The Phototropism of Jurassic Petrified Wood in North China Plate

Abstract

Trees on the side directly exposed to sunlight generally grow faster than on the opposite side, a phenomenon termed plant phototropism. There are in situ vertical trunks of silicified wood in the Xiadelongwan area of Yanqing County, north Beijing, where the first National Geologic Park of Petrified Wood of China has been built since 2002. A few trunks have well‐preserved growth rings. One petrified stump from the formation shows a positive phototropism direction of SW230°. As compared with the modern normal growth stumps in Beijing plain area, which have a positive phototropism direction of SW210 ° ± 5°, the evidence of wood phototropism supports the conclusion of previous palaeomagnetic studies that the North China Plate has rotated clockwise since the Late Jurassic. The known petrified wood stumps in the Yanshan‐Liaoning area are mainly found from the strata of 165–136 Ma, which corresponds to the main stage of the Yanshanian Movement.

Phototropism of Petrified Wood and Its Relation with the Rotation of Different Blocks in China and the Possibility of Application in the World

“…The first author of this paper found that the tree rings of the in situ preserved silicified trunks are clear and characterized by the obvious asymmetry in the SW 220 sides. Compared with the living trees phototropism [6], the result is almost the same. This means that the positive phototropism the trees are in accordance with the present ones, and possibly indicating that the Junggar basin has never rotated since the Late Jurassic.…”

Tree ring phototropism and implications for the rotation of the North China Block

“… No. Formation GPS position locality Dominant Eccentricity The other largest outermost directions TJS 1 the Tiaojishan Formation 41°27′30″N, 120°47′13″E Beipiao of western Liaoning province 233° 305° TJS 2 the Tiaojishan Formation 41°27′30″N, 120°47′12″E Beipiao of western Liaoning province 247° No TJS 3 the Tiaojishan Formation 41°21′30″N, 120°47′12″E Beipiao of western Liaoning province 230° No TCZ 1 the Tuchengzi Formation 40°42′4.1″N, 116°25′15.399″E Yanqing of Beijing 230° No TCZ 2 (modified from reference 34 —Jiang et al ., 2014) the Tuchengzi Formation 40°42′5.301″N, 116°28′15.44″E Yanqing of Beijing 235° No TCZ 3 the Tuchengzi Formation 40°42′5.362″N, 116°23′16.452″E Yanqing of Beijing 236° 44° TCZ 4 the Tuchengzi Formation 40°42′6.023″N, 116°23′17.07″E Yanqing of Beijing 233° No Note: TJS = Tiaojishan TCZ = Tuchengzi. …”

“…In the Northern Hemisphere, trunk phototropism is observed at high latitudes and extends south to at least the Tropic of Cancer (N23°26′) 34 . The magnitude of the phototropic response generally varies from stronger at the poles to weaker at the lower latitudes, finally disappearing near the tropics 34 .…”

“…In the Northern Hemisphere, trunk phototropism is observed at high latitudes and extends south to at least the Tropic of Cancer (N23°26′) 34 . The magnitude of the phototropic response generally varies from stronger at the poles to weaker at the lower latitudes, finally disappearing near the tropics 34 . Observations of living trees indicate that the eccentricity of growth rings in the Northern Hemisphere trends more southwest than south, possibly due to the fact that trees might preferentially grow faster from after high noon, when the sun is in the southwest sky.…”

“…However, little attention has been paid to the trunk phototropism represented by asymmetric growth of tree rings in response to a directed light source. In recent years, increased data have been accumulated for such eccentricity phototropism in both living and fossil tree ring observations, especially in some well-preserved individual fossil trunks 34 , 35 . However, such evidence is still very limited and poorly known in fossil record and the relationship between ring phototropism and rotation of block is undetermined.…”