Chemical comparison of spherules from the Ross Sea and glacial sediment of Antarctica: an SEM study

Four (about 100 ?m in diameter) clear spherules from seafloor sediments of the Ross Sea differ physically and chemically from three microscopic dark spherules of about the same size from glacial deposits in Antarctica and upper New York state. The major-element concentrations (determined by SEM) show that the clear spherules differ in composition from the dark spherules. The clear spherules were found to be similiar in composition to the continental crust, indicating a terrestrial origin. Based on their physical structure and chemical composition, they are likely a biogenically-produced form of opal. The composition of each dark spherule was compared to the compositions of the continental crust and CI chondrites. The results are inconclusive. Therefore, they may be either terrestrial or extraterrestrial in origin. In addition, the dark spherules differ markedly in composition amongst themselves