[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Paleocene hadrosaurs?



From: Ben Creisler bh480@scn.org
In case this ref has not been mentioned yet:

Fassett, J, R.A. Zielinski, & J.R. Budahn, 2002. Dinosaurs 
that did not die; evidence for Paleocene dinosaurs in the 
Ojo Alamo Sandstone, San Juan Basin, New Mexico.
 In: Catastrophic events and mass extinctions; impacts and 
beyond. (Eds.  Koeberl, C. & K. MacLeod): Special Paper - 
Geological Society of America 356: 307-336. (2002). 

AB: Palynologic and paleomagnetic data confirm a Paleocene 
age for the Ojo Alamo Sandstone (and its contained 
dinosaurs) throughout the San Juan Basin of New Mexico. 
The recently reported discovery of 34 skeletal elements 
from a single hadrosaur in the Ojo Alamo provides 
unequivocal evidence that these bones were not reworked 
from underlying Cretaceous strata. Geochemical studies of 
samples from several single-dinosaur-bone specimens from 
the Paleocene Ojo Alamo Sandstone and the underlying Late 
Cretaceous (Campanian) Kirtland Formation show that 
mineralized bones from these two rock units contain 
distinctly different abundances of uranium and rare-earth 
elements and demonstrate that Cretaceous and Paleocene 
bones were mineralized at different times when 
mineralizing fluids had distinctly different chemical 
compositions. These findings indicate that the dinosaur 
bone from the Paleocene Ojo Alamo is indigenous and not 
reworked. These data show that a relatively diverse 
assemblage of dinosaurs survived the end-Cretaceous 
asteroid-impact extinction event of 65.5 Ma. The San Juan 
Basin's Paleocene dinosaur fauna is herein named the 
Alamoan fauna. Magnetic-polarity chronology shows that 
these survivors lived for about one million years into the 
Paleocene and then became extinct around 64.5 Ma. We 
suggest that a plausible survival mechanism for this 
Lazarus fauna may have been the large numbers of buried 
dinosaur eggs, laid just before the asteroid impact 
occurred. These buried eggs would have provided a safe 
haven for developing dinosaur embryos for the first one to 
two years after the impact, thereby making it possible for 
them to survive the worst of the impact's early 
devastation.