| 山东灵山岛莱阳群水下非构造裂缝特征及意义 |
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| 关键词:Lingshan Island Laiyang Group shrinkage cracks seism liquefied |
| 基金项目:国家自然科学基金项目(编号: 40872095; 41272123) |
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| Characteristics and Significance of Underwater Non-tectonic Cracks in Laiyang Group of Lingshan Island, Shandong Province |
| Shrinkage cracks exist in Precambrian–Phanerozoic strata, but their origins remain controversial. Lots of cracks were found in the sandstone and mudstone of Laiyang Group in Lingshan Island, along with some brittle cracks and liquefied sandstone veins. These shrinkage cracks are usually developed in single layers and rarely extend to their adjacent layers. They possess the characteristics of multi-formation, multi-scale, multi-stage, multi-order and multiple filling ways and are distinct from desiccation cracks and post-structural fractures. Since there is no evidence of exposure, they are considered to have been formed under water. A comparison with the characteristics of seismic cracks proposed by Pratt shows that they might have been triggered by earthquakes. Many soft-sediment deformation structures were found in Lingshan Island, implying that seismic activities were frequent at that time and these seismic activities provided the necessary formation conditions for cracks. Different from the previous opinions, the viewpoint held by the authors argues that shrinkage cracks are more likely to be formed and get preserved in rift basins than in compressional basins in the passive continental margin. The interpretation of the cracks found in Lingshan Island as being caused by earthquakes under water bears much geological significance in that such an interpretation can indicate depth of water, record paleoseismic energy and frequencies, reflect paleoseismic rhythm and provide evidence that the Laiyang Group in Lingshan Island was developed in a rift basin. |
| WANG An-dong,ZHOU Yao-qi,ZHANG Zhen-kai,YU Shan-shan,WANG Zi-yang.2014.Characteristics and Significance of Underwater Non-tectonic Cracks in Laiyang Group of Lingshan Island, Shandong Province[J].Acta Geoscientica Sinica,35(3):321-328. |
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