The term iridium anomaly commonly refers to an unusual abundance of the chemical element iridium in a layer of rock strata at the Cretaceous–Paleogene (K–Pg) boundary. The unusually high concentration of a rare metal like iridium is often taken as evidence for an extraterrestrial impact event.

Anomaly characteristics Edit

The type locality of this iridium anomaly is near Raton, New Mexico. [1][2]

Iridium is a very rare element in the Earth's crust, but is found in anomalously high concentrations (around 100 times greater than normal) in a thin worldwide layer of clay marking the boundary between the Cretaceous and Paleogene periods, 66 million years ago. This boundary is marked by a major extinction event, including that of the dinosaurs along with about 70% of all other species. The clay layer also contains small grains of shocked quartz and, in some places, small weathered glass beads thought to be tektites.[3]

Meteorite impact theory Edit

A team consisting of the physicist Luis Alvarez, his son, geologist Walter Alvarez, and chemists Frank Asaro and Helen Vaughn Michel were the first to link the extinction to an extraterrestrial impact event based on the observation that iridium is much more abundant in meteorites than it is on Earth.[4] This theory was later substantiated by other evidence, including the eventual discovery of the impact crater, known as Chicxulub, on the Yucatán Peninsula in Mexico.

See also Edit

References Edit

  1. ^ Goderis, Steven; Sato, Honami; Ferrière, Ludovic; Schmitz, Birger; Burney, David; Kaskes, Pim; Vellekoop, Johan; Wittmann, Axel; Schulz, Toni; Chernonozhkin, Stepan M.; Claeys, Philippe; de Graaff, Sietze J.; Déhais, Thomas; de Winter, Niels J.; Elfman, Mikael (2021-02-26). "Globally distributed iridium layer preserved within the Chicxulub impact structure". Science Advances. 7 (9). doi:10.1126/sciadv.abe3647. ISSN 2375-2548. PMC 7904271. PMID 33627429.
  2. ^ "Raton Iridium Layer". Atlas Obscura. Retrieved 2023-08-12.
  3. ^ Hildebrand, Alan R.; Penfield, Glen T.; et al. (1991). "Chicxulub Crater: A possible Cretaceous/Tertiary boundary impact crater on the Yucatán Peninsula, Mexico". Geology. 19 (9): 867. Bibcode:1991Geo....19..867H. doi:10.1130/0091-7613(1991)019<0867:ccapct>;2. ISSN 0091-7613.
  4. ^ Alvarez, L. W.; Alvarez, W.; Asaro, F.; Michel, H. V. (1980-06-06). "Extraterrestrial Cause for the Cretaceous–Tertiary Extinction". Science. 208 (4448): 1095–1108. Bibcode:1980Sci...208.1095A. doi:10.1126/science.208.4448.1095. ISSN 0036-8075. PMID 17783054. S2CID 16017767.

External links Edit