Skip to Main Content
Book Chapter

Major wildfires at the Cretaceous/Tertiary boundary

By
Wendy S. Wolbach
Wendy S. Wolbach
Search for other works by this author on:
Iain Gilmour
Iain Gilmour
Search for other works by this author on:
Edward Anders
Edward Anders
Search for other works by this author on:
Published:
January 01, 1990

A global charcoal and soot layer, coinciding with the Ir layer, is present at the Cretaceous/Tertiary (K/T) boundary, and apparently comes from a global fire. Soot is present even in the basal layer of the boundary clay, implying that the fire started soon after the impact. No comparable soot enrichments, let alone of global extent, occur in the latest Maastrichtian or in a wide range of other marine sediments.

Much or all of the fuel was biomass, as indicated by the presence of retene (a hydrocarbon diagnostic of resinous wood fires) and by the carbon isotopic composition (δ13C = −25.8 ‰ ± 0.6 ‰), which resembles that of natural charcoal and atmospheric carbon particles from biomass fires. The mean amount of elemental C at 11 K/T boundary sites (11 ± 3 mg/cm2) is very large, and requires that much of the Cretaceous biomass burned down and yielded a larger mass fraction of soot and charcoal than small fires.

At one undisturbed site (Woodside Creek, New Zealand), soot in the boundary clay correlates tightly with Ir, As, Sb, and Zn. A possible reason for this correlation is that soot and Ir-bearing ejecta particles—containing some volatile chalcophiles from the target rock—coagulated in the stratosphere, and then scavenged additional chalcophiles from the hydrosphere. In view of this coagulation, the K/T fire would only slightly prolong the period of darkness and cold caused by impact ejecta. However, it would contribute other environmental stresses, e.g., a CO2 greenhouse and a variety of pyrotoxins and mutagens. Because the total of recognized stresses has risen to 12, there is no basis for the contention that an impact cannot explain the observed selectivity of extinctions.

You do not currently have access to this article.
Don't already have an account? Register

Figures & Tables

Contents

GSA Special Papers

Global Catastrophes in Earth History; An Interdisciplinary Conference on Impacts, Volcanism, and Mass Mortality

Virgil L. Sharpton
Virgil L. Sharpton
Search for other works by this author on:
Peter D. Ward
Peter D. Ward
Search for other works by this author on:
Geological Society of America
Volume
247
ISBN print:
9780813722474
Publication date:
January 01, 1990

References

Related

A comprehensive resource of eBooks for researchers in the Earth Sciences

Related Book Content
Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal