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Re: Keller keeps punchin'
At 06:13 PM 4/14/2003 -0400, Dinogeorge@aol.com wrote:
In a message dated 4/14/03 12:25:40 PM Pacific Daylight Time,
<< Drilling at Yucatan reveal, they say, microfossils 300,000 years after
supposed extinction: >>
Could have washed back in at the time the crater was made. Also, it now seems
as if Chixculub was just one crater from a nearly simultaneous worldwide
Microfossils in the water column settle according to Stokes settling law,
(as does everything) and one must consider factoring in current, both
surface, and stratified, as well as Ekman spiral, among other motion in the
water column. "Fines" - those particles less than 4-Phi in size, settle
very slowly even in a 100% quiet environment (such as a graduated cylinder
lab experiment in which one demonstrates how painfully long it takes to
settle the fines in a 100% quiet water column) "Washing back in" after the
impact doesn't happen exactly the way the mental image the words provide.
Such things as palynomorphs & diatoms, since they are in the very small
fines, must be looked at in conjunction with additional evidence prior to
accepting the date they themselves often provide - why? - because the
smallest sedimentary particles are the most easily picked up and reworked,
and thus, are not always the most convincing chronostratigraphic indicators
when presented by themselves because of the extremely high potential for
reworking. I, and a multitude of other scientists, do trust foraminifera
for biostratigraphic age dating - many of which made it through the K-T
boundary with ease, both sessile and vagrant benthonic forms as well as
many planktonic forms. My personal favorite is Neogloboquadrina pachyderma.
Albeit a little young for this discussion, it descended from survivors. A
lovely little beast prone to switching to sinistral coiling when it gets
Gerta Keller is one of the top marine microfossil researchers in the world
and she is highly respected - I have a suspicion she hammered her data
profusely before she published it. I'm dying to read the entire report, not
just the "bite" ................
Marilyn D. Wegweiser, Ph.D.
Assistant Professor of Geology
Curator, Paleozoic & Mesozoic Collections
Department of Biological and Environmental Sciences
Georgia College & State University
Milledgeville, GA 31061
(works best in Internet Explorer)
Director: This Side Of Hell, WY Research Project; it's north of Pitchfork
Wyoming, north of Hell's Half Acre, Wyoming, west of Hell, North Dakota,
and south of Hellroaring Plateau, Montana. Could it get any better than this?