Research Article| September 01, 2009 CRETACEOUS EROSION IN CENTRAL SOUTH AFRICA: EVIDENCE FROM UPPER-CRUSTAL XENOLITHS IN KIMBERLITE DIATREMES E.K. HANSON; E.K. HANSON Geology Department, Rhodes University, P.O. Box 94, Grahamstown, South Africa email: emilykhanson@gmail.com; j.moore@ru.ac.za; e.bordy@ru.ac.za; goonie.marsh@ru.ac.za; g04h0067@campus.ru.ac.za Search for other works by this author on: GSW Google Scholar J.M. MOORE; J.M. MOORE Geology Department, Rhodes University, P.O. Box 94, Grahamstown, South Africa email: emilykhanson@gmail.com; j.moore@ru.ac.za; e.bordy@ru.ac.za; goonie.marsh@ru.ac.za; g04h0067@campus.ru.ac.za Search for other works by this author on: GSW Google Scholar E.M. BORDY; E.M. BORDY Geology Department, Rhodes University, P.O. Box 94, Grahamstown, South Africa email: emilykhanson@gmail.com; j.moore@ru.ac.za; e.bordy@ru.ac.za; goonie.marsh@ru.ac.za; g04h0067@campus.ru.ac.za Search for other works by this author on: GSW Google Scholar J.S. MARSH; J.S. MARSH Geology Department, Rhodes University, P.O. Box 94, Grahamstown, South Africa email: emilykhanson@gmail.com; j.moore@ru.ac.za; e.bordy@ru.ac.za; goonie.marsh@ru.ac.za; g04h0067@campus.ru.ac.za Search for other works by this author on: GSW Google Scholar G. HOWARTH; G. HOWARTH Geology Department, Rhodes University, P.O. Box 94, Grahamstown, South Africa email: emilykhanson@gmail.com; j.moore@ru.ac.za; e.bordy@ru.ac.za; goonie.marsh@ru.ac.za; g04h0067@campus.ru.ac.za Search for other works by this author on: GSW Google Scholar J.V.A. ROBEY J.V.A. ROBEY De Beers Group Services, P.O. Box 47, Kimberley, South Africa email: jock.robey@debeersgroup.com Search for other works by this author on: GSW Google Scholar South African Journal of Geology (2009) 112 (2): 125–140. https://doi.org/10.2113/gssajg.112.2.125 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation E.K. HANSON, J.M. MOORE, E.M. BORDY, J.S. MARSH, G. HOWARTH, J.V.A. ROBEY; CRETACEOUS EROSION IN CENTRAL SOUTH AFRICA: EVIDENCE FROM UPPER-CRUSTAL XENOLITHS IN KIMBERLITE DIATREMES. South African Journal of Geology 2009;; 112 (2): 125–140. doi: https://doi.org/10.2113/gssajg.112.2.125 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySouth African Journal of Geology Search Advanced Search Abstract Twelve Group II and fourteen Group I kimberlite diatremes in central South Africa were examined for upper crustal xenoliths in order to estimate the extent of various lithological units of the Karoo Supergroup in the main Karoo basin at times of kimberlite eruption, the Cretaceous erosional history of the area, and the approximate vertical extent of the kimberlite diatremes prior to erosion. Sandstone and amygdaloidal basaltic lava xenoliths from the Karoo Supergroup were specifically selected as their modal mineralogies and geochemical compositions respectively can be attributed to specific stratigraphic positions within the Karoo Supergroup. Results indicated that, at the time of Group II kimberlite eruption (~120 Ma), basaltic lavas of the Drakensberg Group covered the entire area, but by the time of Group I kimberlite eruption (~85 Ma), they were restricted to the south-eastern half of the study area. At the latter time, an escarpment is proposed to have existed at the basalt outcrop limit, some 180 km west of its current position. Sandstones of the Stormberg Group had a restricted original distribution in the north and east of the study area, whereas sandstones from all other Karoo groups occurred throughout the entire area. In the Kimberley area, approximately 500 m of erosion is estimated to have occurred from 120 to 85 Ma and 850 meters from 85 Ma to the present day at average rates of approximately 15 m/Ma and 10 m/Ma respectively. Both Group I and II kimberlite diatremes had vertical extents of approximately 1350 m at eruption. An inland scarp-retreat model is proposed for the Cretaceous erosion cycle in central South Africa. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.