ANTIDUNE CROSS‐STRATIFICATION IN A TURBIDITE SEQUENCE, CLORIDORME FORMATION, GASPÉ, QUEBEC

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Abstract
Single‐set cross‐stratification, considered to have been produced by the upstream migration of antidunes, is present in the basal division of certain thick turbidite beds.The basal divisions of these turbidites consist of very coarse to medium sand with a smooth or fluted base and sinusoid top. Internal laminae are inclined upstream at a shallow angle (less than 15°), opposing the local paleocurrent direction shown by flutes and ripple‐drift cross‐lamination.The sinusoid (antidune) bed forms and their associated internal cross‐strata were preserved by the rapid fall‐out of sediment from suspension normal to the bed.A paleohydraulic analysis suggests that during the final stages of antidune growth and migration, the currents moved at approx. 1 m/sec over very low slopes (much less than 1°).