The Sedimentary Origin of Black and White Banded Cherts of the Buck Reef, Barberton, South Africa

The Buck Reef is a 250–400 m thick sequence of banded black and white (BW and the micro-layering within the black layers formed by annual temperature fluctuations, favouring microbial activity in summer and inorganic silica precipitation in winter. Outcrop-scale alternation of B&W layers was associated with major, thousand-year-long climate events: white cherts represent massive silica precipitation resulting from changes in ocean circulation and temperature during cold intervals.