GoWaterfalling’s minor waterfalls page says:
Greenstone Falls is a small scenic falls on the Little Carp River. The falls is about 20′ wide, and less than 10′ high. This is the most easily reached of the “backcountry” falls in Porcupine Mountains State Park, being about 1/2 mile from the trailhead. The trailhead to the falls is at the end of Little Carp River road. If you continue on the trail for another 2+ miles you will reach the much larger Trappers Falls.
Trappers Falls looks like a pretty cool natural waterslide!
Many more Michigan waterfalls on Michigan in Pictures.