- © 2010 Geological Society of South Africa
We welcome Zimmermann’s comments on our paper in that it enables us to explain again why we propose (not “claim”) to correlate the Vingerbreek Unconformity (Nama Group) in Namibia with the Groenefontein Unconformity (Cango Caves Group) in South Africa and the implications of this proposed correlation. However, Zimmermann (this volume) does not contribute any new data that might back up his comments, which are obviously based on the author’s inability to distinguish between glacial deposits sensu stricto and the far-field effects of glaciation (e.g. sea-level fall).
The occurrence of late (or latest) Ediacaran glaciations is not only relevant to the discussion about the palaeoclimatic evolution of the Neoproterozoic (Chumakov, 2009; Gaucher and Poiré, 2009a; Shen et al., 2010), but also critical for the understanding of the causes of the Cambrian Explosion. If the climatic perturbations lasted until the very end of the Neoproterozoic, a good case can be made for glaciations as the ultimate barrier to explosive metazoan evolution (e.g. Knoll et al., 2006; Gaucher and Germs, 2009).
Glacioeustacy and glaciation
Since a long time it has been known that glacial phenomena such as grooves, polished surfaces and soft sediment deformation locally (i.e. in the Klein Karas Mountains) occur in the southern lower Nama Group of Namibia (Schwellnus, 1941; Martin, 1965; Germs, 1972; Cloud, 1988). The Klein Karas glacial phenomena are associated with an unconformity (named the Vingerbreek Unconformity) which not only occurs in southern Namibia (e.g. Germs, 1972; 1974; 1995) but has also been found by Almond and Germs in the area extending from the Orange River southwards to just north of Springbok in South Africa (Almond and Germs, in preparation).
During Pleistocene glaciations, major glaciers predominantly flowing southward occurred in northern Europe which deposited thick and continuous tills. The glaciers did not …