Replacement by silica (silicification) also requires acidic conditions and an abundance of silica. The coral and algae have been silicified. Replacement by calcite is very rare. The original shell ...
in collaboration with Prof Derek Siveter from the University of Oxford investigating the co-occurrence of gigantic trilobites in early Ordovician strata in Morocco systematics of paradoxidids ...
Trenching along the strike of the Bambino Central anomaly has exposed a north-northwest striking zone of limonite-stockwork mineralization within argillic-silicic altered intrusive and metasedimentary ...