Alaskan dinosaurs

[brouwers@gdsvr1.cr.usgs.gov (Elisabeth Brouwers)]

As one of the fortunate group who first located the late Cretaceous 
dinosaurs on the Alaskan North Slope, I have been following the discussion 
with interest.  Bill Clemens and his student at Berkeley and Roland Gangloff 
at U Alaska have been meticulously working up the vertebrate fauna since the 
initial find, and lots of stuff has been recovered, although the vast bulk 
is still the Edmontosaurus bones.  A number of us published a paper in 
Science in 1987, which goes through the arguments on paleolatitude based on 
paleomagnetics and the reconstruction of climate based on plants and 
invertebrates.  Basically, as has been stated, the North Slope has not 
drifted north from warmer climes, but, if anything was at least at 70 
degrees north and maybe as much as 80 degrees.  Because of the earth's 
tilt--and you have read about that--the consequence is months of dusk or 
total darkness.  The vegetation fits this, because, in contrast to the 
forests of southern Canada and the U.S., Alaska had deciduous trees, not the 
typical evergreen forests of lower latitudes.  This deciduousness was a 
consequence most probably of winter darkness, although there may have been 
some seasonality of precip/evap as well.  However, the sediments (no 
indication of drying) and the presence and types of aquatic invertebrates 
(ostracodes, charophytes, occasional forams, aquatic vegetation), the 
environment was mostly wet.  We used the plants and invertebrates to 
reconstruct climate, which left out any preconceptions of what dinosaurs 
needed to live.  All in all a neat study.