Paleocurrent indicators are primary sedimentary structures which indicate either the flow direction, or axis of the current at the time of sediment deposition. In some cases, clasts (such as pebbles or small cobbles) will be preferrentially aligned in such a way that they can serve as indicators of the direction of the current flow (i.e. Imbricated Clasts in conglomerates).
In this particular case, Belemnite fossils have been been aligned with the paleocurrent axis. Unforutnately, due to the lack of any obvious imbrication, while the axis of current flow is apparent, the direction of current flow is not.