Brazos River

Climbing ripples in the Brazos river bed at low river level. Hover your mouse over the image to reveal the climbing ripple structures
climbing ripples in the sandstone event bed at Brazos river

These structures are often regarded as HCS, Hummocky Cross Stratification, (see Yancey, Hansen) but are all actually climbing ripples.
Such ripples originate in a current with extremely high suspension load, and the stoss-side is not, or barely eroded. Deposition is rapid on both the stoss- (but not always) and the lee-side of a ripple. At the Sierrita locality (see below) similar, even more spectacular examples occur in the same position in the K/T event beds. Climbing ripples are known in environments of spring melt in glacial lakes, and in turbidites in the Bouma C-interval.
However, the depositional environment of tsunami's should be an ideal environment for the formation of climbing ripples. Such waves erode large amounts of sands in a very short times and at high currents strengths, bring it in suspension, and deposit the sands again at waning current strenghts leading to climbing ripple structures.

Drawing of the same climbing ripples. Near the top the current direction changes about 150 degrees (measured on the outcrop) in the upslope, upwash direction
Climbing ripples at La Sierrita (Mexico) in the upper part of the K/T event beds. The dominant current direction is SE, which is both the downslope direction and backwash direction of tsunami surges. It is expected that in that direction most of the tsunami deposit will take place.
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