Les sphérules cosmiques dans les nodules de manganèse

A definition is given of an objective criterion for the identification of natural spherles in pelagic sediments, offering the possibility of eliminating technologic spherules from the observational field. This criterion is based on the formation process and rate of formation of manganese nodules. According to the above criterion, natural spherules have been observed in nodules brought back by the Challenger Expedition. The mineralogy, textures and alterations of the observed spherules and their petrographic relations with the manganese hydroxydes are described. A short discussion follows on the consequences of the gathered data for the measurement of cosmic accretion rates, the distribution and stability of spherules in pelagic sediments. © 1970.SCOPUS: ar.j