Secular change in chert distribution: a reflection of evolving biological participation in the silica cycle.
In the modern oceans, the removal of dissolved silica from sea water is principally a biological process carried out by diatoms, with lesser contributions from radiolaria, silicoflagellates, and sponges. Because such silica in sediments is often redistributed locally during diagenesis to from nodular or bedded chert, stratigraphic changes in the facies distribution of early diagenetic chert provide important insights into the development of biological participation in the silica cycle. The abundance of chert in upper Proterozoic peritidal carbonates suggests that at this time silica was removed from seawater principally by abiological processes operating in part of the margins of the oceans. With the evolution of demosponges near the beginning of the Cambrian Period, subtidalSpecial Olympics: Team Ireland wins first golds of games thanks to gym star Kirsty Devlin

Kevin Doyle in Los Angeles
– 29 July 2015 08:06 AM

29 July 2015; Team Irelands Kirsty Devlin, left, a member of SALTO Gymnastics Club, from Belfast, who won 2 Gold and 2 silver medals, in gymnastics, and fellow Team Ireland gymnast Ashleigh OHagan, a member of Lisnagry Special Olympics Club, from Limerick City, with her two Bronze medals at the John Wooden Center, UCLA. Special Olympics World Summer Games, Los Angeles, California, United States. Picture credit: Ray McManus / SPORTSFILE

29 July 2015; Team Ireland gymnast Ashleigh OHagan, a member of Lisnagry Special Olympics Club, from Limerick City, with her two Bronze medals at the John Wooden Center, UCLA. Special Olympics World Summer Games, Los Angeles,