Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Eriksson, P. Articles by van der Neut, M. Search for Related Content GeoRef GeoRef Citation

Palaeohydrological data from the c. 2.0 to 1.8 Ga Waterberg Group, South Africa: discussion of a possibly unique Palaeoproterozoic fluvial style

Department of Geology, University of Pretoria, Pretoria 0002, South Africa, e-mail: pat.Eriksson{at}up.ac.za

Darrel Long

Department of Earth Sciences, Laurentian University, Sudbury, Ontario, Canada P3E 2C6, e-mail: dlong{at}laurentian.ca

Adam Bumby

Department of Geology, University of Pretoria, Pretoria 0002, South Africa, e-mail: adam.bumby{at}up.ac.za

Kenneth Eriksson

Department of Geosciences, 4044 Derring Hall, Virginia Tech., Blacksburg, Virginia 24061, United States of America, e-mail: kaeson{at}vt.edu

Edward Simpson

Department of Physical Sciences, Kutztown University of Pennsylvania, Kutztown, Pennsylvaina 19530, United States of America e-mail: simpson{at}kutztown.edu

Octavian Catuneanu

University of Alberta, Department of Earth and Atmospheric Sciences, 1-26 Earth Sciences Building, Edmonton, T6G 2E3, Alberta, Canada, e-mail: octavian{at}ualberta.ca

Marko Claassen, Mtimkulu Mtimkulu, Kenneth Mudziri, Jacobus Brümer and Markus van der Neut

Department of Geology, University of Pretoria, Pretoria 0002, South Africa e-mail: mclaas{at}up.ac.za

Palaeohydrological data calculated from clast sizes in preserved channel-fills and from trough cross-bed set thicknesses within the Mogalakwena Formation, Main Basin, Palaeoproterozoic Waterberg Group in South Africa are presented. These data are compared to similar, published data, derived from two other Waterberg units, the Blouberg Formation (northeast of Main Basin) and the Wilgerivier Formation (Middelburg Basin, SE of Main Basin). All three data sets exhibit palaeoslope estimates that plot within the "natural depositional gap" defined by Blair and McPherson (1994) which separates alluvial fans (palaeoslopes >0.026 m/m) and fluvial systems (palaeoslopes <0.007 m/m).

These data, derived from what appear to be typical braided fluvial deposits, combined with evidence for subordinate occurrences of sediment gravity-flow and sheetflood deposits, support the presence of raised palaeoslopes (possibly restricted in time and space) for these Palaeoproterozoic fluvial systems. An abundance of fine, argillaceous material within such river systems likely resulted from warm and humid palaeoclimatic conditions, thus enabling localized debris-flow and hyperconcentrated flow processes. We postulate that temporary "floodbasin playas" (cf. Rainbird, 1992) formed localised elevated base levels and provided muddy detritus, thereby resulting in temporarily raised palaeoslopes and Waterberg sandstones with highly variable mud contents. Gravity-flow and sheetflow processes would have been possible at such sites.