Chronological correlations between the Pilbara and Kaapvaal cratons

The early geological development of the Pilbara and Kaapvaal cratons has ma ny features in common. Attempts have been made to correlate geologically si milar features of the two cratons, and it has been postulated that they ori ginated as contiguous components of a single continent, 'Vaalbara', during this time. The early geological histories of the Pilbara and Kaapvaal crato ns are here compared in detail and the evidence that they were initially co ntiguous is assessed. These comparisons indicate significant differences in the chronologies of magmatic events within the granite-greenstone crusts o f the Pilbara and Kaapvaal cratons. In addition, igneous correlatives empla ced during ca 2985 and 2782 Ma magmatic events on the Kaapvaal Craton have not been identified on the Pilbara Craton, and a well-defined 2760 Ma magma tic event, manifest as widespread emplacement of granitic rocks into the Pi lbara granite-greenstone basement and eruption of flood basalts of the lowe r part of the Fortescue Group, is absent from the Kaapvaal Craton. Furtherm ore, similarities in first- and second-order transgression-regression cycle s within the sedimentary supracrustal sequences may be attributable to glob al sea-level fluctuations, and thus may be irrelevant to the question of fo rmer contiguity. However, similarities in some aspects of the geological de velopment of the Pilbara and Kaapvaal cratons imply that there were periods , extending for between 60 and 200 Ma, of the Archaean era during which the style of crust formation, intensity of volcanism and subaerial erosion, an d magnitude of sea-level fluctuations may have varied on a global scale. Su ch similarities include the overall duration of formation of the granite-gr eenstone crusts from ca 3650 to 3100 Ma, the onset of craton-wide erosion i n the interval ca 3125 to 3000 Ma, the major episodes of flood basaltic vol canism between 2760 and 2680 Ma, the predominance of chemical (carbonate an d banded iron-formation) sedimentation between ca 2630 and 2440 Ma and the transition to widespread elastic sedimentation within the interval 2440 to 2200 Ma. (C) 1999 Elsevier Science B.V. All rights reserved.