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Response to Phil Bigelow's post of Fri, 16 Jan 2004 12:07:46.
Hi Phil, for the record, here is my e-mail to you of last Wednesday:
"Just a private note to tell you how much I'm enjoying our exchanges
on the dinosaur listserv. And, also to apologize for being slow with
some of my responses. I've been intensely busy on some other things,
and haven't had as much time as I hoped for the listserv. Maybe
things will loosen up soon. For now, please bear with me, and I'll
respond to your very good questions as soon as I can."
Phil, for your: "Your list is not sufficiently informative. What are
the depositional environments at each of these sites? More
importantly, what is the
*micro*-stratigraphy of these zones?," I simply do not have the time
to abstract this information for you. I provided specific references
for each site in my posts of Wed, 07 Jan 2004 13:19:20, and Wed, 07
Jan 2004 19:10:04 so that interested listmembers could examine the
papers for themselves. Here are excerpts from my posts:
(i) Nanxiong Basin, South China: Zhao et al. titled "A possible
causal relationship between extinction of dinosaurs and K/T iridium
enrichment in the Nanxiong Basin, South China: evidence from dinosaur
eggshells" (Palaeogeography, Palaeoclimatology, Palaeoecology, 2002,
v. 178, pp. 1-17).
(1) Braggs, Alabama: Following are some quotations from the Donovan
et al. paper "Sequence stratigraphy setting of the
Cretaceous-Tertiary boundary in central Alabama" (SEPM Special
Publication no. 42, 1988):
"Of the three iridium anomalies at Braggs, the lowest occurs in the
late Maastrichtian, the middle near the K-T boundary, and the upper
within faunal zone NP1 (Tertiary)....The presence of iridium at these
flooding surfaces suggests that iridium was present in the open ocean
from the latest Maastrichtian through earliest Danian....Thus, it
appears that iridium was not introduced into the atmosphere during a
unique event occurring at the K-T boundary, but was present in the
atmosphere for a much longer period of time."
(2) Lattengebirge, Bavarian Alps: The Graup and Spettel paper
"Mineralogy and phase-chemistry of an Ir-enriched pre-K/T layer from
the Lattengebirge, Bavarian Alps, and significance for the KTB
problem" (Earth and Planetary Science Letters, 95, 1989) notes that
an almost complete K-T section at Lattengebirge, Bavarian Alps, has
three iridium-bearing events over an extended period from latest
Maastrichtian into early Danian. The oldest spike predates the K-T
boundary by 14,000-9,000 years. Geochemically those spikes display
the same signature as the K-T boundary layer, and should have the
(3) Brazos River, Texas: The Ganapathy et al. paper "Iridium anomaly
at the Cretaceous-Tertiary boundary in Texas" (Earth and Planetary
Science Letters, 54, 1981) indicates two iridium spikes, one at the
K-T boundary, and one below.
Certainly, you will want to study the data base, methodology, and
conclusions drawn from each study. You can do that only by actually
reading each individual paper.
"Dewey M. McLean" <email@example.com> writes:
Response to Graydon Saunders' Wed, 14 Jan 2004 21:19:48 post.
"How do you go from the million or so years of intermittent
Deccan eruptions to the neat global iridium anomaly?"
My posts of Wed, 07 Jan 2004 13:19:20 and Wed, 07 Jan 2004 19:10:04
note that several K-T sections from around the world display
K-T transition iridium spikes:
1. Nanxiong Basin, South China (6 spikes)
2. Braggs, Alabama (3 spikes)
3. Lattengebirge, Bavarian Alps (3 spikes)
4. Brazos River, Texas (2 spikes)
Your list is not sufficiently informative. What are the depositional
environments at each of these sites? More importantly, what is the
*micro*-stratigraphy of these zones?