The Deformation Features Of Quartz Grains In The Devonian Sandstone Of Taihu Lake Area

The hypothesis of impact origin of Tai Lake basin proposed in twenty years ago. One of the evidences, the deformation features in quartz grains received many opposite arguments, but never resolved. The goal of this paper is to review and check the similar previous work having been done in twenty years ago, and to discuss the Tai Lake impact hypothesis, based on current observation of the deformation features in quartz grains in sandstone which are widely distribute in islands and surrounding area of Taihu lake. Various deformation features of quartz grains in Devonian sandstone of Tai Lake area, including uneven extinction, deformed lamella and fractures are observed under optical microscopy. The preferred orientations of quartz deformed lamella were measured by using the universal stage. The well developed braided micro-fractures in the thin section of the sandstone samples were observed. We also compare the quartz deformation features from sandstone of Tai Lake area to that from similar formation sandstone from JiuJiang area300km away from Tai Lake. Based on the observation and measurement data, combining with the literature knowledge in the similar research field, the results show that the quartz deformed lamella of sandstone of Tai Lake area are not typical impact-induced planar deformation features (PDF). Most of the deformation features are caused by relatively lower pressure. The origin of these deformation features can be explained by multiple forces. The hypothesis of impact origin of Taihu lake is far from maturation, however, it is rewarded and valuable to intensively study the formation origin of Tai Lake by multiple approaches.