Isotopic evidence for continental ice sheet in mid-latitude region in the supergreenhouse Early Cretaceous.
Cretaceous represents one of the hottest greenhouse periods in the Earth's history, but some recent studies suggest that small ice caps might be present in non-polar regions during certain periods in the Early Cretaceous. Here we report extremely negative δ(18)O values of -18.12‰ to -13.19‰ for early Aptian hydrothermal zircon from an A-type granite at Baerzhe in northeastern China. Given that A-type granite is anhydrous and that magmatic zircon of the Baerzhe granite has δ(18)O value close to mantle values, the extremely negative δ(18)O values for hydrothermal zircon are attributed to addition of meteoric water with extremely low δ(18)O, mostly likely transported by glaciers. Considering the paleoaltitude of the region, continental glaciation is suggested to occur in the early Aptian, indicating much larger temperature fluctuations than previously thought during the supergreenhouse Cretaceous. This may have impact on the evolution of major organism in the Jehol Group during this period.
CAS Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.
Wu-Bin
WB
Yang
He-Cai
HC
Niu
Wei-Dong
WD
Sun
Qiang
Q
Shan
Yong-Fei
YF
Zheng
Ning-Bo
NB
Li
Cong-Ying
CY
Li
Nicholas T
NT
Arndt
Xing
X
Xu
Yu-Hang
YH
Jiang
Xue-Yuan
XY
Yu