The black stuff is biological soil crust (bacteria, lichens, algae, etc). It basically keeps nutrients in the soils and also keeps the soils from eroding away. There are many warning signs asking people not to step on these since it takes about 50 years for it to recover.

The Needles

This is a view along the pothole point trail on the slickrock. No water in the potholes. When it rains, they fill up with fairy shrimp, tadpoles, etc. The tadpoles hatch when it rains. The cairns on the ground (little stacks of rocks) mark the trail.