Imbrication (sedimentology)

In sedimentology, imbrication is a primary depositional fabric consisting of a preferred orientation of clasts such that they overlap one another in a consistent fashion, rather like a run of toppled dominoes.

Imbrication is observed in conglomerates and in some volcaniclastic deposits.

[1][2] The type of imbrication is generally related to paleoflow direction.

[4] Wadell[5] found the long axis aligned with paleocurrent, and dipping basinward in glacial sediments, whereas deltaic gravels may be oppositely inclined.

[6]

Imbricated clasts, with an implied flow direction of left to right.
Note how the clasts are oriented at an angle to the base of the channel (blue line), which was originally approximately horizontal.