Chinese Academy of Geological Sciences, Beijing, 100037, China.
State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, and Center for Excellence in Life and Palaeoenvironment, Chinese Academy of Sciences, Nanjing, 210008, China.
Sci Rep. 2019 Mar 19;9(1):4856. doi: 10.1038/s41598-019-41339-2.
Trees grow towards the sunlight via a process of phototropism. The trunk phototropism processes are frequently observed in Northern Hemisphere from high latitude to at least the Tropic of Cancer region, and also occur in some in situ preserved vertical petrified woods in various geological ages. However, such evidence is still very limited and poorly known in fossil record; and the relationship between tree ring phototropism and rotation of tectonic blocks is unclear. Here we report the eccentricities of living and fossil trees as a proxy to determine geological block rotation at the same latitudes within the North China Block. The dominant eccentricity of living trees is southwest 219° ± 5°. By contrast, standing in situ fossil trunks in the Mid-Late Jurassic Tiaojishan Formation and the Late Jurassic Tuchengzi Formation had average eccentricities of 237° and 233.5°, respectively. These differences shed light on the palaeogeographical changes, indicating that the North China Block rotated clockwise from the Late Jurassic to the present day. This result is largely coincident with the palaeomagnetic results, indicating that the North China Block rotated clockwise by 26.5° ± 5.5° since the Middle to Late Jurassic transition.
树木通过向光性过程朝向阳光生长。树干的向光性过程在北半球高纬度地区到至少北回归线地区经常被观察到，并且也发生在一些不同地质时代的原地保存的垂直石化木中。然而，这种证据在化石记录中仍然非常有限且鲜为人知；并且树木年轮向光性与构造板块旋转之间的关系尚不清楚。在这里，我们报告了活树和化石树的偏心率，以确定华北板块同一纬度范围内的地质板块旋转。活树的主要偏心率为西南 219°±5°。相比之下，中晚侏罗世髫髻山组和晚侏罗世土城子组原地直立的化石树干的平均偏心率分别为 237°和 233.5°。这些差异揭示了古地理位置的变化，表明华北板块从中侏罗世至今一直顺时针旋转。这一结果与古地磁结果基本一致，表明从中侏罗世到现在，华北板块顺时针旋转了 26.5°±5.5°。
