Re: Keller keeps punchin'

[Marilyn Wegweiser <wegweise@mail.gcsu.edu>]

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,
> jbois@umd5.umd.edu writes:
>
> << 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
> bombardment.


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 
colder.......

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" ................

Carry on,


*********************************
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
Office: 478-445-2441
FAX: 478-445-5290

http://www.faculty.de.gcsu.edu/~mwegweis/
(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?