Several authors have demonstrated the dipmeter's ability to resolve internal crossbed dips. Analyses of the dip patterns, which result from paleocurrent flow directions, are interpreted to determine different sand body types.

This paper shows the relation between crossbed variation in a fluvial sand bar and known channel patterns which existed during deposition. The sand bar studied is in the Arkansas River valley approximately 10 mi upstream from Tulsa. From aerial photo sequences plus discharge and river stage records, it can be shown that the entire sand bar (600,000 cu yd) was deposited during two floods--May 19-22, 1957 (60 hours), and October 3-6, 1959 (96 hours).

The sand bar was studied in detail along a 500-ft natural cutbank parallel with the valley and in a 700-ft trench dug at right angles to the valley. Crossbed types were studied and 210 crossbed measurements (true dip direction and true dip angle) were recorded at 12 vertical sections.

Results show that the highly variable patterns of crossbed dips match the erratic and changing flow directions prevalent during flood stages. In some vertical sections crossbed dip directions are at many angles to the overall east-west orientation of the Arkansas River valley. These results verify the expected crossbed variability in fluvial sands and suggest that dipmeter patterns from wells in channel sandstone bodies should be interpreted and projected with caution.

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