New evidence of Early Cretaceous petrified wood in Yumen, north-western Gansu, China and its palaeogeographical implication

ABSTRACT

The phenomenon characterised by faster growth of the side of trees exposed to sunlight relative to the opposite side is termed plant phototropism. Vertical trunks of silicified wood occur in situ in the Hongliuxia area of Yumen City in north-western Gansu Province, China. A few trunks in the area exhibit well-preserved growth rings. Two petrified stumps reveal positive phototropism values of 279°–293° in the northwest direction. Living plants in Yumen City, Lanzhou City of Gansu Province and Beijing City showed positive phototropism values of 210°–255°±5° in the south-west direction. The evidence from wood phototropism supports clockwise rotation of the North China Block from previous palaeomagnetic studies since the Early Cretaceous. The petrified wood stumps in the Hongliuxia area of Yumen City are associated with 109 Ma strata corresponding to the main stage of the Yanshanian movement.

KEYWORDS:

• Cretaceous petrified wood
• phototropism
• North China Block
• block rotation
• palaeogeography

About the first author

Yang Guolin, male; born in 1985 in Tianshui City, Gansu Province; doctoral candidates; work in Lanzhou City University. He is now interesting in the study on the paleobotany and the paleoclimate in the Mesozoic, special in the Mesozoic fossil wood.

Acknowledgments

We would like to thank Sanping Xie for important comments on the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [41662013]; Scientific Research Projects of Universities in Gansu [2014A–098]; Open Fund for Key Laboratory of Oil and Gas Resources Research in Gansu Province [SZDKFJJ20170601]; Investigation and Research on Paleontological Fossils and Database Construction Projects in Gansu Province; the Doctoral Research Fund Project of Lanzhou City University [LZCU-BS2018-11].