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Re: Iridium near fossils?

> I was wondering if anybody had a scientific paper reference on the
> global fire scenario. I know that popular media has mentioned it, but
> is there actual proof? I have looked myself at various places for a
> paper, but nothing specific. So if you can help, that would be great.
> The reason I ask, is I regularly cross the K/T boundary in my line of
> work, at various localites, and never have seen this supposed layer, I
> kind of doubt its existence.

Hello Frank, hello Mike, hello List,

1) GILMOURE I., ORTH C.J., BROOKS R.R. (1989) Carbon at a new K-T
boundary site in New Zealand (Meteoritics 22-4, 1987, pp. 385-388,
excerpts):

" The discovery of soot at the K-T boundary coinciding with the
enrichment in meteoric Ir has led to the suggestion that widespread
major wildfires occurred as the result of a 10 km diameter bolide impact
(Wolbach et al., 1985)."

"Ir and C abundances rise sharply, by around 50x (Ir) and 250x (C) at
the boundary relative to the preceding 20 cm interval."

" ... The presence of soot as a form of reduced C in the boundary clay
and the strong coincidence between Ir and C suggest that, as in other
sites examined, the soot and Ir ejecta fell out simultaneously, which
implies that the fire immediately followed the impact and led to
decreased bioproductivity after the mass extinctions."

2) WOLBACH W.S., ANDERS E., GILMOURE I. (1987) Detailed carbon profiles
across the K-T boundary at Woodside Creek, New Zealand (Meteoritics
22-4, 1987, pp. 531-532, excerpt):

"Soot enriched at the K-T boundary is apparently derived from major
fires (Wolbach et al., 1985) triggered by the impact of a giant
meteorite (Alvarez et al., 1980), as soot and Ir rise simultaneously by
more than 750 x at the boundary (Wolbach et al., 1986)."

3) AHRENS T.J. et al. (1997) Global effects of the impact of the K/T
extinction bolide (Meteoritics 32-4, Supp., 1997, A005, excerpt):

"The rainout of H2SO4 aerosols, with a minor contribution from HNO3
induced by initial bolide passage and reentry of ejecta, gave rise to a
global pH of about 2-4 [see PRINN R.G. et al. (1987) EPSL 83, 1-15].


> Also where are the tektites from this impact?
> Wouldn't they also be found in the KT fossil layer?

1) BOHOR B.F. et al.(1988) Are the hollow spherules in K-T boundary
claystones altered mikrotektites? (Meteoritics 23-3, 1988, 259).

2)BOHOR B.F. et al.(1991) K/T spherules are altered microtektites
(Meteoritics 26-4, 1991, 320).

3) PREMO W.R. et al. (1992) Isotopic signatures of black tektites from
the K-T boundary on Haiti: Implications for the age and type of source
material (Meteoritics 27-4, 1992, 413-423).

4) BOHOR B.F. et al.(1995) Origin and diagenesis of K-T impact spherules
- from Haiti to Wyoming and beyond (Meteoritics 30-2, 1995, 182-198).

5) etc., etc.


Best wishes,

Bernd

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