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.