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Astrochronology for Early Cretaceous Jehol Biota

From: Ben Creisler

A new online paper:

Huaichun Wu, Shihong Zhang, Ganqing Jiang, Tianshui Yang, Junhua Guo &
Haiyan Li (2013)
Astrochronology for the Early Cretaceous Jehol Biota in Northeastern China.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)
doi: http://dx.doi.org/10.1016/j.palaeo.2013.05.017

The Early Cretaceous Jehol Biota in Northeastern China provides an
evolutionary window for ‘feathered’ dinosaurs, primitive birds,
insects and early flowering plants. It also provides critical
information for the biodiversity changes of the Early Cretaceous
terrestrial ecosystem. Here we report a time series analysis for the
11.2-m-thick, fossil-bearing lacustrine deposits at the Sihetun
section in western Liaoning, Northeastern China on the basis of
high-resolution magnetic susceptibility (MS) and anhysteretic remanent
magnetization (ARM) measurements. A hierarchy of sedimentary cycle
bands of 120-260 cm, 50-67 cm and 18-42 cm were recorded in the MS and
ARM series. With available radioisotope age constraints from the same
section, sedimentary cycles of 120-260 cm, 50-67 cm and 18-42 cm were
interpreted as Milankovitch cycles of short eccentricity (130 and 95
kyr), obliquity (36.6 and 46 kyr), and precession (22.1, 20.9 and 18
kyr), respectively. The 100 kyr-tuned ‘floating’ astronomical time
scale indicates that the duration of the 11.2-m-thick section is ~
0.67 Myr and the average depositional rate is ~ 1.70 cm/kyr. The
duration of the 1.8-m-thick, main fossil-bearing interval that
contains 8 beds of ‘feathered’ dinosaur/primitive bird fossils can be
estimated as short as 150 kyr. The results suggest that climate
fluctuations manifested in palaeobotanical, sedimentological and
geochemical records of the Yixian Formation may have been controlled
by orbital forcing during Early Cretaceous.