Chracoal & K/T Unconformity

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I'm with Henry Barwood in thinking that the absence of charcoal, and (even
more importantly) the absence of a thick sediment layer, in terrestrial
basins that were supposedly denuded by an impact-related fireball is mighty
peculiar.  Years ago Keith Rigby pointed out that in the Raton Basin the
Cretaceous coals are capped by a thin K/T clay layer (termed by some the
"fireball layer" that contains the shocked quartz and the Ir anomaly).
Then it's right back into coal-rich fluvial deposits.  If a K/T fireball
burned away everything in that area (as has been suggested by many
impact-extinction proponents) one would expect severe mass wasting.  That's
what happens after the landscape is denuded by forest fires today and those
are highly localized. Where are these sediments?

Also, with respect to Tom Lipka's posting about the erosional unconformity
along the eastern seaboard of the U.S., most stratigraphers familiar with
that region feel that the uppermost Maastrichtian eustatic sea-level fall
is responsible for the interruption in sediment accumulation.  Once again,
the problem is where did the sediment go?  A tsunami will resuspend
sediment that is already deposited, but it can't remove sediment completely
from an area thousands of miles in extent.  The unconformity along the
eastern seaboard resulted in a gap that spans an unknown interval in the
uppermost Maastrichtian and 1-2 planktonic foraminiferal biozones in the
Danian.  This is a pretty long interval of time (approx. .25-.50 m.y.). I
don't see any way for a tsunami to hit that area at the K-T boundary and
produce that kind of record, whereas I can easily envision a global
sea-level regression doing so.  Another way of looking at it is to compare
the New Jersey record to Brazos River, Texas where the so-called tsunami
deposit reaches thicknesses of tens of centimeters.  The duration of that
hiatus is completely confined to the uppermost Maastrichtian (a fact that
also has interesting implications for the timing of the so-called tsunami
and it's alternative interpretation as a lowstand deposit). Since the
energy of the K-T tsunami would fall off rapidly with distance I would
expect a smaller scour surface and a smaller hiatus in New Jersey than in
Texas if a tsunami was really the cause.


Norm MacLeod



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Norman MacLeod
Senior Scientific Officer
N.MacLeod@nhm.ac.uk (Internet)
N.MacLeod@uk.ac.nhm (Janet)

Address: Dept. of Palaeontology, The Natural History Museum,
         Cromwell Road, London, SW7 5BD

Office Phone: 071-938-9006
Dept. FAX:  071-938-9277
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