MICROSPHERULES IN DEVONIAN SEDIMENTS - ORIGINS, GEOLOGICAL SIGNIFICANCE, AND CONTAMINATION PROBLEMS

We have studied various microspherules (<0.5 mm across) that were foun d in Devonian sediments from Canada and China during our micropaleonto logical studies (e.g., conodont picking). These spherules are similar in appearance, but they are quite different in origin. A combined scan ning electron microscope, energy dispersive X-ray, X-ray microdiffract ion, and electron microprobe analysis enables us to determine their pr obable origins: phosphatic conodont pearls of biological origin; silic ate glass microtektites of terrestrial meteorite-impact origin; and bl ack, magnetic iron spherules of probable extraterrestrial origin. We a lso observed some contaminant spherules (glue spatters and steel slag) of artificial origins. Studies of natural spherules in sediments can provide important geological information that may be otherwise undetec table.