Repeated post-flood mapping and trenching of laterally accreting point bars along steep, meandering streams in southeastern Louisiana reveal a characteristic divergence between the azimuths of dip of scoured set boundaries and the cross-strata which they enclose. The interrelation offers a potential criterion for recognition of ancient point-bar deposits.

After floods, long curving sand waves are observed to be normal to the low-stage channel high on the emergent point-bar surfaces, but curve in the direction of flow to near parallelism with the low-stage channel near low water level. Cross-strata sets exposed in trenches on the emergent point bar are bounded by scoured surfaces which slope radially toward the low-stage channel (i.e., they mimic the radial slope of the point-bar surface in the meander bend). The enclosed cross-strata dip generally in a downstream direction or obliquely toward the higher part of the point bar, diverging from the channelward dip direction of the scoured set boundaries by 80°-135°.

Sand waves which generated the cross-strata appear to have migrated downstream parallel with contours on the point bar or obliquely up onto the point bar, as revealed in the "frozen" post-flood surface sand-wave patterns. The inferred sand-wave migration pattern and growth of the point bar by lateral accretion into the flood-scoured channel were confirmed by sonic sounding during floods.

Sandstones of apparent point-bar-lateral accretion origin form part of complex belt-like bodies of sandstone in the Carboniferous of central Pennsylvania. The alleged point-bar sandstones are composed of unidirectionally dipping sets of cross-strata, crudely sigmoid in shape, which thin both up and down the dip of the scour surfaces bounding the sets. Enclosed cross-strata dip, on the average, in directions perpendicular to the dip of the set boundaries, indicating that flow was along the original strike, rather than down the dip, of the scour surfaces. Lateral accretion of the point bar into the channel appears to have progressed by addition of sand deposited in the lee of sand waves migrating parallel with the point-bar surfaces, as observed on the modern point bars.

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