Blackriverian tubicolous build-ups.
Dune shaped-mounds composed of Tymbochoos (suspension feeding polychaet). Microbes associated (abundant where abundance of Tymbochoos decreases).  Rare other fossils (bryozoa, bivalves).
48 mounds in area.
Up to 5 m length and 0.5 m thickness.
Buildups on oolites either in intertidal channels or shallow subtidal shoals.