Stromatolitic associations and their palaeo-environmental significance: A re-appraisal of a lower proterozoic locality from the northern cape province,South Africa

A basal section of the Lower Proterozoic Transvaal Dolomite from the northern Cape has been re-examined. Numerous associations of stromatolites and other structures have been distinguished in it. Forms of domical stromatolite dominate the structures, but columns, and associations built around spheroidal forms, are also represented. This material accumulated in a telescoped range of environments through the intertidal to a high-energy agitated zone and out into the subtidal.Columnar forms and flat domes from the intertidal zone appear to be remarkably similar to features described from Hamelin Pool at Shark Bay, Western Australia. The subtidal elongate domes and mounds increase in size with depth to reach dimensions of 40 by 10 m, heights of 13 m and relief of 2.5 m. Minor structures on these subtidal forms reflect decreasing energy outwards; included within them are columnar forms in the shallow subtidal zone.It is suggested that deposition within an epeiric sea was away from a headland on a relatively steeply shelving floor affected by currents at right angles to the shore. There are indications that an arid to semi-arid climate existed at that time.