Manson structure team will help guide research

Abstract

The Manson impact structure, in northwest‐central Iowa, is about 35 km in diameter and the largest such structure known in the United States. Scientific interest in the Manson structure increased sharply last year when preliminary 40Ar/39Ar data indicated a time for the impact of less than, but not much less than, 70 million years. That age is temptingly close to the time established for the Cretaceous/Tertiary (K/T) boundary, about 66 million years ago, and allows the possibility of a connection between the Manson impact and mass extinctions produced by the K/T boundary event