Making ends meet in Gondwana: retracing the transforms of the Indian Ocean and reconnecting continental shear zones

Abstract

Interpretation of the detailed patterns of ocean‐floor transforms revealed by satellite altimetry enables the creation of the Indian Ocean to be described quantitatively as four consecutive plate‐tectonic regimes separated at 200, 136, 89 and 43 Ma. Each regime is reversed in turn by keeping transform termini coincident and colinear until conjugate points on the margins of pre‐existing plates regain their pre‐regime integrity. Progressive elimination of the Indian Ocean, demonstrable as a smooth computer animation (http://www.kartoweb.itc.nl/gondwana), leads to a refined re‐assembly of the continental fragments of central Gondwana that is substantiated by new geological data. A sequence of Euler interval poles that describes the dispersal of the Gondwana fragments, time‐calibrated against available magnetic anomaly data, is given. The model requires a mid‐Cretaceous position for India’s southern tip about 1000 km south of Madagascar, prior to India’s rapid northward migration.

Deep structure of the western South African passive margin — Results of a combined approach of seismic, gravity and isostatic investigations

“…The Damara Orogeny was succeeded by a tectonically tranquil period, dominated by erosional and sedimentary processes until the opening of the South Atlantic in Early Cretaceous times around 136 Ma (Brown et al, 1995;Reeves and de Wit, 2000;Macdonald et al, 2003;). The continental break-up of Africa and South America was accompanied by massive, transient volcanic activity, which resulted in the emplacement of the Cretaceous igneous intrusions also called the South Atlantic Large Igneous Province.…”

The Kalahari Epeirogeny and climate change: differentiating cause and effect from core to space

“…Some workers believe most of these to be Cenozoic in age (du Toit, 1933;King, 1951;Burke, 1996; and see Partridge and Maud, 1987;2000). Others believe that a significant number of the features date to the Mesozoic (Sahagian 1988;Fairhead and Binks, 1991;Guiraud et al, 1992;de Wit, 1993;de Wit et al, 2000;Brown et al, 1995;2000;2002;Foster and Gleadow, 1996;Partridge and Maud, 1987;Partridge 1998;Moore, 1999;Tinker, 2005;Tinker et al, 2007 in review). Doucouré and de Wit (2003a) quantified an early Mesozoic paleo-topography of Africa by removing topographic effects of significant surface features known to be Cretaceous or younger in age.…”

“…For example, ~ 15 km of such material in the lowermost crust would produce ~2.7 km of permanent uplift assuming a thermal time constant for the lithosphere of ~60 Ma (McKenzie, 1984) The early magmatic event related to the KarooFerrar LIP (Large Igneous Province) occurred between 174-184 Ma during the first breakup between east and west Gondwana, about 20-30 Ma before the initial opening of the Indian Ocean and the Weddell Sea (Cox, 1989;Storey, 1995;Storey and Kyle, 1997;Duncan et al, 1997;Hawkesworth et al, 1999;Storey et al, 1999;2001;Elliot and Fleming, 2000;Reeves and de Wit, 2000;Jokat et al, 2003;Eagles and König, 2007;Jourdan et al, 2007). The large thermal anomaly presumed to underlie the Karoo-Ferrar LIP Elliot and Fleming, 2000) may have initiated substantial uplift and exhumation across southern Africa (Cox, 1989) but this is not recorded in FTA dates of continental rocks or any basin analyses to date.…”

“…However, there are only few dated kimberlites directly associated with the SOUTH AFRICAN JOURNAL OF GEOLOGY THE KALAHARI EPEIROGENY AND CLIMATE CHANGE 380 onset of Gondwana break-up and the early formation of the Indian Ocean (~170 to ~140 Ma) and the Central Atlantic Ocean (~180 to ~160 Ma), and their associated hotspot activity recorded in the Karoo/Ferrar (~180 Ma) and CAMP (~ 200 Ma) flood basalts, respectively (Stern and de Wit, 2004;see Figure 4). Most kimberlites in Africa (and South America) therefore intruded well after the early growth of the Indian Ocean and the early opening phase of the Atlantic Ocean (Reeves and de Wit, 2000;Jokat et al, 2003;König 2006;Eagles, 2007;Eagles and König, 2007).…”

“…To track paleo-epeirogeny and related earth systems on a global scale, such as during Gondwana break-up and continental drift, models must also incorporate the changing paleo-geography of its shifting continental fragments such as Africa. The time-integrated paleo-positions of Gondwana continents are now known to within acceptable limits for high resolution numerical and graphical modeling to facilitate paleogeographical reconstructions (Scotese, 2001;Reeves and de Wit, 2000;Rosenbaum et al, 2002;Jokat et al, 2003;Collins, 2003;Stampfli and Borel, 2004;König, 2006;Smith 2006). Burke and Wilson (1972) and Burke (1976; suggested that because the horizontal motion of the…”