Re: New date for Chicxulub?

[Phil Bigelow <bigelowp@juno.com>]

On Thu, 06 Apr 2006 18:34:34 +0200 Tommy Tyrberg 

> It seems that many geologists simply cannot conceive 
> that near 
> a 200 km impact crater in the hours after the impact sediments might 
> *not* 
> settle out slowly and peacefully in neat stratigraphic order.


This topic (impact-caused sedimentation) is actually a fledgling science
, and frankly, everyone is learning this stuff as they do it.  Everyone
can call themselves an "expert" and a "beginner" in the same sentence and
they would be right.  (Try to find a couple chapters written *solely* on
this subject in a graduate-level strat.-sed. textbook - - you will be
searching for a long time).  Tsunami deposits are the best analog to
impact-caused proximal marine sedimentation, but not all stratigraphers
specialize in the subject.

Tsunami deposits look different from each other depending on the
environment into which they were deposited.  For instance, we know
practically nothing about the appearance of the 2004 tsunami settle-out
on the abyssal plain off the west coast of Java. The same problem exists
for the new strata on Java's continental slope.  Is the stratigraphy of
tsunami-caused turbidites identical to the stratigraphy of "regular"
turbidites?  What is the appearance of the micro-stratigraphy of the
tsunami sediments in the near-shore zone?  Except for scale, do the 2004
tsunami deposits look different between Java and India?

That said, the evidence for a single, short-duration impact-caused
catastrophe ~65 mya is overwhelming.  The naysayers may be
misinterpreting the stratigraphy (but that is only the opinion of this
neophyte).

<pb>
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