea deposits of the Ventura basin, Calif., and other ancient and modern deep-sea deposits, supply evidence that some sediments were transported by turbidity currents to deep-sea bottom and deposited originally as graded beds, but subsequently were reworked by bottom currents. Deep bottom currents exist in modern oceans and are strong enough to ripple the deep-sea bottom, as shown on photographs. Cross-laminated deep-sea sands are, in places, considerably better sorted, and show a quite different direction of transport, than sands supposedly deposited by turbidity currents.

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