While at the Cliffs of Dover a few weeks ago, me and my friends noticed lines of black rocks embedded in the Cliffs in rows. We saw this in an area just North called St. Margarets Beach. We have no idea what type of rocks they would be, do you?
Just a guess (and a bump), but they might be old dirt.
I assume that the cliffs are ancient shell beds from when they were underwater. The dark bands might be layers that were laid down when the area was above ocean level.