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K/T Boundary and Sedimentology
I believe that there is trackway evidence even closer that 1 meter to the
KT
boundary.
The physical distance from the K/T boundary, however it is described (and
remember: it is _not_ defined by a coal layer, a clay layer, or an iridium
spike!), is meaningless unless we know the rate of sedimentation in the
section in question. There could be dinosaur fossils in the lag of a
massive flood deposit tens of meters thick beneath whatever is used as the
boundary indicator; we would then perceive this as an occurrence of
dinosaurs tens of meters below the boundary, yet the entire thickness was
laid down simultaneously, in a very short period of time (days or less),
possibly within days (or less!) of the "boundary event," whatever it was.
Alternatively, there could be dinosaur fossils in distal levee deposits,
which only get covered with a little sediment occasionally and is
consequently rather thin, stratigraphically; between the fossils and the
boundary indicator there could be hundreds of years of time, but less
stratigraphic thickness than in the flood deposit, which represents far less
time. Moral: distance between a fossil and a boundary is meaningless unless
the sedimentological factor is accounted for.
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Jerry D. Harris
Fossil Preparation Lab
New Mexico Museum of Natural History
1801 Mountain Rd NW
Albuquerque NM 87104-1375
Phone: (505) 841-2809
Fax: ; (505) 841-2808
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