Validity of Monocraterion as a separate ichnogenus, considered by some authors as the same trace fossil as Skolithos Haldeman (interpreted as erosionally
truncated Monocraterion) is confirmed (see Fillion and Pickerill, 1990); however, we follow the idea that it is better to separate these with funnel from these without funnel, if the erosional truncation is not evident.
Many of these dykes connect to sills up to 10 m thick, with the dykesill transition forming prominent rock ridges, possibly due to thickening of the erosionally
resistant igneous bodies at this point.
Directly above and locally truncating the folded interval erosionally
, the Macumber Formation contains horizons of intraformational limestone breccia several metres thick that are separated by undisturbed strata.