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Dating the Jiufotang and Jehol Biota
R.-x. Zhu, Y. Pan, R. Shi, D. Li. 2004. New paleomagnetic and
chronological constrains on the Jehol Fauna in northeastern China.
_Geophysical Research_ (Abstracts) 6.
Geophysical Research Abstracts, Vol. 6, 04890, 2004
"In the past decade, much attention has been focused on the diverse
fossil assemblages of the Jehol biota mainly discovered in western
Liaoning Province in northeast China. Numerous vertebrate, invertebrate
and plant fossils were excellently preserved in the lacustrine
We recently carried out a combination of Ar-Ar dating and paleomagnetic
investigation on the Sihetun section in West Liaoning in purpose to
attest the age of the famous fossil assemblage. The datings on the
and upper volcanic rocks yielded ages of 126.5+/-1.4 Ma and 124.5+/-1.5
Ma, respectively. Detailed paleomagnetic investigation on the
fossil-bearing lacustrine interval obtained a normal polarity. In
combination of the new magnetic results with radiometric datings from
both sediments and volcanic rocks, we concluded that the fossil-bearing
lacustrine interval deposited during the normal polarity period of M3n
(marine anomaly), of the early Cretaceous age. And, we proposed that it
was a possibly strong volcanic-associated lake existed in a relatively
He, H.-y., X.-l. Wang, Z.-h. Zhou, F. Wang, A. Boven, G.-h. Shi, and
R.-x. Zhu (2004), Timing of the Jiufotang Formation (Jehol Group) in
Liaoning, northeastern China, and its implications. _Geophysical
Letters_ 31: L12605 / doi:10.1029/2004GL019790.
"The timing of the Jiufotang Formation remains speculative despite
progress in the study of the Jehol Biota. In this paper we contribute
this topic with 40Ar/39Ar dating on K-feldspar (sanidine and
from tuffs interbedded within the fossil-bearing shales of the
Formation, from the upper part of the Jehol Group in Chaoyang,
northeastern China. 40Ar/39Ar step heating analyses of K-feldspar and
the SHRIMP U-Pb zircon data indicate that tuffs at the Shangheshou
section erupted at 120.3 ± 0.7 million years ago. This result confirms
an Aptian age for the Jiufotang Formation that was mainly based on
biostratigraphic evidence. It also places stringent controls on the age
of the fossils from the formation, providing a minimum age (120 Ma) for
the four-winged dinosaur, *Microraptor,* and the seed-eating bird,
Jaime A. Headden
Little steps are often the hardest to take. We are too used to making leaps
in the face of adversity, that a simple skip is so hard to do. We should all
learn to walk soft, walk small, see the world around us rather than zoom by it.
"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
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