Wits Evolutionary Studies Institute (ESI)
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Item Carboniferous pycnoxylic woods from the Dwyka Group of southern Namibia(Bernard Price Institute for Palaeontological Research, 2001) Bangert, Berthold; Bamford, Marion KGlacial deposits of the Dwyka Group between Keetmanshoop and Mariental in southern Namibia have been reinvestigated for palaeontological remains and associated tuff horizons in an attempt to accurately date the deposits. SHRIMP-based dating of juvenile zircons from these tuff horizons provide ages which cumulate in the latest Carboniferous (Gzelian). The pycnoxylic woods Megaporoxylon scherziKrausel and Megaporoxylon kaokense Krausel are described in detail for the first time and are compared with similar permineralised woods from Gondwana. Based on previous fossil wood studies covering the rocks of the main Karoo Basin, these species occur only in the Dwyka and lower Ecca Groups in southern Africa and do not extend to the upper Ecca Group.Item Fossil wood from the Brandvlei area, Bushmanland as an indication of palaeoenvironmental changes during the Cainozoic(Bernard Price Institute for Palaeontological Research, 1993) de Wit, Michiel C J; Bamford, Marion KRemnants of Cainozoic fluvial deposits occur along the northerly flowing Sak River in Bushmanland, between Brandvlei and Sak River Station. The terraces can be subdivided into older and younger deposits, and occur approximately 60m and between 20m and 30m above the present-day river respectively. The older deposits are found to the east of the Sak River in the Geelvloer palaeo-valley. Most of the older 'terraces' are either hill-slope deposits or fans, and represent reworked fluvial sediments. A rounded vertebrate bone and several pieces of sub-rounded fossil wood were found in these deposits, which indicate a mid Miocene age for the original older deposits. Some of the fossil-wood samples have been positively identified as extant angiospermous families. The occurrence of fagaceous wood in two samples is of great interest biogeographically. Both the vertebrate fossil and the wood suggest that the mid Miocene climate was subtropical. At the end of the Miocene the wet period changed to arid conditions, and mature calcretes developed. This dry period was interrupted by pluvials during which the younger gravels were deposited. These alluvial terraces are interpreted as an aggradational sequence of braid bars associated with a wandering river, deposited under semi-arid conditions. Two well-rounded fossil-wood clasts, presumably reworked from the older terraces, were found in these sediments. One of which is identified as Polygalaceae. Based on similarities of lithofacies and style of diagenesis with the Van Wyksvlei sequence to the east, the younger terraces are probably Plio-Pleistocene in age.