A non-catastrophist explanation for the iridium anomaly at the Cretaceous/Tertiary boundary

Research output: Contribution to journalArticle

Abstract

The iridium (Ir) anomaly at the Cretaceous/Tertiary (C/T) boundary can be explained by dissolution of normal pelagic limestones producing an insoluble clay residue containing Ir-rich meteoritic material. Further concentration of Ir and other trace metals in the clay can be explained by deposition under reducing conditions. Clay-mineral analyses indicate that the boundary clay is similar to locally derived clays in the limestones above and below the boundary, and contains no detectable exotic components. This supports a terrestrial origin for the boundary clay. The genesis of the boundary clay is attributed to changes in ocean chemistry (pH and oxygenation), leading to an interval of widespread dissolution of carbonate sequences in the oceans, and culminating in the development of submarine pyritic hardgrounds and a disconformity of global extent.

Original languageEnglish (US)
Pages (from-to)455-460
Number of pages6
JournalSpecial Paper of the Geological Society of America
Volume190
DOIs
StatePublished - Jan 1 1982

ASJC Scopus subject areas

  • Geology

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