Deeply Buried Sediments Tell Story of Sudden Mass Extinction
Shocked minerals identified in the Bass River spherule layer.
Credit: Richard Olsson, Rutgers University
A spherule layer from the asteroid impact at Chicxulub, Mexico, separates the uppermost Cretaceous and lowermost Tertiary sediments in a borehole extracted from the Bass River in New Jersey. Spherules (lower left) settled onto a muddy sea floor, making impressions of their spherical shapes (upper left). A thin, rust-colored layer -- the "fireball layer" -- is visible at the top of the spherule layer in the core sample (upper right), where dark early Tertiary sediments surround brown fragments of Cretaceous sediment. The background shows an experimental oblique impact into powdered dolomite at 5.2 km/s using the NASA Ames Vertical Gun (courtesy of P.H. Schultz).
Credit: Composition by James Browning. See Geology 25(8):759-762, August 1997.