Abstract: Plastic pollution is an environmental problem of global concern, posing potential risks to human health and ecosystems. Mounting evidence suggests that plastic debris can irreversibly adhere to the host rock, providing direct evidence of how human activities are altering Earth's geological record. Based on these findings, this study defines a new type of sedimentary rock called plastistone. Plastistone is a sedimentary rock formed of visible plastic and clasts derived from pre-existing rock that were cemented together. In a plastistone, visible synthetic plastic polymers were irreversibly stuck onto or incorporated within the mineral matrix due to various physical and chemical processes such as melting-freezing, evaporation, and adsorption. This study aimed to examine the generation and size distribution of microplastics derived from plastistones collected in the terrestrial ecosystem during a field survey conducted in Hechi City, Guangxi Zhuang Autonomous Region, China, in July 2022. It was discovered that microplastics generated from plastistones during artificial wet-dry cycling followed a conditional fragmentation pattern. The fragmentation dimension modeling results showed a pseudo-2D fragmentation pattern for plastistones, with values falling within 1.5-2.5. The fragmentation dimension values for PP plastistones remained steady, while those for LDPE first increased and then decreased. Furthermore, more than 60% of the identified microplastics were spherical in shape and had smaller diameters compared to other polymer types. This emphasizes the potential ecological risks associated with these highly mobile microplastic particles. Additionally, it is important to note that the lithification process and long-term environmental behavior of plastistones remain unclear at present. Therefore, future research should focus on investigating these aspects in greater detail.