关键词: 灰岩坑, 碳酸盐台地, 溶蚀, 塌陷, 东沙运动, 珠江口盆地

Abstract: Liuhua carbonate platform was developed in Dongsha uplift in Early Miocene with maximum thickness of more than 600 m. It was overlain by huge thickness of mudstones. A lot of sinkholes were imaged in upper carbonate platform based on coherent slices and three dimension visualization from seismic data. The sinkholes were larger depressions with diameter generally ranging from 200 to 700 m, the maximum more than 900 m, and depth varying from 10 to 90 m. Based on the characteristics that sinkholes developed along the NWW oriented faults which terminated at T₁₀ unconformity or continued to transform into syn-sedimentary faults, and depressions of mudstone stopping at T₁₀ unconformity, Dongsha Movement is considered to be the key factor leading to the occurrence of sinkholes. Concretely, basal magmatic activities might provide acidic hydrothermal fluid to dissolve the carbonate rock. NWW oriented faults produced by Dongsha Movement served as pathways for fluid flow and rooms for fluid exchange. At the end of Late Miocene, exposure caused by Dongsha Movement accelerated the dissolution rate of carbonate rocks. With continuous corrosion, the dissolved cavern became larger and larger until the carbonate strata over the cavern couldn't hold the upper loading, and then carbonate strata collapsed and the sinkhole formed.

Key words: sinkhole, carbonate platform, corrosion, collapse, Dongsha Movement, Pearl River Mouth basin