Two layers of Australasian impact ejecta in the Indian Ocean?

Abstract

Only 2 Australasian tektites have been found in the Indian Ocean, and both are associated with surficial sediments. We collected cores from both locations where the tektites have been reported. The microtektites in these cores (and both the tektites, as reported earlier) have chemical compositions within the compositional range previously reported for Australasian tektites and microtektites. In both locations, while the tektites are occurring at the sediment/water interface, the microtektites are found buried in older horizons beneath the seafloor at stratigraphic levels, conforming to the radiometric age of the strewn field. Thus, at first glance, there appear to be 2 layers of Australasian impact ejecta in the Indian Ocean. However, the manganese nodules are associated with the tektites which, although millions of years old, are invariably resting on recent sediments. Therefore, the mechanism that retains nodules at the seafloor also seems to be operative on the tektites, thus leading to this apparent "age paradox" of tektite/microtektite distribution in the Indian Ocean, although they both belong to the same impact event.