CRETACEOUS ARC VOLCANISM ALONG THE EASTERN GONDWANA MARGIN

Researchers at Ball State University, the University of Auckland, New Zealand, the University of New Caledonia and the Universite l'Orleans are working together to study the tectonic processes active during the break-up of the eastern Gondwana margin. The goal of this project is to define the periods of extensional versus compressional tectonism along the eastern Gondwana margin and more specifically to identify periods of subduction during the late Cretaceous. This work concentrates on geochemical and chronological analyses of on-land igneous associations within the region, including the autochthonous outcrops of late Cretaceous volcanic rocks in New Zealand and New Caledonia. Future work will look to correlate these occurrences with similar sequences in Australia and possibly Antarctica. This research will provide key insight into the break-up of the eastern Gondwana margin and be applicable to global tectonic processes during the Cretaceous.

Preliminary work in New Zealand and New Caledonia has identified two important units: the Mt Camel terrane and the Noumea Basin respectively. Both units are insitu (autochthonous) packages of late Cretaceous marine sediments and volcanic rocks ranging from basaltic to rhyolitic. Preliminary geochemical analyses have identified continental arc signatures in the lavas. This finding is supported by sedimentary petrography suggesting a continental detrital mineral assemblage in both units. These results suggest that there was a well developed continental arc system active on both New Zealand and New Caledonia during the late Cretaceous, which has major implications for tectonic modeling during the break-up of Gondwanaland.