GONDWANA: THE NEXT FRONTIER FOR DEEP SEISMIC EXPLORATION

Systematic exploration of the continental lithosphere by deep seismic reflection profiling over the past 20 years has revolutionized our view of the deep crust and upper mantle. Spectacular though these results have been, efforts have been limited largely to national programs (e.g. COCORP, BIRPS, LITHOPROBE) in “rich” countries. While grids of deep seismic profiles now span North America, Europe, Japan and Australia/New Zealand, with a few notable exceptions most of Asia, Africa, South America and Antarctica remain terra incognita in terms of modern, high resolution deep seismic imaging. From a geological perspective, perhaps the largest, scientifically coherent expanse of unexplored continental lithosphere is represented by those fragments that were once part of the supercontinent of Gondwanaland. With the exception of Australia and, to some degree, India, relatively few deep reflection profiles exist to delineate the gross structure, much less the details, of the continental architecture of this geologically pivotal region. Independent initiatives such as the KRISP refraction experiments in East Africa and the recent Kaapvaal Broadband seismic investigation in southern Africa are a good start. However, we suggest that it is now time to consider a more comprehensive program, perhaps along the lines EUROPROBE, to systematically probe Gondwana along transects cored by deep reflection profiling. Geological and geochemical studies of the rocks in East Africa, Madagascar, India, Sri Lanka, Australia and East Antarctica, for example, now provide a firm basis for framing important geotectonic questions that can be addressed by an integrated program of surveys that sample those fragments. New seismic technologies have made surveys in remote areas more practical. Furthermore, the present-day dispersal of the fragments of Gondwanaland make many of these geological problems accessible to marine deep seismic profiling, which is considerably less expensive than similar surveys on land. In this presentation we will describe LEGENDS (Lithosphere Evolution of Gondwana East from iNterdisciplinary Deep Surveys), an attempt to build upon both the experience of previous deep seismic programs and the geologic perspectives promoted by the IGCP to probe one of the last major frontiers in deep seismic exploration