No. 25: Jan-Feb 1983
Tektites are small glassy stones with drop-like and button-like shapes. They are found primarily in four strew fields in Europe, Australia, North America, and Africa. Just about everyone believes that tektites are once-liquid droplets of rock that were solidified in flight. The major question -- often intemperately debated -- is the location of the tektite source. Are they of terrestrial, lunar, cometary, or some other origin? A recent study by Shaw and Wasserberg, using element abundances as a guide, strongly favors a terrestrial origin, with meteor impacts serving as the liquefying and splashing agents. Indeed, specific craters have long been associated with the European and African strew fields. Those who believe that the tektites were splashed all the way from the moon by meteor impacts have not given up yet. One provocative fact stressed in this article is that the ages of the four groups of tektites are 35, 14, 1.3, and 0.7 million years. Tektites are all quite young!
(Smith, Peter J.; "The Origin of Tektites -- Settled at Last?" Nature, 300: 217, 1982.)
Comment. Were there no tektite-forming meteor impacts prior to 35 millions of years ago? Is this observation related to the great rarity of meteorites in sedimentary rocks? Just what is different about the past 35 million years?
Reference. Twelve tektite "problems" are cataloged at ESM3: in Neglected Geological Anomalies. For more on this book, go to: here.