Yes it did. Water cut through the weathered brown rock and washed it away. Water continued cutting into the underling gray rock. Was some of the gray rock eroded by "weathered rock debris filled flow"? Of course, yet being softer how much damage did it cause? All of it? I don't think so. I don't dispute that the weathered rock contributed to erosion of the gray rock. I think much, if not most, of the erosion of the gray rock was caused by water and occurred after the overburden was washed away.
