The stratigraphy of the Witteberg-Dwyka contact beds
|Loock, J C
|Thesis submitted in partial fulfillment of the requirements for the degree Of M.Sc. in Geology at the University of Stellenbosch
|Effective use is made of a multiple system to subdivide the portion of the Cape-Karroo stratigraphical column investigated into rock, time and in a lesser degree, biostratigraphic units. Heavy mineral studies reveal that distinct vertical variation trends exist for tourmaline. The steady increase in the frequency of brown tourmaline over other types makes this mineral specially suited for correlation, even over long distances. Garnet is indicative of the Dwyka Group. In the southern outcrop areas the Cape and Karroo Supergroups are structurally conformable to each other. Continuity in deposition was the rule. The sandstones of the Wittepoort Formation are interpreted as stable shelf deposits. The mixed sediments of the Lake Mentz Formation mark the rapid transition to a large interior basin with more restricted circulation. The fine-grained proglacial sediments of the Kommadagga Formation were deposited in a basin inherited from the Witteberg Epoch. The overlying tillites were deposited in a marine environment. An interpretation of the tectonic history of the Cape- Karroo sequence indicates that a peneplanation stage was present up to the end of the Witteberg Epoch. A geosynclinal stage then set in. It is convenient to divide the sequence into two major timestratigraphic units of system rank. The base of the Karroo System is chosen in view of historical, lithological, geographical and paleontological considerations.
|The stratigraphy of the Witteberg-Dwyka contact beds